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Clothes Dryer Circuit Breaker Size

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[#1] Posted: 10/16/2009 - 04:30:26 AM
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Practically all of the electric clothes dryers I have observed have had 30 amp double pole circuit breakers protecting their circuits, and I have read somewhere that a 30 amp circuit breaker is considered the minimum size required for the dryer circuit.

In yesterday's inspection the dryer had a 40 amp double pole circuit breaker and the cable was 6 AL.

What should be my standard practice when I observe this?

Should this be called out for further evaluation when the electrician is at the home to correct all of the other routine wiring issues?

Or is there another standard method I should be using to determine what the proper circuit breaker size is for an installed dryer?

For example - should I be going online or contacting the manufacturer?

Should I pulling the dryer away from the wall in order to look for listing and labeling?






Dave Tontarski
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Clothes Dryer Circuit Breaker Size
[#2] Posted: 10/16/2009 - 06:31:27 AM
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Practically all of the electric clothes dryers I have observed have had 30 amp double pole circuit breakers protecting their circuits, and I have read somewhere that a 30 amp circuit breaker is considered the minimum size required for the dryer circuit.

In yesterday's inspection the dryer had a 40 amp double pole circuit breaker and the cable was 6 AL.
uh, ok?
What should be my standard practice when I observe this?
whistle and utter "oh boy"
Should this be called out for further evaluation when the electrician is at the home to correct all of the other routine wiring issues?
Why?
Or is there another standard method I should be using to determine what the proper circuit breaker size is for an installed dryer?is the dryer really installed or is it plugged in?

For example - should I be going online or contacting the manufacturer?
You're awfully interested in dryers
Should I pulling the dryer away from the wall in order to look for listing and labeling? There will be a lot of lint and dust back there


Chad Fabry
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Clothes Dryer Circuit Breaker Size
[#3] Posted: 10/16/2009 - 06:56:22 AM
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Chad -

I read somewhere that a 30 amp cb was the minimum size, but that some dryers required a 40 or a 50.

What I was trying to get a better understanding of was how do I know what the manufacturer's requirements are for a particular dryer?

AC manufacturers list min-max cb sizes and these are generally clearly visibly labeled on the units.

Seems to me that if a dryer manufacturer listed that their unit required a 30 amp cb and that if a 40 amp cb is installed that this should be considered an issue.

Based on your response.....am I hearing that providing the cable has the proper OCP - that is doesn't matter what the dryer manufucturer requires? Or that perhaps dryer manufacturers list a min/max range as well?

I'm just looking for a better unstanding.

Thanks -

Dave

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Clothes Dryer Circuit Breaker Size
[#4] Posted: 10/16/2009 - 07:40:41 AM
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Hi Dave,

It really doesn't matter whether it's a 20, 30, 40 or 50 amp breaker; just look at the size of the conductors connected to the breaker and make sure that the conductors can safely carry at least the amperage of the breaker without being toasted.

So, if it's a 240-volt 30-amp breaker, #10 copper/#8 aluminum or larger is good but smaller is bad; if it's a 40-amp breaker, #8 copper/#4 aluminum or larger is good but smaller is bad, etc.

As long as it's properly sized and installed correctly there isn't anything to report. Now, if I had a dryer running off of a 30 amp breaker with 12-gauge conductors, and the breaker wasn't tripping and the conductors looked fine, without any sign of overheating, I'd be mildly curious as to whether or not that dryer was pulling less than 20-amps but I wouldn't waste my time trying to find a data plate, I'd just write it up as having undersized conductors and I'd move onto the next item.

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Mike

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[#5] Posted: 10/16/2009 - 07:59:56 AM
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Dave,

I've come across this a few times.

Each time, the appliance manufacturer's instructions clearly stated a 30 amp breaker is required. Not minimum or maximum, just 30 amp period.

