220 Volt Questions

[Brian Kent]

I just ordered a 220 volt Grizzly 1023SL table saw. I went for the 3 hp Cabinet saw because I have 220 in the garage shop. Today I learned that every 220 outlet need a dedicated breaker (30 Amp). I do not have any more room in my 100 Amp breaker box.

One electrician said I could daisy chain another outlet off of the one I have for my electric dryer. At Home Depot today their book and their aisle guy said I need a separate circuit and breaker for each outlet.

The first time I asked an electrician doing some unrelatedd work for us, he talked about installing a breaker box in the garage, and replacing my main 100 Amp panel with a 200 Amp panel. Total estimate $3,400. I think not.

For now I am plannning on unplugging the dryer and plugging in the asaw when I use it.

If there are wise ones and / or real live electricians, I sure could use some advice for a path somewhere between switching plugs for free and spending thousands for two new breaker boxes (which I cannot do now).

[Larry Cooke]

Brian,

First off, not every 220 circuit requires a 30 amp breaker. The breaker size is determined the wire size and the wire size is determined by the load it will handle. I have a couple of 20 amp 220v circuits in my garage, but I also have a couple of 30 amp circuits too.

Upgrading your main panel would be a good idea in your case. 100 amp service panel is adequate for a lot of homes, but when you add a work shop with 220v tools into the equation it's calling it a bit close. I think I would agree with upgrading your service panel eventually. By the way, this is something you can do yourself for the most part. Final hookup should be left to a professional though.

In the mean time you could use the dryer circuit assuming they are not shared - you do not want to use both your saw and the dryer at the same time! You'll most likely pop the breaker, but I would never chance that. Remember it's your house we're talking about and it wouldn't be good to burn it down.

I don't have any books at hand (I'm not at home) but there are a lot of how-to books on doing your own electrical work. The biggest thing I'd stress is to have a professional or your local inspector inspect your work before making any final connections. I wired my entire house myself, it's really very easy to do, but I did have inspectors pass my work (actually had to of course.)

Sorry for the long blurb, but suffice it to say you can certainly upgrade your own electrical for a lot less than quoted.

Congrats on the new saw btw!

Larry

[Randy Meijer]

What else are you running off the 220 in the garage?? Something that would be running at the same time as the saw??

[Mike Canaris]

What brand of breaker box you got? There are some breaker box companies that have available twin breakers that take the room of one ...two of these would free up the 220 you need.

One more thing I got a 3 horse cab saw and it don't need no 30 amps...you will be needing a 220 20 amp,30 amp is for 5 horse motors.

[Hoa Dinh]

You may want to upgrade the main box, at least consider it for the future if you don't do it right now.

My insurance agent (State Farm) told me that they gave discount of the premium if the main box was upgraded.

Who told you each 240V outlet needed a dedicated breaker? While this is true for many cities (such as mine), many inspectors let it pass if you tell him/her that there are more than one outlet, but only one is used at a time (such as for power tools in a shop).

But you DC may require 240V outlet as well. If so, you need at least 2 240V outlets in your shop.

[Steve Strickler]

Personal experience with a similar situation: I am rehabing an old house that has 100A main service. When I put in a shop (a 100A subpanel) I was all stressed out about "not having enough capacity". Well, I put in the 100A service to the shop off the 100A main with the thought that I would upgrade the main one asap.

I have never once needed more, nor have I tripped any breakers. I even have a 5HP motor running off of it.

Saying all that, it WOULD be nice to have that 200A, but... "Get 'er done.". Enjoy your saw.

[Al Willits]

200 amp service would be nice, but you'll need to make sure the line from the power company to the house will handle it, some of the older homes here won't and a new line is needed, probably not a problem on newer homes.

You really don't need a 100 amp service if you don't use more than one or two power tools at a time, I have a 5hp compressor, arc welder, wire feed welder and 220 volt smelter that totally would take a ton of power, but I did get by with a 60 amp service and running only one or two of them at a time.

I did convert to a 100 amp panel when I upgraded to circuit breakers over fuses though, but make sure you have the wiring capable of handling the increased load.

Personally if I was gonna have it inspected, I'd get a electrician to do it, every time I had a city inspector out, my property taxes went up shortly afterword's.


Al

[Brian Kent]

Very helpful, guys.
In response to several questions…

Right now I have a 100 Amp panel outside the house and a 100 Amp subpanel inside the house.

