Wire size: water heater, stove, dryer

green.bubbly · Feb 21, 2012

Water Heater is 4500 watts; 10/2 wire

Stove calls for 6/3 wire

Dryer draws 26 amps; 10/3 wire

Is there any reason to up the wire size? I not sure if some stoves or dryers draw more current or is this pretty typical of these devices. I am just thinking down the road if I ever needed to replace these devices, I would hate to be limited in selection because of wire size.

Norcal · Feb 21, 2012

There is no reason to go larger, & if you do you will run afoul of 250.122(B)

(B) Increased in Size. Where ungrounded conductors are
increased in size, equipment grounding conductors, where
installed, shall be increased in size proportionately according
to the circular mil area of the ungrounded conductors. 2008 NEC

In order to upsize you would have to run it in conduit, as the grounding conductor will be too small with NM cable.

Gary S · Feb 21, 2012

These devices are all heating devices, so I see no need to upsize wire to them.

The only place I upsize wires is to devices with large motors. The motor inrush current at startup is easily 2-3x running current, and upsizing wire to a motor results in faster starts and longer life.

green.bubbly · Feb 21, 2012

Norcal said:
There is no reason to go larger, & if you do you will run afoul of 250.122(B)

(B) Increased in Size. Where ungrounded conductors are
increased in size, equipment grounding conductors, where
installed, shall be increased in size proportionately according
to the circular mil area of the ungrounded conductors. 2008 NEC

In order to upsize you would have to run it in conduit, as the grounding conductor will be too small with NM cable.

That confused me, which is not really surprising.

I understand the basic rule, the larger the ungrounded conductor, the larger the ground required. If ran 8/2 NM instead of 10/2 wire, would the ground wire not be sized correctly?

...or am I not understanding the "equipment grounding conductors" term?

pattenp · Feb 21, 2012

The supply wire sizes you listed for those devices are the industry standard.

ishiboo · Feb 21, 2012

green.bubbly said:
That confused me, which is not really surprising.

I understand the basic rule, the larger the ungrounded conductor, the larger the ground required. If ran 8/2 NM instead of 10/2 wire, would the ground wire not be sized correctly?

...or am I not understanding the "equipment grounding conductors" term?

Because it's misapplied, being that the NEC is not entirely clear.

The purpose of that particular section is that if you upsize the current-carrying conductors (normally done due to voltage drop concerns on a long run), you upsize the ground as well to one properly sized for the current-carrying conductors and NOT the load. I believe the only purpose of this is that if someone in the future wants to put a larger breaker on, they're not limited by (or overloading) the small ground.

So, if you were going to run 10/2 NM and you chose 8/2 NM instead, the ground in it is already appropriately sized.

There is no reason to go larger

Unless there are voltage drop concerns based on a long run, we have no idea if this is a 10' run with a 26 amp dryer on 10-3, or if it's a 200' run with a 26 amp dryer on 10-3.

green.bubbly · Feb 21, 2012

ishiboo said:
Because it's misapplied, being that the NEC is not entirely clear.

The purpose of that particular section is that if you upsize the current-carrying conductors (normally done due to voltage drop concerns on a long run), you upsize the ground as well to one properly sized for the current-carrying conductors and NOT the load. I believe the only purpose of this is that if someone in the future wants to put a larger breaker on, they're not limited by (or overloading) the small ground.

So, if you were going to run 10/2 NM and you chose 8/2 NM instead, the ground in it is already appropriately sized.

Unless there are voltage drop concerns based on a long run, we have no idea if this is a 10' run with a 26 amp dryer on 10-3, or if it's a 200' run with a 26 amp dryer on 10-3.

That makes sense. So if I were running single 8 gauge THHN wires, I would have to include a ground wire rated for the 8 gauge conductors and not the 10 gauge required by the load.

FYI, my dryer run is only 22 feet.

Norcal · Feb 21, 2012

If you upsize the ungrounded conductor for ANY reason you have to upsize the grounding conductor, 125.122(B) trumps everything, if you use a 8/2 NM cable where the load is fine W/ 10/2 NM the 10 AWG grounding conductor is too small, no good deed goes unpunished........

BTW, it used to be just if upsized for voltage drop, but that changed a few code cycles back.

MrMark · Feb 21, 2012

man, what kind of stove is that? I think mine would run on 12/3. I did use 8/3 as a recall - total overkill. But 6/3? That is quite a lot of amps there. Without looking I'm going to guess 50. That must be one hell of a stove.

6768rogues · Feb 21, 2012

Use the wire you listed. Typical residential appliances all have the same requirements. The only reason to upsize is if you have a long distance to run the wires.

PRH44 · Feb 21, 2012

I have a 13.5 KW. its nothing special single oven

MrMark · Feb 22, 2012

PRH44 said:
I have a 13.5 KW. its nothing special single oven

I don't get it. Mine is a 2.7 KW Jennair single oven. A built in convection oven, not a range. How could there be such a difference?

green.bubbly · Feb 22, 2012

Kenmore Range. I am not sure what the difference is between the upper set of numbers and the lower set.

oleguy · Feb 22, 2012

the diff.is wattage and operating voltage.if your range is as in the top,you can use a 40 or 50 amp ckt.bottom set says if you are useing a range that is 16.6kw to 22.5 kw you need a 50 amp ckt.

green.bubbly · Feb 22, 2012

oleguy said:
the diff.is wattage and operating voltage.if your range is as in the top,you can use a 40 or 50 amp ckt.bottom set says if you are useing a range that is 16.6kw to 22.5 kw you need a 50 amp ckt.

