York D2CE Heat Anticipator Setting, Heat Anticipator Setpoints, Gas Heating Sequence Of Operation

530.18-N11Y

switch is in the “AUTO” position, the blower will operate only when there is a call for heating by the thermostat.

b)Upon a call for first-stage heat by the thermostat, the heater contactor (6M) (6M & 7M on 72 KW, 240V) will be energized.

If the second stage of heat is required, heater contactor (7M) will be energized. Note that on the 54 KW, 240V heater, heater contactors (7M & 8M) will be energized and on the 72 KW, 240V heater, heater contactors (8M & 9M)

TABLE 9 - HEAT ANTICIPATOR SETTING

HEATER	VOLTAGE	SETTING, AMPS
KW		TH1	TH2
18		0.29	-
36	208/230-3-60	0.29	0.29
54		0.29	0.58
72		0.58	0.58
18		0.29	-
36	460-3-60	0.29	0.29
54		0.29	0.29
72		0.29	0.29
18		0.29	-
36	575-3-60	0.29	0.29
54		0.29	0.29
72		0.29	0.29

will be energized.

c)The thermostat will cycle the electric heat to satisfy the heating requirements of the conditioned space.

HEAT ANTICIPATOR SETPOINTS

It is important that the anticipator setpoint be correct. Too high of a setting will result in longer heat cycles and a greater temperature swing in the conditioned space. Reducing the value below the correct setpoint will give shorter “ON” cycles and may result in the lowering of the temperture within the conditioned space. Refer to the Heat Anticipator Setpoints table for the required .

GAS HEATING SEQUENCE OF OPERATION

The following sequence describes the operation of the gas heat section.

CONTINUOUS BLOWER

With the room thermostat switch set to “ON”, the supply air blower will operate continuously. The normally closed contact “K5-1" provides 24 volt power to the “3M” contactor. The “3M-1, 2 & 3" power contacts close and the blower motor operates.

INTERMITTENT BLOWER

With the room thermostat system switch set to the “AUTO” or “HEAT” position and the fan switch set to “AUTO”, the supply air blower will operate after the room thermostat calls for heat and the time delay relay closes.

The “TH1" closes, the heat relay ”RW1" is energized. The “RW1-1” power contact closes energizing the line voltage draft motor. The “RW1-2" contact is also closed. As the speed of the draft motor reaches approximately 2500 RPM, the centrifugal switch contact located on the end of the draft motor shaft closes to power the first stage ignition module “IC1”.

After a brief pre-purge time, ignition module “IC1" will start the first stage ignitor sparking and will open the redundant valve located inside the first stage main gas valve “GV1” to allow a flow of gas to only the first stage carryover tube. Only after the pilot flame has been ignited and the presence of pilot flame detected at the “IC1” by a signal sent back through the flame sensor is sparking terminated and the first stage main gas valve opened.

Gas flows into each of the main burners and is ignited from the carryover tube flame.

If “IC1” fails to detect a pilot flame, it will continue to try for a maximum of 85 seconds to ignite the pilot tube. If the pilot flame is not detected, then “IC1" will lock out furnace operation for 5 minutes, then retry ignition sequence.

At the same time power was supplied to the “RW1”, a parallel circuit activates “ETD” which closes the “ETD” contact after approximately 35 seconds and energizes “K5" which closes ”K5-2" and starts the blower by energizing “3M”.

When “TH2" closes, heat relay ”RW2" is energized. The “RW2-1" contact is closed energizing the second stage ignition module ”IC2". “IC2" will immediately start the second stage ignitor sparking and will open the redundant valve located inside the second stage main gas valve ”GV2" to allow a flow of gas to the second stage carryover tube. Only after the pilot flame has been ignited and the presence of pilot flame detected at “IC2" by a signal sent back through the flame sensor is sparking terminated and the main gas valve opened.

Gas flows into each of the second stage main burners and is ignited from the carryover tube flame.

If “IC2" fails to detect a pilot flame, it will continue to try for a maximum of 85 seconds to ignite the pilot tube. If the pilot flame is not detected, then ”IC2" will lock out furnace operation for 5 minutes, then retry ignition sequence. Note that the second stage furnace can operate even if first stage has locked out.

When the heating cycle is complete, “TH2" opens de-energizing the ”RW2" then “TH1" opens de-energizing ”RW1" and “ETD”,

REDUNDANT		MAIN VALVE
VALVE
GAS MAIN
GAS		TO MAIN
VALVE	TO PILOT BURNER	BURNER

FIG. 12 - GAS VALVE PIPING

thus closing all gas valves. The blower motor will continue to run (approximately 45 seconds after the furnace is shut down) until “ETD” opens, de-energizing the “K5" relay and ”3M" contactor. The draft motor will continue to run for a brief post-purge cycle.

SAFETY CONTROLS

The control circuit includes the following safety controls:

1.Limit Control(LS).Thiscontrol islocatedinsidethe heatexchanger compartment and is set to open at the temperature indicated in the Limit Control Setting Table. It resets automatically. The limit switch operates when a high temperature condition, caused by inadequate supply air flow occurs, thus shutting down the ignition control and closing the main gas valves and energizing the blower.

2.Centrifugal Switch (CS). If the draft motor should fail, the centrifugal switch attached to the shaft of the motor prevents the ignition controls and gas valves from being energized.

3.Redundant Gas Valve. There are two separate gas valves in the furnace. Each valve contains a main and a redundant valve. The redundant valves are located upstream of the main gas valves. Should either or both of the main gas valves fail in the open position the redundant valves serve as back-ups and shuts off the flow of gas.

4.Flame Sensor Rod / 100% Ignition Control Lock-Out. If an ignition control fails to detect a signal from the flame sensor indicating the pilot flame is properly ignited, then the main gas valve will not open. It will continue to try and ignite the pilot for a maximum of 85 seconds, then if the pilot flame is not detected, the ignition control will lock out furnace operation until 24V power is removed from the module either at the unit or by resetting the room thermostat.

5.Rollout Switch. This switch is located above the main burn- ers in the control compartment which in the event of a sustained main burner rollout shuts off and locks out both ignition controls closing both gas valves. The ignition con- trols lock out furnace operation until 24V power is removed from the controls either at the unit or by resetting the room thermostat. Note the auto reset rollout switch must reset before allowing furnace operation.

16 Unitary Products Group