Oversized Condenser Breaker

Originally Posted By: roconnor
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(pretty close to the 7.5A per ton rule of thumb), with a specified 20A Minimum and 25A Maximum breaker. 25A breakers are not readily available, so it looks like the electrician just rounded up to the next breaker size at 30A.


The installation is not correct, but do any of our resident HVAC experts know how serious that is? Could that really fry the condenser if it locked up (doesn't seem like it would)? "Concern", "Defect/Repair", or Red Flag"?

My gut feeling would be to flag it as "Defect/Repair", but I'm not sure how much wiggle room is built into the nameplate information, or actual field problems as a result of something like this.


--
Robert O'Connor, PE
Eagle Engineering ?
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NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

Originally Posted By: kmcmahon
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That is a very interesting question. I’d like to know the answer also.



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Originally Posted By: jwilliams4
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Probably the most serious aspect would be any warranty concern.


If the nomenclature says 25 amp and a 30 amp breaker is present

the manufacturer could easily deny warranty claims. As for damage

to the compressor -- not likely. If the compressor froze it would most

definitely break the current. (The breaker will not cause the

compressor to freeze up.) And 25 amp breakers are readily available

where ever the installer got the 30 amp. Over-sizing a breaker can

have an effect on swiches or relays that may malfunction, though.


--
"not just an inspection, but an education"

Originally Posted By: dedwards
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Robert,


I see this routinely, especially on homes that are a littel older and the HVAC system has been replaced since the original equipment was installed. Typically, newer equipment is a lot more efficient and does not require the higher rated breaker protection but from what I can gather the HVAC guys do not change the breaker because “that is the job of the electrician”. They just install the new equipement and tell the homeowner they need to get an electrician out to change out the breaker but that just never seems to happen. Just reported one this week for this discrepancy. Like another post states, warranty is void if the instructions on the data plate are ignored. I always write it up and go on. If they do nothing I can not be held responsible for not reporting it. As I tell people all the time, “I can not make you do anything, nor am I going to try”. I just find the discrepancies, what you choose do about them is up to you. I do not have a dog in this fight."


Originally Posted By: lkage
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jwilliams4 wrote:


If the compressor froze it would most definitely break the current.


Jae, where would the current most likely break? At the overcurrent protection device? And would it take longer to break with the bigger than specified breaker?


--
"I have never met a man so ignorant that I couldn't learn something from him."
Galileo Galilei

Originally Posted By: roconnor
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A buddy in the HVAC business indicated it probably isn’t a real serious issue, but could be a major problem under the wrong circumstances.


Said he ran across a condenser that locked up and didn't trip the breaker (older Bulldog Pushmatic breaker ... some historic breaker problems there). The feeders were glowing red when he got there. It cooked the unit and the feeder wires. So instead of possibly repairing a problem, it was a complete tear out and replacement of the unit and the feeders.

I dug a little deeper, and it seems similar condensers would have a Locked Rotor Amp (LRA) rating of 59A. On the specified 25A max breaker, the LRA would be well above 2 times the breaker rating ... which I understand is a rule of thumb for the maximum trip current for an older breaker (couldn't find my copy of the NEMA breaker standard with the permitted trip curves).

Now, on a 30A breaker, twice the breaker rating would be above the LRA at 59A ... hmmmm


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

Originally Posted By: jwilliams4
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Larry, probably it would not take any longer (see Robert’s post above)


to break the current at the breaker. In the case that Robert cited,

it was as much the fault of a faulty breaker as it was the compressor.

If a switching device or a relay shorted, it could conceivable be effected

by the larger breaker. There are a lot of variables to consider.

But if you should find even a minimally over-sized breaker the client

should be informed. What he wants to do about it is his decision. CYA!


--
"not just an inspection, but an education"

Originally Posted By: lkage
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roconnor wrote:
A buddy in the HVAC business indicated it probably isn't a real serious issue, but could be a major problem under the wrong circumstances.


Potential safety hazard...

Quote:
But if you should find even a minimally over-sized breaker the client

should be informed. What he wants to do about it is his decision. CYA!


Abolutely. ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)

Quote:
The feeders were glowing red when he got there.


So...now it's a heater.


--
"I have never met a man so ignorant that I couldn't learn something from him."
Galileo Galilei

Originally Posted By: roconnor
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jwilliams4 wrote:
Larry, probably it would not take any longer ... to break the current at the breaker.

Actually with the oversized breaker and a locked compressor, it would take much longer for the breaker to trip ... and on older breakers maybe not even trip, which is the concern.

jwilliams4 wrote:
it was as much the fault of a faulty breaker as it was the compressor.

