Subpanel Help

[Anonymous]

Hey all - first post - wo ho

Got a Q for a soon to be workshop. I'm planning on enclosing a carport that is attached to our 1957 brick home by way of a wall/built in BBQ. This will be my new wood shop. The carport already has 15 amp 120v power running to it under ground. The BBQ has a 20 amp line ending in the wall. My grand plan is to have 3 240 lines in the new garage along with the existing 20 amp line for smaller shop tools and 15 amp for lighting. My 240 lines will run 1)table saw/jointer/sanding station 2)compressor 3)dust collector.

My existing Main panel is 200 amp service and is located on our back patio and doesn't have many slots left (I think 6 total, including the 2 that boarder the mains). It already has an OLD subpanel tied into it for 60 amp service located in our closet and (I think) needs to be replaced - but thats for a later project.

I've been wanting to put a second subpanel in my new garage to cover the loads in there, but am not sure what I should be looking for as far as available slots and Amp service. My existing OLD sub is 60 amp service. I was thinking about getting another 60 amp sub for my shop, but don't know how to figure service needs.

And finally the Q (sorry for the long windedness) - Am I jumping through too many hoops to get the sub in if I can even add one - I don't really know if I need one? I was also think about just adding slimline breakers to my main and forgetting the sub. I plan on staying in the house for 5-7 more years and prolly won't do anymore 'growing' for my electrical needs.

PS - skill wise I have NOT done messed with breakers before. I plan on getting some help from electrician friends of mine but just wanted to get an idea ahead of time so my plans aren't dangerous/ignorant. Thanks :lol:

[Wgoodrich]

First thing I would do before you spend money on a wasted design where other needs may be present, I would perform a demand load calculation of your home. In this demand load calculation I would include the new loads you plan to install. However of that new load you plan to add be aware if your wood shop is a one man operation then you only need to add to the demand load calculation and to size your sub panel in your wood shop adding the one largest electric tool and the vacuum system equipment that will run at the same time you are working. You may have several large electric tool loads in your shop but one man will only run one machine at a time. That one largest machine is the load being worst scenario of load in your shop adding in any other loads running at same time such as vacuum and any auto start equipment such as air compressors.

Below is a link to a format to perform you own demand load calculation to find the minimum main service required to serve your home. This will tell you if your existing 200 amp main service is big enough to do as you wish or you need to increase that service size.

http://www.homewiringandmore.com/homewiringusa/2002/definitions/demandcalc02/DwlingDmdCalc02.html

If your 200 amp main service is big enough to do the job then a suggestion that may help would be a possibility of removing the existing 60 amp sub panel and rerouting the feeder from the main service panel and rerun it to the new sub panel in your shop creating the old existing sub panel to be a slave of the new sub panel. This would provide your breaker space in your main service panel to serve the new subpanel in the shop that will then serve your old existing sub panel in the closet.

Two things to be aware of;

Size the new sub panel large enough to carry connected load [demand load calculated of intermittent loading] as well as the shop loads again intermittently credited concerning load.

Be aware that your existing panel if in a clothes closet or in a closet designed for storage is a violation of the NEC rules. These to locations as well as inside a bathroom are forbidden to contain breakers or fuses.

Hope this helps

Wg