Division 15 - Mechanial
15.01 GENERAL HVAC
PART ONE
I. General
Because only a small portion of HVAC design is code-driven,
and because the choice of HVAC design concepts bears heavily
on maintenance cost and energy cost, the University has
certain preferences, and expects to see them reflected in
designs submitted our consultants. By not doing so, the
designer risks rejection of the concept and a requirement to
rework without additional compensation.
The intent of this document is not to dictate the design
concept but the interplay of first cost, performance,
maintenance and operating cost related to the mechanical
systems remains the responsibility of the designer. If the
University's preferences are at variance with the application
in design, the onus is on the designer to bring this to the
attention of the University.
Neither is it the intent to discourage creativity.
Alternatives are welcome. In fact, depending on the
circumstances of project funding, State regulations may
require life cycle analysis of several alternatives for HVAC
systems. When such comparative analysis is required, the
concepts, systems, and components described herein by those
favored by the University must be among the alternatives
analyzed.
Unless specifically directed otherwise by the program
document, the following HVAC standards and preferred design
concepts apply to all projects on the College Park campus of
the University of Maryland.
A. Design Conditions - Heating and Cooling
Perform the HVAC load calculations based on the following
outside conditions
Summer - 90 degrees design drybulb, 76 degrees wet bulb
Winter - 10 degrees drybulb (colder than the ASHRAE 99%
value)
Select cooling towers at 78 degree design wet bulb (the
ASHRAE 1% value)
Design for the following Inside conditions:
Summer 75 degrees drybulb +/-2 degrees (range of 73 - 77)
Winter 70 degrees drybulb +/-2 degrees (range of 68 B 72)
B. Humidity control
1. Summer: Unless noted to the contrary in the
program document, inside relative humidity is not
to be directly controlled - the University
recognizes that dehumidification is a byproduct of
the cooling process.
However, it is required that cooling equipment and
systems be selected and sized to produce 50% rh + /
- 5% in the conditioned space when design outside
conditions prevail , and other design parameters
are fulfilled.
HVAC system concepts noted for poor humidity
control at part load conditions are subject to
rejection. Such systems include, but are not
limited to:
Systems which allow outside (ventilation) air to
pass over inactive cooling coil surfaces.
Capacity control schemes which allow coil
temperatures to rise above that required for
dehumidification.
Systems which do not continuously dehumidify all
ventilation (outside) air.
2. Winter: The university standard is to add no
moisture to the air stream. When the program
document indicates that humidity control in winter
is required, it is expected that humidification
equipment will be sized with respect to the
envelopes ability to accommodate elevated levels of
interior air dewpoint.
Conditions that result in condensation on inside
surfaces, visible or concealed must be avoided .
The University's intent is to avoid microbial
growth on interior surfaces. (see Equipment
humidification).
C. Ventilation
1. CFM/person is the university standard for
quantification of ventilation rates.
Population density will be defined in the program
document. Otherwise, refer to ASHRAE Standard 62.
Reasonable assumptions (diversity, etc) are
encouraged in determining the population for
purposes of determining the ventilation air
quantity, but the assumptions must be documented
and understood by the Using agency.
2. Unless the specific application or the applicable
building code mandates higher ventilation air
quantities, HVAC designers must respect the most
current revision of ASHRAE standard 62, while
pursuing reasonable first cost, energy-efficient
HVAC design. Where aspects of energy use and air
quality are in conflict, air quality shall take
precedence.
3. Note: In attempts to use ASHRAE standard 62
interpretations to reduce the volume of ventilation
air, it will not always be possible to assume
scenarios of continuous ventilation, non-continuous
occupancy. A representative of the Using agency
must agree to the occupancy scenarios.
4. The application of CO2 sensors is encouraged where
appropriate to minimize cooling, dehumidification,
and heating of outside ventilation air.
D. Duct liner
Acoustical (fiberglass) duct liner is preferred as the
economical alternative to oversized ducts (low
velocities) and mechanical sound control devices.
However, the duct liner product, and the application
techniques, must be specified with the intent to avoid
IAQ problems. Examples include, but are not limited to:
a. Special coatings to eliminate the erosion of liner
particles
b. Special Installation practices (buttered edges,
etc.) to deter erosion of particles
c. No liner may be used in areas where the liner may
become wetted during normal system operation, or in
abnormal weather conditions.
d. Locate adequately sized and spaced access openings
in duct to facilitate periodic inspection and
cleaning
E. Equipment redundancy, spare capacity and back-up power
a. Redundancy - Generally, because of cost control,
redundancy is mandated only in the case of critical
systems and/or equipment, identified as critical in
the program document.
Regardless of the system redundancy requirements of
the program document, the design shall provide for
redundancy in the following items of mechanical
equipment, if such equipment is a part of the
project design and if the need for redundancy has
not been expressly waived by the program document :
1. Condensate (steam) return units: Duplex pumps
with automatic alternators are required. The
design shall be such that design flows will be
handled by a single pump with 33% run time.
This equipment shall be powered from the
emergency generator, if an emergency generator
is part of the project. It is not the intent
of this provision to create a requirement for
an emergency generator.
2. Package sump pumps (storm water): The design
shall incorporate duplex pumping with
automatic alternators. The design shall be
such that design flows will be handled by a
single pump with 33% run time.
This equipment shall be powered from the
emergency generator, if an emergency generator
is part of the project. It is not the intent
of this provision to create a requirement for
an emergency generator.
The equipment covered by this provision does
not refer to residential-type submersible
pumps, powered from 120 VAC receptacles.
3. Sewage Ejectors - A single sump is
acceptable. Incorporate duplex pumping with
automatic alternators. The design shall be
such that design flows will be handled by a
single pump, with 33% run time.
This equipment shall be powered from the
emergency generator, if an emergency generator
is part of the project. It is not the intent
of this provision to create a requirement for
an emergency generator.
4. Submersible sump pumps in elevator pits, etc.
There is no requirement for redundant pumps.
