Help-Furnace blower motor problem

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  #1  
Old 03-02-03, 06:25 AM
SDlawndawg
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Help-Furnace blower motor problem

The blower motor in my Payne natural gas furnace stopped last night about 4am. I awoke to the smell of burning electrical wire type stench. I ran downstairs to find the furnace not working and the motor making a buzzing type sound. I shut the power off to it and the buzzing stopped. After letting the motor cool for about 20 minutes, I turned the power back on and the furnace ran fine. I then decided to leave it off until morning so I could keep an eye on it. Right now, it is running good. The cause of the problem I think was the fact that it ran all last night on account of the cold winds (and 10 degrees outside) and the fact that the filter desperately needed replacing (it had been about 5 weeks at least). Is there any permanent damage done to the motor and should I replace it. Shouldn't there be a fuse that blew instead of the motor frying.The furnace is 7yrs old. Should I clean the furnace and if so, how do I do it. I am mechanically inclined and have a shop full of tools. Thanks for any responses.
 
  #2  
Old 03-02-03, 07:01 AM
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SDlawndawg:

If the burning smell was coming from the motor it's number will be up, even if it's working now.

These motors are designed for continous duty so your cold snap would not have caused it.
The only unatural conditions that would cause the motor to prematurly fail would be a lack of lubrication, failed run capacitor or overloading by too much airflow.
Funny as it sounds, a dirty filter will have a positive effect on the motor. As when a squirell cage fan has it inlet air restricted, the load goes down along with the motor amperage, The reverse is true with the outlet of the fan.
A dirty filter will cause the bonnet temperature to go up though, causing the burner to cycle on high limit.


I would suggest you replace it and the run capacitor if it has one, and give your furnace a good cleaning.

Furnace cleaning instructions:

http://www.growinglifestyle.com/article/s0/a111199.html
 
  #3  
Old 03-02-03, 07:01 AM
H
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Overheating...

It sounds like the fan motor overheated and went off on thermal overload. If the filter was dirty in 5 weeks you CAN extend the filter replacement time by putting the fan in AUTO, this might end up leaving slightly unbalanced rooms (if you don't mind that). If you don't have an air conditioning coil in the system, you COULD use the cheap fiberglass through-away filters. The motor is called an " air-over " if it has vent holes all aound it meaning, it depends on cool return air, to cool it off. Any heat it gives off would naturally go into the space although very small. Some furnaces don't have a large enough return and MUST use the cheaper filters in heat season because they have less restriction to air flow. Check the temperature difference to the temperature of air going in vs. out. This measured outlet temperature should be 3 or 4 feet from the furnace itself, and after it has warmed up for 10 minutes, be sure to set the room temp 10F higher, and open the windows to keep it from cycling off if you have to. The normal temperature difference should be about 55F higher, less than this will usually produce excessive condensation . Look for motor oilers, it will had either small metal plugs or plastic plugs in them if it is a sleeve motor, alot of motors are life time lube these days however! Check the bearings for any handshaking on the end of the shaft, make sure you kill the power first!
 
  #4  
Old 03-02-03, 09:57 AM
SDlawndawg
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Thanks for the responses. I pulled the blower out and took a look. There are no lube points that I can see. Motor definitely smells burnt. I cleaned with the vacuum. Can I use compressed air or will that do damage? I'm going to Grainger tomorrow to get a new motor and capacitor. I will be using the old motor until then. Not sure what else I can do since it is Sunday and nothing is open. Any suggestions to repair old motor until then?

For filters, I have been using fiberglass mesh type. Is this a mistake since they are more free flowing? We have central air too. What type of filter should be used for my furnace?
 
  #5  
Old 03-02-03, 10:06 AM
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dawg,

glad you are replacing that motor, once they smell burnt their time is VERY limited. there is no repairing the motor, if it is not working now, you will have to wait until tomorrow. as for filters, what size do you use now and how many/size return ducts do you have? i have an air bear 5 inch filter, but duct modifications would be necessary for you, use a good pleated filter, not the 1250 rated 3M ultra allergen unless filter is oversized for amount of flow due to excessive restriction.
 
  #6  
Old 03-02-03, 10:25 AM
H
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air filters..

Fiberglass filters are OK to remove large pieces of dust after they have passed thru the same filter several times. They restrict the air flow less than a pleated air filter because their Mesh, so to speak, is huge, most everything gets by it. The pleated air filter is far superior, tends to keep the coil cleaner thereby saving money on operating costs because the heat exchanger/coil isn't insulated with dirt, this shortens the run time of the unit. If you have an AC coil in the unit, during the summer when the coil is wet, the dust that gets thru will stick to the coil and adventually insulate the coil and then start to reduce or block the airflow. Vacuum and blow out with CO2 or Nitrogen and wash the evaporator coil . The inlet side will have the majority of the dirt. Blow it out against the air flow direction, the dirt should come out the way it went in...Get a case of pleats from Grainger, while your there. Blowing out the motor with compressed air is fine, just don't try peeling paint with it...
 
  #7  
Old 03-02-03, 11:33 AM
SDlawndawg
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I pulled the panel to look at the AC coil but I can only see the outlet side so I'm not sure if it is clogged or not. How do I get a look at the inlet side? Does the coil simply slide out?

Well it's getting chilly. I better put it back together and keep my fingers crossed until tomorrow.
 
  #8  
Old 03-02-03, 02:54 PM
H
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Wait...

Definately pick a warm day to check it. Yes, they usually slide out but I have had occasion where the tin man left no option but to cut a large hole in the side, and a Patch to cover it up and use for access later If needed. Its a pain in the neck especially if you find the coil is fine and have to look elsewhere for problems, but you have to start somewhere!
 
  #9  
Old 03-02-03, 04:44 PM
SDlawndawg
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Still working good... For some reason after I installed the blower, I noticed the pilot light had gone out. I didn't even know the furnace had a pilot light. I thought most newer furnaces had a different heat source to light the burner. No big deal though.

My wife and I had the AC installed after the furnace was put in. There is a panel that can be unscrewed. Looks like the drain will have to be unhooked. I think the condenser hookups can flex enough to have a look.

Thanks again for all the help. Just found this website this morning and looks like it will come in handy later on. Much cheaper than paying a repairman on a Sunday!
 
  #10  
Old 03-03-03, 08:33 AM
SDlawndawg
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Heat's on!

The old motor gave up last night about 8:00pm and it got cold. This morning it was 15 below. I was at Grainger when they unlocked the doors this morning to pick up the new motor and capacitor. The fella working there didn't know much about motors but I figured out the hookups from the schematics on the furnace and old motor. When I first turned it on, the motor was spinning the wrong way. I reversed polarity and wha-la- HEAT! The temp on the thermostat said 45 degrees so it's going to be running for quite a while to catch up. Thanks again
 
 

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