200a subpanel for new large garage

[Kevin C]

When a jurisdiction adopts the NEC, it is law.

http://www.nema.org/Technical/FieldReps/Documents/NEC-Adoption-Map-PDF.pdf

NEC Adoption map... Seems to cover a bit of ground. Surprised that some states are still on 2005. 2014 is not that far off.

 

[encantofred]

it is a siemens /MC3040MB22 if that helps. i need to figure out how to hook a 200a subpanel on it. it is not really an option to put a second service on the shop.

can anyone help me figure out what to do?

thanks

tom

 

[shamrock12]

Since you seem to use the ULC, Urban Legend Code ...

Nope, I use the NEC and actually have a few copies of 'em. That's why I don't need to take them out cuz I already know what it says. I have already made my case and nothing will change that. I don't see why you need to repeat your own. Just get over with it

When a jurisdiction adopts the NEC, it is law.

Umm ... didn't I just say that? Why are you restating that?

Also, the NEC book is a GUIDELINE, not the law ... unless the local jurisdiction demands it.

The sad part is, this argument is really pointless since I've already recommended the OP to run 250kcmil to compensate for the voltage drop. The OP has already stated that he will be running 250kcmil as well. It is never my intention to cause a thread to become hijacked and unfortunately it did, so I am not going to comment any further regarding this conductor sizing "issue." Any further disagreement regarding my opinion about subfeed sizing will be ignored.

 

[shamrock12]

it is a siemens /MC3040MB22 if that helps. i need to figure out how to hook a 200a subpanel on it. it is not really an option to put a second service on the shop.

can anyone help me figure out what to do?

thanks

tom

My suggestion would be to check with POCO and see if that 400a meter have another tap in which you could run a separate 200amp disconnect switch next to it (outdoor) and then use it to feed for your garage. This would likely be the easiest way to do it.

 

[shamrock12]

from you guys who are experienced at pulling big wires through conduit, is 2 1/2" pvc conduit enough to pull 3 250kcmil and 1 #2 ground 185 feet.

According to my calculations, 2.5" schedule 40 and 80 would be too small for three 250kcmil and #2 conductors. You will need the PVC to be at least 3". I would do schedule 40 underground with schedule 80 above ground.

 

[shamrock12]

http://www.nema.org/Technical/FieldReps/Documents/NEC-Adoption-Map-PDF.pdf

NEC Adoption map... Seems to cover a bit of ground. Surprised that some states are still on 2005. 2014 is not that far off.

That's a neat map ... I've always been curious how close (or far behind) the states are with adopting the latest NEC. Thanks for sharing that.

 

[Charles (in GA)]

Siemens Fast Fact Sheet for the MC3040MB22

My suggestion would be to check with POCO and see if that 400a meter have another tap in which you could run a separate 200amp disconnect switch next to it (outdoor) and then use it to feed for your garage. This would likely be the easiest way to do it.

The top main breaker in the pic is supplying the 200 amp subpanel, and taps directly off the meters supply, not thru any other breaker. The lower main is the 200 amp factory installed that supplies the bus bars in that combo panel. Thats 400 amps off the meter, it isn't rated for any more. His only choice is to somehow do a 200 amp breaker off the stabs of the combo panel by using another one of the 200 amp breakers like are being used for the mains now.

The OP will need a QN2200RH breaker from THIS BROCHURE and install it on the stabs of the combo panel. Probably will need to punch a larger hole in the panel than now exists in the bottom, on the Right side of the panel. Install the breaker opposite direction of the ones presently installed.

Charles

 

[Norcal]

Siemens Fast Fact Sheet for the MC3040MB22



The top main breaker in the pic is supplying the 200 amp subpanel, and taps directly off the meters supply, not thru any other breaker. The lower main is the 200 amp factory installed that supplies the bus bars in that combo panel. Thats 400 amps off the meter, it isn't rated for any more. His only choice is to somehow do a 200 amp breaker off the stabs of the combo panel by using another one of the 200 amp breakers like are being used for the mains now.

The OP will need a QN2200RH breaker from THIS BROCHURE and install it on the stabs of the combo panel. Probably will need to punch a larger hole in the panel than now exists in the bottom, on the Right side of the panel. Install the breaker opposite direction of the ones presently installed.

Charles

I do not see any provision for a 3rd 200A breaker being allowed, only the 2nd one above the factory installed main.

 

[Charles (in GA)]

I do not see any provision for a 3rd 200A breaker being allowed, only the 2nd one above the factory installed main.

No, not as a main breaker, as you already have two, one for this panel, and one for the house sub.

The use of the 200 amp breaker would be the same as any other breaker on the stab, being used as a branch or feeder breaker, getting its power thru the lower of the two mains.

There is no rule that limits the size of a breaker in comparison to the main.

Charles

 

[shamrock12]

Charles, you're right. The brochure for the OP's meter combo really helped illustrate the bus bars circuits. It looks like the combo has split bus bars with the upper four spaces is being used exclusively for 200amp subfeed to the indoor panelboard. And the jumpers from that short bus bars goes to the second 200amp breaker to feed the outdoor panelboard circuits.

It looks like the indoor panelboard is full and it would be a very difficult task to tap it there so that would be out of option. The outdoor panelboard does have some spaces left in which the OP could install another 200amp breaker downstream; however, I noticed that outdoor panelboard already have quite some heavy loads there too. Unfortunately, that would limit the power supply to the garage. I do have a suggestion:

Install a third 200amp breaker downstream of the outdoor panelboard. Move the conductors for subfeeding the indoor panelboard to that third 200amp breaker. Connect the subfeed conductors for the garage to the topmost 200amp breaker that originally was used for subfeeding indoor panelboard. This will limits the total house capacity to 200amp but will free up a full 200amp for the garage.

