125
Main (On/Off) Gas Valve (VA-01)
Figure 61 - Main Gas Valve
The main gas valve (
) is located in the burner cabinet.
Units that use 500MBH and larger furnaces are equipped with two
shut-off valves internal to a single body.
1. Make sure the wiring is connected properly.
2. Make sure the gas valve is ON.
3. Turn the unit ON. Check for voltage. Check for voltage across
the pins on the gas valve. There should be
24-28V AC
.
- If the voltage reading is incorrect, check the wiring for an
open or short circuit.
- If the voltage reading is correct, the gas valve may be faulty.
Modulating Gas Valve (VA-05)
Figure 62 - Modulating Gas Valve
The modulating gas valve (
) is located in the main
burner cabinet.
1. Make sure the wiring is connected properly. Check the
wiring using a multi-meter for open or short circuits.
• Terminal 1 – Signal (
+
) to J7 pin 6
• Terminal 2 – Signal (
-
) to J7 pin 7
• Terminal 3 – Power
24V DC
(
+
) to H4
• Terminal 4 – Power (
-
) to N4
- If any damaged wiring is found, repair or replace.
- If any open or short circuits are found, repair or
replace.
- If any wiring is connected incorrectly, correct the
wiring.
NOTE: The wiring connection is polarity sensitive.
2. Make sure the DIP switches are all in the OFF position
(factory setting). This will set the valve to receive a
0-10V
DC
signal. If the unit is set up for an analog control
system, refer to
.
3. Make sure the valve has been adjusted properly. refer to
“Start-Up Procedure Heating” on page 80
.
4. If the unit has been running, restart the unit. Check for voltage:
• Connector J7 pin 6 to ground. There should be
10V DC
. The voltage reading will drop after the unit has
been running.
• Check for voltage between H4 to N4 on the terminal block. There should be
24-28V AC
. This voltage
reading will be constant.
- If the voltage reading is incorrect, check voltage to the IBT control board.
- If the voltage reading is correct, there may be an issue with the modulating valve.
Main Gas
Valve
VA-05
P1
P2
RD
GY
RD
BK
STP Wire
RD
BK
J7
6
7
8
SHD