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13. Door Switch (Option BX1; required on
C.G.A.-certified units)
Location: The control is installed on an over-
head door opening to control the operation of
the heater to coincide with the opening and clos-
ing of the door.
Function: The function of the switch is to ener-
gize and interlock the heating unit when an out-
side overhead door reaches approximately 80%
of full open travel. The switch will de-energize
the furnace when the overhead door closes ap-
proximately 20%. The complete switch includes
a limit switch electrically wired to the heater and a roller yoke for
mechanical activation by a field-supplied trigger on the overhead door.
Figure 22 -
Door Switch,
P/N 124253
14. Inlet Air Controls
WARNING: Burner profile plates are factory set
to match CFM requirements.
Do not adjust profile plates without contacting your
Sales Representative for technical assistance.
Description: The system is equipped with one of the 11 types of
inlet air control arrangements listed below. All systems provide a con-
stant flow of outside air across the burner at the required air volume
(CFM).
Refer to the wiring diagrams in the main electrical box to determine
which controls are on the system being serviced.
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zOption AR1 - a constant supply of 100% makeup air
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zOption AR19 - 100% outside makeup air with variable supply air
volume (CFM). The discharge damper controlling the variable air sup-
ply is controlled by a manually set remote potentiometer and can be
varied from 100% to 20% of total rated air flow (CFM). In response to
changes in the discharge damper setting, the bypass damper balances
the volume of air so that the required fixed amount of air volume flows
over the burner.
zz
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zOption AR20- 100% outside makeup air with variable supply air
volume (CFM). The discharge damper controlling the variable air sup-
ply is automatically controlled by a building pressure sensor and can be
varied from 100% to 20% of total rated air flow (CFM). In response to
changes in the discharge damper setting, the bypass damper balances
the volume of air so that the required fixed amount of air volume flows
over the burner.
zz
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zOption AR22 - a combination of outside makeup air and bypass
return air including modulating return air and bypass air dampers. The
volume of outside air is regulated by a remotely located, manually set
potentiometer.
zz
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zOption AR23 - a combination of outside makeup air and bypass
return air including modulating return air and bypass air dampers. The
volume of outside air is regulated automatically by a remotely located
building pressure sensor.
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zOption AR32 - a combination of outside makeup air and bypass
return air including a two-position actuator. The two position actuator
changes the position of the damper to provide either 100% outside air
or 20% outside/80% return air. Control is from a SPDT toggle switch
mounted on a 4x4 box (or if ordered, the switch is mounted on a remote
console).
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zOption AR33 - 100% outside makeup air with variable supply air
volume (CFM). The discharge damper controlling the variable air sup-
ply is automatically controlled by a 0-10 VCD or 4-20 milliamp signal.
In response to changes in the discharge damper setting, the bypass
damper balances the volume of air so that the required fixed amount of
air volume flows over the burner.
zz
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zOption AR34 - a combination of outside makeup air and bypass
return air including modulating return air and bypass air dampers. The
volume of outside air is regulated by a 0-10 VCD or 4-20 milliamp
signal.
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zOption AR35 - a constant supply of 100% makeup air to the unit but
including a two-position inlet shutoff damper that closes the dampers
when the system is not operating. The damper attaches to the duct
flange of the optional inlet base (used only with the optional inlet base
that has three closed sides and a duct connection for outside air).
zz
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zOption AR36 - 100% outside makeup air with variable supply air
volume (CFM). The discharge damper controlling the variable air sup-
ply is automatically controlled by a remotely located photohelic pres-
sure sensor. In response to changes in the discharge damper setting, the
bypass damper balances the volume of air so that the required fixed
amount of air volume flows over the burner.
zz
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zOption AR37 - a combination of outside makeup air and bypass
return air including modulating return air and bypass air dampers. The
volume of outside air is regulated by a remotely located photohelic
pressure sensor.
Air Flow Dampers
Function: Dampers operate in response to controls to provide the
rated flow of makeup air to the building.
Service: Clean dampers of dust or dirt.
Damper Motor
Function: The damper motor automatically ac-
tuates the return air, bypass, and/or discharge
dampers in response to an electrical control de-
vice. The damper motor is direct-coupled to the
dampers so there is no damper linkage to ad-
just.
Service: There is no service required on these
motors other than external cleaning. If the mo-
tors need replaced, replace with an identical
damper motor.
Potentiometer
Function: The potentiometer is a manually set
switch that operates either the discharge damper
(Option AR19) or the return air damper (Op-
tion AR22) providing a mixture of return and
outside air. It is a remotely located switch that
requires manual adjustment.
Service: If the potentiometer does not func-
tion properly, replace it with an identical switch.
Pressure Null
Switch (automatic
building pressure
sensor)
Description/Function:
The pressure null switch is
a diaphragm operated differ-
ential pressure switch used
in makeup air applications
to automatically control
Figure 23 -
Damper Motor
Figure 24 -
Potentiometer,
P/N 16110
Figure 25 -
Pressure
Null Switch
(building
pressure
sensor),
P/N 88052
Burner shutdown or modulating operation will depend on the tem-
perature rise between the outside air and the discharge air setting.
• may remain on continuous low fire.
If the outside air control is set too high, the burner will continuously
burn on low fire as long as the control switch is set to "winter".
When the outside air control is set properly for the climate, the system
blower will continue to provide the required makeup air (ventilation) at
the ambient outdoor temperature (burner not operating) even when the
control switch is set to "winter".
Service: If the control does not function properly, replace it with an
identical switch.