However, a high water alarm shall be
installed, connected to the CCMS, and the
submersible pump shall be powered from the
emergency generator, if an emergency generator
is part of the project. It is not the intent
of this provision to create a requirement for
an emergency generator.
5. Chilled water pumps - In single chiller
applications, a second, full sized pump/motor
assembly shall be designed. The second pump
shall be designed for manual valving in and
starting after a failure of the main pump.
It is permissible to use the spare pump as a
standby pump for an associated single
condenser water pump.
The use of parallel pumping arrangement for
purposes of creating spare capacity (with the
second pump) is not allowed.
6. Primary chilled water pumps. In multiple
chiller / dedicated pump applications, one
spare primary chilled water pump motor shall
be specified, stored on site in corrosion-resistant packaging.
7. Secondary chilled water pumps. Where used,
secondary chilled pumps will typically be a
single pump, VFD controlled. If the water
flow rate is such that two pumps are
indicated, the designer shall bring this to
the attention of the University for discussion
in the schematic design phase. Unless two
pumps are needed to handle design flow, a
second, standby secondary pump is required,
with a dedicated VFD. The second pump shall
be designed for manual valving in and manual
starting after a failure of the main pump
system. Generally, the University prefers
end-suction pumps, but this preference may be
waived in the interest of limiting the number
of pumps.
8. Condenser water pumps. In single chiller /
tower applications, a second condenser water
pump, full size shall be designed. The second
pump shall be designed for manual valving in
and starting after a failure of the main pump.
The use of parallel pumping for purposes of
creating spare capacity is not allowed.
It is permissible to use the spare condenser
water pump as a standby pump for a single
chilled water pump. Note: In multiple
chiller/pump applications, with a dedicated
condenser water pump in each condenser water
circuit, a spare pump motor shall be
specified, stored on site in corrosion-resistant packaging.
9. Primary hot water pumps - In single boiler
applications, a second, full sized pump/motor
assembly shall be designed. The second pump
shall be designed for manual valving in and
starting after a failure of the main pump.
The use of parallel pumping for spare capacity
will be disallowed. Note: In multiple boiler
/dedicated HW pump applications (such as in
primary/secondary pumping) one spare primary
hot water pump motor shall be specified,
stored on site in corrosion-resistant
packaging.
10. Secondary hot water pumps. Where used,
secondary hot water pumps shall typically be a
single pump, VFD controlled. If the water
flow rate is such that two pumps are
indicated, the designer shall bring this to
the attention of the University in the
schematic design phase. A second, standby
pump shall be designed, with a dedicated VFD.
The second pump shall be designed for manual
valving in and manual starting after a failure
of the main pump system. Generally, the
University prefers end-suction pumps, but this
preference is waived in the interest of
limiting the number of pumps.
11. Control air compressors. A single tank is
acceptable. The design shall incorporate
duplex air compressors / motors with
automatic alternator. The design shall be
predicated on one third run time for one
compressor, with the second compressor
designed as a full standby. There is no
requirement for redundancy in the refrigerated
air dryer or oil filter system.
a. Spare Capacity - Generally, equipment shall be
sized at half capacity and used in multiples of
two. Allowance for load growth beyond that
specified below will be stated in the program
documents.
1. In the case of local heating boilers, size
each boiler for the full calculated boiler
load.
2. In the case of steam boilers intended for use
only during the annual steam outage, there is
no requirement for spare capacity or
redundancy.
3. Chilled water cooling coils and filter banks -
size the coil for 450 fpm face initial
velocity to allow for air quantity growth to
550 fpm. Size the fan (but not the fan motor)
for the resistance at the future (higher air)
flow.
F. Firestopping. The designer shall note in the
specifications that firestopping of floor and wall
penetrations related to the trades in division 15 of the
specifications is to be specified, furnished and
installed under another section of the specification.
The division 15 specification shall require that the
subcontractors furnish, when transmitting prices to the
prime contractor, a list, with sizes, of all openings to
be firestopped.
15.02 HVAC SYSTEMS
A. General
The University encourages the HVAC consultant to employ
energy-efficient design, consistent with the project
budget. The University desires to maximize all
opportunities to participate in funding assistance from
utilities, including rebates, design fee subsidies, and
other incentives to stimulate energy-efficient design.
Also, the University recognizes that, depending on the
circumstances of project funding, State regulations may
require life cycle analysis of alternative HVAC systems.
When such comparative analysis is required, at a minimum,
the following systems shall be presented as alternatives.
The intent is for the University to receive state of the
art, energy-efficient HVAC design, but not necessarily at
a first cost premium.
1. Being committed to the SCUB (Satellite Central
Utility Building) concept, the University's
preference is for chilled water based systems. The
HVAC designer is required to rule out using chilled
water concepts capacity before relying on DX
equipment.
2. Air handlers with air-cooled package chillers are
preferable to field-piped (spilt system) direct
expansion (DX) systems. Among other shortcomings,
the university perceives that the direct expansion
approach is relatively inflexible because cooling
load growth and changes in space layouts are a
given at the campus.
Field-piped DX evaporators with condensing units
will be rejected unless, in the schematic design
phase, the case can be made that a nuance of the
application or of the site requires a DX approach.
