4

I want to add a washer & dryer to my garage, but breaker box is on the wrong side of house. No matter which way I run the wire, its 110 feet of wire required.

Will 8-3 with ground work?

Or is the run too long and I need to have 6-3 with ground?

ArchonOSX
  • 19,804
  • 3
  • 29
  • 50
Rollie Meloy
  • 41
  • 1
  • 1
  • 2
  • 2
    How many amps will your dryer require? – BMitch May 01 '16 at 13:25
  • Depends on the dryer. While the "standard electric resistance heat dryer" needs a 30A-240V outlet, you could potentially save quite a bit on the install and operation by getting a (more expensive to buy) heat-pump dryer that happily runs on 15A or 20A of 120 or 240V (depending on specific model) (and also skips the need for a vent, in many/most cases.) Given your question, gas is not a heat option? – Ecnerwal Oct 10 '21 at 17:12

3 Answers3

3

10/3 is FINE for the dryer. 12/2 for the washer.

Speedy Petey
  • 16,413
  • 2
  • 28
  • 50
3

Typically a 220v/30 amp Dryer circuit would utilize 10/3 with ground.

According to this voltage drop table, it looks like for 100' run you would want to up-size the wire to #8 copper, to maintain voltage drop less than 3%.

So you have arrived at the correct conclusion within your question to use 8/3 with ground.

Tyson
  • 4,230
  • 1
  • 18
  • 27
  • "220V" is a generic term, although it is incorrect. 240V would be correct, but a typical electric dryer in North America would be 120/240V. ....Also, 5% would be perfectly acceptable for this type of circuit. – Speedy Petey May 01 '16 at 20:00
  • I based the text of the answer (220v) on the table heading to avoid confusion. @SpeedyPetey – Tyson May 01 '16 at 20:02
  • The NEC recommends the voltage drop be limited to 3% for branch circuits or feeders and 5% for both. This this is always contained in an informational note so it is not an enforceable part of the code but it is advisable. So, 5% for a branch circuit is too high according to the Code but 5% for the entire circuit from the service to receptacle is acceptable. – ArchonOSX May 07 '16 at 11:29
  • I'd have to agree with Tyson. A 100 foot run in commercial / industrial work is usually required by the job specifications to be upsized one wire size. This is a good general rule of thumb to follow. – ArchonOSX May 07 '16 at 11:35
2

Depending on whether you have an electrical dryer or a gas dryer, the answer will be different. I am going to assume you are in the US, and using an electrical dryer. Then the calculation goes like this:

Assuming you have an electrical dryer, typical power use might be anywhere from 1800 W to 5000 W source. But let's assume the dryer you have is right at the limit of your electrical circuit - that is a 30 A, 240 V dedicated circuit. I will compute the voltage and power drop resulting from using different gages of wire, assuming that current (which is high... more likely the current is somewhere between 8 or 22 A).

Resistance of 220 (round trip!) feet of wire source and associated voltage drop and power loss (assuming 30 A current):

AWG      Ohms      Drop(V)   Power loss
  6     0.087       2.61       2.2%
  8     0.138       4.14       3.5%
 10     0.220       6.60       5.5%
 12     0.349      10.47       8.7%

The voltage drop you will get is current times resistance (V = I x R), for example 30 x 0.087 ~ 2.61 V. The power drop goes as the square of the voltage drop, so if you lose 1% of voltage to the dryer, you lose 2% of power.

According to the National Electrical Code, you need to use 10 AWG or better to carry 30 A safely::

enter image description here

But just because it's code doesn't mean your dryer will be working well. All that power going into heating the wire and not drying the clothes - that's probably not what you want.

Do be careful about making sure that your wire "can breathe". If you bury it under carpets etc, it will get MUCH hotter because the heat won't be able to get away. To be safe, I would probably go with the 8 AWG wire and make sure all the power ends up drying clothes, not heating the wires.

Floris
  • 131
  • 4
  • Typical power for an electric dryer IS NOT 1800 watts. Even your link says 1800-5000 W with typical being 3000 watts. ...... I have yet to see a typical full-sized electric dryer that required less than a 30A circuit. – Speedy Petey May 01 '16 at 19:59
  • @SpeedyPetey - you're right, I updated for the whole range of power from 1800 to 5000. But since the original question didn't specify the wattage, it's hard to give a definitive answer. Better to show the method. – Floris May 01 '16 at 20:03
  • Oh no, thats wrong. Most dryers demand a dedicated 30A circuit. If they don't actually draw 30A, they require a de-rate that requires you to compute load as if they do. That's because they are engineered to the alllowed limits of a 30A circuit - makers would prefer to go higher still, because even at 30A they are slow to dry compared to gas. Your thoroughness is admirable, but please! Recompute for an honest 7200W (240V x 30A). – Harper - Reinstate Monica May 02 '16 at 02:34
  • That site led you wrong on the estimate of dryer energy use, That is talking about money, trying to provide universal, dumb-down explanation of how appliances affect your electric bill, based on averages from survey data and averaging both gas and electric dryers, and then normalizing to "minutes per day". These are the same people who say a 150MW generator can power 100,000 homes. – Harper - Reinstate Monica May 02 '16 at 02:50
  • According to this link the GE GTDP490EDWS 7 cu ft (pretty big) electric dryer draws 22 A. – Floris May 02 '16 at 03:01
  • @Harper I have updated the calculation for 30 A - although I don't believe there are any domestic dryers that actually go that high in current draw. But as you point out, that's what the dedicated circuit is rated for. – Floris May 02 '16 at 03:08
  • 1
    @Floris 22A or 23A is typical for dryers and hot water heaters. Code requires a derate so you multiply by 125%, so, 27.5A to 28.75A. See how that nicely dovetails to a 30A dedicated circuit. By design. You don't to get to throw in a bunch of fudge factors, because a committee of pretty smart people who look at fire reports all day, have already done so and written NEC. – Harper - Reinstate Monica May 02 '16 at 03:47
  • @Harper - yes, that makes sense. And working from the dedicated circuit rating also seems like a better decision than trying to figure this out from a "possible rating of this dryer" - you never know what it's going to be replaced with when this one gives us the ghost. So "compute for the circuit, not the appliance" is actually the only right approach. I see that now. – Floris May 02 '16 at 03:50
  • 2
    Yes, coming from an EE perspective, code electrical is a perplexing beast, full of strange idioms, awful compromises and clever hacks. Eventually you go "OH. That's why they do that." The committee does have EEs but also boots-on-ground code electricians, fire inspectors, insurers, manufacturers and homebuilders. Oh, and lawyers, as civil liability is a factor too. An astonishing amount of, well not engineering exactly, but "grand design" has gone into keeping things K.I.S.S., partly to minimize arguments between electricians and code inspectors. – Harper - Reinstate Monica May 02 '16 at 04:09
  • The 125% rule of thumb is for continuous loads. Those loads that continue for 3 hours or more. Most dryers wouldn't be run for that long continuously. Very few loads (if any) in a house would qualify as continuous. – ArchonOSX May 07 '16 at 11:25