If the compressor goes that one thing, and can be repaired. If it fries the unit and feeder wires because a breaker doesn't trip when it should that is quite another thing and the breaker's/installer's fault completely.

lkage wrote:
Potential safety hazard...

dedwards wrote:
I always write it up and go on.

It's a no-brainier it's wrong and gets written up. But there are different degrees of how something is written up and the verbal/written recommendations to your client. I look at safety hazards as Red Flags. Just not sure if a 25A max condenser on a 30A breaker is really that serious a problem, and looking for some feedback from some of our resident HVAC experts.


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

Originally Posted By: dandersen
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The breaker protects the wire not the device.


If you over size a breaker, you need oversized wire. This oversized wire often does not fit the connector terminals.

Many (not all) HVAC equipment designers put "equipment breakers" or fuses in the equipment.

I don't think you have to be concerned with a 5 amp difference so long as the wire is rated for it.

There is all kinds of circuits in the HVAC equipment that will be toast and will never trip the disconnect breaker.


Originally Posted By: roconnor
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dandersen wrote:
The breaker protects the wire not the device.

I don't agree. The elec codes clearly indicate the intent is to protect both the feeders and the equipment

dandersen wrote:
If you over size a breaker, you need oversized wire. This oversized wire does not fit the connector terminals.

Even with the oversized 30A breaker and #10 Cu wire (could be smaller based on the nameplate info), there was plenty of room at the terminals for an even larger wire.


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

Originally Posted By: lkage
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dandersen wrote:
I don't think you have to be concerned with a 5 amp difference so long as the wire is rated for it.


When the manufacturer states "maximum breaker size" on the technical plate of the unit and the installed breaker is larger than the one specified I am concerned (because I am there and see the contradiction) so I write it up as a potential safety hazard recommending correction.


--
"I have never met a man so ignorant that I couldn't learn something from him."
Galileo Galilei

Originally Posted By: jhugenroth
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roconnor wrote:

It's a no-brainier it's wrong and gets written up. But there are different degrees of how something is written up and the verbal/written recommendations to your client. I look at safety hazards as Red Flags. Just not sure if a 25A max condenser on a 30A breaker is really that serious a problem, and looking for some feedback from some of our resident HVAC experts.


Robert,
I agree with the "degree" factor in writing something up. I find oversized breakers on A/C units all the time (average two or three a week). If it is 5 amps over as you described, my report will say that the manufacturer's recommendations have been exceeded (I include a picture of the plate, as well as the breaker) and that it may void any warranty.
If you get into the 10-20 amp range, then I recommend further evaluation by ______. I did see one that had a 60A breaker on a 3 ton unit! ![icon_eek.gif](upload://yuxgmvDDEGIQPAyP9sRnK0D0CCY.gif) Needless to say, that got written up as a possible safety hazard.

A general rule of thumb for newer units is to add a zero to the tonnage and you get the approximate breaker amperage. A 2 ton unit should have a 20 amp breaker, 3 ton 30 amp, etc. This is good info in case you can't read some of the data. Even if you can't read the breaker information, if can read the unit BTU, you can approximate the size breaker needed.

For the newbies, one ton is 12,000 BTU. If you can't read the BTU rating but can read the model number you can usually approximate the unit capacity. If the model number has a 36 in it, it is most likely a 3 ton unit, a 42 would be 3 1/2 ton, a 48 would be 4 ton, etc.

So even if I can't read the info for the maximum recommended breaker size, if I can determine the unit is a 4 ton unit, and the breaker is 60 amps, I will write it up as needing further evaluation.


Originally Posted By: roconnor
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jhugenroth wrote:
A general rule of thumb for newer units is to add a zero to the tonnage and you get the approximate breaker amperage ... if I can determine the unit is a 4 ton unit, and the breaker is 60 amps, I will write it up as needing further evaluation.

Be careful with that rule of thumb, as it doesn't work for some older or lower end less efficient models. For example, a new 4-ton Rheem/Ruud 10 SEER compressor would be listed as needing a 45A Minimum to 60A Maximum breaker.

It's pretty good as a guide for newer more efficient units, and a mind flag to look a little closer when way off. But I wouldn't write up a defect just based on that.

P.S. What rubbed me the wrong way to begin with was the 2-ton unit on a 30A breaker ... I was expecting about a 20A breaker, and for that unit the requirements turned out to be 20A minimum and 25A maximum breaker.


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

Originally Posted By: jhugenroth
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Robert,


I agree with you, but in my post I mentioned that IF I couldn’t determine the maximum breaker size from the plate, (be it from wear or whatever), AND the breaker size seemed large for the unit, THEN I would recommend it for evaluation. Granted, there are some units that have a higher rating, but look at your original post on this thread. Let’s say you couldn’t determine the maximum breaker size on the plate because it was worn, but you knew it was a two ton unit. Would you have let it go, or would you call for further evaluation? My gut would tell me a two ton unit with a 30 amp breaker is wrong.