3. When field piped DX systems are employed, it shall
be incumbent upon the engineer of record to develop
the details of the field - piped refrigeration
system layout and show the details on the bid
documents. (oriented around the equipment which is
the basis of design) The intent is for all bidders
to be able to include in the price the equipment,
accessories and specialties needed for proper
operation and compressor protection.
a. If field-piped DX systems above 7.5 tons are
employed, refrigerant piping layouts shall be
included in the bid documents. Refrigerant
piping layouts shall be oriented around the
equipment which is the basis of design and
shall be complete in all details, including
face and row split arrangements, pipe sizes,
pipe pitch, and all required refrigerant
control components and specialties identified
by model number. Face split only coils,
because of the bypassed air at low loads, will
be rejected unless the designer, in the
schematic design phase, can make a case that
the application requires the technique.
b. For DX split systems above 20 tons, and for
any size field-piped DX application handling
100% outside air, refrigerant piping layouts,
including an isometric view, shall be included
in the bid documents. The refrigerant piping
layout shall be specific to the equipment
which is the basis of design; the layout shall
be complete in all details, including, but not
limited to: face and row split arrangements,
pipe sizes, pipe pitch, suction riser detail,
insulation, vibration isolation, and trap
details. Thermostatic control valve size,
orifice size, and all other required
refrigerant control components, accessories
and specialties shall be identified by model
number on the drawing. The maximum and
minimum evaporator coil loads shall be stated
and the bid documents shall include a
certification by an officer of the (basis of
design) compressor manufacturer that the
piping layout is approved for the particular
application.
c. The DX equipment specification shall require
compressor and coil to be by the same
manufacturer. The rationale here is that the
compressor manufacturer is typically a design
resource.
d. The specification shall require that, if other
than the basis of design is submitted, the
submittal will be accompanied by an equivalent
piping drawing and compressor manufacturer
certification.
e. Submittal data will be required to include ARI
coil selections at various load points. The
load points will include, but are not limited
to the following:
- Full cooling load
- Outside temperature at 75 degrees db, 75
degrees wb, no solar load
- Outside temperature 2 degrees ABOVE that
which will produce mixed air at 55
degrees (cooling without compressor
operation)
At other than full load points, the designer
shall comment on refrigerant velocity in tubes
and critical pipe sections with regard to oil
return to the compressor.
4. Water-cooled or evaporative cooled condensing shall
be the basis of design unless the case can be made,
in the schematic design phase, that the
application mandates air-cooled condensing
equipment.
5. It is acceptable for capacity ratings of air-cooled
refrigeration equipment to be based on operation at
95 degrees ambient, but the air-cooled equipment
must be capable of operating continuously in the
highest temperatures to be expected on campus, in
the particular equipment location.
6. All buildings are candidates for SCUB service
(central chilled water). Accordingly:
a. If an on site chiller is the basis of design,
select air handler cooling coils, delta t,
etc., in anticipation of a future conversion
to SCUB service. Rationale: SCUB produced
chilled water can be expected to be delivered
to the building at no colder than 45 degrees.
b. Avoid chilled water systems which rely on
glycol.
7. When cooling coil freezing is a risk, unless all
piping is within mechanical spaces, avoid the use
of glycol in chilled water systems. The intent is
to avoid glycol-containing pipes in occupied
spaces; local heat exchangers may be required. In
safeguarding against cooling coil freezing, first
rule out glycol/water preheat coils or electric /
steam preheat coils. Arrange non-freeze steam
coils for positive gravity condensate drainage.
Annual draining of coils is not an acceptable
design solution.
8. Winter cooling without refrigeration may be either
100% outside air (airside economizer) or condenser
water based free cooling.
a. With air side economizers, barometric relief
is the preferred means of relieving building
pressurization. Where return air fans are
used, take particular note to avoid
overpressurization of the building. Acceptance
testing will, among other aspects of HVAC
operation, require proof of system operation
with 100% outside air with no adverse effect
on building pressurization.
b. When 100% outdoor air is used for winter
cooling, the control system shall also employ
enthalpy cycle cooling for cooling with 100%
outside air with the refrigeration system
operational when outside air humidity allows.
c. When heat exchangers are used to produce free
cooling chilled water from cooling tower
water, the design shall incorporate provisions
to accommodate the following:
1) Avoid elevated chilled water temperatures
during the waterside economizer
operation.
2) Include a means of maintaining chilled
water at design temperature while
extending the operating hours of the
water side economizer. A chiller in
series with the free cooling heat
exchanger is a method which would not
necessarily be rejected.
3) Assure that the system can revert to
chiller operation immediately, i.e.
without waiting for cooling tower loop
temperature (condenser water) to rise.
d. Regardless of the presence of a waterside
economizer, the design shall incorporate
provisions for purging the building with high
volumes of outside air while the construction
materials are outgassing.
9. Heating
a. Hot water is the preferred space heating
medium. Electric resistance heat will be
rejected unless a case for it can be made in
the schematic design phase.
b. Heating systems with steam terminal units in
occupied spaces will be rejected.
c. Where glycol is used, restrict glycol use to
piping within mechanical rooms. This may
require the use of local heat exchangers. The
intent is to have no glycol-containing pipes
in / above occupied spaces.
d. When the envelope heat loss exceeds 400 btuh
per linear foot of building perimeter, the
designer must justify why heat is not being
added at floor level.
10. Ceiling plenums. Using the above - ceiling plenum
to convey return air is strongly discouraged and
may result in a design submission being rejected.
The rationale is:
IAQ - The very low velocities of plenum-conveyed
return air tend to allow particulate matter to
precipitate out rather than be removed at the
filters. Also, If roof or other leaks occur, mold
growth can develop - and mold spore propagation can
occur - in the return air stream.
Sound transmission. By definition, the above
ceiling plenum has no vertical separation between
spaces. Cross-talk between adjacent spaces is a
near certainty.
Similarly, use of mechanical rooms as return air
plenums is prohibited.
B. New Construction
1. Educational and office space.
a. Note the HVAC references in Division 12 of the
DCFS: Design Standards for Instructional
Space.
b. A thermostat in every classroom is the
University standard. Offices with similar
thermal profiles can be grouped in accordance
with good design practice.
c. Ventilation: Decoupling the ventilation
function from the cooling and heating
functions is the University standard, where
practical. The intent is to centrally cool,
dehumidify heat and filter the mandated amount
of ventilation (outdoor) air, then deliver the
ventilation air at room temperature to all
occupied spaces, while accomplishing space
temperature control with generic (i.e.
relatively low cost) terminal equipment.
Other concepts will be rejected unless, in the
schematic design phase, a project-specific
case can be made that the decoupled
ventilation concept is not feasible.
