No slots in Panel -- Would tandems make sense?

sconwayNovember 3, 2012

I have two panels each 200A in my basement. They are both full; each box has 20 slots. I am in the process of buying a 20KW generator for my home and finishing a small unfinished area in the basement.

The unfinished area houses the water heater, sump pump, an extra refrigerator and a furnance; I have breakers for these. I want to add a few more ceiling lights, a ceiling fan, some more outlets to handle a treadmill, a stairmaster, tv, and radio.

I am assuming that I will need to add some breakers to satisfy these new things.

Question1, can I replace some of the breakers for tandems to make room for any other "wishes?" My box says that I can use tandems in almost all spots.

Also, will I need anything special to connect my generator (I will have an electrician do it but I want to educate myself so I don't get ripped off). I will have an automatic transfer switch.

Question2, if I can combine breakers, how can I calculate the true load on each braker to prevent from tripping? I have many breakers with the same reference - i.e., Kitchen/Dining Room (3 breakers of 20A/120V each)

thank you for your help!

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What I would do is to first 'map out' the circuits in the house to find out exactly what is on each breaker. This will help you decide which underused circuits may be able to be combined as well as which ones you will want to have powered by the generator.
I restrict my usage of tandems to lighting and lightly used convenience outlet circuits, but maybe that's just me.
If you haven't done so already, I recommend you do a little on-line research about transfer switches. The cost can go up considerably as you add more circuits to its load.

    Bookmark   November 4, 2012 at 8:13AM
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If the panel is listed for them, not a problem.

    Bookmark   November 4, 2012 at 2:39PM
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I have looked at both panels. My problem (for the generator) is that the AC units are in separate panels. One houses a 3ton the other a 4ton. Also, I have 3 refrigerators which are spread out (kitchen, basement, garage). Other than heat/AC and refrigerators,I can live without the rest. But I understand that I cannot have both AC's in the same panel so I would need 2-200ATS?

As for the basement redo, I was thinking of tandems except for the ones with refrigerators (not marked but easy to find out).

I am looking at a Cummins Onan and Generac. I have read bad reviews for Generac so I am afraid of going with them. Costco has an Onin 20KW cold weather with a 200 ATS for $5699. Will I need to buy another ATS to handle both panels? Also, how much do you think the installation will cost? I amhoping to stay at $8K total. Is this possible?

    Bookmark   November 12, 2012 at 9:07PM
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" But I understand that I cannot have both AC's in the same panel so I would need 2-200ATS? "

How big are the units?

Their requirements determine if they can be in the same panel.

Adding up breakers does not tell you anything.

The load diversity allows the breakers to add up to well over the main rating in a panel.

    Bookmark   November 13, 2012 at 1:44PM
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I don't understand why you didn't get a 64 slot panel in the first place. At tandems you will only get 40 connections in one panel. Two panels ? That must take up a lot of room. Probably doesn't look that good either.

    Bookmark   November 13, 2012 at 4:42PM
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I have two units AC/furnace units: a 4 ton/basement and a 3 ton/Attic.
I did not get a 64 slot panel in the first place because what I have is what came with the house!

Anyway, this is all getting more involved as I need to consider the following:
1)this is the time to upgrade my panel since I will need to get permits to work on the generator but my breakers are Thomas&Betts. Will I need to replace the panel and all the circuit brakers or are there any compatible UL brakers?

2)Will I need to upgrade my gas pressure? I have standard meter that holds up to 325K BTUs.

3All installers are familiar with generac but all I have read is that generac has many customer service problems. Is this still valid? the comparable cumins Onan is about $1200. Is it worth the extra expense?

thank you to all who have answered and are helping to educate me.

    Bookmark   November 16, 2012 at 11:19AM
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Breakers are rarely listed in anything except the manufacturer's a panel.

    Bookmark   November 16, 2012 at 5:01PM
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