Heat Pumps and Electric Heating - Modifying fan speed

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ddsmith60
09-29-09, 07:48 PM
I have a Goodman SSX160361 + AEPF42601 installed at my home. The problem I have is that when the fan is turned to the ON position the unit cuts air flow to 30% of what it would be in the cooling mode. They did this to save energy. The problem is that in the winter time I run a gas log set in my livingroom. The cold air return is at the peak of this room but due to the slow speed that the fan runs at it is incapable of providing sufficient air flow to heat the distant rooms. The heat does make it to the thermostat and prevent the heat pump from running which just causes the distant rooms to get even colder. Does anyone know what wires need to be jumpered or changed to provide a normal fan speed in the fan ON position? Goodman, of course, is of no help. I'm sure they would know exactly what needs to be done to make it work but feed me the line about liability because I'm a homeowner and not a licensed AC tech. This is an electrical/control problem more than an A/C problem. Anyone have any insight?
My unit does have dip switches which control the fan speed in the heating mode or the cooling mode but the switches have no effect on the fan speed in the fan ON mode.


dac122
09-30-09, 10:41 AM
What you have is a VS blower that has various CFMs depending on its heating or cooling modes. The diagram I looked at does not immediately suggest a solution so I would begin by studying which control wire inputs give you the desired CFM (likely Y/Y1 or Y2) and what are your control wire inputs for fan-only (likely just G). There may be a way to trick the unit into switching to that CFM. Be prepared that there may be no easy way to do this.

Someone who is intimately familiar with this unit may have a solution for you.

ddsmith60
09-30-09, 07:18 PM
The fan is the G wire from the thermostat to the unit. The thermostat manual says the Y wire is for the compressor. The Y wire is attached to the Y/Y2 connection at the air handler. The air handler manual has a note that says Y enables high speed fan cooling. I wish I had a wiring schematic of the control board. I would then be able to determine if it is possible to make this work. What I'm not sure of is the trigger to start the heat pump compressor. The thermostat manual saying that Y wire is for the compressor has me questioning whether it is the trigger or the "O" wire is for compressor start. If the O wire is what is the trigger then I should be able to run the G wire to the Y/Y2 air handler connection to get the desired result. Anyone else have input on this. The thermostat is a Honeywell C3611.


dac122
10-01-09, 05:59 AM
Y energized the outdoor unit, and O energizes its reversing valve for heating or cooling mode. I would make sure you understand which control wires are energized at the air handler in heating, cooling and fan-only mode. Post if you map that out.

I'll bet Goodman does not make the Control Board, so perhaps you can contact that company for a schematic.

I understand you are trying to tweak your system for your personal optimal performance, so go slow and make sure you understand exactly how it works. One wrong move and you could blow the transformer or an expensive board, which would make you regret embarking on this task.

We'll be here so feel free to post pics, schematics or info you have if you need help.

ddsmith60
10-01-09, 01:58 PM
Thanks DAC122 for the replies. I will definately take it slow on what I am doing. In my line of work, we have electrical schematic for everything. It gets a little frustrating when you don't have them and you are not able to walk through a circuit to see how everything works. I have a feeling that you are correct about the wiring and that there may not be a way to force the air handler to run at the speed it does when cooling. If that is the case I guess I could change the dip switch settings to the highest CFM rating and the fan ON mode is 30% of that speed. It would at least increase the air flow several hundred CFM.

ddsmith60
10-01-09, 08:30 PM
I found the Control Board number is B1368274 well actually it is PCBEM102 but the B1368274 changed it's name twice before being the PCBEM102 number. I still can't find a schematic of it but found out I can replace it for $47. I guess that is a good thing. I changed the dip switches to raise airflow rate but I don't know if that will be enough. I suppose I could have a licensed HVAC guy call Goodman to ask if it is possible but I would rather have the schematic.

dun11
10-02-09, 05:20 AM
There should be a schematic on the back side of the access panel of the air handler. Also in the installation manual, which should have been left with the unit.

Houston204
10-02-09, 05:08 PM
http://i151.photobucket.com/albums/s160/Houston204/GoodmanAEPFdiagram.jpg

I do not see a Fan Only adjustment.

ddsmith60
10-03-09, 04:52 AM
In that schematic the thing I need a wiring diagram for is the VSTB which is the circuit board and I don't think I'm going to be able to locate one. The green wire from the thermostat starts the fan in slow speed whether called for by the thermostat being selected to Fan ON or Auto with a cooling demand start but there is the Y wire enabling Hi Speed Fan Operation when cooling so the fan pushes 1200 cfm versus a little less than 400 cfm. So it looks like all this stuff takes place on that VSTB in the picture. How that happens, I'm not sure, but that is what I will need to figure out to make this work like I think it should.

dac122
10-03-09, 07:38 AM
http://i151.photobucket.com/albums/s160/Houston204/GoodmanAEPFdiagram.jpg

I do not see a Fan Only adjustment.

By fan-only what I meant was turn the tstat to heating and check the control wires at the air handler. Then switch the tstat to cooling and check the wires. Then switch the tstat to fan only and check the control wires.

For completeness you could also map out what control wires are active when your tstat is in EM/Aux heat mode.