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Old 02-26-2008, 03:05 PM   #1
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150amp main - Replace or Sub??


I have a SqD QO 150amp main, not rated for tandems based on model number. All spaces full (including the 3 tandems already installed when we bought the house, inspector must not have known the model).
long story longer,
I called the city and they install 100, 200, or 400 amp service drops to the meter. I looked and my house has 4/0 Al service drop behind the meter (so rated for up to 200 amp), not sure awg between meter and main.

I need one new circuit for a swimming pool install. house is 3400 sq ft, family of 4 with all sorts of electrical devices. Also have a 50a dedicated hot tub disconnect branch.

Only browning/dimming we get is in bedrooms with space heaters, they must have saved a buck not only on the main but also wired lights off the outlets.

at this point with our house/family/etc. is 150amps enough (I started a load calc. and gave up)? we are not tripping anything so I could just install a subpanel and move a few branches over to it along with the new pool branch, Or bite the bullet and go new SqD QO 200a main, reuse breakers to save cost, rewire from meter to main, and then add branch?

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Old 02-26-2008, 04:15 PM   #2
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150amp main - Replace or Sub??


Just based on square footage the house should have a 200amp service, but I would need more info....do you have gas or electric appliances, how many a/c's. If all gas I would just go with the sub-panel. How many spaces are in the existing panel? Does the pool just call for a single 120v 20amp circuit?

You may be able to just swap out the guts from a 200amp QO depending on the size of the cabinet, in which case it's almost easier than installing a sub-panel.

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Old 02-26-2008, 04:24 PM   #3
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150amp main - Replace or Sub??


never though of that...swapping the guts! ummm, 30 slots, gas waterheater, furnace, range; elec dryer, oven, a/c (3.5 ton)

14in x 30in QON30M150

yup, pool needs one 20a branch.

Last edited by steve f; 02-26-2008 at 04:32 PM. Reason: add info
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Old 02-26-2008, 04:31 PM   #4
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150amp main - Replace or Sub??


What is the age and condition of the existing panel?

The only issue I would have is the look. I like everything to be clean and an added sub sometimes looks....i don't know....added.


I can't imagine that you are anywhere near your 150 amp capacity. Turn EVERYTHING on and take a reading.
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Old 02-26-2008, 05:21 PM   #5
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150amp main - Replace or Sub??


existing panel is 12 yr old... the issue is more the additional circuit. since the box was not rated for tandems, i really hate to add any more than whats there. a sub does look added, but way easier than swapping boxes - especially if i am not maxed out on amps.
i dont like sub panels either, but could hide it in/behind a cabinet door...

just yank the meter, pull new cable to the main, and reconnect the branches! that makes it sound easy!
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Old 02-26-2008, 05:50 PM   #6
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150amp main - Replace or Sub??


Well, if your going to pull in new mains (assuming their too small) I would just swap out the guts for a 200amp. QO hasn't changed their panels much, if at all in 12 years, and your cabinet is the same size as a 40 circuit. It usually takes me an 1 - 1 1/2hrs to change the guts in a panel depending on how clean the original install was. I think you'll be suprised how easy it is.
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Old 02-26-2008, 06:11 PM   #7
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150amp main - Replace or Sub??


you sold me, swapping internals. what about cable size from meter to mains?
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Old 02-26-2008, 06:24 PM   #8
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150amp main - Replace or Sub??


For me it pretty much SOP for 200 amp boxes i useally go the 40 or 42 space breaker box.

The 30 spaces useally run out of room fast espcally this is true with both 100 and 200amp sizes.

Steve if you going to swap the guts i will go other way go with much larger box and change the service entrance cable anyway yeah you have to get ahold of POCO to disconnect your drop while you the change over and yes you need to get the permit anyway because there are some thing you have to bring it up to the code anyway.

Merci, Marc
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Old 02-27-2008, 06:58 AM   #9
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150amp main - Replace or Sub??


You can purchase a 200 amp starter panel cheaper than the guts. You will still have to purchase any special breakers either way.
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Old 02-27-2008, 08:00 AM   #10
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150amp main - Replace or Sub??


Quote:
Originally Posted by steve f View Post
what about cable size from meter to mains?
I have a similar situation- 4/0 AL UG drop to the meter (confirmed by me when I recently pulled the meter), 150a Murray panel installed when the house was built 1971. My current meter to main is 2/0 AL -SE which I am considering in the future changing to 2/0 CU and a 200a panel. My meterbox was stamped 200A so I knew that wouldn't need a change.

You will need 4/0 AL or 2/0 CU between meter and main for 200a service.
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Old 02-27-2008, 08:25 AM   #11
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150amp main - Replace or Sub??


He doesn't have to change the cabinet, a new 200amp QO is the same size as the existing. Doing that would be a complete waste of time. Right now only 40space panels are available for residential work but you can use two tandems for a total of 42 circuits.

Getting a permit is up to him, I've done plenty of service changes without one. The only code issues he should have would be a ground rod and cold water bond.

I'm not saying just buy the guts, I'm saying buy a 200amp QO 40 circuit panel, and swap the guts with his existing panel. That way he can still reuse the breakers. What special breakers will he need?

You can use 2/0 or 3/0 copper for the mains.
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Old 02-27-2008, 09:14 AM   #12
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150amp main - Replace or Sub??


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Originally Posted by steve f View Post
you sold me, swapping internals. what about cable size from meter to mains?
4/0 aluminum or 2/0 copper for 200 amp.
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Old 02-27-2008, 12:48 PM   #13
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150amp main - Replace or Sub??


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Originally Posted by BrntWS6 View Post
He doesn't have to change the cabinet, a new 200amp QO is the same size as the existing. Doing that would be a complete waste of time. Right now only 40space panels are available for residential work but you can use two tandems for a total of 42 circuits.

Getting a permit is up to him, I've done plenty of service changes without one. The only code issues he should have would be a ground rod and cold water bond.

I'm not saying just buy the guts, I'm saying buy a 200amp QO 40 circuit panel, and swap the guts with his existing panel. That way he can still reuse the breakers. What special breakers will he need?

You can use 2/0 or 3/0 copper for the mains.

this is exactly as I planned, buying a new boxed QO kit and using only the internals so I could use my existing breakers - to rebuy all those alone would be fairly pricey, not to mention redundant! then pulling 4ft of new 4/0 AL (or 2/0 copper) thru existing 2in pipe to the mains.
I have a 1/2" gnd rod now and a gnd clamp on both water main and gas main. is there a different type of bonded gnd?
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Old 02-27-2008, 03:16 PM   #14
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150amp main - Replace or Sub??


I would check with local inspectors about the water bond as it can vary slightly depending on where you live. Double check the gnd rod, if it's really 1/2" you might need to drive in a 5/8".
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Old 02-27-2008, 06:05 PM   #15
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150amp main - Replace or Sub??


yeah, unfortunately it is 1/2in. looks like I need to break out the fence post driver!!

I will make a new run of stranded copper to the new 5/8" rod, as well as bare #4 to the water/gas pipe clamps to address the bonding/grounding issue.


Last edited by steve f; 02-27-2008 at 06:07 PM. Reason: add info
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