Originally Posted By: dbowers
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Guys - You’re all spending a lot of time talking and the bottom line is … if the data tag says the maximum breaker size should be 25, 35, etc and whats in the panel is bigger - - its wrong. It does not conform to the manufacturers design criteria. Write it up and MOVE ON…


Originally Posted By: thejnicki
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I have found that manufacturers specifications have presidence over anything> In new construction a county inspector will take manufacturers specs over any arcitect or structural designs… Just my experience…


Originally Posted By: dandersen
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Quote:
dandersen wrote:
The breaker protects the wire not the device.

I don't agree. The elec codes clearly indicate the intent is to protect both the feeders and the equipment


Robert,

Can you point me to the Code, if you have it off hand?

I am interested in what they have to say.
When you design HVAC equipment, as you drop wire size, your wire protection (Fuse/breaker) should also be reduced, all the way down to the 24 volt control circuit. Some MFG's don't do this. Goodman/Janatrol for one, takes 60 amps to the air handler (heat pump) without ever protecting anything below the 10kw heater.

In my opinion, this is a whole lot more than 5 amp over capacity we were talking about in this thread! But that's what THEY do.
If the sticker says 25 amps and the breaker is >25 I think it should be called out. However, just for info, the unit will burn without tripping a breaker even if the max breaker size is correct!

What is the FLA/LRA of a 1.2 amp/240vac motor?
>25 amps? You bet.
How about 60 amps?

The breaker will trip though, once the fire reaches a wire with a >25 amp capacity (or 60 amps in the case of Janatrol).

The original post to this thread appeared to be just a "for my info only" type of question. We all know that 30 on a 25 is wrong. Just how wrong is it? is the question here.

The nameplate lists 16 - 25 amp range. Can anyone post how they come up with that range? What happens if we go over or under?


Originally Posted By: roconnor
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roconnor wrote:
The elec codes clearly indicate the intent is to protect both the feeders and the equipment

dandersen wrote:
Can you point me to the Code, if you have it off hand?

Look at NEC 240.3 which states "Equipment shall be protected against overcurrent ... " and references Article 440 for AC equipment, which also repeats that intent.

The breaker is allowed to be sized larger than the running load to handle the start up, but needs to be less than the locked rotor load to protect the equipment.

In the case my buddy described, the breaker didn't trip at the higher locked rotor load (it should have), which ended up frying both the wires and the equipment, instead of just being a repair of the compressor. Not a good thing ... ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

Originally Posted By: roconnor
This post was automatically imported from our archived forum.



dandersen wrote:
The original post to this thread appeared to be just a "for my info only" type of question.

Actually it's a little deeper than that, which is why I asked for some input from some of our resident HVAC experts. The discussion goes beyond a home inspection, but if you are going to require further evaluation/repair (as opposed to just writing it up as a "concern") it is helpful to have some idea where that is headed. Dan seemed to miss that intent too.

dandersen wrote:
The nameplate lists 16 - 25 amp range. Can anyone post how they come up with that range?

The equipment has a running or rated load (RLA) of 11.5A. The circuit capacity must be at least 125% of that, which was rounded up to the listed 16A Circuit Capacity. Per NEC 440.22 the breaker can be between 175% of the rated load (11.5A x 1.75 = 20.1A) to 225% of the rated load (11.5A x 2.25 = 25.9A). Accordingly the nameplate listed the breaker/fuse sizes as 20A Minimum (to avoid start up trips) and 25A Maximum to match the circuit.

dandersen wrote:
What happens if we go over or under?

That really is the question. Going under may result in breaker/fuse trips at start up. Going over may result in the wires being overloaded and may not trip if the compressor motor locks up.

In this case the feeder wires were oversized, so limiting the breaker to 175% to 225% of the rated load (to allow for a higher start up current, but still protect the wires for that short duration) doesn't really seem to be the issue. That circuit will be able to handle both a higher running load, as well as a higher start up load and overload.

Per a call to the manufacturer, the breaker/fuse ratings listed on the equipment are calculated to match the running load and minimum circuit capacity listed on the nameplate. If the feeders are somewhat oversized, then the breakers could also be slightly oversized, as long as it's still well below the locked rotor load to protect the compressor. But they couldn't be specific, and indicated they would have to review the individual case through a local supplier/representative. There are additional limitations with the internal equipment wiring.

So a slightly oversized breaker might not be a real issue after all, as long as the feeder wires are not being overloaded ... but nothing definitive ... ![icon_confused.gif](upload://qv5zppiN69qCk2Y6JzaFYhrff8S.gif)


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong