Goodman heat pump - blower motor run capacitor failed twice, what's wrong?

[Jessie james]

Something has - I think - destroyed the motor run capacitor on my heat pump, but I am not sure what it is.

Back story:

I have a Goodman 3.5 ton heat pump, model ARUF036-00A-1A. Two nights ago I woke up to the smell of something electric burning, and the sound of the blower motor stalled while trying to start.

The motor run capacitor is a 7.5uf and 370v, part number 27L566. I picked up a replacement capacitor, which is the same except it is rated 440v/370v at the recommendation of the local HVAC shop. This is a Mars #12931. I installed that, turned the HVAC power on, and it worked fine.

At that time I noticed a transformer (see below, left side) in the air handler was buzzing, and I don't recall it making any noise before. I looked at it, and the fuse that is installed was not blown, so I buttoned things up.

Last night I again woke up to the smell of something electric burning and a stalled blower motor. I turned the power off to the heat pump.

I took photos of the heat pump innards, CLICK to get full-sized image:

Transformer on the LEFT is buzzing:



Motor run capacitor:



Can someone tell me if this is a simple fix - is the transformer? Computer board? Or do I need to call someone?

Thanks!

[vstech]

you need to call someone.
ignore the buzzing, it's normal from the transformer.
capacitors fail. and sometimes they are bad out of the box, but I'd have someone out to actually check out the system and find the fault.

[Justhowe]

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[Jessie james]

I agree

Thanks guys, I appreciate the advice.

[Jessie james]

Thought you'd appreciate an update - the technician diagnosed the blower motor had failed. It has ... uh ... one of the windings grounded out. Basically, it is shorting out. In addition, it spins very poorly. I've ordered a new one and will have it installed.

He also discovered that it was the wrong sized motor. The motor is one size too small, which he says can cause premature wear because it's working too hard, and additionally it causes poor airflow. Poor airflow has been a big issue since we moved in, so hopefully the correctly sized motor will fix that, as well as better heat/cool my house.

[Brent Ridley]

Jesse J,

Having a blower motor fail after run capacitor replacement is actually a regular occurrence. I always tell customers after I change a bad run cap on a blower that there is 50/50 chance of the blower dying within the next few weeks.

My theory on this is below, I have no proof to back it up so take from it what you will.

Blower run caps get weak over time. I believe that the prolonged restarting under a reduced valued capacitor causes the bearing/windings to fail prematurely.

Condenser fan motors don't have the same issue because blower run caps are exposed to significantly less inrush current than a dual cap on a condensing unit. The dual cap fails when weakened enough that the inrush current blows the capacitor before the bearings/windings receive any damage.

Hope that makes sense. And if this is completely inaccurate; someone feel free to correct me.

[Jessie james]

That's interesting, thanks for the info.

Now, onto new questions I forgot to ask.

While the HVAC serviceman was here he noticed that one of the wires to one of the emergency heat strips was burned up, and you can actually sort of see it in the photo I took - it's burned all the way OFF of the connector and bubbled the wire coating:



This clearly was the burning smell I noticed. So ...

1. Does that mean my heat pump has been using the heat strips (emergency heat) during daily use?

2. Shouldn't that wire be fused?

I'm AMAZED and frightened that the wire burned up before something tripped, this just seems stupid dangerous to me! Yes, I know it's a big current draw, but I've used 30-50-100 amp fuses/breakers on car stereo applications, why wouldn't there be one here?

I am also not thrilled that the emergency heat has been in use, because that just means a bigger bill for me. I'd rather use my portable oil-filled radiators if needed...

[jtrammel]

The heat strips will come on during normal use if the heat pump can't maintain temp and during defrost. The electric heat wire probably burned due to them being on when the motor stopped blowing air over them so the overheated. It should have opened the high temp limit safety though.

[hvacvegas]

The model number you posted for your indoor unit does not match with the outdoor.

You posted a 3 ton air handler, and you said you have a 3.5 ton outdoor.
Not good, but unrelated.

[fliks]

Looks to me like loose connections at breaker. Breaker protects the loads downstream, the connections that got hot were upstream of the breaker.

[beenthere]

The model number you posted for your indoor unit does not match with the outdoor.

