What Will Happen If I... - Electrical - Contractor Talk

What Will Happen If I...

 
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Old 07-01-2010, 09:13 PM   #1
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What Will Happen If I...


The new ac unit calls for a 40 amp 2 pole breaker on a dedicated circuit. The PM says to hook it up to a 50 amp 2 pole breaker since we don't have the proper size on site and his lazy ass won't go get a new one the right size...

why is this not the right thing to do?

what's the worst that can happen?
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Old 07-01-2010, 09:21 PM   #2
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Re: What Will Happen If I...


It's 'not the right thing' because you probably are not properly protecting the conductors and/or the unit.

The worst thing that can happen? There's a fire, everyone in the building dies, and the lawyers get rich.

What likely will happen? Nothing.

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Old 07-01-2010, 10:14 PM   #3
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Also... It's illegal.
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Old 07-02-2010, 07:03 PM   #4
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Re: What Will Happen If I...


Quote:
Originally Posted by 480sparky View Post
It's 'not the right thing' because you probably are not properly protecting the conductors and/or the unit.

The worst thing that can happen? There's a fire, everyone in the building dies, and the lawyers get rich.

What likely will happen? Nothing.
Thanks for your reply guys.

Sparky, I'm not sure what you mean when you say "you probably are not properly protecting the conductors and/or the unit." Would you mind elaborating a bit on the do's and don'ts?

As far as the fire goes, it probably wouldn't kill everyone in the building because the house is still under construction, and if you can't use your hammer to bust a window or door to get out, you probably deserve to die...eheh just kiddin.

The hook up is temporary to a temporary breaker. Just getting the ac on to acclimate the wood.
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Old 07-02-2010, 07:25 PM   #5
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Re: What Will Happen If I...


Quote:
Originally Posted by Hoof Hearted View Post
Thanks for your reply guys.

Sparky, I'm not sure what you mean when you say "you probably are not properly protecting the conductors and/or the unit." Would you mind elaborating a bit on the do's and don'ts?

As far as the fire goes, it probably wouldn't kill everyone in the building because the house is still under construction, and if you can't use your hammer to bust a window or door to get out, you probably deserve to die...eheh just kiddin.

The hook up is temporary to a temporary breaker. Just getting the ac on to acclimate the wood.
There's going to be a nameplate on the unit, listing the largest overcurrent device allowed. If it says 40 and you put in a 50, you're not properly protecting the unit against faults. It also may exceed the allowable ampacity protection of the wire.

As for the fire and everyone inside of it croaking...... well, you asked for a worst-case scenario. Lawyers getting rich from others suffering, misery and loss is about as bad as it can get.


Think of it this way: You have a truck with a 2500-lb payload capacity, and you load it up with 2700 pounds of stuff and drive it 5 miles. Will everyone on the road be killed? Possibly, but highly unlikely.
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Old 07-02-2010, 09:52 PM   #6
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Re: What Will Happen If I...


I've got to speak up on this one. As a GC and carpenter by trade, this is exactly why I hire a licenced electrician.

I assume, and expect everything will be done properly and to code. If I wanted it f####ed up, I'd do it.

Glad to hear proper responses to the OP's question. Keep up the good work
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Old 07-03-2010, 07:52 AM   #7
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Re: What Will Happen If I...


Quote:
Originally Posted by Hoof Hearted View Post
The new ac unit calls for a 40 amp 2 pole breaker on a dedicated circuit. The PM says to hook it up to a 50 amp 2 pole breaker since we don't have the proper size on site and his lazy ass won't go get a new one the right size...

why is this not the right thing to do?

what's the worst that can happen?
Is the 50 amp circuit an existing circuit?

If it is the equipment is not being properly protected.

The worse that can happen is the unit may exceed the amp draw before it trips the breaker if there is a problem with the unit.

IMO for a temporary situation it is not that big of a deal but a licensed electrician or mechanical contractor should be wiring the unit up, not the GC, and it is not that big of a deal to change a breaker out to the right size.
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Old 07-03-2010, 09:00 AM   #8
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Re: What Will Happen If I...


If there is 6 ga run then the 50 amp breaker will protect the wire properly. If it is 8 ga and you draw enough current the wire could melt, be damaged or burst into flames. In general, the circuit breaker is only there to protect the wire and not the unit. If the unit overloads having the proper breaker in there can prevent it from going into a full meltdown mode and make repairs easier instead of having to replace the unit.
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Old 07-03-2010, 09:21 PM   #9
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Re: What Will Happen If I...


I am sitting here wondering why your PM wants the A/C units running at all?

I have never seen someone turn on the A/C till after usually LONG after the construction is done.

If you are the electrician, and you install something incorrectly, even though you are ordered to, It is still you who gets in trouble if a problem occurs.
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Old 07-03-2010, 09:28 PM   #10
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Re: What Will Happen If I...


Quote:
Originally Posted by JohnR View Post
I am sitting here wondering why your PM wants the A/C units running at all...
He already answered that.

