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RT-PRC031-EN 105
Mechanical Specifications
Economizer Control with
Comparative Enthalpy
Used with the fresh air economizer,
two enthalpy sensors are provided to
compare total heat content of the
indoor air and outdoor air to
determine the most efficient air
source when economizing.
Economizer Control with
Reference Enthalpy
Used with the fresh air economizer,
an outdoor enthalpy sensor is
provided to compare the total heat
content of outdoor air to a locally
adjustable setpoint. The setpoint is
programmed at the human interface,
or remote human interface, to
determine if the outdoor enthalpy
condition is suitable for economizer
operation.
Economizer Control with Dry
Bulb
Used with the fresh air economizer,
an outdoor temperature sensor is
included for comparing the outdoor
dry bulb temperature to a locally
adjustable temperature setpoint. The
setpoint is programmed at the
human interface, or remote human
interface, to determine if outdoor air
temperature is suitable for
economizer operation.
Heating System
Electric Heating Option
All electric heat models shall be
completely assembled and have
wired electric heating system integral
within the air handler. Heavy duty
nickel chromium elements internally
wired with a maximum density of 40
watts per square inch shall be
provided.
Heater circuits shall be 48 amps or
less, each individually fused.
Automatic reset high limit control
shall operate through heater backup
contactors. The units shall have
optional factory mounted non-fused
disconnect switch located in the main
control panel to serve the entire unit.
Gas Fired Heating Option
All gas fired units shall be completely
assembled and have a wired gas
fired heating system integral within
unit. Units shall be UL/CSA approved
specifically for outdoor applications
downstream from chilled water coils.
All gas piping shall be threaded
connection with a pipe cap provided.
Gas supply connection shall be
provided through the side on
horizontal discharge units, and
through the bottom and side for
downflow discharge units. All units
shall be fire tested prior to shipment.
• Heat Exchanger shall be tubular
two pass design with stainless
steel primary and secondary
surfaces. Free floating design
shall eliminate expansion and
contraction stresses and noises.
Gasketed cleanout plate shall be
provided for cleaning of tubes/
turbulators. Heat exchanger shall
be factory pressure and leak
tested.
• Burner shall be a stainless steel
industrial type with an air
proving switch to prevent burner
operation if the burner is open
for maintenance or inspection.
Ceramic cone shall be provided
to shape the flame to prevent
impingement on sides of heat
exchanger drum. Burner
assembly shall house ignition
and monitoring electrode.
• Combustion Blower shall be
centrifugal type fan to provide air
required for combustion. Fan
motor shall have built-in thermal
overload protection.
• Gas Safety Controls shall include
electronic flame safety controls
to require proving of combustion
air prior to ignition sequence
which shall include a 60 second
pre-purge cycle. Pilot ignition
shall be provided on 850, 1100
and 1800 MBH heat exchanger
units. Sixty second delay shall be
provided between first and
second stage gas valve operation
on two-stage heaters.
Continuous electronic flame
supervision shall be provided as
standard.
• Full Modulation Gas Heaters
shall be made from grades of
stainless steel suitable for
condensing conditions. The
heater shall have a turn down
ratio of at least 10 to 1 on the 850
and 20 to 1 on the 1100 and 1800
MBH
Steam Heating Option
Steam coils shall be Type NS with
non-freeze steam distribution
circuits. Distributor tubes shall be
located concentrically within
condensing tubes to assure even
steam distribution. Coils shall be
pitched to provide complete
drainage. Steam modulating valve
with actuator shall be provided.
Hot water Heating Option
Hot water coils shall be Type 5W and
factory mounted in the air handling
unit to provide complete drainage of
coil. Hot water modulating valve with
actuator shall be provided.
Accessories
Roof Mounting Curb
Roof mounting curb shall be heavy
gauge zinc coated steel with nominal
two-inch by four-inch nailer setup.
Piping enclosure and supply/return
air opening gasketing shall be
provided. Curb shall ship knocked
down for easy assembly. Channel
shall be provided to allow for
adjustment of return air opening
location. Curb shall be manufactured
to National Roofing Contractors
Association guidelines.
Electronic Zone Sensors
• Zone Sensors shall provide two
temperature setpoint levers,
Heat, Auto, Off, or Cool system
switch, Fan Auto or Fan On
switch. Optional status indication
LED lights, System On, Heat,
Cool, and Service shall be
available. These sensors shall be
used with CV units.
• Programmable Night Setback
Sensors shall be electronic
programmable sensors with
auto or manual changeover with
7 day programming. Keyboard
shall provide selection of Heat,
Cool, Fan Auto or On. All
programmable sensors shall
have System On, Heat, Cool,
Service LED/indicators as
standard. Night setback sensors
shall have (1) Occupied, (1)
Unoccupied and (2) Override
programs per day. Sensors shall
be available for CV zone