Thomas & Betts RZ-NA 441-OMS Door Switch Option BX1 required on C.G.A.-certified units

Figure 22 -

Door Switch,

P/N 124253

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.

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.

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.

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).

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.

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.

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). 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.

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.

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.

zOption AR1 - a constant supply of 100% makeup air

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

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.

Figure 23 - DamperMotor

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.

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.

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.

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.

zOption AR32 - a combination of outside makeup air and bypass return air including a two-position actuator. The two position actuator

Potentiometer	Figure 24 -
Function: The potentiometer is a manually set
	Potentiometer,
switch that operates either the discharge damper
	P/N 16110
(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
	Figure 25 -
building pressure
	Pressure
sensor)
	Null Switch
Description/Function:	(building
The pressure null switch is	pressure
a diaphragm operated differ-	sensor),
ential pressure switch used	P/N 88052
in makeup air applications
to automatically control
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