In the garage / shop my only 220 so far is the electric dryer, soon to be accompanied by the table saw. I assume when I get a dust collector, that can be 110. (Right now I use just a shop vac and Jet dust filter) If for now I just plug in one and unplug the other, I can avoid using them at the same time.

That's an interesting idea to do the work myself and hire the electrician for the inspection and hookup. I have a friend who built his own shop and did the electrical up to inspection and hookup. He would probably help me out on the first part.

[glenn bradley]

I second Mike's comments. you generally only run one tool plus a DC at a time.

[Larry James]

Very helpful, guys.
In response to several questions…

...That's an interesting idea to do the work myself and hire the electrician for the inspection and hookup. I have a friend who built his own shop and did the electrical up to inspection and hookup. He would probably help me out on the first part.
Doing the work yourself may sound like a good idea. However, consider how do you change the wiring from the old breaker box to the new one. Are they side by side - are you going to work with the system "hot"? What about grounding? Is the supply into the house adequate? Will you be required to go with out power while waiting for inspection?

I've been there, done that. It takes a lot of coordination to bring everything together so you have a safe installation and minimum down time. Don't assume you will pass the inspection. Don't assume the electrician will take responsibility for the work you do. Will you apply for the permit or will the electrician?

I suggest you do more research locally before proceeding into the unknown. It my neck of the woods, both the local inspection authority and the power company had handouts for DIY. You need more info - this may not be as easy as you think.

Just my opinion, Larry

[Jim Becker]

It's best to stick with what is code compliant for your area. That said, many of us have more than one physical outlet on a given 240v circuit in our shops (dedicated tool circuits) for practical reasons. BUT...if you do this, you should branch the circuit in a j-box, not "daisy chain" from one to another. That may be difficult in your situation since the dryer outlet is likely installed in the wall with inaccessible wiring to do the necessary branching in a j-box.

For your current situation, if your dryer outlet is easily accessible, you could make up a 10 gage rubber extension with an appropriate male plug on the dryer end and an appropriate female connector on the saw end or put a long cord on the saw that will reach the dryer outlet when you need to use the saw. There is no harm in running the saw on the existing 30 amp circuit and physically unplugging the dryer to plug in the saw meets the "one circuit/one outlet" situation if that is important in your area. I offered both methods as some folks prefer not to use extensions.

Again, whatever you do, it should be code-compliant.

[Dale Sandford]

Can you switch to a gas dryer? Gas dryers usually only need 110V and can be run off the same circuit as the washing machine. That would free up the 220V dryer circuit for shop use. While not inexpensive, it is would be less than the cost of upgrading the main panel.

However, if you're going to need additional breakers for a dust collector or home improvements, you might want to look at upgrading the panel.


-- Dale

[Rob Russell]

Brian,

The best approach IMO is to install a subpanel in the garage. Use the 2 slots in your main panel that currently feed your dryer. Install a 60 amp breaker and run #4 NM, #4 SER or conduit with #6 THHN/THWN (individual conductors). Relocate your dryer to the subpanel. You will probably be able to run the dryer and a 240v saw and a 240v dust collector at the same time.

You'll need to pull a permit to do this. Your local AHJ (Authority Having Jurisdiction) will inspect it. You can hire an electrician to check your work after you're done and before the inspection if you wish, but I doubt that s/he let their license be on the inspection if they don't do the work.

Installing a subpanel is pretty much like running a circuit, with a few extra rules. If it's something you want to do on your own, I'd suggest buying a book on basic wiring. While not necessary, it'll make it a lot easier for you to complete your task safely. If you have questions about this, holler.

Rob
Addy protocol: unlicensed, but experienced homeowner electrician

[Kent Fitzgerald]

BUT...if you do this, you should branch the circuit in a j-box, not "daisy chain" from one to another.
Jim, what's your reason for this suggestion? Unecessary junction boxes are generally frowned upon.

Just curious,
Kent

[Bill Hughes]

Brian,

As mentioned earlier, the fastest, most economical way, is to just replace a couple of existing breakers with "split" breakers of the same amperage. These are the size of one existing breaker, but are actually 2 smaller (physically in size) breakers that will occupy the space of one existing breaker. This will free up space in your panel, and is safe and by code.

Bill

[Rob Russell]

Brian,

As mentioned earlier, the fastest, most economical way, is to just replace a couple of existing breakers with "split" breakers of the same amperage. These are the size of one existing breaker, but are actually 2 smaller (physically in size) breakers that will occupy the space of one existing breaker. This will free up space in your panel, and is safe and by code.