Quote:
Originally Posted by Hoof Hearted View Post
......... Just getting the ac on to acclimate the wood.
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Old 07-03-2010, 10:51 PM   #11
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Re: What Will Happen If I...


Like the others have stated the circuit and the device/unit would not be properly protected if a problem were to occur. If a problem were to occur and personal injury were to come from this problem the owner and installer would be held negligent in the court of law. Is that really worth the cost of the correct size beaker?
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Old 07-03-2010, 11:06 PM   #12
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Re: What Will Happen If I...


I think you're all missing the point... this is a temporary installation just to be able to fire up the AC to get the wood to acclimate.

The OP never stated the 50a breaker will remain in place.



That said, if anyone (and by that I mean anyone not qualified) started effing around with my electrical installation, we'd be having a serious nose-to-nose discussion.
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Old 07-04-2010, 10:01 AM   #13
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Re: What Will Happen If I...


50 amps going to a load that states 40 amps max? The worse thing that could happen: The compressor or fan motor fries up, the hvac contractor reads this post, sees that there is a possibility that it's not the manufacturers fault, so, all warranties are void.

If the wiring is setup for 50 amps (sized right), and there is a circuit breaker, I don't see how there is potential for a fire. It's the appliance that is "vulnerable".
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Old 07-04-2010, 10:05 AM   #14
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Re: What Will Happen If I...


While on this subject, I was always under the impression that you are providing 240volts and that the circuit can handle up to 50 amps. Others have said to me that this circuit is delivering 50 amps @ 240v.

If I am incorrect, can someone explain this thing in layman's terms.
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Old 07-04-2010, 10:18 AM   #15
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flash........ installing a 50a breaker does not induce/force 50 amps of current to flow. It simply means it takes a larger fault current to trip the breaker than if a 40 amp breaker were installed.

If the unit functions properly, and draws, say 28 amps, then a 30 amp breaker will work just as well as a 1000 amp breaker (start-up current notwithstanding).

The danger comes from a fault other than a short-circuit. If the compressor starts to overheat, a 40a breaker should, by design, shut power off before it becomes a fire hazard. Installing a 50a breaker simply would cause the compressor to heat up beyond a limit that a 40a one would open at.

What could cause such a fault? Over-filling the freon, a physical stopping of a moving part, lack of enough air-flow of the fan blades........
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Old 07-04-2010, 11:19 AM   #16
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Re: What Will Happen If I...


Quote:
Originally Posted by 480sparky View Post
flash........ installing a 50a breaker does not induce/force 50 amps of current to flow. It simply means it takes a larger fault current to trip the breaker than if a 40 amp breaker were installed.

If the unit functions properly, and draws, say 28 amps, then a 30 amp breaker will work just as well as a 1000 amp breaker (start-up current notwithstanding).

The danger comes from a fault other than a short-circuit. If the compressor starts to overheat, a 40a breaker should, by design, shut power off before it becomes a fire hazard. Installing a 50a breaker simply would cause the compressor to heat up beyond a limit that a 40a one would open at.

What could cause such a fault? Over-filling the freon, a physical stopping of a moving part, lack of enough air-flow of the fan blades........
If the compressor starts to overheat if you lose a condensing fan motor it will trip on IOL, the breaker will not trip, a 50 amp breaker will not cause a compressor to overheat anymore than a 40 amp would.

As a mechanical contractor I wouldn't have a problem hooking the unit up to a 50 amp breaker temporarily, if I was concerned I would either change out the breaker or have the electrician change it out.
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Old 07-04-2010, 11:21 AM   #17
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Re: What Will Happen If I...


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......., a 50 amp breaker will not cause a compressor to overheat anymore than a 40 amp would.............
Breakers cannot cause a motor to overheat. An improperly-sized breaker can only allow a motor to overheat.
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Old 07-04-2010, 11:40 AM   #18
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Quote:
Originally Posted by 480sparky View Post
Breakers cannot cause a motor to overheat. An improperly-sized breaker can only allow a motor to overheat.
That is correct.
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Old 07-04-2010, 12:16 PM   #19
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Re: What Will Happen If I...


What could cause a fault?

Really, nothing. Most compressors have an internal overload, so one really cannot by-pass this device. Some units do have an external O/L but assuming all is wired ok. It never should get to the point of tripping the breaker.

However if you are wondering what can cause an excessive amp draw, without getting too wordy, I would say poor air flow over the outdoor coil (dirty coil or bad compressor fan motor) or a restriction in the refrigerant lines. Overcharge can increase the amp draw, but it would have to overcharged like a M.F. to trip the breaker.
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Old 07-04-2010, 12:33 PM   #20
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Re: What Will Happen If I...


WHy not just buy a 40 amp breaker and be DONE WITH IT??? we aren't talking hundreds and hundreds of dollars here for a breaker.
what if you hook it to a 50 and it never gets done the right way later, for any number of reasons.

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