need to downgrade breaker (from 40amp to 15amp) for new hvac?

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See if the paper work mentions the word amp, or ampacity.
Since this is greek, please leave the panel box closed. For your safety, you see.
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Christopher A. Young
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Maybe the inspector is talking about the size of the conducter on the breaker? If it's #8, it is correct for the 40A breaker. If it's smaller, the breaker needs to be changed appropriately.
Bill

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snipped-for-privacy@aol.com wrote:

I have a feeling the inspector doesn't have a clue, but...
Is this a new HVAC installation? Is this an existing breaker w/ a new unit or a new installation for it? Either way, if the unit has been recently installed, I'd first just check w/ the installers and find out what they say before anything else. If it is a new installation, you may well have some information for the unit that describes the required service feed(s) -- check for that.
As someone else noted, if the service feed to the unit is sized properly for the existing wiring, it's unlikely the breaker needs to be changed. The point of breakers in distribution panels is to protect the wiring, _not_ the device. The unit itself will be protected by internal fusing or breakers or a combination of both. Thinking a breaker must match a nameplate load rating for "protection" of the load device is a common misconception I've found more than one inspector to have (hence my first comment).
If you don't get a satisfactory response from the HVAC guys or from what you can learn from the information left w/ the unit (again, assuming it's new), then if you don't have sufficient expertise to determine for sure it's time to ask an electrician out to check. I'd think it unlikely to need that much, but you may have to go that route if the inspection report has actually gone to the potential buyer to have sufficient pedigree to satisfy...
Methinks this will turn out to be a tempest in a teapot...
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Thank you for your reply dpb, I missed it when I posted a few minutes ago, I lost a post somewhere, so if this one is a duplicate, my apologies.
See, I think you could be right about the inspector. I'm sure he's quite knowledgable, but if he's seen this problem often, I figure hvac units are installed by certified hvac techs.. who would be more likely to be the expert? Additionally, the lack of any liability for his findings/report makes me hesitate to take his word as gospel... if he's wrong & there's a problem w/the unit after we switch to 15amp, who is liable? maybe me? I may end up telling the buyers if they want me to have it changed, I'll have it changed, but I've let them know I'm not certain it should be done. I'd contact the manufacturer, but I'm afraid of voiding the warranty.
This is a new unit, installed a few months ago, installer seemed quite competent and knowledgable.
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Unfortunately, in my experience in many cases it is the inspector. Many "certified" HVAC techs take shortcuts if they can get away with it. After the #1 shortcut (inadequate evacuation prior to system charging), failing to downsize a breaker when installing a more efficient system is probably the #2 shortcut taken. Having said this a reduction is breaker size from 40A to 15A seems a bit extreme unless there was a significant change in the system (for example, the elimination of resistive heat strips in the air handler).

See comment above. Did the installation require a permit in your municipality? Was one pulled? Did the installation pass the municipality's final inspection? If no permit was pulled and one is required, the HVAC installer was probably a hack.
Finally, are we talking about the breaker for the air handler or the condenser? Does the air handler have heat strips (aka emergency heat)? What is the make and model of the air handler and condenser, and what are the specifications for the electrical supply for each (note: should be on manufacturer's nameplate)?
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Travis Jordan wrote:

What, precisely, is the "shortcut"? If the existing wiring is sized for 40A, the circuit breaker isn't intended to do anything but protect the wiring from short circuit faults, _NOT_ the load device, whatever it is.
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The circuit breaker is there to protect the load device and the wiring. The shortcut is that some installers don't downsize the breaker when installing a more efficient system. The NEC, most state building codes require appropriate sizing. Most HVAC manufacturers specify the maximum fuse size (MFS) and maximum circuit breaker size (MCB) for protection of their equipment. Of course the wire size has to be large enough for the intended load.
Generally the calculation is: MCB = 2.25 x largest motor amps (FLA or RLA) + the sum of the remaining motor amps.
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Travis Jordan wrote:

40A to 15A more efficient???? Now THAT is one efficient system...
I ain't buyin', sorry.
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Normally I'd agree, but if a resistive heat air handler was changed out for a variable speed heatpump only air handler, it would be completely logical. Or maybe the original breaker was oversized.
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I just checked Trane's documentation and all of their 1.5T and smaller heat pump systems state a MCB of 15A. It is quite possible the old system (1987 vintage, probably twice the load) had an oversized breaker installed also.
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Travis Jordan wrote:

Except OP specifically spoke of "emergency heat" kicking on which seems to preclude that -- or, of course, could be he just does not know what he just bought and paid for and had installed...

