Carrier electric heat

[jdman]

Unit tripped breaker when heat came on. After resetting the breaker the fan would not come on. The ICM board had a burnt spot on it so I replace the board. The fan still will not come on. I have 240V coming into the board and have 24V from R-C. No where else do I have 24V. The fan will work if wired directly. Jumpering R-G at the board will not run the fan. Also replaced the sequencer. Still nothing. Any suggestions?

40YA030300

[jdman]

Forgat to mention that the 5 amp fuse on the board is good as well

[Repair-man]

Is this a new installation? If so, did you add heat strips to the air handler?

Is the thermostat digital, and has it been programmed correctly? (You said the problem started with the Heat mode)

From here it amost sounds like both hi and low speeds of the fan were energized simultaneously for this to have happened. Something in your low voltage wiring is shorting out the board when heat is called for. We can't see your wiring installation from here so this is speculation, you understand.

[JWWebster]

The heat coils are supposed to come on first and then 30 to 45 seconds later the fan kicks in. Are you waiting long enough for the fan to kick in?

[jdman]

Yes I wait for the delay for the fan to come on.Only the hi speed is connected. The med and low speed are connected to the dummy post. The outside unit will come on in cooling but not the fan.

[jdman]

"not the fan." Meaning the inside fan

[Repair-man]

More on the installation, please.



Verify that you have no grounded wiring on any of the motor leads and that there is at least continuity between the common and other speed taps for the motor.


Once the basics are covered, then got to the T-stat put FAN to "ON" and then verify 24 VAC from the T-stat to the control board terminal on the G (or fan) terminal and then verify that the high volts are coming out of the board to the motor lead terminals.

Doing this will clear the breaker, fuses, transformer, board, T-stat, and motor.


Your hi speed lead should be connected to the proper terminal on the relay board , and the low speed will be connected to the fan relay side for heat (n/c), as it will be regulated by the sequencer program in the board. The white motor wire should be connected to L2 somewhere. The medium speed wire can be taped off. The ICM board should have dip switches on it that must be programed according to the installation. The Install manual should show this.



JW, I'd like to have my questions answered before you throw the subject off on a tangent, thanks. On second thought, I'm going to let you walk this gent thru the problem. You apparently have the experience needed to handle this by yourself...

[jdman]

I have continuity between C and speed taps on motor

I but fan on "on" but do not get 24 V at the board from R-G but do get 24 V from C-G

This board does not contain dip switches

The board has C for motor and power for motor to use ether hi, low or med and 2 dummy leads to park the 2 speeds not used.

[Repair-man]

The 24 volts should come from the wall thermostat and should be readable at the air handler at the G and C terminals. (There will be no reading between R ad G since they are closed by the thermostat contacts). This means that 24 volts is being sent to the fan relay. If it is not energizing the fan, there's your problem.

Also, if you only have high speed, how is the fan supposed to perform on the Heat mode? Usually a high speed is not desirable for heating.

[jdman]

I do have 24V from C-G at airhandler. It is a digital, non programable one. So you think the problem is the thermostat??

To change from hi to low speed, you must manually switch the motor leads.

[jdman]

PS I do hear a click at the thermostat when I click the fan to on

[Repair-man]

Ok, so if you hear a click then the fan relay is likely operating. It is now a question of voltage coming from the board to the blower motor. Had the board been wired properly and the output was 240 volts between BLK and COM on the fan leads, then all would work.

Some of these units have more than one circuit breaker depending on the Kw output of the heat strips.

[jdman]

I do not hear the relay clicking but a click at the thermostat

[jdman]

Another thing I should add is the C is not connected at the thermostat as it is battery operated

[Repair-man]

Depending on the thermostat, the clicking is the internal  fan relay on the thermostat board.

Tell you what I always do anyway... open the thermostat and disconnect the G wire and place it directly on the R terminal along with the red wire. This will guarantee that the 24 volts is being sent to the upstair air handler. Then go up there and find out  what happens. I would expect to find the  air handler supplying  power to the fan motor at this point.