You posted a 3 ton air handler, and you said you have a 3.5 ton outdoor.
Not good, but unrelated.

I think he was calling his air handler a heat pump.

[Bsmith816]

They are not like batteries that get weak and you have to change them. A capacitor should stay the same forever. Remember the old capacitors that they used to put in units that had PCB in them, you can check the microfarads in them and they still have what they did 30 yrs ago. The parts made nowadays are just cheap crap from china. These capacitors I replace sometime only last 1 summer.mthey don't make things like they used to

[hvacvegas]

I think he was calling his air handler a heat pump.

Sheez. Using logic and junk.
well....
Then it's not a 3.5 ton, NOW IS IT! XD

[Jessie james]

You posted a 3 ton air handler, and you said you have a 3.5 ton outdoor.
Not good, but unrelated.

Oops, good catch. It's a 3 ton unit all around.

I think he was calling his air handler a heat pump.

I didn't mean to, while I'm not a pro by a long shot I do know the air handler is the inside portion. I refer to my entire system as a "heat pump".

The heat strips will come on during normal use if the heat pump can't maintain temp and during defrost. The electric heat wire probably burned due to them being on when the motor stopped blowing air over them so the overheated. It should have opened the high temp limit safety though.

That's not good. Is there any way I can test those sensors? They are the round black fittings with yellow stickers that are mounted inline with the heat strips wiring, right? I assume I measure across for continuity, but I guess I don't understand how the limit switch would protect the wire from overloading & melting like it did, like a fuse or breaker could. Isn't the function different?

Looks to me like loose connections at breaker. Breaker protects the loads downstream, the connections that got hot were upstream of the breaker.

The connection that melted was the push-on at one of the heat strips. It's literally burned through the wire. Does that mean anything?

Thanks for all the info guys, I really appreciate it.

[westval]

I am also not thrilled that the emergency heat has been in use, because that just means a bigger bill for me. I'd rather use my portable oil-filled radiators if needed...

Jessie,

Just so you know. Your portable oil filled units are 115 volt. The electric strips on your air handler are 230 volt. To produce the same amount of btu output from your portable units you will consume twice the KW at the electric meter. With that being said. I concure that we would rather see more btu's introduced from high HSPF heat pumps and wider differential settings on thermostats than run on electric back up heat.

[beenthere]

Jessie,

Just so you know. Your portable oil filled units are 115 volt. The electric strips on your air handler are 230 volt. To produce the same amount of btu output from your portable units you will consume twice the KW at the electric meter. With that being said. I concure that we would rather see more btu's introduced from high HSPF heat pumps and wider differential settings on thermostats than run on electric back up heat.

The amps will be twice as much, but the KW will be the same.

[fliks]

Most of the time the reason a wire burns off is because of a loose connection or wire undersized. I see wires burned off at strips often do too loose connection.

[westval]

The amps will be twice as much, but the KW will be the same.

Of course you are correct. I misspoke. I was trying to convey the idea that a lot of portable heaters would be needed to replace the electric heat kit, and I did a poor job of that. Sorry to the OP for bad information!

[Jessie james]

Most of the time the reason a wire burns off is because of a loose connection or wire undersized. I see wires burned off at strips often do too loose connection.

Ok, that is reassuring. The tech replaced the wire with a wire that feels like it's 1 gauge heavier, so I guess it's fine.

Of course you are correct. I misspoke. I was trying to convey the idea that a lot of portable heaters would be needed to replace the electric heat kit, and I did a poor job of that. Sorry to the OP for bad information!

Thanks for the corrected info! Since my new blower motor is somewhere with UPS until Tuesday I will have to suffer a big bill in the meanwhile. I have a wife so ... haha!

[vstech]

The amps will be twice as much, but the KW will be the same.

keep in mind that a few 115v "oil filled heaters" will result in an imbalanced load on the meter, causing a higher power bill than a balanced load from the 240v electric strips will.

in the old days, each strip would have it's own fuse, and it would blow if there was too much current draw. now the entire heat strip set will be on a single breaker sized for the load, and if a single wire gets too much current, it fails. it's all in a metal box, and it's designed to fail and stay inside the box preventing a fire.