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I'm getting tired of defending my HVAC circuits to HVAC installers who do not understand the meaning of MCA. Last week it was a mini split with a FLA of 9.3 and an MCA of 15. We ran #12s. The installer refused to connect it, saying it had to be #10 and he was not going to be responsible for damage to the unit or a fire.
Today another installer told a homeowner I should have ran #8s to his condenser with an MCA of 26 (30-40 foot run). We ran #10s. He told her I violated the NEC and the wire could start a fire because it is on a 40 amp breaker (per the nameplate). He said the warranty is void on the unit thanks to me. I haven't had a chance to speak to this guy yet.
Whaddya do?
 

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Estwing magic
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A what?????:blink:
Well, pull the permit now and get it inspected. Otherwise, it's just a pi$$ing contest and telling someone to shove it won't solve the issue.

What is minimum circuit ampacity anyway? I'm just asking. I don't know...
Never mind, I just figured that out. Brain fart.
 

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I guess I'm lucky. I am the electrician for an HVAC company and do all the electrical work. The installers just look at me with a blank stare when I start talking wire. I prefer it that way. :thumbup:
 

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Electrical Simpleton
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Well, pull the permit now and get it inspected. Otherwise, it's just a pi$$ing contest and telling someone to shove it won't solve the issue.

What is minimum circuit ampacity anyway? I'm just asking. I don't know.
I agree that telling someone to go pound sand, even though that would probably make you feel better, isn't the answer.

Unless the manufacturers spec's call for a certain wire size you are permitted, by the NEC, to size your wire to the minimum circuit ampacity listed on the unit nameplate and then provide a OCPD device sized to the maximum permitted.

Pete
 

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I would do two things. Firstly I would call the homeowner and explain why it is perfectly okay to do what you did and let her know that you could arrange a conversation with the electrical inspector if she wishes.
Secondly I would call the hvac guys boss and explain to them that it is inappropriate to bad you to the customer and it is twice as bad when they are wrong.

I am assuming vd is not an issue here.
 

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Estwing magic
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I would do two things. Firstly I would call the homeowner and explain why it is perfectly okay to do what you did and let her know that you could arrange a conversation with the electrical inspector if she wishes.
Secondly I would call the hvac guys boss and explain to them that it is inappropriate to bad you to the customer and it is twice as bad when they are wrong.

I am assuming vd is not an issue here.
I like that idea. Suggesting that a conversation with an inspector can be arranged is a way of saying you have nothing to hide. I find that technical explanations, particularly with home owners, can lead to blank stares very quickly. I asked an inspector a question one time and he simply said to me, "If you wouldn't do it in your own home then don't do it in someone else's". That stuck with me and it is something I sometimes tell clients.
 

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I like that idea. Suggesting that a conversation with an inspector can be arranged is a way of saying you have nothing to hide. I find that technical explanations, particularly with home owners, can lead to blank stares very quickly. I asked an inspector a question one time and he simply said to me, "If you wouldn't do it in your own home then don't do it in someone else's". That stuck with me and it is something I sometimes tell clients.
The blank stares are fine and I don't expect them to understand however if you sound like you know what you are talking about it looks good to the home owner.

I bet I can explain it well enough that most home owners would understand.
 

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Estwing magic
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The blank stares are fine and I don't expect them to understand however if you sound like you know what you are talking about it looks good to the home owner.

I bet I can explain it well enough that most home owners would understand.
...and I assume that VD never becomes an issue either :)
 

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Voltage drop, bundling more than 2', and/or excessive temperature (any of this running in an attic?) are the possible reasons you'd need to upsize.

I agree with talking to the HVAC's management regarding badmouthing you in front of the customer. But then, it might be management's idea to cut down on warranty work by immediately disavowing the warranty due to a BS excuse.
 

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I'm getting tired of defending my HVAC circuits to HVAC installers who do not understand the meaning of MCA. Last week it was a mini split with a FLA of 9.3 and an MCA of 15. We ran #12s. The installer refused to connect it, saying it had to be #10 and he was not going to be responsible for damage to the unit or a fire.
Today another installer told a homeowner I should have ran #8s to his condenser with an MCA of 26 (30-40 foot run). We ran #10s. He told her I violated the NEC and the wire could start a fire because it is on a 40 amp breaker (per the nameplate). He said the warranty is void on the unit thanks to me. I haven't had a chance to speak to this guy yet.
Whaddya do?

Tell the HVAC guy there is a reason hes not an electrician.
 

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I've gotten into this argument several times with one HVAC contractor in particular. I wound up faxing over 440.6 to their shop
 

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Discussion Starter · #17 · (Edited)
No vd issues, the mini split circuit is already bigger than the nameplate requires anyway and the 26 amp unit is about 50 feet away. No permits by the way, owners did not want to get them. If I pull one just for my elec everyone else gets busted. Whuddya do? I'm not going to turn work away. Then again if the hvac guys give me grief I like the idea of mentioning let's call in the inspector!

No ambient factor either.....crawl space under house. Are you saying maybe the hvac guys are thinking ambient? Ha
 

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NJ-IEC
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It's never a good idea to bad mouth another contractor because Karma's a bitch. I would boast to the customer of my experience and knowledge required to obtain the electrical license and simply explain as clearly as possible that code allows for this installation. The trouble with getting the electrical inspector involved is that half of them don't even know the HVAC and motor sizing rules for conductor, disconnects, and overcurrent protection so that could make you look even worse.
 

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Magnettica said:
The trouble with getting the electrical inspector involved is that half of them don't even know the HVAC and motor sizing rules for conductor, disconnects, and overcurrent protection so that could make you look even worse.
I can't relate to this statement. I feel like grasping the concept of circuit ampacity and it's relation to motor loads is a very basic electrical concept and can't see how an electrical inspector could obtain his position without knowing all that
 

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NJ-IEC
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I can't relate to this statement. I feel like grasping the concept of circuit ampacity and it's relation to motor loads is a very basic electrical concept and can't see how an electrical inspector could obtain his position without knowing all that
You must not be from New Jersey :whistling2:

There's plenty of brain dead inspectors out there who got their positions only God knows how. I don't know how else to explain it. Maybe it's an NJ thing, I dunno.
 
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