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MLO 10-01-2006 02:22 AM

How big of panel?
I will be needing to completely re-wire a Ranch home built in 53' that is going through a extensive remodel. It will be 1600 sq.ft. 3br, 2bath, gas forced air, elec dryer. I also have a detached 18x24 shop with it's own 150 amp panel that is currently run off a 100 amp from the the house. I would like to make the shop 240v in the future for a small lathe and mill.

I currently have a gas water heater. I would like to eliminate it mostly because of the space it requires. I'm very intrigued with "point of use" electric water heaters. Any insight?

jwhite 10-01-2006 04:11 AM

I am not sure what you are intending to do with the shop building, but at a glance it looks like a 200 amp main panel at the house should suite your needs with a 100 amp sub panel for the shop feed off of it.

To be entirely sure you may want to consult with an electrician who you can meet face to face. After your meeting he will be able to do an actual load calculation based on your needs.

mdshunk 10-01-2006 07:53 AM

While sizing a panel can be somewhat intuitive for an experienced electrician, the actual determination must be done by doing a 'demand load calculation'. See this link for very good instructions on doing a demand load calculation:

If you have a bit of experience under your belt, here's a nice spreadsheet that will help you do that demand load calc:

MLO 10-01-2006 09:23 AM

My question was more for my own curiosity in preparing to talk with an electrician. I will also be moving the panel location and was trying to get an idea of the space needed for the new one.

The shop is wired to code, and uses a water heater for the hydronic slab heating. It is wired for exterior lights, 8' flourecents, equipment such as drill presses, disc sanders, grinder, compressor (240v), mill (240v).

No doubt some load calcs should be done, Thanks.

mdshunk 10-01-2006 09:29 AM

My gut feeling, without doing the calcs and you having such a big shop... I might hang a 320 amp meter can on the house and feed 200 to the house and 150 to the shop from the meter can. I might even do a 400 amp meter can and do 200 to the house and 200 to the shop, depending on what you might do out there in the future. I think you could get your calculation to work out that 200 would be okay for everything. It would really take a visit to your site to iron it out for sure, and evaluate your budget a little.

RobertJude 10-01-2006 12:11 PM

I am planning on installing a sub box in my basement , 50-60 amp breaker from the main panel to the Sub. After finishing / wiring the basement. Then I Plan on running a sub box from the Basement sub box to a ( 12 x 16) shed/shop outside the main house. Any advice or suggestions are greatly appreciated. Thanks in advance for the help.

jwhite 10-01-2006 01:15 PM

Welcome to the forum robert.

In order to keep the conversations clear, it is best to start a new question with a new thread. (first suggestion, though not electrical related.) :)

RobertJude 10-02-2006 03:37 PM

J white
Thanks for the suggestion. Still trying to figure out how to use this forum without clumsily stepping on toes.
Regards, R McG

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