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Our breaker panel is exactly opposite of the corner of the house of the best site for minisplits. We really should have gotten minisplits a long time ago, our house is currently heated with electric radiative ceiling heat, but I would really hate to give up the space needed to put in ducting.
I'm thinking about putting in a 100 amp subpanel on that side of the house to avoid running multiple wires. Aluminum is cheaper, for one thing. I feel like if I can ever get an HVAC company to put in the minisplits, it would avoid a lot of disruption to have much of the electric already done. And I'm also into the basement ceiling right now. I also want to put in a subpanel in the garage. Our breaker box is full, duplex breakers are not allowed, and I need some outlets in the garage. I figure I might as well get my money's worth out of the building permit.
Can anyone point out a good reason not to do this other than it's overkill?
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Sounds good to me. Except the 100a part. 60 would likely be enough. And check with your local authorities on the aluminum. In my area it is not allowed inside a dwelling. Not even to connect from the mast head to the box.
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(06-15-2021, 08:53 AM)kencombs Wrote: Sounds good to me. Except the 100a part. 60 would likely be enough. And check with your local authorities on the aluminum. In my area it is not allowed inside a dwelling. Not even to connect from the mast head to the box.
Check on the minimum size sub panel box in your area.
Ours is a 100 amp panel but can be fed with a smaller breaker such as a 60a. Roly
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(06-15-2021, 09:05 AM)Roly Wrote: Check on the minimum size sub panel box in your area.
Ours is a 100 amp panel but can be fed with a smaller breaker such as a 60a. Roly
I don;t think I can buy a subpanel here that is rated for less than 100A. Of course you can feed it with a smaller breaker. However I'm a big believer in 'just in case' so I would feed it for the full 100A. The difference in cost is the larger breaker and the wiring.
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Is aluminum prohibited by the IEC inside a building? The code guys previously let me run aluminum to my shop, which is wholly inside the house.
I thought the problems with aluminum wires are mostly related to small wires going to outlets and lights. I don't think most of those are rated for aluminum even today, but subpanels are.
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06-15-2021, 11:55 AM
(This post was last modified: 06-15-2021, 11:56 AM by Roly.)
EricUIs aluminum prohibited by the IEC inside a building? The code guys previously let me run aluminum to my shop, which is wholly inside the house.
I thought the problems with aluminum wires are mostly related to small wires going to outlets and lights. I don't think most of those are rated for aluminum even today, but subpanels are.
Aluminum is not prohibited by IEC inside. Widely used for larger conductors such as feeders to main panel inside, ranges, furnaces,etc. All devices must be rated for AL and proper installs. A 100a sub panel does not need to be fed by a 100 amp breaker, as long as the sub feeder cable and breaker for the sub panel match you are ok. Between main and sub panel you need four conductors with the neutral and ground separated in sub panel.
You can still by receptacles and switches rated for aluminum .
I would run copper from sub panel to the mini splits. Roly
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(06-15-2021, 11:01 AM)EricU Wrote: Is aluminum prohibited by the IEC inside a building? The code guys previously let me run aluminum to my shop, which is wholly inside the house.
I thought the problems with aluminum wires are mostly related to small wires going to outlets and lights. I don't think most of those are rated for aluminum even today, but subpanels are.
Any prohibition of aluminium inside (or outside) of a building would be a local thing. The NEC has no such prohibitions, and it's still common practice to use aluminium SE cable into your main panel and SER for subpanels. There are code prohibitions against using certain insulation types inside buildings, like USE cable, but that's due to the fumes released in a fire, and is independent of the chemistry of the actual conductor.
The problem with Al wiring had a lot to do with the wire chemistry, which didn't like the heat/cool cycling which resulted in either embrittlement and eventually mechanical failure (then arcing, then fire), or the heat/cool cycling caused deformation which eventually loosened the connection (then arcing, then fire). I don't recall the details any more, as things came to a head way long ago, like the 70's.
Tom
“This place smells like that odd combination of flop sweat, hopelessness, aaaand feet"
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How do I tell if wire is rated for indoor use?
(06-15-2021, 11:55 AM)Roly Wrote: I would run copper from sub panel to the mini splits. Roly Yeah, that was the plan. But I think the difference in price for the panel to subpanel would make it worth it. I was around for the house fires caused by aluminum wiring, so I'm biased against it even though everyone says its safe now.
I think I will run wire big enough for 100a and possibly protect it with a smaller breaker. It's not a horrible amount of work, but I don't want to regret my decision later.
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06-15-2021, 12:47 PM
(This post was last modified: 06-15-2021, 12:48 PM by Roly.)
(06-15-2021, 12:20 PM)EricU Wrote: How do I tell if wire is rated for indoor use?
Yeah, that was the plan. But I think the difference in price for the panel to subpanel would make it worth it. I was around for the house fires caused by aluminum wiring, so I'm biased against it even though everyone says its safe now.
I think I will run wire big enough for 100a and possibly protect it with a smaller breaker. It's not a horrible amount of work, but I don't want to regret my decision later.
Make sure the smaller breaker will accept the size wire you install. Why a smaller breaker ?
A lot of the aluminum problems was the difference in the expansion rate of aluminum and copper/brass. When the aluminum wire expanded from heat but the other part of the connector did not expand as much the aluminum would try and squeeze out, then when cooled the aluminum that squeezed out was no longer keeping the connection tight.
Old adage you can surround copper with aluminum but cannot surround aluminum with copper. i.e. Don't use copper lugs with aluminum wire. Roly
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The easiest way to get the cable from one end of the house to the other is through the chase they made when they put a soffit around the I beam that holds up the house. It seems like if I just run it down that chase, it will be protected and supported. Anyone want to speculate if they will make me fasten it to the I beam? I think it wouldn't be much of a problem to cut into the drywall periodically and clamp it to the web of the beam, but I don't know that I see a reason to do that.
I'm not sure if they blocked it, so I might try running my fish tape down the beam
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