It is preferred that the central ventilation
air handler(s) incorporate state-of-the-art
devices (dessicant dehumidification, heat
pipes, etc.) to minimize energy consumption in
the face of high dehumidification and heating
loads. Recognizing the inevitability of
budget constraints, the University does not
mandate such devices, but the HVAC designer
shall layout the equipment to allow the future
retrofit of such devices.
d. If other than decoupled ventilation systems
are proposed, the ventilation air quantity
must be independently controlled such that it
does not fall below the minimum during air
handler operation.
e. CO2 sensor - controlled variable volume
ventilation in each high density space is
encouraged, but not required.
f. Generally, do not consider recovering heat
from normal quantities of toilet exhaust. If
building exhaust air quantities exceed normal
toilet exhaust, consider heat recovery, at the
decoupled ventilation unit or elsewhere.
If heat recovery is warranted, but is not to
be constructed at the outset, the designer
shall make provisions to terminate exhaust in
reasonable proximity to intake to allow future
design and installation.
g. Unit ventilators will be rejected unless, in
the schematic design phase, a project-specific
case can be made that the use of this concept
is required.
h. Fan coil units (4-pipe) as a means of space
temperature control will not be rejected.
Using the fan-coil units to introduce and
condition outside ventilation air is not
acceptable.
2. Laboratory space.
a. Generally, the comments for classroom and
office spaces apply; plus:
b. The specifics of the application will govern.
However, the University has preferences:
- Variable volume exhaust and makeup
systems with Direct Digital Controls
- Heat recovery
c. Consider locating mechanical equipment in
equipment mezzanines, etc. with special
consideration to facilitate the required
periodic maintenance, especially filter
changes. (Bag-in, bag-out filter change
methodology is preferred). Avoid equipment
located outside. When this is unavoidable, pay
particular attention to protecting the
surrounding roof. Do not discharge condensate
to the roof.
C. Major renovations of older buildings.
Generally, a major renovation is expected to allow for an
additional 30 year cycle of use. Concepts not conducive
to this are likely to be rejected. The designer should be
guided accordingly.
1. Educational and Office space
a. Provisions for new construction apply. In
addition:
b. Ventilation by operable windows is not favored
by the University, but the concept may be
acceptable under project-specific conditions
if:
1. It is shown by the designer during
schematic design to meet the intent of
the latest version of ASHRAE standard 62
and if:
2. 4 pipe fan coil units are employed and
the designer allows for the ventilation
load in the fan-coil unit sizing (at high
fan speed) and allows for the outside air
load in chiller sizing.
3. The designer makes provisions (space
allocation for ducts, equipment) for the
future design and installation of a
decoupled ventilation system.
4. All occupied spaces, in fact, have
windows. If ventilation spaces have to
be designed to ventilate some spaces, the
designer must show why it is not feasible
to incorporated decoupled ventilation
throughout.
2. Laboratory space.
Educational and office space preferences apply.
New construction guidelines apply to the greatest extent
practical.
D. Small scale renovations of existing buildings
1. Classroom and office space
a) With regard to classrooms, note the HVAC references
in section 12 of the DCFS: Design Standards for
Instructional Space.
b) Regardless of project size, the University's
preference is for chilled water - based cooling
systems. Often, existing chillers will have spare
capacity. This should be pursued, within the limits
of practicality, to reduce cost, even when the
project budget envisions a dedicated chiller.
The onus is on the HVAC designer early in the
design phase, to ascertain whether spare capacity
is available in existing chillers, unless it has
been stated in the program that such a search is
not required (by virtue of prior University
research). University personnel will cooperate to
a reasonable extent.
c) The University preference for chilled water does
not extend to water-cooled chillers in the smaller
sizes implied in this discussion. Air-cooled
package chillers are acceptable. In such
applications, moderate oversizing of chillers for
possible future use will not automatically be
rejected.
d) Consider also chilled water piping header concept,
sized with expansion in mind, with valved and
capped taps to facilitate future chiller tie ins.
Consider chilled water surge tanks to improve
control with a small volume of water in the piping
circuit and spare chiller capacity.
e) As a practical matter, on the smaller applications,
the University expects that it may have to accept
ventilation to be combined with cooling and
heating. The designer shall make provisions to
avoid coil freezing with the often high outside air
percentages resulting from current ventilation
requirements. DX equipment is not an acceptable
provision solely to avoid coil freezing.
2. Laboratory space
a. Generally, provisions for classroom and office
applications apply.
b. It is recognized that, without an existing make-up
air system, 100% outside air applications will
often be necessary.
c. The designer shall make provisions to avoid coil
freezing with the high outside air percentages
(including 100%) resulting from laboratory air flow
requirements. DX equipment is not an acceptable
choice merely to avoid coil freezing. The onus is
on the HVAC designer to rule out small package
chillers because of the inherent problems with DX
applications, and the construction cost premiums
required to prevent them; to wit
Light load operation
Operation at outside temperatures above design
Oil return at light load operation
Nuisance tripouts
Achieving practical redundant refrigerant circuits
The need for hot gas bypass energy / maintenance
implications
The need for specialized refrigerant specialties
multiple circuited coils, accumulators, electric
unloaders
The need for multiple accessible hermetic
compressors
d. Variable volume supply and makeup systems with
Direct Digital Controls are preferred, but given
the diseconomies of scale, the HVAC designer may
successfully make a case for constant volume
reheat. If reheat is inevitable, design to
minimize it, emphasize hot water (made with campus
steam) over electric resistance heat, and allow
space for retrofitting more efficient concepts in
the future.
15.03 HVAC EQUIPMENT
A. General
1. Electric motors
a. "Premium efficiency" motors are the university
standard for motors larger than 3/4
horsepower(to be distinguished from high
efficiency).
Where utility (Pepco) rebates are in effect,
Premium efficiency motor is intended to mean
the efficiency required to earn the utility
rebate in effect at the time.
In the absence of utility rebates, the Pepco
definition of "premium efficiency" motors will
define the University's standard for minimum
efficiency
b. Power factor correction capacitors are
required.