In about the same category as the above...
imo, ymmv, $0.02, etc., etc., ...
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Travis J beat me to the puch on the question: Is this breaker for the outside condensing unit, or for the inside air handler? Very few condensing units call for a 15amp breaker. I have only seen a couple--certain brands of 1.5 and possibly 2 ton units. Regardless, the unit will have a maximum breaker size on the data plate, and some brands list a minimum as well. Go with whatever it says, making sure the wire is large enough. Larger wire than necessary is fine. If it is the air handler you are referring to, even the smallest heat strips made will require a lot more than 15 amps. The problem is that the airhandlers are usually ordered without heat strips, and they are ordered separately and installed when the unit is installed. You have to first know what size heat strips you have ---they can be from 3KW to 20 KW. They are sized according to the amount of heat desired, and the available power. Call the installer and get all the info from them. They may be willing to talk to the inspector and get this resolved over the phone. Our service mgr gets involved with things like this from time to time. Good luck Larry
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snipped-for-privacy@aol.com wrote: ..

I'm not that confident in his expertise... :) In fact, I'm giving pretty low odds that he is right on this and, conversely, the other way 'round that he has the misconception of the breaker supposedly protecting the device...I fully expect that the vendor requirement will be for a _minimum_ of some value and as long as the original circuit wasn't miswired the larger breaker is perfectly find for its intended purpose.

The worst that can happen is the unit will trip so guess you could just leave them w/ the problem. My understanding of the disclosure rules is you make a disclosure of existing conditions, it's up to the buyer to agree/reject/negotiate.

No how, no way can simply asking a question affect the warranty.

And I'd wager they probably were/are. If you haven't, I'd check w/ them and get an explanation of their understanding of the inspector's concern. If it makes sense (as I suspect it will) I'd give it to the buyer and go on. If not, then you can decide whether an independent opinion is worth the $$ or not.
OBTW, changing a breaker is pretty simple. Of course, be sure to turn the feeder breaker off...
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First time posting so this is a test.
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On Sun, 24 Jun 2007 05:03:32 -0700, snipped-for-privacy@aol.com wrote:

I would as why?
Gauge of wire too small, per maker's instructions, etc. Oh, are you sure you got this right, did you get it on paper or overhead a conversation. I'm guessing a communication error first. ;)
tom @ www.NoCostAds.com
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What I have seen done a lot is for the breaker in the main panel to NOT be changed when a new unit is installed but the correct sized breaker to be installed in the disconnect box located next to the unit. Assuming the wire from the breaker to the disconnect box is properly sized this would be fine. Not something the average home inspector is smart enough to realize.
The final protection for the unit is at the disconnect box. The wiring may be able to carry 40 amps to the disconnect but if that is a 20 amp breaker only 20 can pass to the unit.
By doing it this way the HVAC contractor has not messed with your wiring or your breaker box and is only liable for the disconnect and the unit. It is a CYA (his A) type of thing.
If that is the case a simple letter from the HVAC contractor should be enough to satisfy the "repair requirements" of the home inspection. You should offer to pay the HVAC for the time to write the letter. Most will not charge.
I have never seen a home inspector argue with a licensed person who is willing to commit something to writing.
Colbyt
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If the unit has aux heat, it may very well need 40 amps. Read the manual.
If you have to ask, you don't have the skills. I wouldn't reccomend to open a panel box unless you've seen it done several times, and have someone experienced working with you.
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