Bill Kibbel, Historic & Commercial Building Inspections - Old House Resources
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[#6] Posted: 10/16/2009 - 08:19:58 AM
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Thanks -

My situation was that as I was calling out panel issues, I mentioned that dryers generally require a 30 amp 240 volt circuit breaker. As I was recommending a number of other issues be corrected, I recommend that the electrician evaluate this while he was at the home.

Then the client called me and wanted me to state that it was wrong and needed replacement. I told them that I could not do that without seeing the dryer's installation manual.

I just wanted to assure that I did the right thing.

If the majority opinion was that I was remiss for not further investigating this myself so that I could report this as wrong with certainty (due to the manufacturer's requirements), then I wanted to mend my ways.

So far the majority opinion seems to be that I should of not have even brought it up.

Thanks again.

Dave Tontarski
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Clothes Dryer Circuit Breaker Size
[#7] Posted: 10/16/2009 - 08:41:26 AM
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Gentlemen:

Please see Section 210.3 for branch circuit ratings, and Section 220.54 for Electric Clothes Dryers — Dwelling Unit(s).

Question:

Was the dryer cord and plug connected? If so, that cord cap and receptacle should be rated at 30 amperes which is typical for that type of equipment.

I have discovered where an electric range was installed and protected by the circuit you describe; and where that range was replaced with the electric dryer. Just another item to check. Also, I recall at some terminations where they call for copper only so that would be another item to check, or verify AL/CU identification at the lugs.


Joe Tedesco, NEC Consultant
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[#8] Posted: 10/16/2009 - 09:22:27 AM
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Hi Joe,

Well, since we're not all electricians, couldn't you just explain it and break it down to terms and concepts we can easily understand instead of pointing to a code cite?

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Clothes Dryer Circuit Breaker Size
[#9] Posted: 10/16/2009 - 3:57:35 PM
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210.3 Rating. Branch circuits recognized by this article
shall be rated in accordance with the maximum permitted
ampere rating or setting of the overcurrent device. The rating
for other than individual branch circuits shall be 15, 20,
30, 40, and 50 amperes. Where conductors of higher ampacity
are used for any reason, the ampere rating or setting
of the specified overcurrent device shall determine the circuit
rating.


220.54 Electric Clothes Dryers — Dwelling Unit(s). The
load for household electric clothes dryers in a dwelling
unit(s) shall be either 5000 watts (volt-amperes) or the
nameplate rating, whichever is larger, for each dryer
served.

Joe Tedesco, NEC Consultant
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Clothes Dryer Circuit Breaker Size
[#10] Posted: 10/16/2009 - 4:21:26 PM
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Quote: Originally posted by Joe Tedesco

210.3 Rating. Branch circuits recognized by this article
shall be rated in accordance with the maximum permitted
ampere rating or setting of the overcurrent device. The rating
for other than individual branch circuits shall be 15, 20,
30, 40, and 50 amperes. Where conductors of higher ampacity
are used for any reason, the ampere rating or setting
of the specified overcurrent device shall determine the circuit
rating.


220.54 Electric Clothes Dryers — Dwelling Unit(s). The
load for household electric clothes dryers in a dwelling
unit(s) shall be either 5000 watts (volt-amperes) or the
nameplate rating, whichever is larger, for each dryer
served.


Why would the NEC specify the seemingly arbitrary 21 amps (5000w/240v= 21a) for a clothes dryer rather than play it safe and simply require the 30 amp circuit most manufacturers mandate? Especially when the circuit is installed before the machine is plugged in?

Seems a little loopy to me . . .

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Clothes Dryer Circuit Breaker Size
[#11] Posted: 10/16/2009 - 4:36:39 PM
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UL Standard for Safety for Electric Clothes Dryers, UL 2158
23.12 Overcurrent protection

23.12.1 If an appliance is intended to be connected to a branch circuit rated more than 30 A, overcurrent protection shall be provided for the control circuits.





