Furnace air not strong

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  #1  
Old 03-04-15, 07:27 PM
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Furnace air not strong

I have a Rheem furnace in my attic. I have to replace my filter about every 4 weeks when it is under 20 degrees F outside. This is in order to keep the air blowing strong through the vents. I use a Rheem merv4 filter so it is not that restrictive. The issue is the filter I replace is barely even dirty. If I don't replace the filter and it is very cold out my furnace blows for a period of time, then the blower turns off but I can still hear the furnace on, then the blower turns on again after a minute.

Could the issue be the blower is dirty causing it not to push the air out hard enough?

Thanks,

Doug
 
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  #2  
Old 03-05-15, 05:46 AM
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I don't think the filter is your issue. Normally, when a filter becomes restrictive, the furnace will shut down on high limit. In your case, it's the blower turning off, not the furnace.
You could have a control issue, or the blower motor may be tripping out on a limit.
Post the model # of the unit and look for an LED light that may be flashing, count the flashes.
 
  #3  
Old 03-05-15, 07:15 AM
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It is a Rheem Classic 80 which is heating up about 1500sq ft. Where would the flashing LED be located? If I take off the cover there is a kill switch that automatically turns off the furnace. Should it be flashing when the blower turns off but the furnace is still on?

What would be the reason why the furnace doesn't blow air out as strong until I change the filter to a new one. It seems just a little dusting on the filter causes it to be restrictive.

Thanks,

Doug
 

Last edited by freshwun; 03-05-15 at 07:55 AM.
  #4  
Old 03-05-15, 08:18 AM
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Is that the original filter spec that came with the furnace? Is there an evaporator coil that may be restricted by dirt (only if you have AC) How long has this been going on?
Geo
 
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Old 03-05-15, 08:52 AM
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Are sure it's the blower shutting off and the burner staying lit ?
It's usually the other way around.
 
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Old 03-05-15, 09:17 AM
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I don't know what the original filter specs are as the furnace was here when I moved in. This does have an evap coil since it also functions as my A/C. Not sure where I would look for this at.

The process my furnace goes through to start blowing air or at least what I hear is:

1. The furnace turns on
2. I hear the gas ignite the fire
3. The blower turns on and the air comes out

The blower and fire turns off between cycles when it has reached a certain limit but the furnace stays on. Then after a minute or so the flames light and the blower turns on again. I assume this happens because the house isn't warm enough and it's giving the furnace a break.
 
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Old 03-05-15, 09:24 AM
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That may need to be looked at. When the unit is overheating..... the burner should shut down but the blower should remain running to cool the furnace back down. ]

Keep in mind there are two blowers..... one is in the bottom of the furnace and circulates the air thru the house and the other one is on the face of the furnace for the exhaust flue gasses.

You could post the complete model number for your furnace. It will be behind the burner access door on the side wall.
 
  #8  
Old 03-08-15, 08:03 PM
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When the blower turns off after being on it goes back to the stage right before the burners turn on. I still can hear the furnace on and the humidifier water running. The leds are solid green and yellow which I believe do not indicate an issue.

This is a Rheem Classic Quiet 80 - RGPN-07EAMER
Serial - FU5D302F450400967
 
  #9  
Old 03-09-15, 06:09 PM
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20 degree weather I believe is the problem. What is the temp by the return air? It may be the cold air across a the fan control( I'm assuming it has a fan switch not fan timer) is cooling the control and it opens. Another possibility is a failing capacitor or motor.
 
  #10  
Old 03-09-15, 08:17 PM
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Why would the temperature affect how strong the air is coming out though? I would lean more towards the motor or capacitor.

Can anyone tell me if this sounds like an issue with either the motor or capacitor going bad?

I just replaced the filter again after 3 weeks and the vents are blowing strong enough that I can feel it standing underneath it from my 9ft ceiling. The old filter only had a slight dusting on it. Hard to believe that this is causing the air to be that restrictive unless there is another issue at hand.

Thanks,

Doug
 
  #11  
Old 03-09-15, 08:18 PM
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Because you said the blower was shutting off
 
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