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whizkid3
Premium,MVM
join:2002-02-21
Queens, NY
kudos:9
reply to nunya

Re: What's reasonable to expect in this case?

said by Jack_in_VA:

The amount and type of damage you describe is more indicative of a large electrical surge either from the power company or lightning strike. A simple shorted compressor would not likely do the damage to other components especially the fan motor.

said by nunya:

line voltage spade terminal or screw rumbled off the contactor and hit the LowV spade ...fried the circuit board in the furnace. ...
Now on to the blower motor: I can't fathom how this previous scenario would damage the blower motor. I think it was probably just bad on it's own.

I agree with both Jack & nunya. Yeah, the short in the compressor may have fried the furnace board. It didn't do anything to the blower motor - nor could it. The blower motor likely went bad on its own. Really, only a nearby lightning strike or similar transient event on the utility side could 'fry' the blower. And if that happened, you would likely have a lot of other noticeable damage in the house.


Styvas
Go Canucks Go
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join:2004-09-15
Hamilton, ON

If the blower ran for a bit without the compressor running, is it possible that something with the evaporator that could have caused the blower failure? For example, would running in this state possibly cause condensation that could have dripped onto the blower and caused it to short? I have no idea of the configuration inside the furnace, so it could be a ridiculous suggestion.
--
"Moving your Tylenol to the low shelf in your medicine cabinet is not the way to prevent children from falling off a stool when reaching for the top shelf." (said by Savant, May 2008)



nunya
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O Fallon, MO
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Not really. Ex: My blower runs 24/7/365 irregardless of whether the A/C or heat is on.
The blower is simply a fan. That's it. It's no different in principle than any other fan.
--
If someone refers to herself / himself as a "guru", they probably aren't.



Styvas
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Hamilton, ON

Does it make any sense that the furnace tech was able to make some change (rewiring?) so that the fan would run at a slower speed while we wait for the new part?

He warned us to be careful that the AC doesn't freeze up while using it like this. It was already showing condensation after a couple of hours so we just turned it off. It hasn't been too hot, anyways, so we're just living without it.
--
"Moving your Tylenol to the low shelf in your medicine cabinet is not the way to prevent children from falling off a stool when reaching for the top shelf." (said by Savant, May 2008)



nunya
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O Fallon, MO
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Yes. Most blower motors are 2 to 4 speed motors. The high speed winding burned up and he moved it to the low or medium speed winding.
When in heat mode, the motor usually runs at a lower speed. When on A/C mode, the motor usually runs at a higher speed. The copious amount of air keeps the evaporator coil (A-coil) from icing over and freezing up.
A dirty air filter or dirty A-coil will cause a freeze-up too.
--
If someone refers to herself / himself as a "guru", they probably aren't.



Styvas
Go Canucks Go
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join:2004-09-15
Hamilton, ON

Interesting. What is the consequence of a freeze up?



nunya
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join:2000-12-23
O Fallon, MO
kudos:12

On some systems, it could possibly damage the compressor.



Styvas
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join:2004-09-15
Hamilton, ON

Could it cause the short that we've been discussing?



whizkid3
Premium,MVM
join:2002-02-21
Queens, NY
kudos:9

said by Styvas:

Simply put, wires inside the compressor were loose and, presumably, the vibration of the frequent fan activity caused them to touch and short out.

Isn't this how the short was caused?


Styvas
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Hamilton, ON

Yes, the wires inside the compressor were loose as described. I'm just curious as to any other possible explanation.



nunya
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reply to Styvas

Most likely no. It would be a huge stretch. Did they actually install a new compressor? I doubt it. I'm willing to bet the short was in the outdoor condenser unit itself (wiring / contactor cubby), and not the compressor.
The only electrical connection between the A/C and the furnace is the LV circuti that controls the contactor coil. Think of a contactor as a "switch". Think of the contactor coil as the person who flips the switch. They are only mechanically connected.
--
If someone refers to herself / himself as a "guru", they probably aren't.



whizkid3
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Queens, NY
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reply to Styvas

No, if the wires disconnected & shorted as described, it was probably from vibrations; not the coils freezing.