Download Attachment: Pages from 2009 White Book Final.pdf
63.45 KB

Joe Tedesco, NEC Consultant
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Clothes Dryer Circuit Breaker Size
[#12] Posted: 10/16/2009 - 10:55:08 PM
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Quote: Originally posted by dtontarski

Practically all of the electric clothes dryers I have observed have had 30 amp double pole circuit breakers protecting their circuits, and I have read somewhere that a 30 amp circuit breaker is considered the minimum size required for the dryer circuit.

There isn't anything that says it has to be a 30 amps circuit, though that's how it usually comes out. As nearly as I can tell it works like this: 220.54, that Joe posted before, is part of the section of the code that has to do with calculating the load of the service. For the purpose of calculating that load, you're supposed to consider that the dryer will use 5,000 watt or the actual nameplate rating, whichever is larger. So, as Bain noted, that leave us with a strange 21 amp requirement. But if we look at 210.23(A)(1), it tells us that a single cord & plug connected appliance can't exceed 80% of the rating of the circuit. So that brings us up to a minimum 30-amp circuit. If the actual dryer has more than 5760 watts (very rare), then you'd need an even larger circuit.


Quote: In yesterday's inspection the dryer had a 40 amp double pole circuit breaker and the cable was 6 AL.

What should be my standard practice when I observe this?

Should this be called out for further evaluation when the electrician is at the home to correct all of the other routine wiring issues?

Or is there another standard method I should be using to determine what the proper circuit breaker size is for an installed dryer?

For example - should I be going online or contacting the manufacturer?

Should I pulling the dryer away from the wall in order to look for listing and labeling?


I don't see a problem with it. The breaker is adequately sized to protect the wire. As far as I know, the dryer doesn't require a maximum breaker size such as an AC compressor does.

- Jim in Oregon

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[#13] Posted: 10/17/2009 - 04:57:56 AM
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Quote: Originally posted by Jim Katen

As far as I know, the dryer doesn't require a maximum breaker size such as an AC compressor does.

- Jim in Oregon
Like I posted above. Each time I checked the manufacturer's installation instructions, they require a 30 amp breaker. Not minimum or maximum, just 30 amp period. Should I ignore that?

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[#14] Posted: 10/17/2009 - 08:31:03 AM
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Quote: Originally posted by inspecthistoric

Quote: Originally posted by Jim Katen

As far as I know, the dryer doesn't require a maximum breaker size such as an AC compressor does.

- Jim in Oregon
Like I posted above. Each time I checked the manufacturer's installation instructions, they require a 30 amp breaker. Not minimum or maximum, just 30 amp period. Should I ignore that?


No, if the dryer manufacturer calls for a 30-amp breaker, there should be a 30-amp breaker. I wonder, though, why they don't print that information on the data plate of the dryer. Hunting down printed instructions for appliances that are as long-lived as dryers can be quite a chore.

- Jim in Oregon

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[#15] Posted: 10/17/2009 - 09:29:26 AM
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I don't get it; why would anyone really care about looking at the data plate on a dryer?

A dryer is an accessory that's not even part of the house or it's fixed electro-mechanical systems, so I'm only interested in the circuitry. As long as the cables are compatible with the breaker and the breaker is adequately sized for the typical load for a dyer (30-amps) I couldn't care less about the dryer data plate.

What am I missing here? Should we now be calling ourselves Home and Appliance inspectors?

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Mike

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[#16] Posted: 10/17/2009 - 10:43:14 AM
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Quote: Originally posted by hausdok

I don't get it; why would anyone really care about looking at the data plate on a dryer?

A dryer is an accessory that's not even part of the house or it's fixed electro-mechanical systems, so I'm only interested in the circuitry. As long as the cables are compatible with the breaker and the breaker is adequately sized for the typical load for a dyer (30-amps) I couldn't care less about the dryer data plate.

What am I missing here? Should we now be calling ourselves Home and Appliance inspectors?

