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Wire size and breaker discrepancy

5K views 22 replies 10 participants last post by  nap 
#1 ·
I bought a Nutone bathroom heater/vent combo for a new install. The manufacturer's recommendation for the wire size and breaker is #14/3 on a 20 amp breaker.

I was under the impression that #14 was only rated at 15 amps. Are there some finer points I'm missing?
 
#13 ·
I'm new here, but some of this info being presented by so called "contractors" is poor at best. These DIYer's are going take this info without doing any credible research and take it as gospel.

Aren't there any moderators or whatever to watch out for this mis-information. This is very dangerous.
while hpp58 did post incorrect information, it was caught and corrected by several others. There are also mods that do watch and correct when they do see a problem but many of the regulars here are electricians and do know the correct answers.

As a member of this forum, joba fett, if you see an incorrect post, you are hereby required to make a corrective post. As well, you may report that thread to the moderator who will look at the thread and attach their corrective post, if they believe it is needed.

and yes, electrical work is very dangerous. That is why most here do take it very seriously and do what they can to make sure correct info is provided.
 
#4 ·
hpp58,

Could you please elaborate? When I read 240.4(D) it says nothing about dedicated circuits and seems to me to state very clearly that 14 ga. is limited to 15 amps.
 
#6 ·
This is one of those instances where the manufacturer's recommendation is wrong. If it is a heater/vent (no light) you need to use 12/3 w/g on a 20A circuit. Using 14ga on a 20A is not permitted in this situation.
 
#7 ·
Randy

More accurately 240.4(D) restricts the protection of 14 awg to a 15 amp circuit breaker in your case. 14 awg copper is rated at 20 amps (table 310.16). There are situations where you can put a 20 amp breaker on 14 awg copper however this heater/vent combo is not one of them.

What is the model#?
 
#9 · (Edited)
Yeah it appears to be a screw up...not all that uncommon. I posted the links to nutone and at the bottom it shows the specification sheet and installation guide.

The specifications sheet says connect to a dedicated 15 amp branch circuit.

The installation guide says in bold type to be sure to use a 20 amp branch circuit.

http://www.nutone.com/product-detail.asp?ProductID=10150
 
#10 ·
I should add that the unit operates at 11.5 amps total. The heater is 1300 watts which makes it 10.8 amps and the motor would be another 3/4 of an amp or so. Since this is fixed space heat the heater would require conductors rated 13.5 amps. So a 15 amp branch circuit will do the trick.
 
#12 ·
I'm new here, but some of this info being presented by so called "contractors" is poor at best. These DIYer's are going take this info without doing any credible research and take it as gospel.

Aren't there any moderators or whatever to watch out for this mis-information. This is very dangerous.
Isn't this credible research? There are plenty of licensed electricians on the board that will catch and correct any "mis-information" that is posted.
--A conservative liberal
 
#15 ·
Thank you gentleman for pointing out my error.
I was responding to the original post, namplate information 14 gauge, 20 amp breaker.
There are some instances that you can have a 20 amp breaker on 14 gauge wire, the code allows it (see table 310.16)(422.62(B)(1)), but is only for certain applications, and/or if the manufacture specifies it.
Not in this case. I contacted Nutone and they confermed that it was a misprint and this unit should be wired with 12 gauge wire.
 
#16 ·
I'm not understanding why they want this wired with 12 awg...? It only uses 11.5 amps (heater and fan combined) and is a dedicated requirement for the branch circuit. Theres nothing wrong with 12 awg but I don't see where it is a requirement based on a fixed appliance load.
 
#17 ·
This whole thing is screwed up, and it starts with the nameplate information.
For me the amperage draw is very close to the 80% load limit on 14 gauge wire, and thats not counting the starting current of the motor. I would install the 12 gauge wire with a 20 amp breaker and not have to worry about it. This way the inspector doesn't shoot it down.
 
#18 ·
I hate manufacturer 'mistakes' like the one you encountered. I bought a door latch that came with the 'wrong' template for cutting the holes. Thankfully, it was only off by an 1/8th and the decorative plate around the knob hid the problem. Seems a lot more trivial than messing up what gauge wire/breaker.
 
#20 ·
That's why you pull permits, and get inspections.
There's another set of eyes to help you out.
With 800 pages of the the NEC and who knows how many in the UCC, I don't want to tax my brain too much. I just keep the code book with me all the time so I can refer to it.
 
#23 ·
hpp58

Thank you gentleman for pointing out my error.
I was responding to the original post, namplate information 14 gauge, 20 amp breaker.
There are some instances that you can have a 20 amp breaker on 14 gauge wire, the code allows it (see table 310.16)(422.62(B)(1)), but is only for certain applications, and/or if the manufacture specifies it.
Not in this case. I contacted Nutone and they confermed that it was a misprint and this unit should be wired with 12 gauge wire.
Again, you are wrong. Please explain how 422.62 B 1 would allow 14awg on a 20 amp breaker.

What that section states is the manufacturer can list the minimum AMPACITY (not size) of the supply conductor and the max OCPD allowed for the circuit. That does not mean they can tell you to use 14 on a 20 amp breaker. What they can tell you is they require a conductor that will carry a minimum of xx amps and the OCPD must not be greater than xx amps. That does not allow you to disregard the NEC and their limitations they impose on the conductors.

and to the continuous load rating and your statement of:

Can it run for three hrs?
Chances are it won't, but it could.
NEC defines a continuous load as one that is EXPECTED to run for 3 hours or more.

By your own statement, the appliance would not be a continuous load.

For me the amperage draw is very close to the 80% load limit on 14 gauge wire,
14 awg does not have a load limit of, what I believe you are referring to, 15 amps. Depending upon the type of wire used, it varies. thhn actually has a rating of 25 amps. The 80% you speak of would be concerning the OCPD which by code, is limited, except is a few situations, to 15 amps on a #14 wire.

stubbies post:


Yeah it appears to be a screw up...not all that uncommon. I posted the links to nutone and at the bottom it shows the specification sheet and installation guide.

The specifications sheet says connect to a dedicated 15 amp branch circuit.

The installation guide says in bold type to be sure to use a 20 amp branch circuit.

http://www.nutone.com/product-detail...roductID=10150
Ok, it does give different ampacities of circuits required but I could find nothing in either piece of literature that specified a wire of any size, let alone an incorrect wire size.

So randall, where did you get the wire size recommendation?
 
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