B. Specific
1. Electric centrifugal chillers
Carrier, York, Trane, McQuay are generally
acceptable
Water-cooled condensers are mandated above
approximately 100 tons, but the designer may make a
case for air-cooled versions.
Approved refrigerants are HFC 134a, HCFC 123, HCFC
22.
The provisions of ASHRAE standard 15 shall apply to
the chiller installation.
Microprocessor-based controls are required
2. Absorption cycle refrigeration shall not be
considered unless, in the schematic design phase,
the case can be made that the application requires
it.
3. Cooling towers
a. Select towers for operation at 78 degree wet
bulb.
b. VFD control of tower capacity is the
university standard.
c. The cooling tower specification shall require
that the cooling tower be CTI certified, and
shall require the vendor (through the
contractor) to state the cost of a CTI -
certified field capacity test on demand by the
University, the cost of which is to be
initially paid by the vendor. The
specification shall further state that, should
such a test be demanded - and the test shows
that the correct capacity is being produced,
the University will reimburse the vendor for
the quoted cost of the test. The bid
documents shall require the contractor to
expose the quote for the test.
d. The specification shall require stainless
steel sumps and strainer to extend the service
life of this component.
e. Specify as an alternate (a low priority
alternate in the MD DGS system) proprietary
coatings, materials, etc. on the rest of the
tower.
f. Unless a water-side economizer is used, to
operate towers in below - freezing
temperatures is not the norm, but the tower
selected shall be capable of part load
operation in sub-freezing ambient
temperatures. The university understands that
it may be required to purchase field-installed
accessories when and if sub-freezing tower
operation later becomes necessary.
g. Steam is generally available on campus, but
the standard is electric sump heaters. Sump
heaters shall be powered from the emergency
generator.
h. Multiple towers are the standard, arranged and
piped such that one can be drained and
maintenance performed while others continue to
operate.
4. Chilled water coils. The university standard is
copper tube, aluminum fin. To extend performance,
specify added rows rather than closer fin spacing
to assure that the coils are cleanable.
a. Regardless of whether an on site chiller is
employed in the design, select coils
anticipating SCUB-related entering chilled
water temperatures in the future.
b. Select coils at 450 fpm to allow for growth in
air quantity. Do not apply a growth factor to
fan and drive selection, but the air handler
must be capable of being upgraded to 550 fpm.
c. Drain pans shall be specified to be completely
drainable, with no standing water. Where
intermediate drain pans are used, they shall
be arranged for complete draining, with no
standing water and no condensate carry-over
from pans or interconnecting piping.
Stainless steel drain pans are not required.
d. The specification shall state that the coil
manufacturer shall coordinate the coil design
with the fan installation. The specification
shall state that the coil manufacturer is
required to install baffles at the coil as may
be required to prevent areas of high coil face
velocity causing moisture carry-over.
Larger fan motors, if required as a
consequence of such modifications are the
responsibility of the coil manufacturer.
The specification shall state that the
university will test the coil for moisture
carry-over while dehumidifying with coil
entering air at the highest conditions
expected in the campus area (higher than the
design conditions) . The acceptable result is
no moisture carry-over.
5. Humidification equipment. Where required by the
program document, steam humidification is the
standard. Produce low pressure steam for
humidification with a steam generator fired by
high / medium pressure central steam, supplied with
domestic water. Where central steam is not
available, produce low pressure steam with a gas
steam boiler. If natural gas is unavailable, use
electric steam generators.
6. Heat tracing cable. Shall be specified such that
the furnishing and installation of all control
components is the responsibility of the control
contractor. The specification shall mandate a UM -
witnessed test to prove continuity before the
wiring is installed and again before the wiring is
covered with insulation.
Heating cable with integral thermostats will be
rejected. The intent is to control the heat tracing
cable from a control panel with input from a global
signal from the CCMS (with a back-up sensor). Heat
tracing cable shall be powered from the emergency
generator. Avoid using heat tracing cable whenever
possible.
7. Valves: refer to Plumbing.
8. Pumps
a. Acceptable pump manufacturers include: Bell
and Gossett, TACO, or Armstrong.
b. In-line pumps are not desired except for
fractional horsepower circulators.
Pumps shall be capable of being serviced
without disturbing piping connections or
motors.
c. The University prefers base mounted, end
suction pumps, but this preference may be
waived in the interest of limiting the number
of pumps.
d. Unless the application requires otherwise:
- Pump motors shall not exceed 1750 RPM.
- Impellers shall be selected to be no more
than 5% below the point of maximum
efficiency.
- Impellers shall be selected at no more
than 85% of volute diameter.
- Pump motor horsepower shall be selected
with a service factor of no less than 15%
greater than the motor rating.
e. A means of vibration isolation shall be
provided for all pumps. Transmission of pump-related sound throughout the piping systems
and/or the building will be cause for
requiring redesign and rebuilding, at the
expense of the designer.
Note: the location of the pump has a bearing
on the type of vibration isolation. For
example, a case can be made - by the designer
- that vibration isolation bases might be
eliminated in the case of a pump located on a
slab-on-grade.
f. Hot water pumps shall utilize seals capable of
operating at 250 degrees F.
9. Heat exchangers
Plate-and-frame type are preferred by the
University, and the designer should make
provisions early in the design process for the
space required.
Tranter, Alfa-Laval are acceptable brands,
subject to performance.
The specification shall quantify the minimum
surface area.
The heat exchanger specification shall require
the vendor (through the contractor) to state
the cost of a certified field capacity test on
demand by the University, the cost for which
is to be initially paid by the vendor. The
specification shall further state that, should
such a test be demanded - and the test shows
that the correct capacity is being produced,
the University will reimburse the vendor for
the quoted cost of the test.
The bid documents shall require the contractor
to expose the quote for the test.
