Taps, ranges, ovens and dryers

Status
Not open for further replies.
D

dellphinus

Member
Location
Southern Illinois, USA
Had a request to install a second dryer in a residence. We ran a separte branch circuit for it, no problems, room in the box for new breakers, etc.

But afterward, got to wondering; it's allowable to run a circuit for a cooktop and oven, and tap both of them to the branch circuit. Why (technically) is that any different than running two dryers off one circuit, and tapping the receptacles off the branch circuit, as long as the branch and breaker was sized for both dryers as continuous loads?

Just curious.
 
Re: Taps, ranges, ovens and dryers

I can't think of any reason you couldn't do that. The breaker and conductors would have to be sized to handle the start of the second dryer while the first is running, but that should be possible. What I don't know is whether the size of the usual circuit for a dryer could handle a seond dryer, if the homeowner wants to install one on some future date. I would guess that a second circuit would normally be needed, because the first won't have enough capacity to add a second dryer.
 
Re: Taps, ranges, ovens and dryers

If you size the circuit to handle two dryers you will then have to up size the receptacles, cord caps, cords etc.

I believe you will also end up with an overcurrent device larger than UL tested the appliance with.

The wiring in the appliance may not be adequate to open the larger overcurrent device.
 
Re: Taps, ranges, ovens and dryers

OK, I think I can see how 210.21(B)(3) might be a stopper. But that was not easy for a lowly engineer to prove to himself. For starters, I have always had a gas dryer, and I think its circuit is only 20 amps. And of course, I have never installed a dryer circuit, so there are things I would not have known. Like the available rating sizes for dryer receptacles.

If I had two dryers that each pulled only 18 amps, I had thought that it would be possible to feed them both with a single 40 amp circuit. The load on each receptacle would have been 18 amps, the total load would be 36 amps. Dryers don?t run continuously for 3 hours, so they need not be called continuous loads. (Or is that a topic for a separate discussion?) So long as I could find two dryer receptacles rated at 40 amps, Table 210.21(B)(3) would have been satisfied.

Then I saw 220.18 raising its hand. No matter what the dryer actually draws, its load has to be computed at 5000 VA, or about 20.8 amps. Two of them would have a load of 41.6 amps. To feed a pair of such receptacles, the circuit and the receptacles would have to be rated at 50 amps. Am I right in guessing that nobody makes a dryer receptacle rated at 50 amps. Is that the reason this installation can?t be done?
 
Re: Taps, ranges, ovens and dryers

Originally posted by cs409:
hotlegs quoted
are you licensed, bonded, and insured?
Click to expand...
where did that come from and what does that have to do with the post?
Click to expand...
Dell has been a member of this forum as far back as I can recall, meaning a few years and the old, old forum.
 
Re: Taps, ranges, ovens and dryers

In all fairness and in defense of CharlieB, I see a real legit thought on putting side by side electrical dryers in residential. I myself have installed at least 3 dozen single 5Kva units at one time or another and just the thought of arranging room for the exhaust hookup challenges the mind.
The DP 50A breaker and 6-3nm line is easy but setting up the parallel load physical connection is the trick. Two paralleled single four squares using NEMA 14-30 receptacles with 6-3 (x2) in the upstream box is beyond maximum wire fill allowance let alone making the terminal connections and heat rating feasible. If there is a larger box that can take a standard 4 sq mudring..I don't know of one that exists. So running two 10-3 branch circuits may be the practical answer. Any thoughts?
rbj
 
Re: Taps, ranges, ovens and dryers

I myself at times have seen a need for second dryer.My thinking says just pull both sets of 10-3 at same time unless we are lacking breaker space.Only other way would be a small sub panel and i dought that would be cheaper.
 
Re: Taps, ranges, ovens and dryers

The original post asked what the diffence between this and the exception permitted by 210.19 is. In my opinion, 210.19 exception is there because you have a 50 amp circuit for a range...you just have the two components (cooktop and oven) of a range isolated from each other, but you stil basically have one range. With two dryers that is not the case.
 
Re: Taps, ranges, ovens and dryers

Originally posted by hotlegs: are you licensed, bonded, and insured?
Click to expand...
Are you asking that question of me? If so, the answers are,
</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Yes I am licensed. I am a licensed Professional Engineer (in 6 States), and a licensed Electrical Administrator in Washington State. I also have a license as an Elec Trainee in Washington. But I don?t have any work experience as an electrician, and I will probably let that license lapse.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">No I am not bonded, but nothing requires me to be bonded.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Yes I am insured. I am covered under my company?s Professional Insurance for Errors and Omissions.</font>
<font size="2" face="Verdana, Helvetica, sans-serif">Did that answer your question? May I now ask why you asked that question?
 
Re: Taps, ranges, ovens and dryers

Originally posted by ryan_618:
The original post asked what the diffence between this and the exception permitted by 210.19 is. In my opinion, 210.19 exception is there because you have a 50 amp circuit for a range...you just have the two components (cooktop and oven) of a range isolated from each other, but you stil basically have one range. With two dryers that is not the case.
Click to expand...
BINGO! That's what I was looking for!

Just to clarify a few things:

We did pull a separate 30 amp branch.
Had there not been sufficient space in the box, we would've added a sub and fed two separate branches from it.
Rural Illinois does not require licensing, bonding, or insurance, and most of the work you see around here reflects that.
I was just curious as to what would prevent you from wiring it like a cooktop/oven, technically. I knew it was not allowed.

Thanks again all.
 
Status
Not open for further replies.
Top