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Maximum Breaker Size for Condenser Units


Brian G
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Even the oldest units I've seen have this stamped into the label, so I've always assumed it was a legal requirement from way back. Does anyone know exactly where and / or when this stems from? Is it UL, manufacturer's, NEC, or what? I've also assumed it was to prevent an overload situation, but I'm open to further enlightenment about that too.

Brian G.

Girding My Loins for Next Time [:-fight]

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Originally posted by Brian G.

Even the oldest units I've seen have this stamped into the label, so I've always assumed it was a legal requirement from way back. Does anyone know exactly where and / or when this stems from? Is it UL, manufacturer's, NEC, or what?

The requirements for all the stuff on the AC unit's nameplate are in 440.4(A).

110.3(b) requires the electrician to install the system per the nameplate.

Is that what you were wondering?

I've also assumed it was to prevent an overload situation, but I'm open to further enlightenment about that too.

No. In an air conditioning circuit, the overload protection comes from the compressor motor's thermal protection device. It's built in and it protects both the motor and the conductors. The breaker or fuse is there to protect against ground faults and line-to-line shorts.

If we sized the breaker to protect the wire at it's rated ampacity, we'd get constant nuisance trips on startup when the motor draws lots of current.

Make sense?

- Jim Katen, Oregon

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Originally posted by Jim Katen

The requirements for all the stuff on the AC unit's nameplate are in 440.4(A).

110.3(b) requires the electrician to install the system per the nameplate.

Is that what you were wondering?

Yep.

In an air conditioning circuit, the overload protection comes from the compressor motor's thermal protection device. It's built in and it protects both the motor and the conductors. The breaker or fuse is there to protect against ground faults and line-to-line shorts.

Okay, one more trip down Erroneous Assumption Alley. I've been told that any size breaker will trip on a ground fault or a line-to-line short (or was that a dead short?). I'm sure I couldn't have that mixed up... but just in case, exactly why does the requirement for a breaker "no larger than" become important?

If we sized the breaker to protect the wire at it's rated ampacity, we'd get constant nuisance trips on startup when the motor draws lots of current.

That I get. [:-party]

Brian G.

Man of a Thousand and One Questions [:-batman] (and counting)

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Originally posted by Brian G.

Okay, one more trip down Erroneous Assumption Alley. I've been told that any size breaker will trip on a ground fault or a line-to-line short (or was that a dead short?). I'm sure I couldn't have that mixed up... but just in case, exactly why does the requirement for a breaker "no larger than" become important?

Hell, I don't know. I just repeat the stuff that Douglas explained to me 10 years ago. I never figured anyone was actually paying attention let alone applying critical thinking.

FWIW, here's my guess. I figure it's like seat belts. My car has both front and side-impact air bags. If I'm in an accident, the air bags are designed to protect me. But I'm also wearing a seat belt. It's a redundant safety feature. My hunch is that it's something along those lines. We want the breaker to be as small as possible and still not be a nuisance when the motor starts.

I'll post the question over at Mike Holt's forum and see what else folks say.

- Jim Katen, Oregon

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Originally posted by Jim Katen

I just repeat the stuff that Douglas explained to me 10 years ago.

Not a bad plan, and strangely similar to my own. [;)]

We want the breaker to be as small as possible and still not be a nuisance when the motor starts.

Sounds logical enough, but as you know that doesn't always hold in electrical.

I'll post the question over at Mike Holt's forum and see what else folks say.

Ah, the plot thickens....

Brian G.

Pesky Frickin' Question-Asker From Hell [:-headach [:-dopey]

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  • 2 weeks later...

The guys over at Mike Holt's forum more or less agreed with my line of reasoning.

Here was one particularly well put response:

They're looking for the lowest breaker or fuse that will consistanly hold the startup load without tripping. With the smallest size that holds the load, rather than a larger size for protecting against a fault, your trip curve is such that it will trip faster with the smaller overcurrent protection than with a larger ampacity breaker or fuse.

- Jim Katen, Oregon

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Hmmm...well it makes sense, but doesn't sound like a particularly big deal, especially if the size is very close. I frequently see the manufacturer's calling for in-between sized breakers (25, 35, 45) with the next larger size installed (30, 40, 50). I think I'll stop writing it up unless they go more than the size right above in those cases.

Mucho Gracias Lord Jim. [:-angel]

Brian G.

