# I have a new 220V Table saw, but my main panel is full



## Chewmanfoo (Jun 17, 2014)

My first post - sorry if this question is in the wrong thread or somehow inappropriate…

I just bought a new 220V table saw. I have assembled it and it's sitting there grinning at me. I can't plug it in yet.

In my 100 amp main panel, I noticed a few double 15amp breakers where two breakers are living in one space. Can I double up a few 20amp breakers to make room for a new 30amp service? Suppose I wanted to add a sub panel closer to my woodshop - could I add a 60amp breaker in my main panel, then string the wire and add my new 30amp breaker in the sub panel? Or, since my main panel is full, do I really need to upgrade the main panel to a new 200amp panel with more room?


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## MrRon (Jul 9, 2009)

Yes! you can double up on your breakers. Add up all the current being used at any one time to see if you have enough capacity to run a saw. Lights should not dim when the saw is starting. If they do, you need to upgrade service.


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## English (May 10, 2014)

Panels are usually labeled if you can add tandum breakers. Labels will show something like 12/24 circuits in this example all 12 circuits can be changed to tandum breakers giving you 24 circuit, some panels are labeled 12/16. In this case only 4 of the 12 original circuits can be tandum breakers. There are many other labels, read the labels completely, it should tell you if you can expand the number of circuits.

If you are not sure what to do, please call an electrican. We don't want to lose any of our LJ family.


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## shawnmasterson (Jan 24, 2013)

Your current panel, how many spaces are there? My old panel was 100 amp and only had 20 spaces. I replaced it with a 100 amp panel with 30 spaces. Going to a 200 amp means there may be some other incurred expenses. I believe that you will need a new service from the pole, meter base, and the rest of the house will have to be brought up to current code. I am not a sparkey, but I believe that is what is involved with upgrading to a 200 amp panel.

If I were you I would pull a 220 breaker and put in a sub-panel. I have a 60 amp breaker feeding my sub-panel. from there I have 12 circuits in the shop. it's really not enough. There is plenty of power, but not enough slots.


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## pmayer (Jan 3, 2010)

I would install a sub-panel. It's easy (if you can wire a new circuit you can install a sub-panel), relatively inexpensive, and you will appreciate the flexibility that this affords you.

I added a 100amp subpanel with 20 slots for my shop and I have used nearly all of them. Yes, my wiring is way overkill for a 1-2 person shop, but it is a nice luxury to have.


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## Chewmanfoo (Jun 17, 2014)

Wow this board is chock full of helpful folks with good ideas!

A few follow-up questions.

(fear not - I have a bachelor's in Computer Engineering, I understand Ohm's law etc. I won't burn down my house!)

I have 100amp service.

If I add an additional 100amp sub panel, that's OK, just as long as I sum the total amps in use simultaneously (at ANY time of day) in my main panel, subtract that from 100amps, the remaining amps are available simultaneously on my sub panel. So considering lights, computers, TV, HVAC, oven, clothes dryer on the main panel, I come up with, say, 60 amps - then I can have 40 amps simultaneously on my sub-panel without fear. 40 amps is my table saw + dust extraction, for example.

It might be safer to just add a 40 amp sub-panel, correct?

TIA!


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## TheFridge (May 1, 2014)

Must be an older house.

If the saw draws 16A and the total length is under 100' #12 on a 20A breaker is more than enough.

You could size the wire up bit I don't recommend sizing the breaker up to a 30A if the FLA of the saw is 16A or less.

A sub panel would be great if you can do it. You could also get a quad breaker. It's 2 tandem breakers with handle ties on the inner and outer sets, so you could double up a 2 pole breaker.

Technically, you're only supposed to use up to 80% of the capacity on any given breaker, from the mains on down to a branch ckt breaker. There are exceptions, but cord and plug connected equipment in a house (your saw and portable power tools) ,isn't one of them.

Just rules of thumb. You usually don't need to upgrade your service unless you are adding a large appliance (bigger A/C), or a generator.

And if you double up a ckt from a cable that has 2 hots and are sharing a neutral, make sure the 2 hots are on opposite phases or the neutral will carry a double load. Which isn't good.

Sub panel or doubling up. Up to you really.


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## Chewmanfoo (Jun 17, 2014)

My saw (http://cdn0.grizzly.com/specsheets/g1023rlwx_ds.pdf) says 5HP, 14amp, minimum circuit 30amp.