 

[Charles (in GA)]

I'll add THIS BROCHURE as it has the latest and greatest of the large BRANCH breakers. My 200 amp main lug Siemens 4040 panel does not list any amp restrictions on individual lug loads, and lists Branch breaker styles that cross over to the ones in this brochure.

WE NEED SOME CLOSE UPS OF THE PLACARD IN THE PANEL.

 

[Aceman]

Step 1.

What is the calculated load of the home? How much of that load is on each of the 200 amp breakers?

Step 2.

What is the power company cost to drop another service to the shop?

 

[encantofred]

you guys are amazing. you are firing questions and ideas faster than i can research and react.

i am going to check with the power company, but i am guessing that is not a good option. it is a small 8 home subdivision and i would be surprised if the transformer is rated high enough, but i dont know for sure but will find out. the biggest reason i dont want to do a separate meter is that is has to be billed as a commerical account with minimum billing per month. and the rates are a lot higher.

i have the siemens tech rep researching what my options are as well. i have a higher def picture of the panel label, but the site restricts file sizes.

it sounds like i need to do load calc (and learn how to do one) for the house itself.

the house is 4500sq feet. it has 3 air conditioners, electric hot water, gas furnace, gas dryer and gas range. and electric oven.

i have to believe that the 400a breaker has lots of headroom for the house. the summer would be the biggest current draw time.

totally separate question. can i run TWO 100a subpanels to the shop? much easier to use 100a breakers, and much smaller wiring, though it would be twice as much wire?

are there limits as to how many panels could be at the shop?

just reaching for ideas.

thanks again to all of you.

tom

 

[encantofred]

i made closeups of the panel schematic. a top and bottom.

tom

 

[Norcal]

This is off topic but why is the water heater electric when the other appliances are gas?
Unless the gas supply is propane it's odd IMO.

 

[shamrock12]

I was thinking the same thing as Norcal. I was going to suggest you to replace it with a gas unit once the electric one is at the end of its life.

Then I would feel more comfortable doing the suggestion as I have indicated earlier about installing a third 200amp breaker downstream on the outdoor panelboard to subfeed the indoor panelboard.

 

[pattenp]

Nope... only one power feed is allowed to the building. But you can have more than one panel in the garage.

totally separate question. can i run TWO 100a subpanels to the shop? much easier to use 100a breakers, and much smaller wiring, though it would be twice as much wire?

are there limits as to how many panels could be at the shop?

just reaching for ideas.

thanks again to all of you.

tom

 

[Gerald O]

My suggestion would be to check with POCO and see if that 400a meter have another tap in which you could run a separate 200amp disconnect switch next to it (outdoor) and then use it to feed for your garage. This would likely be the easiest way to do it.

That was essentially the solution I went with. The existing house panel was full. We had to replace the existing 200A meter base with a 400A one that had dual lugs. Now there are two 200amp main panels on the exterior fed from the one meter base. Each of these has space for circuits but their primary use is to feed the interior load center panels for the garage and the house.

The POCO wanted to see the projected load calcs for the house and the garage and then gave their go-ahead for the split service arrangement.

The feeders to the inside panels now route from the outside boxes through the rim joist and into the crawlspace.
Before and after pics.

 

[encantofred]

hi gang, yea, the gas in this case is propane.

tom

 

[2ManyProjects]

This is off topic but why is the water heater electric when the other appliances are gas?
Unless the gas supply is propane it's odd IMO.

hi gang, yea, the gas in this case is propane.

tom

So what am I missing here? Propane-fired water heaters (both tank-type and tankless) are commonly available, and widely used in such applications as mobile homes, rural areas, etc.

If that will help lighten the load on the electrical system (which is the OP's most acute problem at the moment), it seems well worth exploring the idea.

 

[encantofred]

my primitive load calcs come up with 123a for the shop, 115a outside panel and 70a inside panel.

and realistically, in the shop i will hardly ever having 2 rv's hooked up drawing full current. and generally will only be using 15a to keep batteries charged and lights. welder hardly ever. lots of lights though. compressor not much. hot water heater on timer. (or a higher amperage on demand). and a mini split system air con for a 400 sq foot office in the shop. only running when needed.

i used a spreadsheet calculator for them and i dont see where i could be too far off.

as for converting to propane hot water heater. that will be a last resort. not going to be an easy thing to do.

tom

 

[encantofred]

an update. i ended up being able to get a 2nd electrical service for my garage. 200a.

they had to run it about 350 feet to the shop, but it worked out great.

thanks for all the comments in the past on this.

tom

 

[Aceman]

an update. i ended up being able to get a 2nd electrical service for my garage. 200a.

they had to run it about 350 feet to the shop, but it worked out great.

thanks for all the comments in the past on this.

tom

Good deal.

Just out of curiousity, what did they end up charging you to do this? Do you have a minimum monthly usage charge with this second meter?

 

[encantofred]

i am just at the finishing stages. i should have final on the garage within 2 weeks. the builder included 350 of conduit from the street to the garage in his bid. the wire will be run by the local power company after or near the final inspection. i am led to believe and hope that the wire run from the street to the garage will be free since i am getting a second electrical service.

i had a very tough time getting approval for the second electrical service. but they finally approved it. it was the county, no the power company that had issues.

i have not selected the rate plan yet, but the bad part is it will be a commercial account since it is not considered a living area.

time will tell if i can get that changed or not.

hey...the sacrifices we make for our garages....eh?

when i know more i will post it

tom