Ahh, ok. So the instructions cover multiple models and I need to check my range data plate and see what it is rated at.

That sure had me scratching my head trying to figure that one out.

Thanks.

MrMark · Feb 22, 2012

I'm really confused now. I have a 30 inch Jenn Air wall over built in. It's rating plate says 2.7 KW, which is around 11 amps @ 240. I put number 8 on for total overkill and a downsized 30 amp breaker rather than the 40. I had the 30 I guess. Anyway, I clamped it and it's 11 amps. No surprise.

So how is it possible that this oven only runs 11 amps and the ones in this thread are around 50 amps? Doesn't make sense.

SGKent · Feb 22, 2012

depends on efficiency and number of elements. 11 amps at 240 is about double a hair dryer so that sounds low although you are clamping it. At 11 amps do you have both ovens on and all the burners on high? Maybe you have just an OVEN and he has a RANGE/STOVE with burners too.

MrMark · Feb 22, 2012

SGKent said:
depends on efficiency and number of elements. 11 amps at 240 is about double a hair dryer so that sounds low although you are clamping it. At 11 amps do you have both ovens on and all the burners on high? Maybe you have just an OVEN and he has a RANGE/STOVE with burners too.

Just a single wall oven. That's what I was thinking that he must have a range with burners and that the burners are what can create such an enormous demand.

green.bubbly · Feb 22, 2012

Correct, four burner with an oven. One burner is a 12"

ishiboo · Feb 22, 2012

MrMark said:
man, what kind of stove is that? I think mine would run on 12/3. I did use 8/3 as a recall - total overkill. But 6/3? That is quite a lot of amps there. Without looking I'm going to guess 50. That must be one hell of a stove.

8/3 is the typical minimum for a residential stove. (Burners + single oven). Many require 6/3.

I have never seen an electric stove wired with 10/3 or less.

MrMark · Feb 22, 2012

ishiboo said:
8/3 is the typical minimum for a residential stove. (Burners + single oven). Many require 6/3.

I have never seen an electric stove wired with 10/3 or less.

Yeah, I'm getting that now. I have never had an electric "stove" with the burners, just the wall oven with the gas cooktop. I am very glad to find this info though as I am doing another house that I want to set up for potential all electric oven (however remote). The burners must eat power. Makes sense now that 4 burners are like 4 little ovens. Anyway, with the price of wire I was thinking 8/3 (it is a long run) but a guess I should do 6/3 to be safe.

Thanks this is a good thread.

ishiboo · Feb 22, 2012

MrMark said:
Yeah, I'm getting that now. I have never had an electric "stove" with the burners, just the wall oven with the gas cooktop. I am very glad to find this info though as I am doing another house that I want to set up for potential all electric oven (however remote). The burners must eat power. Makes sense now that 4 burners are like 4 little ovens. Anyway, with the price of wire I was thinking 8/3 (it is a long run) but a guess I should do 6/3 to be safe.

Thanks this is a good thread.

That'll do it... gas is the way to go :thumb up: Burners **** a lot of juice. I think a single burner is more than an oven, since an oven pre-heats and is insulated/etc., the burner must cook something in open air. Maybe that's more duty cycle than current though.

green.bubbly · Feb 23, 2012

Alright, here is an update. I ripped the box off the range to find the darn data plate. I now fully understand the figures given in the manual. At first, I did not realize that the manual was giving the electrical data for multiple models. The manual was basically stating that if your particular stove was was rated to use between 8.8 and 16.5kW (120/240) than you can use a 40 amp. But if your particular range was rated to draw between 16.6 and 22.5, then you must use the 50 amp protection.

Thanks oleguy for helping me understand those numbers.

Back to my data plate. My particular range draws 11.3kW. Now I am back to being confused again. Why would I need a breaker rated at 40 amps? The manual states that if I draw between 8.8 and 16.5kW, I can use a 40 or a 50 amp breaker...

P/V = A

11,300/240 = 47A

If I figured this right, at full power, this range would draw 47 amps on a circuit that is protected at 40 amps. Even if I went with a 50A breaker, that would still be under rated???

MrMark · Feb 23, 2012

I guess they are figuring you would never have absolutely everything full blast at once for more than a very small time.

I would use a 50 amp breaker.

PRH44 · Feb 23, 2012

Range nameplate KWs are subject to demand factors.
Ranges 3.5KW up to 8.75KW are calculated at 80 percent.
Over 8.75 up to 12 KW will have a maximum demand of 8 KW.
Greater than 12KW but no more than 27KW are calculated as follows:
Each KW over 12 will add 5 percent to the 8KW demand.

Clear as mud

green.bubbly · Feb 23, 2012

PRH44 said:
Range nameplate KWs are subject to demand factors.
Ranges 3.5KW up to 8.75KW are calculated at 80 percent.
Over 8.75 up to 12 KW will have a maximum demand of 8 KW.
Greater than 12KW but no more than 27KW are calculated as follows:
Each KW over 12 will add 5 percent to the 8KW demand.

Clear as mud

Don't know how I missed that. :willy_nil

Wire size: water heater, stove, dryer

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