The test must be performed by, and certified
by an AABC certified air and water balance
firm ( not the balancing contractor for the
project), and sealed by a Maryland registered
Professional Engineer (Mechanical)
10. Variable Speed Drives: Variable speed drives are
preferred on applicable motors 5 horsepower and
greater. Drives shall be by Toshiba, ABB, or York.
15.04 AUTOMATIC TEMPERATURE CONTROL (ATC)
Generally, the University prefers simple control systems and
concepts.
Pneumatic actuators are generally acceptable, but DDC is to be
used in lieu of receiver-controllers.
Straight through control valve operation, facilitating primary
/ secondary pumping, is desired where practical.
The University's CCMS front end will support STAEFA control
systems within buildings.
Among other commissioning events, a "15 day acceptance test is
required", and the ATC specification must describe the
requirements. This document is available, on disc, through
the University's Project Manager, from the University's HVAC
Services group.
15.05 HVAC DESIGN FOR ENERGY EFFICIENCY
The University is committed to energy-efficient design within
the limits of budget constraints. The HVAC designer is
required to be alert to opportunities to reduce first cost
with less-than-optimal concepts (but within the bounds of good
practice and applicable energy codes), yet allow for the
future retrofit to state-of-the-art energy-efficient equipment
and concepts.
Expanding: The University anticipates executing an
arrangement with a performance contractor such that no cash
retrofits funded by provable future energy savings could be
routine.
When a future retrofit opportunity has been identified, and
the University agrees, the HVAC design must allow for the
future installation (adequate space, etc.).
The HVAC design must also allow provisions in the base design
(pressure/temperature taps, flowmeter stations, etc.) for
measurement techniques which will be used to establish a
baseline of energy use, then to quantify the post-retrofit
savings.
15.06 PLUMBING
A. Generally, the provisions of WSSC apply, as well as
industry standard good design practice for educational
institutions. The plumbing designer must reflect the
University's need, to the greatest extent practical, to
perform maintenance and repair to system components
without interruption to educational activity.
Examples of maintenance sensitive design practices
include, but are not limited to, location of cleanouts,
access panels, layout of distribution systems, location
of isolation valves, etc. The University has the right
to reject design drawings and/or shop drawings which
violate the intent.
For example, unacceptable plumbing design - subject to
rejection is a layout is such that an entire multi-floor
riser has to be secured to isolate one toilet room.
B. Certain hardware standards apply.
1. Piping:
Gas lines shall be of all welded black steel
construction inside of the building, connected to
emergency shut-off valves. Valves are to be
clearly labeled. Gas lines from valve to lab table
or appliances may be screwed black steel with screw
type fittings for 3/4" and smaller. All building
gas piping must be labeled (below ceiling).
Piping shall not be:
a. Buried beneath the lowest floor level (except
for soil pipe.)
b. Run in concrete floors. If pressure piping
placement under slab is unavoidable then the
piping must be run in a steel pipe sleeve so
leakage can be channeled off, and clearance
provided so repairs can be made
c. Direct burial of steam piping is not
acceptable. A conduit system shall be
provided.
2. Color code all piping valves and fixtures in
accordance with the University's color schedule
(depicted elsewhere in this document).
3. Provide flexible copper tubing with removable key
cut-off valves at all lavatories and sinks.
4. Valves
a. All control valves shall be listed in a
schedule on the drawing showing identification
number, body size, port size, if applicable,
whether normally open or closed, spring range,
and CV.
b. HVAC and plumbing system valves less than 2-1/2" shall be ball type, and greater than 2-1/2" shall be OSY.
c. All valves installed at heights greater than
six feet shall have chain activators provided.
d. Butterfly valves shall be used only for
automatic isolation, temperature control, and
automation functions. Use Globe, Angle and
"Y" valves for throttling services. Gate
valves are not acceptable.
e. All valves in copper piping systems 2-1/2" or
smaller shall be ball, single piece type
unless otherwise noted.
f. The University standard for DWV piping within
buildings is cast iron. Connection method is
the contractor's option, but no-hub is
prohibited underground.
g. Chilled water and heating water valves in
underground systems shall have as an enclosure
a concrete valve box with sufficient space to
maintain and operate valves.
15.07 FIRE SPRINKLERS
The University recognizes the contribution of sprinklers to
life safety. However, the cost to install them in renovation
projects often dictates that they be forsaken, to be
substituted with other measures to bring renovation projects
into minimal code conformance.
Unless stated to the contrary in the program, the decision to
not incorporate sprinklers into the mechanical design must be
based on a total project cost approach.
The cross-discipline comparative cost analysis, as a minimum,
must address:
The presence/absence of a University installed standpipe
system, which minimizes the cost of the sprinkler system
The need to remove ceilings to install other work
The extent and cost of other fire code-mandated work, the need
for which would be eliminated were a sprinkler system to be
incorporated.
Programmatic needs which conflict with alternative (not
sprinkler) solutions to code issues added fire rated walls,
doors, additional stairwells, areas of refuge, smoke exhaust
systems, restrictions on use, etc.
15.08 DESIGN AND BID DOCUMENTS
A. Division 15 drawings must show the following:
1) University assigned room numbers
2) Column line designations.
3) Sequence of ATC operations, point lists and
control diagrams for the control system which is
the basis of design.
4) Evidence of study and establishment of adequate,
industry standard, clearance to maintain, remove
and repair all equipment. In laboratory and other
high technology buildings, 3D CAD mechanical space
layouts are strongly recommended to preclude the
University mandating redesign and rebuilding - at
the designer=s cost - if service access barriers
are discovered after construction.
The University has the right of document review and
will attempt to discover problems in this regard,
but the onus is on the designer to establish
adequate service clearance. In disputes arising
out of this, and other aspects, the standard of
care is institutional, not commercial design
practice. After two reviews, the University will
charge an hourly rate according to a schedule in
the specifications.
The designer is required to incorporate this review
provision in the contract documents such that it
applies as well to the contractor's submission of
shop drawings.
"Industry standard adequate service and maintenance
provisions" extend to (OSHA-compliant) platforms
(and ladders) permanently erected around equipment
which is not floor mounted.