Bill

You have to be a little careful about the half-size breakers. Panelboards have a maximum of 42 allowed circuits. Smaller panelboards will have a lower number of allowable circuits. If you have a panelboard with 32 slots in it and the manufacturer's label says max of 32 - you can't swap out full-size breakers for half-size breakers in that panelboard because you're already at the max.

My point is that you need to read the manufacturer's label on the panelboard before you start installing half-size breakers.

Rob

[Jim Becker]

Jim, what's your reason for this suggestion? unnecessary junction boxes are generally frowned upon.

Branching a 240v circuit in a j-box is much easier to do and easier to maintain than trying to jam a lot of wires into the outlet box, even a big one. Further, the 240 v receptacles aren't really designed to "daisy chain", so you'd need to pig-tail in the box...requiring a bigger box to handle the amount of cable, etc. (#10 cable is really tough in this respect if it's on the plate like for a 30a circuit) So I personally don't view these as "unnecessary" j-boxes like they might be in other applications. They give you room to work. Of course, they need to remain accessible which is probably something that too many folks don't consider.

When the inspector was checking my service upgrade two years ago, he specifically remarked favorably on the fact that the two 240v circuits that I have multiple outlets on in the shop were branched in j-boxes...even though they were not part of the inspection. He noticed them for some reason...

[Rick Christopherson]

I went for the 3 hp Cabinet saw because I have 220 in the garage shop. Today I learned that every 220 outlet need a dedicated breaker (30 Amp). I do not have any more room in my 100 Amp breaker box.
If I'm reading this correctly, some misinformation got overlooked in all of the replies so far. First off, there is nothing wrong with having multiple outlets on a single 240 volt circuit. Yes, some have implied this, but did not specifically state it to clear up the confusion.

If you already have a 240 volt outlet (not counting the dryer) you can tap into this outlet to run the saw. Jim's posting above explains this, with the exception of suggesting that #10 wire is mandatory. Adding pigtails to a 20 amp circuit is not only very easy, but is the way virtually all outlets are wired under current code.

The other thing that is incorrect is the breaker size. There is nothing wrong with using a 30 amp breaker, but you need to know that it is not the size required for a 3 hp saw. The 3 hp saw requires only a 20 amp breaker. Technically, it can even be operated from a 15 amp breaker, but it may trip under maximum load (Unisaws even ship with a NEMA 6-15 plug).

[Bill Hughes]

You have to be a little careful about the half-size breakers. Panelboards have a maximum of 42 allowed circuits. Smaller panelboards will have a lower number of allowable circuits. If you have a panelboard with 32 slots in it and the manufacturer's label says max of 32 - you can't swap out full-size breakers for half-size breakers in that panelboard because you're already at the max.

My point is that you need to read the manufacturer's label on the panelboard before you start installing half-size breakers.

Rob

Rob,
That is the exact reason for "split" breakers, to increase the circuit capability of an existing panel. The major concern or limitation would be that you don't want to excede the designated amperage rating of the panel. That does not mean that the total of the breaker amperages should not exceed the main breaker, but that the estimated load of the panel is not expected to be exceeded during normal usage.

Bill

[Randy Meijer]

.....If you have a panelboard with 32 slots in it and the manufacturer's label says max of 32 - you can't swap out full-size breakers for half-size breakers in that panelboard because you're already at the max.....

Why not?? I understand that you do not want to run 33 circuits from a 32 circuit box by running 2 circuits from a single breaker; but if you can use half-size breakers, what difference does it make if you run more circuits than than what the box could support using full-sized breakers?? I'm not suggesting the above informatioin is incorrect, just want to know the reason for the "rule." Randy

[Rob Russell]

Bill,

I understand what the purpose of the split breakers is. All I'm saying is that you need to look at the manufacturer's label to see if you can use the half-size breakers in your particular panel per the panelboard manufacturer's specifications.

Just because the half-size breakers will fit doesn't mean that the panelboard's manufacturer says it's OK to use them.

Randy,

Why not? I can't answer that - it's a manufacturer's call when they design the panelboard. If your panelboard has 32 slots and the listing label says a max of 32 circuits and you put in more - you've violated the manufacturer's listing. Will it work? I guess so - probably - your call. What's the downsize/risk of violating the manufacturer's listing? I suppose they might say a higher risk of fire.

Rob
Addy protocol: unlicensed, but experienced homeowner electrician