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huazshi
join:2014-03-01
USA

huazshi

Member

[HVAC] Heat pump blower control fan timer frequently broken

I have a 11-year-old comformaker heat pump in which the control fan timer (part #1085928) in the blower malfunctioned each one and half year. I have changed about five control fan timers since I move in this house (2-year-old at that time). Each time after I change a new control timer, the fan in the blower will work fine for about one and half year, then the fan in the blower will not stop when the thermostat reach the setting temperature and the outside condenser stops. I have to turn the switch on the blower off to stop the blower fan. Generally when this symptom starts and each time after I do this, the fan will work fine for relatively longer time (a month?) then the problem will become more frequent until I have to switch off the blower to stop the fan every two days to a week. At this point, I change the control fan timer. Today I went to Morrison Supply and purchase a new control fan timer, and I asked the sales man about this and he said that maybe something else is causing the problem of control fan timer. If this is true, why each time after I change it to a new one, it will work fine for at least a year? One the other hand, I just did not believe that this circuit board is so not durable. I am thinking that I probably need ask a heat pump technician to check if there is any other problem causing this, but I would like to get your suggestions about this. The control fan timer costs about ~$120, but if I ask somebody coming in, it will cost more even if he could not find any problems. Thanks!

tp0d
yabbazooie
Premium Member
join:2001-02-13
Bulger, PA

tp0d

Premium Member

Have you ever changed the capacitor in the 11 years? Probably couldnt hurt, a cap is pretty cheap.

What switch are you turning off on your thermostat? Usually it is a "Auto" or "On", but not an "Off" setting. Do you have to turn the tstat heat setting off? Which blower are we talking about here, the house air circulation fan, or the fan inside the pump outside?

-j
huazshi
join:2014-03-01
USA

huazshi

Member

The blower fan is the inside unit (called fan coil unit), and once it was continuing runing when the themperature reaches the setting temp (outside unit-the condenser also stops), I had to turn off the switches in the blower (two swithes there) to stop the fan. Changing the thermostat to off did not stop the fan. Usually when this happens very freqently, I buy a new control fan timer and the whole system will work fine for at leat one and half year. The outside unit is working fine for both heating and cooling (I changed a new compressor about six year ago and a new fan for the outside unit). I did not change the capacitor in the blower (I can see a big capacitor there), but I do not think it is the capacitor because generally speaking, malfunctioning capacitor would cause the fan could not kick in. Thanks!

nunya
LXI 483
MVM
join:2000-12-23
O Fallon, MO
·Charter

nunya

MVM

The "heat pump" is the outdoor unit.

If I understand, it seems like the problem is with the fan controller on the air handler. If it only failed while you were using the heat pump, that might be a different story.

Some (all the ones I've seen) HPs will call for indoor fan while the HP is in defrost mode. This can override the "fan" switch on the T-Stat. The colder it is, the less efficient HPs are, and they have to defrost more often. Maybe you have a bad defrost controller outside.
If you live in a climate where it isn't terribly cold all the time, the HP may not need to defrost too often.

Otherwise, if it works fine for that long, then it's probably a design flaw that has never been fixed.

Jack_in_VA
Premium Member
join:2007-11-26
North, VA

2 edits

Jack_in_VA to huazshi

Premium Member

to huazshi
When a Heat Pump goes into defrost mode the indoor AHU fan is not effected in any way. It would be running when the condenser unit goes into defrost, continues to run during the defrost cycle and only turns off after a small time delay when the indoor temperature is satisfied by the thermostat setting.

The AHU fan relay is a time delay type and obviously the time delay is the problem for some reason. The relay picks up when heat or cool is called for by the thermostat and when the thermostat is satisfied a time delay (about 80 seconds) keeps the fan running to use the remaining hot or cold air. Apparently the OP's time delay (electronic board) is failing.

OP What is the Manufacturer and model number of your air handling unit?

Some Google search on the issue:

These relays have a tendency to stick. If you feed comfortable opening up your air handler there are a few tests you can do. One test you can do is to remove the "G" wire from from your thermostat. I always shut the power off to the system before removing/re-connecting wires on the thermostat to avoid blowing the 5V fuse in the air handler. If the blower shuts off then you probably have a thermostat issue. If it does not shut off then you can open up the air handler. Sometimes you can use the handle end of a plastic screwdriver handle and gently tap the relay a few times and it will unstick the contacts in the relay. You can shut the power off the the air handler and remove the access panel where the relay is located. Then find the green wire and remove it from the terminal marked "T". Then turn the power back on. If the fan stops that probably means the relay is bad.

