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Mystery breakers in my breaker box

Discussion in 'Charging Standards and Infrastructure' started by dbullard, Nov 10, 2012.

  1. dbullard

    dbullard Member

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    I'm looking at my existing breaker box (circa 1975) as a prelude to mapping everything out (i.e., which outlets, switches, etc. map to which breakers) before I get a new outlet in the garage for charging my S, and found I have some which I can't really identify what they do.

    I have two pairs of breakers that are 2x60-amp ganged - that is, each is effectively a 120-amp breaker, for a total of 240 amps (see picture - they occupy numbers 25-32). Considering the master breaker for the box is only 200 amps, that seems like a lot.

    The major users of electricity are already mapped out (heat pump, fan, dryer, lights, etc). I have no idea what these do. I know when I bring an electrician over to give me an estimate, they'll probably be able to tell me, but I'm curious.

    My plan is to get two estimates - assuming all the breakers in the box are actually in use, how much for a new breaker box with an extra for the charging outlet, the other estimate would be keeping the existing box and adding the charging outlet to the dryer circuit. I can deal with not using the dryer while the car is charging overnight.

    Of course, if one of the mystery breakers is truly not used, then I don't need a new box.

    Anyone have an idea what these might be used for?

    Thanks,

    Doug
     

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  2. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    The simplest way is to turn them off and see what goes off. You can also look for any high power wall sockets that don't have anything plugged into them. It's possible they were for the old HVAC system before the heat pump installation.
     
  3. rabar10

    rabar10 FFE until Model 3

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    Ganged breakers are for 240V loads; each breaker is on one 120V leg of the feed. So each is only for a 60A 240V load. Still big, though, especially not knowing their use. I agree with jerry33 - flip one at a time and see what happens...
     
  4. Tommy

    Tommy Member

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    Some homes use to have electrical radiant heating either as baseboard units or actually wired into the ceiling. Might be that.
     
  5. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    Tommy is right. If a direct circuit, 60A will likely be a heating load of some sort - radiant ceiling heating (embedded wires), or baseboard, or ceiling tile heat. It could also be a 60A subpanel located somewhere - say a garage, or attic, that you don't know about. I'd recommend poking your head in the attic too.

    But I have some other bad news that you might need to consider. That's a Federal-Pacific Electric (FPE) breaker panel. FPE breakers are notorious for failure to trip, and I've experienced it myself in an old panel in a rental house when I lived in the bay area. Many insurance companies will refuse to insure a house with an FPE panel. It's not going to be inexpensive, but you may want to consider an electrician's help in replacing that panel anyway.
     
  6. qwk

    qwk Model S P2681

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    Yes, this is very important. I would never in a million years want to put a long continuous load(EV) on a FPE box breaker. It's not a question of whether you will have a fire, but when it will catch on fire.

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  7. dbullard

    dbullard Member

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    Hmm, not great news, but good to know. I'll definitely check with the electrician. Older houses can be such a pain for stuff like this, always surprises...

    To answer some of the suggestions, though - no electrical heating other than the heat pump and aux elements. No other breaker boxes I know of in the attic or elsewhere.

    After some playing around, one of them seems to be the auxiliary heat elements for the heat pump (for when it gets too cold for the the heat pump to work effectively). Makes sense to have that on a separate breaker from the heap pump itself, and 240V at that. I turned the breakers off and set the temp for 90+ degrees - saw what the temp was coming out of the floor registers was with just the heat pumps. Flipped the breakers on, and the hot air temp jumped 15 degrees. Flipped'em off again, and it dropped, so that's a pretty good indication that's what it was. Some more binary flipping and I identified which one was responsible.

    I thought the other must the hot water heater - it's electric, and 240V, and I don't see a breaker listed for that. It was hard to tell if it's on or not if I flip the switch, so I had to run the hot water until it was cold and see if it heated up again. It did - that must be breakers 10&11.

    The one I know is now labeled (who installs stuff like that and then doesn't bother labeling them?)

    I'd reserved $1500 for a new breaker box, looks like that was a wise decision. Thanks for the tip on the FPE panel - you never know when someone like an electrician is trying to scam you for extra $, now I know it'll be for real.

    Still gonna drive me nuts not knowing what that breakers for!


    Doug
     
  8. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Right. I replaced the FPE box in my house a couple of years ago--fortunately, no fire.

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    An unfortunately large number of people and sometimes the ink fades into illegibility. Or worse, the use of a breaker changes and the original label is still there.
     
  9. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    I know the feeling. While doing my inventory, I had my boys running around with a handheld lamp trying to find the breakers that I didn't have labeled. We got them all except one. Turns out when I pulled the cover to the front panel, there was a breaker in place but no tap from it, so I had found them all.

    One of mine was a circuit intended for a built-in microwave where the oven+microwave combo exists (which uses only the 240V oven circuit). So you're likely to find small ones like that too.
     

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