I'm not suggesting that we look on the data plate on every dryer. But if what Bill says is correct, and so far, the dryer instructions that I've been able to google up have all corroborated his statement, then it's important for us to understand that. It means that every dryer circuit that we look at should be protected at 30 amps, not 25 amps and not 35 or 40 amps.

We're inspecting a circuit that has one, single purpose. It's intended to power a clothes dryer. If this thread teaches us that it has to be a 30-amp circuit, then that's a useful nugget of information.

- Jim in Oregon


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[#17] Posted: 10/17/2009 - 10:53:53 AM
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Quote: It's intended to power a clothes dryer. If this thread teaches us that it has to be a 30-amp circuit, then that's a useful nugget of information.


That's very true.

I read 210.3 early on in the thread and except for ranges/ stoves, no branch circuits larger than 30 amps in dwelling unitsare allowed unless it is specifically required by the equipment manufacturer.

I admit that my dryer circuit is 40 amps and that I occasionally use it for my MIG welder.


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Clothes Dryer Circuit Breaker Size
[#18] Posted: 10/17/2009 - 11:44:23 AM
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Quote: Originally posted by Chad Fabry
[
I admit that my dryer circuit is 40 amps and that I occasionally use it for my MIG welder.




What are you welding in the laundry room??

-Brad

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[#19] Posted: 10/17/2009 - 11:55:04 AM
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Quote: Originally posted by hausdok

What am I missing here? Should we now be calling ourselves Home and Appliance inspectors?
Mike, I don't inspect non-attached appliances. When I see something unusual in the electrical system of a home (like something other than a 30 amp rating for a dryer circuit), I'll do some research. In this case, I've found this issue several times and the research led to me reviewing some installation instructions. I was able to report the issue as something needing correction.

It would be like inspecting a very short garage and ignoring the fact that every car I've seen wouldn't fit - 'cuz we don't inspect cars.

Bill Kibbel, Historic & Commercial Building Inspections - Old House Resources
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[#20] Posted: 10/17/2009 - 12:33:36 PM
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Quote: Are we reading the same 210.3? That's not what mine says.


I must be confused but my NEC is at the office. I'll find the correct section and post it later.

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[#21] Posted: 10/20/2009 - 10:39:47 AM
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Quote: That's very true.

I read 210.3 early on in the thread and except for ranges/ stoves, no branch circuits larger than 30 amps in dwelling units are allowed unless it is specifically required by the equipment manufacturer.

I admit that my dryer circuit is 40 amps and that I occasionally use it for my MIG welder.


Ok, I was wrong about that.

I was thinking of 210.23 (C) A 40 or 50 amp branch circuit shall be permitted to supply cooking appliances that are fastened in place in any occupancy. In other than dwelling units, such circuits shall be permitted to supply fixed lighting units with heavy duty lamp holders, infrared heating units or other utilization equipment.

I interpreted the sentence that begins "In other than dwelling units..." to exclude any unspecified use for dwelling units and it doesn't.

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[#22] Posted: 10/23/2009 - 12:20:19 PM
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I may have missed it in the discussion, but the code requires all outlets to be rated for the circuit they are attached to. This means that you can not attach a 30 amp outlet to a 40 amp circuit. For information the NEC reference is 210.21 B-1.
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[#23] Posted: 10/23/2009 - 2:06:57 PM
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Quote: Originally posted by Mr. Electric

I may have missed it in the discussion, but the code requires all outlets to be rated for the circuit they are attached to. This means that you can not attach a 30 amp outlet to a 40 amp circuit. For information the NEC reference is 210.21 B-1.


Of course that applies only when there's just one receptacle on the whole circuit. Otherwise, we wouldn't be allowed to use 15-amp receptacles on 20-amp circuits.

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[#24] Posted: 10/26/2009 - 12:37:23 PM
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Very true Jim K.
Jim P. Simmons
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