Fan Stays on intermittenly

Problems related to residential installations.

Fan Stays on intermittenly

Postby 17macae1 » Fri Jan 11, 2013 9:56 am

I have a trane xl1200 heat pump and my controller is a White Rodgers programmable 1F94-371.

The system has worked for about 7 years and now the fan will get stuck on occasionally. The system is controlling temperature fine.

I have to pull the controller off the wall to get the fan to stop. I've installed the original Braeburn controller (non programmable) and the system works fine. So I replaced the White Rodgers controller with a new one (same model) and the fan occasionally stays on again. With the controller removed, I can touch the green wire to the 24vac wire and the fan will cycle fine.

If I don't intervene, the fan will stay on until the next program cycle and then it will usually operate normally for a few days or more.

Any Suggestions
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Postby Freon » Fri Jan 11, 2013 12:33 pm

Can you tell us the make and model of the indoor air handler and the thermostat. You use the word "controller". I assume you are referring to the thermostat.

I would check all wiring from the thermostat to the air handler. Since you seem to have it working perfectly with the old thermostat I would look at how you have connected the White Rogers thermostat. Is it battery powered or powered from the air handler.
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Postby 17macae1 » Fri Jan 11, 2013 5:52 pm

It's a WCX036G100BB Single package heat pump by trane about 3 tons. I was refering to the thermostat when I said controller. Everything is outside on a single pad.

The wiring colors coming to the thermostat are brown, blue , red, white , yellow, orange and green.
I have the tstat -

E to Brown,C to Blue,R to Red,W2 to White,y1 to yellow,O to orange,G to green

I have carefully reviewed the programming features and they are not asking for the fan. White Rodgers says it's my system - "Call an Expert they say".
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Postby Freon » Sat Jan 12, 2013 12:38 pm

You wrote "I have to pull the controller off the wall to get the fan to stop. I've installed the original Braeburn controller (non programmable) and the system works fine."

When you first replaced the Braeburn thermostat with the White Rodgers, did the fan issue start immediately or did the fan issue start months later?

What are the terminals (R, G, W, Y etc.) on the Braeburn thermostat.

Double check that the same colored wires connect to the corresponding terminals at the hair handler... Blue to C, Red to R, etc.
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Postby 17macae1 » Sat Jan 12, 2013 4:30 pm

The Braeburn came with the unit and I installed the White Rodgers shortly thereafter. The White Rodger worked perfectly for maybe 7 years and nothing was done to the unit. It has malfunctioned twice this week. Once in the evening and once in the morning on different days.

The Braeburn 3200 wiring -

R is 24 VAC, Y1 is 1st stg compressor contact, Y2 is 2nd stg, W2 is aux heat relay, E is emergency heat realy, G is fan, O is changover cool, B is changeover heat, L is system monitor, C is transformer common.

The wires colors at the air handler all match except white & black from the Tstat go to brown and the Green from the Tstat goes to black. All wire nuts were tight.
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Postby Freon » Sun Jan 13, 2013 12:36 pm

It seems, since the White Rogers thermostat worked perfectly for 7 years and you rewired the new WR thermostat the same way, the problem isn't in the thermostat.
One question. When the indoor blower is running when you think it should not be running, can you tell if the aux heat (I assume the Aux is electric heat strips) is also on.

I ask because if we assume the control board at the main unit is good, then the only reason for the blower to be on is for the normal heating cycle and when there's a call for the electric heat. Possibly there's a call for the Aux heat for some reason.

If it's warm enough this week, you might try disconnecting the W2 and E connections at the thermostat and tape them. These wires activate the heat strips and also the blower. If the problem goes away you'll be closer to an answer.
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Postby 17macae1 » Sun Jan 13, 2013 9:54 pm

I ran for years with the e and W2 jumpered so the aux heat would not cycle. When this problem arose (this summer), I removed the jumper just to get the wiring back to standard and the problem continued. Recently, I've been running with the W2 taped back. I'll pull the E back also and see what happens.

This problem started this summer during the AC season.

When the fan is stuck, I can remove the WR tsat and the fan will stop in about a minute. Then install the Braeburn and the fan will not come on until called. At this point , I think I can reinstall the WR and the fan will come on.

When I checked the wiring outside, everything looked brand new. No ants or trash, no visibly burned cicuits. My coils in the return duct were dirty but I cleaned them.

Could low voltage confuse the WR and not the Braeburn and every thing else work fine?
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Postby Freon » Mon Jan 14, 2013 12:27 pm

Low voltage could cause intermittent problems and is a good idea. Next heating cycle go to the unit and measure the AC voltage between R and Common terminals. See if there are any visible fluctuations. Sadly some voltage dips or spikes happen so quickly you can't see them on an analog meter. It's even hard on a digital one.

Also double check the ground to the unit. A weak ground can cause the voltages to float. Check at the unit itself, the disconnect box and at the main circuit breaker box. Make sure the bond between neutral and ground at the main breaker box is solid. Make sure the neutral from the power company connection at the main breaker box is sound.

Check the PC board at the unit for any signs of a cold solder joint or corrosion. Look for white powder (lead oxide) on the solder leads.

When the WR is being used and you unexpectedly get the fan to run, does the thermostat show that the fan is ON in the display screen.

What is the WR thermostat model number.

Any chance there's a poltergeist loose in your house.
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Postby 17macae1 » Tue Jan 15, 2013 3:48 pm

The voltage looks good right now at 27.6 vac. No signs of corrosion or solder joint problems.

WR model 1F94 371
Braeburn model 3200

The manual is available online at emersonclimate.

Unit is not running much due to warm weather.
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Postby Freon » Wed Jan 16, 2013 12:03 pm

Please repost the WR model number and the Braeburn model number. Try and avoid dashes or slashes since they get censored.

Since all works well with the Braeburn thermostat and not the WR it seems you have a thermostat issue.
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