Mechanical rooms at grade level are strongly
preferred.
It is recognized that component layout for
industry-standard service access sometime runs
contrary to lowest first cost. The University
expects that proper design will minimize the
diseconomies. Long shutdowns of systems for
routine maintenance will negatively impact the
educational process and cannot be tolerated.
B. Plumbing, HVAC and Sprinkler shall be presented as three
separate drawing sets.
C. Special HVAC issues
It is not the intent of the DCFS to dictate process.
However, the designer shall specify certain procedures
for the purpose of binding the Contractor to the
requirements of the University, in particular:
1. When the designer specifies equipment installation
to be "In accordance with the manufacturer's
direction", the specification shall list the
applicable manufacturer=s publication, title and
date. The specification shall state which
instructions in that publication, if any, do not
apply to the particular application.
2. The specification shall require that, if equipment
other than that which is the basis of design is
submitted, the submittal will be accompanied by the
applicable manufacturer's installation
instructions, again with instructions that do not
apply clearly noted.
3. "Interrelated Systems" will be so identified on the
design documents. With regard to submittals of the
components of interrelated mechanical, electrical,
life safety and / or other systems, the
specification shall include words to the following
effect :
"The design documents depict a coordinated system
comprised of equipment which is selected as the
basis of design, but is not intended to exclude
others. Submission of any one component other than
that which is the basis of design is considered to
be a substitution of the entire Interrelated System
and the submittal must be identified by the
Contractor to be :
a. An interrelated system
b. A substitution
The Contractor, as part of the submittal, must
provide supporting documentation to show that the
submitted equipment has been coordinated to the
same extent as the equipment which is the basis of
design.
The University will be a participant in the
submittal review process. The Contractor is
entitled to two submittal reviews. After the
second review session, the University will be
reimbursed for subsequent review time at an hourly
rate to be published in the contract documents,
such amount to be withheld from funds payable to
the Prime Contractor."
D. The University standard for Piping identification and
color coding
1. Chilled Water
Primary - Supply PCHWS Imperial Blue 34
Return PCHWR Imperial Blue 34
Secondary - Supply SCHWS Blue Tint #9637
Return SCHWR Blue Tint #9637
2. Dual Temperature Water
Supply DTWS Safety Green
Return DTWR Safety Green
3. Utility Hot Water Heating
Supply HWS Accent Yellow
Return HWR Accent Yellow
4. Steam - High Pressure HPS Aluminum
Intermediate Pressure IPS Aluminum Low Pressure LPS Aluminum
5. Steam Condensate
High Pressure CHP Safety Orange
Intermediate Pressure CIP Safety Orange
Low Pressure CLP Safety Orange
6. Condenser Water
Supply CWS ANSI Safety Gray
Return CWR ANSI Safety Gray
7. Domestic (Potable) Water
Cold DWS Spring Green #9728
Hot w/Dark
Green Band) DWH Spring Green #9728
8. Fire Protection --- Red #9903
9. Fuel Oil FO Safety Black
10. Gas GAS Safety Yellow
11. Vacuum V Platform Gray #9453
12. Compressed Air CA Light Gray #9454
13. Drain --- Traffic Signal Green #9722
14. Hazardous Waste --- OSHA Safety Purple
The above colors are based upon Duron "Dura Clad"
(Alkyd Gloss Enamel Modified With Urethane)
Industrial Maintenance Finishes
E. The following information should be clearly shown
on the drawings, expanded or modified as required
by the application.
1. Design conditions (occupied):
Summer Outside db, wb
Summer Inside db, rh
Winter Outside db
Winter Inside db
Unoccupied
Summer db
Winter db
Total Cooling Capacity Avail. (Tons)
Total Cooling Max. Demand Load (Tons)
Total Heating Capacity (BTUH)
Total Heating Max. Demand (BTUH)
Population (# of persons)
Ventilation (outside) air handled by the
equipment:
occupied (cfm)
unoccupied (cfm)
Domestic Hot Water, Capacity Available (gph)
Domestic Hot Water Max. Demand Load (gpm)
Steam, Capacity Available (#/hr.)
Steam Max. Demand Load (#/hr.)
Fixtures (Plumbing) (Fixture units)
Sanitary Sewer (gpd)
Gas, natural, demand load (max.) (cfh)
15.09 SCUB CONCEPT
The University, with a central steam distribution system
and an electric distribution system, has standardized on
a concept called the Satellite Central Utilities Building
(SCUB).
At strategic locations around campus, steam and
electricity is used to produce chilled water, hot water
and sometimes, domestic hot water. From the SCUB, these
services are delivered to the surrounding buildings.
SCUBs are either stand alone buildings, or integrated
into new campus buildings.
The program document will make it clear whether a SCUB is
to be part of the design. In the event that it is,
standards and guidelines for SCUB design will be given to
the designer.
15.10 APPENDIX
Discussion of what could be alleged to be cost
premiums resulting from these standards.
Generally, the baseline standard is that of
Institutional design, not commercial design.
Part One HVAC
I. General
A. HVAC Design Conditions
The prohibition of control schemes which vary the cooling
coil temperature rules out using the more common, low
cost control schemes; but these have generally been
discredited as institutions seek to avoid litigation
related to Indoor Air Quality (IAQ).
Related is:
B. Ventilation - Granted, the University's adherence to ASHRAE
Standard 62 is beyond the requirements of typical local codes.
For example, the ASHRAE standard rules out using windows for
ventilation of remodeled campus buildings unless the
ventilation can be demonstrated (a defacto prohibition of this
typical low-cost approach). Local codes atypically do not
incorporate this demonstration provision. However, in
litigating IAQ issues, liability has been assessed in cases
where local codes allowed less stringent ventilation
practices, but the professional HVAC designers were aware of
the more stringent provisions of the ASHRAE standard.