I've decided to put a sub panel in the wood shop (attached garage) about 50 ft away from the main panel. I'll put in a 30amp and a 20amp circuit in it, as well as some 15 amp circuits for lights, a PC and chargers etc.

Now, to figure out how big a wire is required for this sub panel. Googling this little conundrum is yielding quite a disagreement among the "experts"!


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## nicksmurf111 (Jun 6, 2014)

Yeah, your correct. You would need a 30 amp breaker. That must be an efficient motor though if it's 14 fla.


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## crank49 (Apr 7, 2010)

I could understand a 15/30 amp rating. That would be the amp loading for 230/115V.
But if it says minimum circuit 30 amp then you will need a 30 amp circuit. Probably due to inrush current for starting a 5 hp motor.
NEC (National Electrical Code) specifies #8 awg = 50 amps . . . #6 awg = 65 amps . . . #4 awg = 85 amps.
These ratings are for maximum of 3 conductors in a conduit or cable. These ratings get reduced by 0.88 for 104 degrees F.


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## Chewmanfoo (Jun 17, 2014)

You guys are great!

so, if I wanted to have room for reasonable future expansion, i need to run a #4 3 conductor wire from my main panel to this sub-panel?


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## nicksmurf111 (Jun 6, 2014)

Probably…

You have to do the calculation for the length of conduit you will be using. I would suggest pulling a permit and run your plans past the inspector. Or at least have an electrician go over your plans with you. Depending where you put the sub-panel, the grounding requirements will be different.


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## Chewmanfoo (Jun 17, 2014)

Why does the notion of pulling a permit fill me with dread? I'm completely ignorant of that whole process.


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## RichardHillius (Oct 19, 2013)

Depending on if you have AC or not and if you use electric heat or gas 100 Amps is a good sized service for most residences. A sub panel is probably the best long term answer but the easiest solution if you don't see yourself needing to expand much in the future and if your panel is rated for it would be to go with the tandem breakers.

Panel work is something I always just hire out myself. It's not that I don't understand the work I just feel like it's better in the long run to get someone who does that kind of work everyday to do it. You could run the wire to the new outlet and install the box and have a electrician do the actual panel hookup. They should also be able to quickly tell you when quoting the job if you need a sub panel or not. Think of permitting the work as a safety net. If the inspector finds issues with either your or the electricians work than they are pointing out things that may potentially end up costing you much more in the future to fix than to just resolve when you install it.


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## shawnmasterson (Jan 24, 2013)

You need a 4 conductor wire. You have to have your grounds and neutrals separate in the sub-panel. I can say I know that #4 aluminum will get you 60 amps. Yes aluminum is fine for a sub-panel, and will save some money.


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## ColonelTravis (Mar 19, 2013)

I'm in your same situation, Chew. Made an extension cord for now but long-term I need a sub-panel. I can do outlets, ceiling fans, lights, etc. But with panels, I'm with Richard above. That's a whole new level I don't want to deal with - not because it's difficult. It doesn't seem to be, I've watched videos and read stuff, blah, blah, blah. but I wouldn't know if I messed up until the house burned down. I don't have the background to check and double-check everything properly.

My wife's uncle does a lot of electric work, he's going to come over for my garage, so you don't have to hire an electrician off Angie's List. Poke around, maybe you can find someone who won't charge you an arm and a leg, because that kind of work ain't cheap.


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## Chewmanfoo (Jun 17, 2014)

Here's my panel. I'm afraid to take the cover off for fear that there's an entire civilization of intelligent beings living in the wall cavity who possess weapons of mass distruction.

I have a few questions - in the top left there appears to be two 50 amp breakers which are attached together so that both go off or both go on simultaneously. I'm not sure if this means 50 amps or 100 amps. Probably 50 amps - with the black wire coming from one of the breakers and the red wire coming from the other one.

In the middle on the right there appear to be two doubled-up 20 amp breakers. I wonder if I can buy breakers for the left side to ado this as well, so I have more spaces for a sub-panel breaker of 100 amps.

OR it could be that this panel is a complete mess, way under-sized and very risky to crack open because of the complexity of it, and hiring an electrician is the only way forward.

A few more words of advice before I close off this thread?