Styvas
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Hamilton, ON
reply to nunya

I hope I haven't been using the wrong terminology. When I've been referring to the compressor I've meant the unit outside with the fan in it. The wires that shorted were inside a panel on the side/corner of the unit outside (and not the small box beside it that's attached to the side of the house).
--
"Moving your Tylenol to the low shelf in your medicine cabinet is not the way to prevent children from falling off a stool when reaching for the top shelf." (said by Savant, May 2008)



alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

said by Styvas:

(and not the small box beside it that's attached to the side of the house).

Why would we think the compressor is the disconnect switch?


Styvas
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Hamilton, ON

It's not you, it's me. Someone said something about a condenser, and that made me realize that I don't know for certain which part is which. I suspect I've been identifying them correctly, but don't know for sure.
--
"Moving your Tylenol to the low shelf in your medicine cabinet is not the way to prevent children from falling off a stool when reaching for the top shelf." (said by Savant, May 2008)



nunya
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A picture: »www.howstuffworks.com/how-to-mai···oner.htm
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Styvas
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Hamilton, ON

Okay. When I've been referring to the compressor, I guess I've meant the condenser unit. Either way, it's all in the unit outside, so I don't think my terminology would have messed things up with regards to this discussion. As far as the wires that shorted, I couldn't tell you exactly what in that unit they are related to, but I suspect that those here who know about these things already know what they are.
--
"Moving your Tylenol to the low shelf in your medicine cabinet is not the way to prevent children from falling off a stool when reaching for the top shelf." (said by Savant, May 2008)



alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

said by Styvas:

Okay. When I've been referring to the compressor, I guess I've meant the condenser unit. Either way, it's all in the unit outside, so I don't think my terminology would have messed things up with regards to this discussion. As far as the wires that shorted, I couldn't tell you exactly what in that unit they are related to, but I suspect that those here who know about these things already know what they are.

Don't worry buddy, we all know you were talking about the whole big box unit outside.


Styvas
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Hamilton, ON
reply to Styvas

One of the questions that came up in this thread relates to the blower motor and why, if the AC unit had fried the control board and motor circuit, it would keep running for a while.

The furnace guy was finally out on Tuesday replacing the motor and I asked him this. His explanation (for what it's worth) was that only the higher speed circuit was fried (since that's the one the AC unit uses) and after it was toast the blower fell back to a lower speed (the same speed that he rigged it to use so we'd have some air if wee needed it while we waited for the replacement). At some point the error codes that the furnace was now getting due to the damage reset the system and the blower shut down entirely.

I don't know if that makes any sense, but it's what he explained.

I also asked him again why he was so sure that it couldn't have been the furnace causing the spike that shorted out the AC unit and burned out the furnace control panel and blower motor. His explanation (again, for what it's worth) was that the only power going that direction from the furnace is 24 volts. A surge would blow the fuses on the control board and that's as far as it would go. If the spike was so large as to be powerful enough to fuse the 24 volt to the line voltage in the AC unit, it would have burned out the 24 volt wire long before it reached the AC unit.

Again, I don't know if that makes sense, but that's what he said.
--
"Moving your Tylenol to the low shelf in your medicine cabinet is not the way to prevent children from falling off a stool when reaching for the top shelf." (said by Savant, May 2008)



alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

said by Styvas:

If the spike was so large as to be powerful enough to fuse the 24 volt to the line voltage in the AC unit, it would have burned out the 24 volt wire long before it reached the AC unit.

I think he meant that if a powerful enough surge went through the 24v wire to damage the AC, that wire would have been visibly damaged/burned.

What I'm curious about is whether or not you had to pay for parts (furnace and AC)