Furnace Blower Replacement

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Sean Sean

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Hello Helpers,

I think my 20-years furnace blower is going out. The model is GE 5KCP39LG V569BS, which is a 0.5 HP 1075 rpm with capacitor starter. Since this is no longer on market, I wonder if there is any suggestion as to which made and model is a direct replacement? And where to get it? I live in Central Ohio. Thanks for your suggestions.

In the last 5 years, when the blower is on during Winter, the thermostat would intermittently shut off for 1 minute, then come back on. During thermostat shut off and before back to operation, the blower and furnace would continue to run blowing out hot air. After thermostat turns back on and complete initialization, the furnace and blower would stop, wait for couple minutes, and start blowing hot air again, until temperature reaches ideal target.

I found that putting in new air-filter would help reducing the frequency of this shut-off. However, starting this year, it does not help much. I don't observe this issue during summer air-conditioning time. I read somewhere that this is considered as "overloading" which means somewhere in the motor is over consuming the electricity.

Thanks
 

Reach4

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I did not look at your link, but if the blower turns smoothly by hand, hums, and did not smoke, you might try changing the start cap.
 

Sean Sean

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I did not look at your link, but if the blower turns smoothly by hand, hums, and did not smoke, you might try changing the start cap.

Oh Thanks.

However, my cap has no label on it. I see that the motor label says "CAP 10.00/370". Does that give me a clue? Thanks
 

Reach4

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"CAP 10.00/370"
Yes. 10 μF 370 volt. Common value. They come in different shapes. If you have an electric motor shop in your area, I would check there.
pocf10a-2.jpg


(Edit: replaced mf, which is the old way to abbreviate microfarad, with μF) https://www.dictionary.com/browse/microfarad

A 10 millifarad 370 volt capacitor would be very far from common.

pF was called mmf or mmF in the old days.
 
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Sean Sean

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Is that 10 mf as in Milli Farad, or 10 μf as in Micro Farad? It seems like most sellers online is selling the 10 Micro Farad unit.

Thanks again
 

Dana

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A 10 milli Farad (10,000 uF) 370 VAC capacitor would be truly HUGE. (Such capacitors exist, but would never be used in a residential air handler's AC motor startup circuit.)
 

Sean Sean

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All right, I have replaced the Capacitor, and the issue still remain, i.e. thermostat intermittently shut off. Actually, after the blower start to run, thermostat shut off at about 1 minute 30 seconds. After 2 minutes of blank, thermostat comes back again, initialize, then blower stop. Within 30 seconds, the blower would start again, and whole cycle repeat.

Another interesting observation -- if I take away the air-filter, the thermostat would not turn off, problem solved! But the air-filter is only 2 weeks old, and it has been the exact same brand same model for years. I did notice in the past that new air-filter would alleviate this intermittent shut-off issue, but it just getting real bad this winter.

I have not tried to manually turn the blower yet. But I guess my last option is to replace the furnace blower? I live in Columbus ohio, and I do not know which reseller to contact. The model is GE 5KCP39LG V569BS, which is a 0.5 HP 1075 rpm.

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Reach4

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Sounds as if the high-limit temperature may have been reached, cutting off the gas. And then the low limit is set too high, and shuts off the blower while there is still heat to be distributed.

What are the limit settings on your switch? Maybe that switch has a problem.

I am not a pro. You could also try a lower-restriction filter. Try one of the cheap fiberglass filters.
 

Sean Sean

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I think I may have found the root-cause. It is the combination of high temperature safety switch, and the more restrictive air filter.

My wife bought this package 1st time this year. It was usually MERV 8 in the past, which was associated with less tripped-off of the thermostat.
It's a merv 10 filter now, bought from Amazon https://www.amazon.com/gp/product/B004PVVC8O/

This is why the thermostat switch-off is observed during winter time and not summer air conditioning time.

Guess this means I should get a new motor to give the air a little extra push?
biggrin.gif


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Dana

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I think I may have found the root-cause. It is the combination of high temperature safety switch, and the more restrictive air filter.

My wife bought this package 1st time this year. It was usually MERV 8 in the past, which was associated with less tripped-off of the thermostat.
It's a merv 10 filter now,
This is why the thermostat switch-off is observed during winter time and not summer air conditioning time.

Guess this means I should get a new motor to give the air a little extra push?
biggrin.gif


Thanks

What it really means is that it's time to step away from junky 1" thick filters, set it up for a big 3" or deeper pleated filter, which even at MERV 13 usually don't have a huge static pressure drop. (They last a lot longer too.)
 

Sean Sean

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Thanks Reach.

Since we already have this MERV 10 and it causes the temperature limit switch to turn off the furnace, I am thinking to use it during the summer air-conditioning time. However, is the risk high that the cooling coil could freeze and break in the heat exchanger, due to lower air-flow? I have seen the HVAC guy put in the aluminium cooling coil right above the furnace gas burner, which I presume it's the Heat Exchanger section.
 

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Thanks Reach.

Since we already have this MERV 10 and it causes the temperature limit switch to turn off the furnace, I am thinking to use it during the summer air-conditioning time. However, is the risk high that the cooling coil could freeze and break in the heat exchanger, due to lower air-flow? I have seen the HVAC guy put in the aluminium cooling coil right above the furnace gas burner, which I presume it's the Heat Exchanger section.

Yes the risk of freezing up the coil (or even sending damaging amounts of liquid refrigerant back to the AC compressor) is pretty high.

Seriously, all 1" filters are junk, and frequently damaging at high MERV ratings.

Large 3" to 6" thick pleated filters deliver a fraction of the static pressure drop, work better, and often only need to be swapped out annually. Yes, it takes some sheet metal work to make that change, but it's a lot cheaper than fixing damaged equipment. I've managed to forget to swap out the MERV 13 media for well over a year in the AprilAire 2400 (6" thick, pleated) filter on the system at my house, without creating low cfm ice up or overtemp issues.

The difference in performance or static pressure drop between 3" and 6" filters is pretty small, but a 1" thick MERV 10 filter is just begging for trouble (and it seems you've found it.)
 
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