(Note that "decoupled ventilation" is promulgated as the
University's preferred method. The first cost
implications of this are worth noting:
a. If designed simply, i.e. not incorporating heat-reclaim and other costly enhancements, the
decoupled (stand-alone) ventilation unit is
typically a small portion of the total HVAC system
first cost. Most of the total HVAC system first
cost relates to the other, heating/cooling
functions.
To quantify: If the sheet metal ventilation duct
system is taken to be the element which would not
otherwise have been installed, the first cost
premium is around $0.60/ s.f. (1999 dollars); less
than 2 of 1% of the total cost to construct a
typical campus building.
And there are compensating savings which approach,
and may exceed, the premium cost. Using this
(relatively high cost) approach to ventilation
allows the use of simple, low cost, easy to
maintain heating/cooling components elsewhere
throughout the HVAC system ( including fan-coil
units).
To illustrate, in the case of a fan-coil unit
system, the avoided costs include :
- The cost to create openings in the outside
wall for ventilation air.
- The cost of the associated louvers
- The cost to upsize all the air side terminals
to handle the ventilation cooling,
dehumidification and heating load
- The cost of more sophisticated fan-coil unit
controls ( decoupling the ventilation allows
fan cycling (no automatic control valve) for
space temperature control.
b. Further, the University, at a later date, can solicit
proposals from performance contractors to replace /
augment the decoupled ventilation units in order to
reduce the operating energy cost. Typically,
performance contractors receive their payment from the
savings, which can be demonstrated by measurements before
and after.
The first cost premium situation and the offsetting
savings - varies with each application.
Generally, our position is that no first cost
premium is involved. In addition, the litigation
cost avoidance is a benefit.
Part One - D. Duct liner
Control of sound in HVAC systems is necessary. It is accomplished
by one of the following methods:
a. Mechanical means such as oversized, more costly ducts ( for
low air velocity), sound traps inserted into ducts custom
fabricated sound attenuators. The premium cost implications
are obvious.
b. "Noise cancellation" electronically generated sound, the
Amirror image of the offensive noise - propagated such that it
cancels the offensive noise. Again, the premium cost
implications are obvious
c. Acoustical (fiberglass) duct liner.
Note - Fiberglass liners which erode and discharge
particles into the HVAC supply air stream, have been
implicated in IAQ problems. Also, fiberglass duct liner
which becomes wett can harbor colonies of microbial
growth, with IAQ liability implications.
Fiberglass, including fiberglass duct liners, has not
been declared an IAQ issue, so the University chooses to
not impose an outright ban on the use of the material.
The University reserves the right to ban the product in
special cases, and the program will state this.
Instead, the University requires that all duct liner,
where used, be polymer coated.
The University's requirement for coated fiberglass liners
parallels the industry trend toward standardizing on this
variation on the formerly common (uncoated) duct liner
material.
Uncoated fiberglass duct liner will shortly become
unavailable, so the cost premium for the coated variety
is, we suggest, a moot point.
The limitation on the application of even coated
fiberglass duct liner (where the application is subject
to wetting) mandates alternative (closed cell foam)
materials, at a premium of around $2.50 per s.f. of
liner, but the premium applies only to a very limited
area of the entire duct system.
To quantify: In a 100,000 s.f building renovation
project, with a $15, 000,000 budget (1999 dollars),
300,000 s.f. of duct surface area would be typical. Of
that, 10% of the liner area is likely to be subject to
wetting, thus prescribed to be a more expensive, closed
cell product.
30,000 s.f. at $2.50 / s.f. = $75,000; less than one half
of one percent first cost premium to the project.
$75,000 is also less than the cost of the typical
mechanical means of HVAC noise control such as low speed
fans, large ducts, insertion sound traps ( attenuators)
etc.
The avoidance of IAQ liability, we submit, compensates
for the slight cost premiumPart One HVAC systems
General
Prohibition on ceiling plenums and mechanical rooms used as return
air plenums.
Installing a system of return air sheet metal ductwork throughout
the building is the alternative. Such a system adds around
$2.50/s.f. to construction cost, approximately 1.6% of the total
construction cost.
However, it is difficult to consider this a premium:
a. Ceiling plenums are common in commercial applications, where
flexibility in office layouts is a paramount concern. Space
layouts in institutions are more permanent and institutions
generally rely on return air ducts, and use HVAC concepts that
support them.
b. Absent a return air duct system, speech privacy between
adjacent spaces must be developed, and the cost of
accomplishing this can exceed $2.50 / s.f.
Part Three Sprinkler systems
In cases of new construction, the life safety code mandates
sprinklers, so there is no cost premium.
The "premium cost" issue arises in the case of considering
sprinkler systems in the smaller renovation projects - where the
renovation cost is less than the cost of a new building - i.e. the
codes do not mandate sprinklers and the University is free to use
a minimal compliance to codes strategy in the (understandable)
pursuit of lowest cost construction.
The point is that sprinkler systems, even where not specifically
required by code, can sometime avoid the cost of other, often
costly, architectural modifications to meet code in renovation
projects.
By way of illustration, it is not unusual for a renovation project
to pose the following design (and cost) dilemma:
- Double loaded corridors requiring a fire rating of the
corridor walls
- Non rated doors opening to the corridor
- A required retrofit to rated corridor doors, with door closers
to establish and maintain the fire rating. Open fire rated
doors are not fire rated
- A programmatic requirement to keep the fire rated corridor
doors open, begetting:
- A need for electric door hold-open devices, tied into the fire
detection/alarm system is expensive and a tripping hazard
In similar cases on campus, installing a sprinkler system has
been shown to cost the same, or less, than making all the
required architectural modifications for code and program
compliance.
Furthermore, in the stairwells of many older campus buildings,
there will already exist a (University-installed) fire
standpipe. This amounts to a head start on the cost of a
sprinkler system installation.
Thus - Before opting for no sprinklers to control cost, the
University will exercise and require the A/E to exercise - due
diligence to examine the total cost of code compliance.
The adjusted differential cost even if a premium - may be
tolerable in light of the other life safety advantages
afforded by sprinklers.