AEG CGA 75 WOK Specifications download pdf (Page 34)

UH-PRC002-EN34

Electric

Power

Sequence of Operation

Electronic Modulating Control

(with duct thermostat)

With power applied to the unit:

1

The thermostat calls for heat.

2

The pilot valve opens.

3

The ignitor sparks continuously to ignite

the pilot.

4

The sensor proves pilot ignition and

shuts off the ignitor.

5

With the pilot lit, the gas valve opens.

6

Main burners are lit at 100 percent of

unit’s rated input.

7

The fan time delay relay (optional on

duct furnaces) allows the heat exchanger

to come up to operating temperature. At

this time, the fan time delay relay closes

and activates the fan motor.

8

The unit is controlled by the duct

thermostat which modulates the unit

from 100 to 50 percent of unit’s rated

input. An amplifier receives a small

electrical signal from the thermostat and

converts this into a working voltage. This

working voltage determines the position

of the modulating valve. With no voltage

applied to the valve, the valve will be full

open and full fire will occur. As

increasing voltage is applied to the valve,

the valve will modulate closed. At

approximately 12V dc, the valve will

be at its minimum low fire position. If the

voltage continues to increase, indicating

a further reduction in the unit’s firing is

required, the increased voltage closes a

relay which closes the automatic gas

valve. As temperature drops, the voltage

also drops causing the relay to re-open

the valve. The unit will continue to cycle

in this manner until either an increase in

the unit’s firing rate is required or the

thermostat is satisfied and no longer

calls for heat.

9

When the thermostat is satisfied, the

main and pilot valves close.

10

The fan time delay relay (optional on

duct furnaces) remains closed keeping

the fan motor operating to dissipate

residual heat from the heat exchanger. At

this time, the fan time delay relay opens

and deactivates the fan motor.

11

If optional room override thermostat is

ordered…when setpoint is reached, it

will cause the unit to go to full-fire,

overriding both the duct sensor and the

remote setpoint adjustment.

**NOTE: Sensor and selector wires to

amplifier must not be run close to, or in

conduit with, power or ignition wires.

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