Wiring questions

[Itzkwik]

I'm in the process of roughing in the wiring in the garage. Trying to save a few bucks before the electrician gets here. I want to have all the wiring in place so he just has to hook up the panel box/meter, etc. The compressors I'm looking at are true 5hp. Should draw about 22 amps. I know I'll need 30 amp circuit. For 30 amp/240 do I need 10/2 or 10/3 wire?
Also want to wire for a welder so its ready when I get some extra cash. I'm looking at the Miller 175. What size wire and breaker will I need for this welder?
Thanks,
Bret

 

[Charles (in GA)]

I'm in the process of roughing in the wiring in the garage. Trying to save a few bucks before the electrician gets here. I want to have all the wiring in place so he just has to hook up the panel box/meter, etc. The compressors I'm looking at are true 5hp. Should draw about 22 amps. I know I'll need 30 amp circuit. For 30 amp/240 do I need 10/2 or 10/3 wire?
Also want to wire for a welder so its ready when I get some extra cash. I'm looking at the Miller 175. What size wire and breaker will I need for this welder?
Thanks,
Bret

Odds are, the compressor doesn't use the netural, so all you would need is 10/2 with a ground. Make sure you re-mark the white wire ends to red. Its rare to see something like this with a netural. If you are not sure, I'd run the 10/3 w/grd and you can always fold back the netural. Might need it someday if you use the circuit for something else.

Something to consider, Compressors have high start up current draw. You are much better off to oversize the wire if there is any doubt. Also, this may not be the last compressor you ever own, you might get the itch to buy something bigger, so consider that when running wires. If the run is not too long, even 6 gauge wire would be good, then you could hook up something as big as a true 7.5 hp compressor in the future. Yes, it might cost more now, but will save hassles in the future.

I assume you are talking of a Millermatic 175 MIG welder. According to the specs on the Miller web site.........

Input Power

* Requires 1-Phase Power
* 230 V, 19.5 A, 60 Hz

So again, you will need a 30 amp breaker, and 10/2 or 10/3 wire. If the runs are very long, you need to consult the appropriate charts and tables for voltage drop, to determine if you need to possibly use 8 gauge instead of 10.

Charles

 

[Itzkwik]

Charles, thanks for the quick reply. The run for both will be about 50'. Guess I'll go with 8/3 wire for "just in case". The 12/2 Romex for the recepticles was kind of a pain to pull. Can't wait to see how much fun the 8 will be. And yes, its the Millermatic 175 I'm thinking of getting.

 

[Ironcrow]

Charles, thanks for the quick reply. The run for both will be about 50'. Guess I'll go with 8/3 wire for "just in case". The 12/2 Romex for the recepticles was kind of a pain to pull. Can't wait to see how much fun the 8 will be. And yes, its the Millermatic 175 I'm thinking of getting.

Yeah, I just did this. 8/3 seems like a good choice for you. I used 6/3 on a 50A breaker, pulled it down to a subpanel with a 30A breaker for the welder receptacle. My run was 100 ft. Just like you never regret making sure the wire gauge is generous, if you are pulling it through conduit...well, I always oversize the conduit too. Costs a little more but it sure makes pulling easier. And if worst comes to worst, and you want more wire in the conduit, there's room.

 

[sberry]

Both of those appliances run from a 10/2 wire and 30A breaker. 50 ft isnt too far especially for that welder. Id you went to 8 it is overkill but would allow for use with larger machines with simple breaker changes. In fact with dedicated circuits you could anyway but that is another story. Technically the little Miller will run from a 14 wire with a 30A max breaker or with 50 A circuits if the wire is larger but the receptical listed for it is only approved with 10 and up wire. The manual that comes with the machine can be very confusing without some code background and NEMA understanding, I wish they would re-write it and up the min wire size one especially considering the way they are marketed to hobby types.

 

[Rrumbler]

Minimum wire size for 30 amps is 10; if you are running romex, use 10/3 with ground - that would be a black, red, white, and a bare copper. My rule of thumb is to go up one size for fifty feet or over, up to 100', then up another. If you are going to wire with #8, I'd recomend using conduit - use 3/4 inch flex if it's going to be inside the wall, and pulling individual wires, rather than using sheathed cable. Overkill?? Only if you never need to upgrade, or repair. The added expense is worth the benefit to be gained. That's a thumbnail view from my forty years of chasing killywiggles and bending wire.

 

[Stuart in MN]

What Sberry said about the wire size for a welder circuit comes from Article 630 of the National Electric Code - for a dedicated welder circuit, the wire can sometimes be undersized, depending on the duty cycle rating of the welder. The trouble is that sometime down the road someone will come along and want to plug in some other piece of equipment that is continuous duty, and then the wire size will be inadequate. For a home shop it makes sense to stick with full size wire.

As mentioned, 10awg wire would be fine for this application but 8awg won't hurt anything, it'll just cost more and be a little harder to install. Generally, I find that voltage drop is not a problem for distances less than 75 or 100 feet, but it is a good idea to check it anyway if you're not sure - there are a number of online voltage drop calculators out there that make it easy to do.

On occasion I design electrical systems with branch circuits that are a couple thousand feet long...voltage drop suddenly becomes a pretty big deal in those situations.

 

[bobbyd]

my forty years of chasing killywiggles

I guess what happens in Vegas, stays in Vegas.

 

[Itzkwik]

Thanks for the replies. I went with the 8awg. Picked it up on the way home today. Damn, wire prices are going crazy. I bought a 250' roll of 12/2 Romex two weeks ago for $78 at Home Depot. Looked today and it was $111. Are the prices nutts everywhere or just at my HD?

 

[Dave Carney]

Thanks for the replies. I went with the 8awg. Picked it up on the way home today. Damn, wire prices are going crazy. I bought a 250' roll of 12/2 Romex two weeks ago for $78 at Home Depot. Looked today and it was $111. Are the prices nutts everywhere or just at my HD?

Same here. I bought last month and now I wish I would have bought more. It's going up so fast I need to buy some just for an investment.

 

[Der Bugmeister]

They're nuts everywhere. If I had bought the wire 2 months ago when I started checking prices, I probably would have saved a couple hundred dollars.

Local cops just did a sting operation on scrap metal yards for buying stolen material - aluminum ladders (some stolen from the fire department), copper cable stolen from service companies...including cable actually in use! It's crazy...the payback for selling stolen metal is more lucrative than holding up a convenience store!

http://www.canada.com/globaltv/bc/news/story.html?id=1324b064-abc9-48ea-8f46-e9fd471b147e&k=1601

 

[Dave Carney]

Found a Lowes who hadn't taken last weeks price increase yet. 250' 10/2 with ground $149. 250' 12/2 with ground $102.