Thomas & Betts RZ-NA 441-OMS Direct-Fired Burner, Makeup Air Gas Control Systems, Selector, P/N

tioning properly. If the ignition controller locks out and there is no other cause, the controller module must be replaced.

11.Gas Train Including Direct-Fired Burner, Gas Control Systems, Manifold Arrange-ments, and Gas Pressure Switches

Direct-Fired Burner

Function: The design of the direct-fired burner and the con- trolled velocity of air at the burner ensure complete combustion through the full range of burner sizes and gas inputs as determined by the gas control system. The velocity of air is controlled by the profile plates and monitored by a standard low and high air pres- sure switch.

Service: Refer to Paragraph 6 in the Maintenance Section for instructions on burner maintenance.

WARNING: Burner profile plates are factory set to match CFM requirements. Do not adjust profile plates without contacting your Sales Representative for technical assistance.

Makeup Air Gas Control Systems

•Electronic Modulation Gas Control Options AG30, AG31, AG32, AG33, AG35, AG36

Refer to the wiring diagrams in the main electrical box to deter- mine which controls are on the system being serviced. NOTE: All field-supplied control wiring for Maxitrol controls must not be run inside conduit with line voltage wiring. To avoid any potential electrical interference, all field-supplied wiring for Maxitrol con- trols should be shielded wiring and must be grounded at the unit only.

Function: These makeup air gas control systems provide heated makeup air at a temperature controlled by a discharge air sensor. Each system is equipped with electronic modulation controls that modulate burner flame from 1/25th of full fire input to full fire.

The electronic modulating-type gas controls act in response to discharge and/or room air temperature sensors to change the gas flow rate to the burner, thus lengthening or shortening the flame. The BTU output is varied (modulated) to maintain the required discharge air temperature.

These modulating gas control options are electronic because in all cases the gas valve acts to adjust the flow of the gas to the main burner in response to DC volts emanating from an amplifier. When the DC voltage is between 0 and 5 volts, the main valve seat is closed. Low fire flow is accomplished through a mechanical bypass. The low fire flow rate is set at the factory and should not need adjustment. However, if adjustment is necessary, refer to the Maxitrol literature that is included in the heater owner's enve- lope.

For troubleshooting guides and further explanation of Maxitrol Series 14 and 44 electronic modulation gas control systems, refer to the Maxitrol literature in the owner's envelope.

The Option AG30, AG31, AG32 and AG35 electronic modulation systems are comprised of Maxitrol Series 14 controls. Options AG30 and AG31 systems electronically maintain a constant discharge air temperature in the range of 55-90°F(55-75°F for C.G.A.). Option AG31 includes an overriding thermostat. Option AG32 system will maintain a constant discharge air temperature in the range of 80-130°F. Option AG35 maintains a discharge temperature range of 120-160°F.

Figure 15 - Components of the Gas Control System (Maxitrol Series 14) used in Gas Control Options AG30, AG31, AG32, andAG35

Amplifier,	Mixing
P/N 148590	Tube

TemperatureTemperature

SelectorSensor

Option AG33 electronic modulation system is comprised of Maxitrol Series 44 controls. The low limit (20-60°F) and the high limit (60-140°F) for con- trol of discharge air temperature are set at the amplifier located in the control compartment. The space temperature is set at the remote selectrastat (55- 90°F range) located in the space. When the temperature is below the space temperature setpoint, the control system operates the burner to automati- cally adjust the discharge air temperature within the maximum and minimum limits set on the amplifier.

Figure 16 - Components of the Gas Control System (Maxitrol Series 44) used in Gas Control Option AG33

Temperature Sensor, P/N 119617

Mixing Tube,	Amplifier,	Temperature
	P/N 157915
P/N 90323		Selector, P/N 86990

Option AG36 is a special application gas train that is designed for controlling the environment of a paint booth operation. The system includes a Maxitrol A1494 amplifier, discharge air temperature sensor, dual remote discharge air temperature selector (drying selector 80-140°F and a spray selector 60- 90°F), and two switches to control the operation of the modulating gas valve.

Figure 17 - Components of the Gas Control System used in Option AG36 designed specifically for paint booths - controls are mounted on a remote console

	Selector,
Amplifier,	P/N
P/N 133229	133230

All of the electronic modulating gas control burner systems in- clude low fire start. On an initial call for heat, the main burner ignites at its lowest input. During mild weather, the burner may then cycle off. Such full shutdown can be dictated by the outdoor ambient cutoff control. As the outside air temperature climbs above the setpoint of the outdoor ambient control, the burner control circuit is de-energized. When moderately cold outside air temperatures exist, the burner will modulate between low flame and high flame. Low fire start and the outdoor ambient control prevent the makeup air system from heating already warm air and providing "too much" heat to the building.

Electronic Modulation

Gas Control Option

AG37

Function: Control Option AG37 does not have a duct sensor or ampli- fier. Instead, a Maxitrol A200 signal conditioner is activated by a cus- tomer-supplied input signal (either 4- 20 milliamps or 0-10 volt) to control the modulation of the gas valve.

Figure 18 - Maxitrol A200 Signal Conditioner,

P/N 134170, used in Gas Control Option AG37

Page 7