Read more: »www.doityourself.com/for ··· uobwIieR
huazshi
join:2014-03-01
USA

huazshi

Member

Thanks! the air handler (it is called fan coil unit) was made by comfortmaker, model No NFCP4800C2. I am living in Texas, so it is not that cold in winter (although it is cold this year). I knew the fan was constantly runing was not because defrost. It was just because the relay in the control fan time (a circuit board) was stuck. Each time I changed it to a new one, it worked fine for about one and half year, then the air handler fan started continously runing when outside unit stoped (T-stat reaches the temperature). My question is why the circuit board lasts for only one and half year? Is it because of the quality of the circuit board or something else might be causing this?

Jack_in_VA
Premium Member
join:2007-11-26
North, VA

Jack_in_VA

Premium Member

Forget defrost cycle it has nothing to do with your problem. The relay gets it's signal from power supplied by the thermostat either automatic operation which follows the heat/cool initiate or the constant fan on switch setting. Absent incorrect (high) voltage to the control board it would just about have to be a crappy design or the quality of the relay.

nunya
LXI 483
MVM
join:2000-12-23
O Fallon, MO
·Charter

nunya to huazshi

MVM

to huazshi
The fan (blower) does run in defrost mode. I'm not stupid. Otherwise the inside coil can ice up. Every HP I've ever owned or seen does this.

»www.nachi.org/defrost-cy ··· pump.htm

Jack_in_VA
Premium Member
join:2007-11-26
North, VA

2 edits

Jack_in_VA

Premium Member

Nobody says the AHU fan does not run in defrost. In fact it does run because the electric strip heaters are on to overcome the effects of the Heatpump being in defrost (cooling mode). The defrost cycle will not properly work unless the evaporator fan is operating.

The AHU fan never cuts off unless the thermostat is satisfied or the fan switch is turned to off position. Its operation has nothing at all to do whether or not the unit is in defrost It follows the thermostat calling for heating/cooling or manual operation of the thermostat fan control switch.

If the unit is not actually running in the heat mode and the timer or temperature sensor on the coil is at the correct low temperature it will not go into defrost .

Tex
Dave's not here
Premium Member
join:2012-10-20

Tex to huazshi

Premium Member

to huazshi
If, indeed, the relay contacts on the multiple boards you've been replacing are getting "stuck", then there is definitely a problem. Calling in a service company probably isn't going to do you much good. However, if I were you, I would make an effort to contact someone with Comfortmaker. I checked their website and I couldn't find a telephone number; I only found an online feedback form. Give that a shot and see if it gets you anywhere.

FYI, back in the days when I was running service, I can't tell you how many fan control boards I replaced over the years. I replaced so many Lennox control boards, I contacted the state attorney general's office about it. Nothing ever came of it because the complaint process was too convoluted. I gave up and didn't follow through.

By the way, it probably doesn't affect you, but there is a safety recall on certain Comfortmaker package units with defective control boards catching fire.

»icpindexing.toddsit.com/ ··· tice.pdf

Good luck.

Jack_in_VA
Premium Member
join:2007-11-26
North, VA

Jack_in_VA

Premium Member

said by Tex:

If, indeed, the relay contacts on the multiple boards you've been replacing are getting "stuck", then there is definitely a problem. Calling in a service company probably isn't going to do you much good.

Good luck.

Good points. I haven't figured out which problem the OP has. Stuck contacts or defective electronics.
huazshi
join:2014-03-01
USA

huazshi to Tex

Member

to Tex
Thanks! I believed that the circuit board design may be crappy causing the problems I had. The last three circuit boards I replaced were all made in Mexico, but the new one I just installed yesterday was made in USA and I see some changes on the board. Hopefully this one can last longer.

Jack_in_VA
Premium Member
join:2007-11-26
North, VA

Jack_in_VA

Premium Member

said by huazshi:

Thanks! I believed that the circuit board design may be crappy causing the problems I had. The last three circuit boards I replaced were all made in Mexico, but the new one I just installed yesterday was made in USA and I see some changes on the board. Hopefully this one can last longer.

Good luck with this new relay. Keep us up to date if you have problems.

leibold
MVM
join:2002-07-09
Sunnyvale, CA

leibold to huazshi

MVM

to huazshi
If it is not too much effort it would be interesting to see pictures of the old and new board to see what changed.

pende_tim
Premium Member
join:2004-01-04
Selbyville, DE

pende_tim to Tex

Premium Member

to Tex
said by Tex:

I checked their website and I couldn't find a telephone number; I only found an online feedback form. Give that a shot and see if it gets you anywhere.

The recall notice has some contact information.

Consumer Contact: For more information, contact ICP at (800) 649-4706 anytime, or visit
the ICP Web site at www.icpusa.com.

May be worth a shot.