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I'm rewiring my 1957 house because there was no ground. I have a main panel and a subpanel in the crawlspace that currently only give power to the gas furnace. I want to add the air conditioner on the subpanel (30amp breaker), a 20 amp breaker for microwave and some outlets in kitchen, a 15amp for furnace, and a 20 amp for my bathrooms outlets.

Can I keep aluminium wire feeder? What size breaker at the main panel? I understand I need a ground kit for my subpanel, can I install it anywhere in the panel? Thank you.

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    Welcome to Home Improvement! Can you add some clarity, please. Are both the main & sub panel in the crawlspace, or just the sub? Are both panels preexisting, or have you already installed 1 as part of the project? Is there a main shutoff breaker in the sub panel, if so, what amp rating? In general Al wiring is just fine so long as the terminals it's attaching to are rated for Al wiring. Also, please take the tour and read the help center. We prefer to have one question at a time, even if the questions are closely related. It makes it easier for those answering and for those who find it in the future. – FreeMan Jun 15 at 20:32
  • Thank you, both panels are preexisting. Main panel is in laundry closet and the subpanel in crawlspace. There is no main breaker in the subpanel. Breaker on feeder line is a 90amp – Sylvain Cussonnier Jun 15 at 20:39
  • Electrical regulations vary from place to place. Check you local code, rather than make an expensive mistake that will need to be fixed and inspected. – DrMoishe Pippik Jun 15 at 20:49
  • How tall is your crawl space, I had a split level that had a section 6’ tall 30x20 We dug out the area 6’7”tall 3’ wide and 48” in front. We had a nice work space down there changed the door way so lawn equipment could be worked on and stored in there, the height was checked several times by the inspector but that panel made it much easier to add a hot tub and lights receptacles down there, today the receptacles would have to be GFCI but if you have 6’6” it is code compliant , I know many inspectors will let the height slide a little if it was preexisting and was being updated to breakers. – Ed Beal Jun 15 at 23:32
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That sub has a laundry list of issues. It probably has to go.

First, it can't be in a space unless it can be walked to by an erect human being, who can stand up, and there's a never-blocked space 30" wide x 36" deep x 78" tall in front of the panel. Crawlspaces are Right Out unless "crawlspace" is slang for an underfinished part of your basement.

Generally the best place for panels is in mandatory pathways that cannot be blocked with stuff, such as hallways or entrance thresholds. Because that required working space overlaps with the pathway space which is already reserved, and it is unlikely to be blocked in since it's a practical pathway.

Second, it's wired "3-wire" with 2 hots, a neutral, and no ground. First, there needs to be a ground wire (this could be retrofit if the location wasn't prohibited), and second, neutral needs to be entirely separate from ground. Not sharing a bar.

You can retrofit an accessory ground bar in those panels which don't include them from the factory. You can force-fit them anywhere by drilling and tapping #10-32 or 8-32 screws, but the manufacturer usually leaves you some holes perfectly spaced, formed and pre-tapped for their ground bars. Ground bars are one of the few things that are OK to mix-n-match across panels, but then the holes won't line up, and they're so cheap that who cares?

A ground could be retrofit normally, but since this panel location is no good, the panel must be moved anyway. So you can't upcycle this cable for a new panel installation - you'll have to run modern 4-wire including ground.

Third, this panel is much too small to be useful. It's likely that a lot of projects were not pursued because of the lack of sufficient spaces to support them. Aim for a 24 or 30 space. It's OK if the panel ampacity exceeds the feed breaker, just as it's legal to drive 70 mph on 130-mph-rated tires.

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  • My crawlspace is around 4ft where the panel is, I thought it was possible because of this "110.26 (E) exception" – Sylvain Cussonnier Jun 16 at 1:33
  • (E) Headroom The minimum headroom of working spaces about service equipment, switchboards, panelboards, or motor control centers shall be 2.0 m (6 1/ 2 ft). Where the electrical equipment exceeds 2.0 m (6 1/ 2 ft) in height, the minimum headroom shall not be less than the height of the equipment. Exception: In existing dwelling units, service equipment or panelboards that do not exceed 200 amperes shall be permitted in spaces where the headroom is less than 2.0 m (6 1/ 2 ft) – Sylvain Cussonnier Jun 16 at 1:35

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