Gittin' Me Some Mor Edjumacationing! [:-glasses

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  • 5 weeks later...

I got a call from an agent this morning, saying the "expert" contractor they called about one of these situations told them it was fine as is, and there are "other considerations" besides the manufacturer's specs. *sigh* [:-indiffe

This particular unit called for no larger than a 45, but no smaller than a 40; a 30 was installed. I don't recall seeing many "no smaller than" specs, but I went with it. The agent noted twice that "They are the experts". Right. Experts like these are my job security.

I'm sick of this crap. I'm going down to get the "experts" explanation face-to-face, then I'm gonna email 5 or 6 of the big manufacturer's to get their position on this issue, in writing. If the manufacturer's say what I think they'll say (no warranty for units installed outside of specs), I'm just going to include the info right in with the reports from now on (starting with the NEC provisions Brother Jim cites above)...enough already. I'm thinking I may eventually want to add a page at the back to cite code and manufacturer's specs on, but something tells me I'd still get a few of these calls. Right now I'm getting this kind of BS on different issues from roofers, electricians, and HVAC guys. I suppose it goes with the territory.

Brian G.

Holding Out at Fort Goodman, in the Code Wilderness [:-cowboy]

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Originally posted by Brian G.

I got a call from an agent this morning, saying the "expert" contractor they called about one of these situations told them it was fine as is, and there are "other considerations" besides the manufacturer's specs. *sigh* [:-indiffe

Why is anyone arguing about $1.50 worth of fuses?

This particular unit called for no larger than a 45, but no smaller than a 40; a 30 was installed. I don't recall seeing many "no smaller than" specs, but I went with it. The agent noted twice that "They are the experts". Right. Experts like these are my job security.

Now hang on a minute. If the installed fuses are too small, the worst thing that can happen is a nuisance trip. It'll give the homeowner the chance to install the proper fuse. It seems to me that the equipment and conductors are amply protected. What's the big deal?

I'm sick of this crap. I'm going down to get the "experts" explanation face-to-face, then I'm gonna email 5 or 6 of the big manufacturer's to get their position on this issue, in writing. If the manufacturer's say what I think they'll say (no warranty for units installed outside of specs), I'm just going to include the info right in with the reports from now on (starting with the NEC provisions Brother Jim cites above)...enough already.

Good luck. You're more likely to get a serious case of the corporate Cha-Cha. When you ask a manufacturer for this, they start dancing. Better to just photocopy their installation instructions.

I'm thinking I may eventually want to add a page at the back to cite code and manufacturer's specs on, but something tells me I'd still get a few of these calls. Right now I'm getting this kind of BS on different issues from roofers, electricians, and HVAC guys. I suppose it goes with the territory.

If you're consistent about it, and if you're right every time, your efforts will eventually have an effect.

- Jim Katen, Oregon

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Originally posted by Jim Katen

Why is anyone arguing about $1.50 worth of fuses?

It's actually breakers, no one around here installs a fused disconnect. Still, not much moola.

Now hang on a minute. If the installed fuses are too small, the worst thing that can happen is a nuisance trip. It'll give the homeowner the chance to install the proper fuse. It seems to me that the equipment and conductors are amply protected. What's the big deal?

It's that same stupid circle as the mixed neutrals & grounds. The unit also said "no smaller than", so I wrote it up. They call some contractor / repair guy who tells them I'm full of it and it's proper as is, so they come back to me wanting me to tell the client it's okay (or in this case, stop writing it up). If they don't want to fix it, fine...not my area of concern. If they want me to say it's black when I've always been told it's blue, forget it. Believe me, these are not the sort of issues I would choose to argue or make a big point of, but I'm being put on the spot.

Most of this is coming from one agency. I have the sneaking feeling there may be a gradual effort underway to build-up a little catalog of errors (real or imagined) to justify strongly steering clients elsewhere.

Good luck. You're more likely to get a serious case of the corporate Cha-Cha. When you ask a manufacturer for this, they start dancing. Better to just photocopy their installation instructions.

You're probably right, but it's worth a shot. I'll bet the installation instructions don't really address it either, other than the label.

If you're consistent about it, and if you're right every time, your efforts will eventually have an effect.

Probably right again.

I'm wondering though...

