Ask Me Help Desk - Do I have enough for a sub-panel

This is my first post to this board so please bear with me. My question is regarding a sub-panel for a small addition to my home. I presently have a 200 amp main panel located in the attached garage. The garage and upper floor are part of an addition that was built in 1993 and the original panel box (located in the basement) is now a sub-panel that is being fed by the newer panel with 100 amps. In the 200 amp panel I have the following breakers: LEFT SIDE: 15, 20, 20, 15, 20, 15, 20 DBL 40, DBL 30 and Dbl 20. On the RIGHT SIDE: 20, 20, DBL 50 (feeds the sub-panel), 20, DBL 40, 15, 30 GCFI, 20, 15.
On the left side the double 40 was originally for a welder’s outlet and is not used. On the right side the double 40 is also off and was originally for a stove which has been replaced with a gas unit.
My home is a ranch with approximately 2000 square feet and I have an AC condenser and air handler, submersible well pump, small free standing freezer, electric dryer, oil fired furnace as well as the usual kitchen appliance.
I plan on adding a 500 square foot family room with a full bath on the opposite end of the house from the main panel. (Approximately 80 feet.) My plan is to install a 100amp sub panel for the addition’s general lighting and bath circuit and have 40-50 amps + left over for an outside hot tub in the future.
My question is do I have enough in my main panel to allow for the 100 amp sub panel with the elimination of the two double 40 amp breakers that I no longer have any use for. Also what size wire do I need to run to safely power the sub with an 80 foot run.
Thank you.

Dave

Please get back with the total actual livable square footage, do not include attic, garage, crawlspace, or porches. Also let me know more detail on the AC, hopefully the amperage rating of the compressor. I think the hot tub is going to bring you over,but with more detail I can do the service rating calculations.

I do not show how to do the calcs here, way too many variables and explanations to deal with. If anyone else cares to, be my guest.

TK,

Thanks for getting back to me. The house is a ranch and has approximately1800-1900 square feet of living space. The new family room with bath will be approximately 500 of new space. The AC was installed in June of 2004 and the Trane compressor is rated at 2.5 tons, 13 SEER and is connected to a 2 pole 30 amp breaker. I am having trouble finding out what the amperage rating is on the compressor, but hope that this info will help.

Dave

I believe you do. I haven't had a chance to work the numbers (Generally-since we have no hard numbers), but from what I read, you should have a enough--seeing that you have a gas range, and have decided to rid the 40A welder.

Your Current lighting load/ w derating is approx=5520watts
Hypo: Now even if you add a Range@8000; heat@10,000 (with the heat omitting the AC unit); dryer@5000;dispo@1200;Hot water tank@2000;Diswash@800=32,520/240=135A

Note: You can add as many non-service rated panels as you want--->It's what you add (load on panel) that matters.

Assuming a total of a 30 amp load both for the AC and air handler, and a full 40 amp load for the hot tub, using the Optional AC Larger than Heat method, I arrive at at service rating of 122 amps, which is still a bit liberal.

So your 200 amp service has plenty of capacity. Your last question, use #2 Aluminum SER 4 wire cable to feed the new panel with a 100 amp breaker in the main panel. Be sure to use a separate equipment ground bar in the new panel and do not connect the neutral to the equipment ground.

Be sure to use anti-oxidant compound on the aluminum wire connections.

FYI, thanks for the list of breakers in the main panel, however that info is irrelevant, as the total and ratings of branch circuit breakers do not have anything to do with sizing a service.

You will be doing this work under a permit and have the work inspected?

QUOTE=Washington1]I believe you do. I haven't had a chance to work the numbers (Generally-since we have no hard numbers), but from what I read, you should have a enough--seeing that you have a gas range, and have decided to rid the 40A welder.

Your Current lighting load/ w derating is approx=5520watts
Hypo: Now even if you add a Range@8000; heat@10,000 (with the heat omitting the AC unit); dryer@5000;dispo@1200;Hot water tank@2000;Diswash@800=32,520/240=135A

Note: You can add as many non-service rated panels as you want--->It's what you add (load on panel) that matters.[/QUOTE]

Thanks for responding. With reference to the above, I have no plans other than the future hot tub to be connected. The heat and hot water are from the oil burner/furnance.

Quote:

Originally Posted by tkrussell

Assuming a total of a 30 amp load both for the AC and air handler, and a full 40 amp load for the hot tub, using the Optional AC Larger than Heat method, I arrive at at service rating of 122 amps, which is still a bit liberal.

So your 200 amp service has plenty of capacity. Your last question, use #2 Aluminum SER 4 wire cable to feed the new panel with a 100 amp breaker in the main panel. be sure to use a separate equipment ground bar in the new panel and do not connect the neutral to the equipment ground.

Be sure to use anti-oxidant compound on the aluminum wire connections.

FYI, thanx for the list of breakers in the main panel, however that info is irrelevant, as the total and ratings of branch circuit breakers do not have anything to do with sizing a service.

You will be doing this work under a permit and have the work inspected?

Thank you again TK.

Yes it will be under a permit and will be inspected.