Goodman [A/G]PG, Service Instructions Manual

SERVICING

49

For 

PROPANE GAS:

a.

Inlet pressure should be a nominal 11" w.c.

b.

Manifold pressure should be a nominal 10" w.c.

If operating pressures differ from above, make necessary pres-
sure regulator adjustments, check piping size, etc., and/or
consult with local utility.

S-308 CHECKING FOR DELAYED IGNITION

Delayed ignition is a delay in lighting a combustible mixture of
gas and air which has accumulated in the combustion cham-
ber.

When the mixture does ignite, it may explode and/or rollout
causing burning in the burner venturi.

If delayed ignition should occur, the following should be
checked:

1. Improper gas pressure - adjust to proper pressure.  (See S-

307)

2. Improper burner positioning - burners should be in locating

slots, level front to rear and left to right.

3. Carry over (lighter tube or cross lighter) obstructed - clean.

4. Main burner orifice(s) deformed, or out of alignment to burner

- replace.

S-309 CHECKING FOR FLASHBACK

Flashback will also cause burning in the burner venturi, but is
caused by the burning speed being greater than the gas-air
flow velocity coming from a burner port.

Flashback may occur at the moment of ignition, after a burner
heats up or when the burner turns off.  The latter is known as
extinction pop.

Since the end results of flashback and delayed ignition can be
the same (burning in the burner venturi) a definite attempt should
be made to determine which has occurred.

If flashback should occur, check for the following:

1. Improper gas pressure - adjust to proper pressure.  See 

S-

307

.

2. Check burner for proper alignment and/or replace burner.

3. Improper orifice size - check orifice for obstruction.

S-310 CHECKING PRESSURE CONTROL

A pressure control device is used to measure negative pres-
sure at the induced draft blower motor inlet to detect a partial
or blocked flue.

Pressure Switch Operation (DSI Direct Spark System)

The pressure switch is ignored unless there is a call for heat.
When the control receives a call for heat, the control checks to
see that the pressure switch is open.  If the control sees that
the pressure switch is closed before the induced draft blower
is energized, the LED will flash a code of "3" (to indicate the
pressure switch is stuck closed) and the inducer will remain off
until the pressure switch opens.

If the pressure switch opens before the ignition period, the in-
duced draft blower will remain on and the control will stay in
pre-purge until the pressure switch is closed for an entire 15
second pre-purge period.  The LED will flash a code of "2" to
indicate open pressure switch.

If the pressure switch opens after the gas valve has been ener-
gized, the control will de-energize the gas valve and run the
indoor blower through the heat off delay.  The inducer stays on
until the pressure switch re-closes.  Then the control makes
another ignition attempt.

1. Remove wires from the electrical terminals.

2. Using a VOM check from Common to NO (Normally Open)

- should read open.

If switch reads as noted proceed to Step 3, otherwise replace
control.

3. Remove the pressure control hose from the control and

interconnect with an inclined manometer as shown:

PRESSURE SWITCH

INCLINED

MANOMETER

1/4"  COPPER TEE

HOSE
TO J-TUBE

Reconnect wires to the Common and normally open (NO) ter-
minals.

WITH POWER ON:

Line Voltage now present.

4. Energize unit for heating cycle.  The induced draft blower

motor will begin to run. The inclined manometer should
read approximately -1.25" ±  0.1"  W.C.  with no combus-
tion.

5. Remove and check the two electrical wires and using the

VOM check from Common to NO (Normally Open), it should
read closed (with I.D. motor running). If not as above, re-
place the pressure switch.

6. Reconnect all wires to the control and place in heating

cycle.