I was reading the NEC stuff you cited. As far as I can see it never really nails this down either, unless the manufacturer's specs do. The one part {110.3(b)} just says it has to be done to the specs, and the other says it has to be protected in any one of three ways. One of those ways is the built-in thermal protection, which I understand is on all HVAC compressors these days (yes? no?). If so, it seems to me that you could install absolutely any size breaker without violating the code (at least that part). If the specs don't nail it down either, I may be wrong to write it up, but that's what I was taught and have always read on these forums.

I think the idiotic aspect of this problem bothers me the most. Why in the world wouldn't one simply install whatever size breaker the unit label called for? Why would anyone with half a brain purposely choose to take the less sure, safe, and defendable path?

Brian G.

To Strain at Gnats or Kiss the Feet of "Experts"...What a Choice [:-headach

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"No warranty for units installed outside of specs"

See:

http://www.alpinehomeair.com/related/Go ... 20Inst.pdf

See pages 4 & 10

Extract:

Over current protection less than that recommended on the

unit's "Specification Sheet" could result in unnecessary fuse

failure and service call. The manufacturer bears no

responsibility for damage caused to the equipment as a result

of not using the recommended size for the protective devices

as listed on the unit's rating plate.

===

NOTE the second sentence.

===

This is just the first installation instructions that came up in a quick search.

Bet you most of the others say the same thing.

Ask the local yokel "expert" if he's going to warranty the unit after he voids the manufacturer's warranty by not following the installation instructions, because the manufacturer won't!

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Damn Erby, that's way more dead-on-point than I dared hope for. I looked back at my notes for the brand & model, which was a Trane. I couldn't find any installation specs on their site so I emailed them asking for the specs for that specific system. I hope they send me something as unambiguous as that.

Brian G.

Waiting......

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Brian,

Feel free to steal this, it stops many arguments before they start.

I, as a home inspector, do not claim to be an expert in anyone one area or field. I was contracted to provide a written opinion. In this case I also provided back up documentation and signed my name to it. If a qualified licensed contractor or expert disagrees with the statements in this report I suggest they provide written documentation and sign their name to it.

I use this when I quote manufactures installation instructions like the roof tile manual. When they call and say, Cocky the Contractor says there's nothing wrong with the way it is installed, I reply, I provided backup documentation and signed my name to it. Did Cocky?

They say, No.

Well if it is right I would love to see where the manufacture says so. When Cocky gives you those documents, could you let me know so I can have a copy?

I have only had 1 person return that call and that was to say the contractor couldn't find anything so they fixed it.

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The response from Trane:

Your email has reached the Help Desk for the Trane Dealer ComfortSite and we are currently not involved in the process of sending out product related information to non Trane dealers. Please contact your local distributor/sales office or a local Trane Dealer to get access to the XE 1000 specs you need.

Obviously I can't ask the local guy, he's the "expert". Anybody out there know a friendly Trane dealer you can get this from? I'll dance at your wedding (or funeral if you prefer).

Brian G.

I Hear That Trane A-Comin' [:-bigeyes

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I have found that a simple picture of the data label that says "35 amp max" and then a picture of the 60 amp fuse or breaker works every time.

Download Attachment: icon_photo.gif IMG_4830.JPG

92.81 KB

And then the data plate.

Download Attachment: icon_photo.gif IMG_4831.JPG

110.89 KB

This was one of todays inspection. I bet that 75% of the homes I inspect are like this.

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http://216.122.22.11/FetchDocument.aspx ... 50c39ad3aa

Is a pdf file as Scott said off of the Rheem/Rudd site.

Spec data with a list of their breaker sizing for 10 of their units just for an example.

If you'd like to do your own search at the Rheem/Rudd site:

http://www.rheem.com/Entrance/index3.html

Works for most MFG. other than Trane.

I guess Trane thinks their units are too COOL.

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I figured it out, thanks Barry. For some reason when I open Adobe it doesn't show those aspx things, I had to insert the file name in the box myself. I notice they refer to the warranty, but I can't find it on their site. I also notice they have both a minimum and maximum fuse / breaker size for every unit. I'll have to start watching more closely for that. I usually only see a maximum.

And yeah, Trane seems sort of...aloof.

I did find someone who's sending me the specs for my Trane via snail mail. Should have em' in a day or two.

Brian G.

Waiting Quietly in the Shadows..... [:-vamp]

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