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Brian HVAC Guy
Brian HVAC Guy, HVAC Technician
Category: HVAC
Satisfied Customers: 915
Experience:  I have been an HVAC/R mechanic/technician for 30+ years.
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Tech said compressor is going out and overamping. this

Customer Question

tech said compressor is going out and overamping. this causes the breaker to trip. CHecked the breaker and said the beaker is bad and needs to be replaced. I purchased a new breaker and now they are balking on installing the breaker. They say the breaker is way to big and should never been there. It has been this way for 40 years. I feel like they are trying to orce me into a new unit.
JA: Did you double-check the thermostat? And what about the unit's filters?
Customer: i dont know
JA: Do you plan on doing the work yourself?
Customer: but they dotn want to install the replacement breaker now. Says it is too big and could be a bigger problem
JA: Anything else we should know to help you best?
Customer: they checked it Monday and it has not tripped again sincve then. been running and cooling perfectly
Submitted: 1 month ago.
Category: HVAC
Expert:  Brian HVAC Guy replied 1 month ago.

Hi J, I'm Brian and I can help you with this.

I'll do my best to help you sort this out. It will require me to gather quite a bit more info from you.

1) Can you tell me the make, model number and serial number of the ac unit in question please?

2) Do you happen to know what gauge the wire is that is supplying the compressor branch circuit from your main panel (where the breaker for that branch circuit should be)?

Customer: replied 1 month ago.
The labels for the unit are too old and can not be read. I believe it is a 4 ton condensing unit. It uses r22 and has infoor coils. I have no clue about the wire. Also interesting to note: this is the third time this company has replaced this breaker and it has never been an issue of size before.
Expert:  Brian HVAC Guy replied 1 month ago.

Ok thanks for that info. I would say if the wire size wasn't large enough for the breaker you purchased for them install, they are well within their duty and rights to refuse to install it. That could create a liability issue for them. However, it does seem pretty odd and is very suspect that they replaced it three times without issue. The fact the breaker has been replaced three times is an issue though. A breaker should last a very long time if sized correctly. This is the reason I asked for the unit data and wire size, I would have looked everything up for you and told you what you should have. If the wire size is too small for the unit size and/or the breaker is marginally sized for the unit, heat will develop in the circuit and that is a compressor killer and will also take out breakers.

A four ton unit is a fairly large ac current load (amperage). It would probably call for a 50 or 60 amp breaker and require #8 or #6 copper line wires in the branch circuit respectively. I suspect yours may be smaller. If, for instance, you have a 50 amp breaker on a four ton unit with a branch circuit fed with #10 gauge wire which is rated for 30 or 35 amps depending on wire type, you could easily overload the branch circuit wire causing heat to build up. What happens in that case is the branch circuit line wires become like a resistors and actually start to draw current as a separate load than the compressor. This in turn lowers the voltage available to the compressor and will cause the compressor to run higher amperage as a result.

If breaker replacement gets the unit up and running and cooling good, I'd say my example above is a pretty good bet for the scenario you have. Also, as compressors age, they get less efficient which also causes them to draw higher current (amps). This will only make the situation that much worse. What they are telling you is not a stretch if you have a branch circuit with too small of a wire size. However, if the compressor runs and cools fine, chances are it's fine.

I would suggest having an electrician have a look and if the branch circuit wire size is too small, have them replace the wiring with the proper size. I cannot count how many ac systems I've seen with a branch circuit wire that was too small! It was pretty common many years ago, even in new construction. I remember the code enforcement inspectors on new construction starting to look at and require unit breaker size info for new homes as late as the 90's! Before that, it wasn't really looked at. They didn't start looking at unit branch size data, wire and breaker size in existing hvac replacement applications until the turn of the century! That was in SW Florida too, where ac is very heavily used!

If I were a betting man, from your description of symptoms and what the service company said, I'd bet you have a branch circuit too small and an older ac system that is probably just fine. However a small branch circuit will take its toll pretty quickly on an older ac system (compressor)!

Let me know if you have further questions on this subject. Otherwise, please remember to rate before leaving (3 stars or higher please!). Bonuses are always appreciated! And remember, follow up questions about this topic are free even after rating. Just post a new reply on this same question and I'll be notified. Thanks for allowing me to help and thanks for using Just Answer!

Thank you,
Brian

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