Help adding 230v outlet at subpanel in the garage

[aczlan]

The breaker panel should be sized to how much power you are actually pulling through it, not how many breakers you have in it.
Also, the breakers alternate which one is on which leg of the 220 coming in, so I labeled your picture to reflect that.

That appears to be a 20 space 200 amp panel, they make 40 space 200 amp panels, so the number of breakers shouldn't be an issue.
As for putting too much load, get a cheap clamp on ammeter (such as Digital Clamp-On Multimeter ) and check each leg where the power is coming in to see how well balanced it is.
By my calculation, you have 260 amps of breakers on the "1" leg and 285 amps of breakers on the "2" leg.

Aaron Z

 

[Sodo]

OK got it. Thanks very much. I should probably change my image to not send folks off on the wrong path.

But do you think 260 / 285 is close enough to "balanced" by breaker size?

Are people actually doing this "balance measurement" if there is no "problem" to solve? Some stuff I can turn on; but how can you possibly know the moment when freezer & refer & sump pump & furnace are pumping all at the same time? I don't have any breakers blowing. If I did tho, now I have a better understanding, so thanks very much for that!

I'm wondering it I will ever weld at full power (in my driveway) off this outlet period. I only weld at home once in a blue moon and 120v has always been plenty (for the projects that follow me home). But I'm ready for action!

 

[aczlan]

OK got it. Thanks very much. I should probably change my image to not send folks off on the wrong path.

But do you think 260 / 285 is close enough to "balanced" by breaker size?

Are people actually doing this "balance measurement" if there is no "problem" to solve? Some stuff I can turn on; but how can you possibly know the moment when freezer & refer & sump pump & furnace are pumping all at the same time? I don't have any breakers blowing. If I did tho, now I have a better understanding, so thanks very much for that!

I would think you should be fine unless you have a bunch of unused outlets on one side.
Where it is important is when setting up for a backup generator. For example: A generator that puts out 30 amps of 220v will be unhappy with 30 amps of 120v on one leg and 10 amps of 120v on the other leg.

Aaron Z

 

[mikehaugen]

I wouldn't worry about balancing too much. I think you are close enough. You just don't want to have all of your high-load stuff on the same leg.

 

[Rock knocker]

But do you think 260 / 285 is close enough to "balanced" by breaker size?

Close enough.

Being numerically balanced doesn't even address whether you are in fact balanced. Four 15A shop outlets are not balanced by a dishwasher, refer, washing machine and microwave all on dedicated circuits. Sixty amp draw on either, but one is likely to have all four running at once, while the other will have one or the most two running simultaneously under most circumstances

 

[Sodo]

I would think you should be fine unless you have a bunch of unused outlets on one side.
Where it is important is when setting up for a backup generator. For example: A generator that puts out 30 amps of 220v will be unhappy with 30 amps of 120v on one leg and 10 amps of 120v on the other leg.

Aaron Z

There was a time when I would add an outlet quicker than someone could return with an extension cord, but now I kinda wish I had more wall space . Just kidding. Possible in some cases more than code allows but not far over code.

Have not ever considered tying in a backup generator, but I like to have a handle on info like this in case the need arises (and no internet to search for answers). Very much appreciated.

Being numerically balanced doesn't even address whether you are in fact balanced.

True. Thx for clarification. Range has a gas cooktop & water heater is Gas. I'm not worried about actually using 200A at any one time. I can't even get my 20% duty cycle welder to shut itself down.

 

[s219]

4) Ground rod: S219 and another says it's not req'd. Do you think it's necessary?

Hows my pic look?

Looking good, but you *do* need a ground rod, since you are feeding multiple circuits on that detached structure. You wouldn't need it if only one circuit (when a branch).

 

[Sodo]

Looking good, but you *do* need a ground rod, since you are feeding multiple circuits on that detached structure. You wouldn't need it if only one circuit (when a branch).

OK I thought this might be the case. I suppose to do this step I might as well use a ground rod and ground wire sized for 100A feed, but where would I ground that on MY subpanel?

 

[s219]

You will want two rods, about 7 feet apart. Run #4 copper from one rod to the other and then to panel (continuous, no breaks). You can snake it up into panel (see the small round knockout at bottom/back middle/left of box, about 1/4" round, in your photo). Then connect to ground bar -- it should have at least one hole that is larger than others, or all might be large enough. #6 enough for now, but #4 would cover you for 100A service in future.

If you have clay or rocky soil, it can be a chore driving a rod in, so google for some techniques. I have clay soil over most of my property, and it's a pain. However, my pier circuit panel is over sandy soil, and I about fell over when I put those ground rods in -- the first rod went halfway in with just hand pressure, and then light taps from a small sledge got it the rest of the way.

 

[aczlan]

OK I thought this might be the case. I suppose to do this step I might as well use a ground rod and ground wire sized for 100A feed, but where would I ground that on MY subpanel?

If you dont have any holes in the ground buss large enough to fit your ground wire, you can use one of these: GE Power Mark Plus Grounding Lug for Load Centers-TGL20CP at The Home Depot

Aaron Z