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## nicksmurf111 (Jun 6, 2014)

That panel looks old! Make sure it's in good condition before moving forward. You may want to upgrade the service.

Those single 20's on the left hand side, and move them up and put in some of those skinny double breakers in. As long as you can get the correct breakers that are compatible with the box, and the position that you put the new dual pole breaker has a lug for both phases.

Here are the Square D breakers, Eaton and Murray make the same ones too, they are all cross-listed and are supposed to be compatible.

http://www.homedepot.com/p/Square-D-by-Schneider-Electric-Homeline-2-20-Amp-Single-Pole-Tandem-Circuit-Breaker-HOMT2020CP/202353308

Just wondering, what kind of box is that?


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## nicksmurf111 (Jun 6, 2014)

To try to answer your question: the double breakers like the 50 and 20 attach to both phases. See the image below, the lugs in the back of the box are staggered. The double pull breakers attach to both lugs, the two 110v lines that come into your house are 180 degrees out of phase and sum up to 220v (single phase). I believe they are tied together for convenience, that's all. And it's still 50 amps, just twice the voltage. Voltage x Amps = Watts, so twice the power.

http://news.yeselectric.com/wp-content/uploads/2013/04/eaton-before-and-after-1024x677.jpg


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## b2rtch (Jan 20, 2010)

When I built my shop I upgraded my service to 200Amp and I installed 100Amp in the shop.
If you can do it , this is the way to go as you have plenty Amp for the shop and for the house


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## Chewmanfoo (Jun 17, 2014)

I have a couple of bids on upgrading this service to 200amp - average about $1600. I have a lot of the materials required already bought.


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## nicksmurf111 (Jun 6, 2014)

I had mine upgraded to 200 amp after I bought my house last year. The entrance cable(s), conduit, meter box, electrical box, grounding and labor came out to $1,225. They just tied on all the old circuits base on wire gauge and left everything else for me to deal with. I didn't have any large electric appliances, so that saved a couple dollars.


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## EEngineer (Jul 4, 2008)

so, if I wanted to have room for reasonable future expansion, i need to run a #4 3 conductor wire from my main panel to this sub-panel?

If you are going to do this yourself, you must camp out with the NEC for a while. I rewired my shop 2 summers ago and I spent several weeks of spare time researching the NEC before starting.

For an attached garage, you might get away with 3-wire. For a detached garage, 4-wire, separate neutral and ground out to the subpanel and grounding posts at the subpanel. Don't take my word for it, read the NEC!

There are restrictions on the number of sockets on each circuit, restrictions on the size of motor circuits (must be sized to 125% of rated motor current, lots of things you must consider. Again, don't take my word for it, read the NEC!

Did I mention you should read the NEC?


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## nicksmurf111 (Jun 6, 2014)

If you go to the website, you can sign up for a password and read it online. {Insert evil maniacal laugh}.


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## MT_Stringer (Jul 21, 2009)

Regardless of your education, I would have a qualified electrician survey your situation.

"If you are not sure what to do, please call an electrician."

What John said.

My panel is full. The electrician said there was no way to add anything else without changing out the panel…and the wire coming from the service provider… and that is a lot of money.

I run my 220v saw from the elect dryer receptacle. We have been in this house 27 years and never used an electric dryer, and don;t plan to in the future.


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## Woodmaster1 (Apr 26, 2011)

When I built my detached garage a 200amp service was installed. I did most of the work myself and had my brother inlaw check it. 200 amps is overkill but I got it when I need it. I got lucky and only had to buy 25' of service entrance cable. The pole is 5 feet from the garage.


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## WhyMe (Feb 15, 2014)

A sub-panel requires a 4 wire feeder. Depending on the type of wire used, #8 Cu is either 40A or 50A, #6 Cu is 55A or 65A. The temperature rating is different between NM-b (Romex) and THHN/THWN in conduit so the amp liimit is different. Aluminum SER cable is the most economical to use and is about a forth of the cost of copper. If you want good information go to http://www.garagejournal.com/forum/ and search through the lighting and electrical forum for "subpanel".


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## TopamaxSurvivor (May 2, 2008)

That panel is a Sq D QO breaker style. You can't get a better panel. Too bad it is too small. There are probably physical obstructions that will limit how many and the location of tandem breakers. Good luck.


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