I have to add an outdoor sub panel rated 60 AMPs and I need at least 8 spaces for breakers. I am not finding this anywhere unless I buy a 125 AMP rated breaker box. Is it acceptable to install a 125 AMP rated panel when the need is only 60 AMPs. I have 200 AMPS service in the house and have space for a 60 AMP breaker in my main panel
Electrical – install 125 AMP rated sub-panel when the need is 60 AMPS
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You can't just throw in a bigger breaker, and expect it to work the way you want.
First of all, you're going to have to have the utility install conductors sized appropriately for 200 ampere service. Depending on how the building is wired, you'll also have to upgrade the conductors that run from the service drop to the meter (this might be handled by the utility, depending on how the building is wired). Next, you're going to have to upgrade the conductors that run between the meter and the disconnect (likely handled by installing the new panel pictured). Finally, you may have to upgrade some of your grounding and bonding conductors, as they are typically sized based on the size of the service.
Once all that's done, then you can likely proceed as you've described. However, you're going to have to evaluate how the system is grounded. The service neutral will have to be bonded in the new panel, where the 200 amp disconnect lives. Then you'll have to feed the existing panel (now a secondary panel), with a 4 wire feeder (hot, hot, neutral, ground). You'll also have to isolate the grounded (neutral) bar in the existing panel, if it's not already.
Long story short, this is not a simple job. There are a lot of subtle details, that can easily be missed by a DIYer. I would recommend having an Electrician at least help you plan the project, and inspect the completed work.
Does the sub-panel seem over loaded? If so, I could keep the water-heater in the main panel and free up space in the panel another way.
Seems reasonable to me. Most of the equipment won't draw anywhere near the overcurrent rating, at least not during normal operation. Motor loads will draw a higher current on start, but you shouldn't have a problem.
I know I need four-strand wire to run to the sub-panel (2 hot, neutral, ground) but copper or aluminum and what gauge?
You can use either copper or aluminum, though I recommend copper for DIYers. Copper is quite a bit more expensive, but it's easier to work with (in my opinion). If you feel confident working with aluminum conductors, you can save some money using it.
I've covered the topic of feeder sizing here, so I won't go into detail. If you're using copper, you'll want to use 3 AWG conductors. If you choose to use aluminum, you'll need 1 AWG conductors.
If you want to run a single cable, instead of individual conductors in conduit. You can buy what's called 3-3-3-5 SER cable (1-1-1-3 for aluminum), which will contain three 3 AWG conductors (hot,hot,neutral) and a 5 AWG grounding conductor.
When I run the wire along the floor joist, does it need to be secured to the joist or can it just hang there and rest on the drop ceiling? Seems like it should be secured to the joist with wire hanger or something.
You'll have to attach the cable to the joists, using 1 - 1 1/4" staples or other approved means. Check the packaging, to make sure they are rated for the size cable you're using.
What are the things about this project that I don't know that I don't know. :) These are the scary things IMO...i.e. the questions I don't know enough to ask.
The cable you'll be working with is thick and heavy, and it's not going to be fun pulling it. You'll probably want a couple helpers, to help you wrangle it.
Make sure all your connections are tightened to the manufacturer's specified torque.
If you choose aluminum conductors, make doubly sure you tighten the connections. And don't forget the anti-oxidant.
Come back a day or two after the panel has been put into service, and tighten any connections that need it.
Don't forget to remove the bonding jumper between the grounded and grounding bus bars.
You'll need clamps big enough for the cable, to secure it to the panels.
should I put a 100 amp breaker in the sub-panel to act as the "main" for the sub-panel? Or is the 100 amp breaker in the main panel sufficient?
You can usually pick up a main breaker panel, for about the same price as a main lug only (MLO) panel. In my opinion, unless the secondary panel is next to; or within sight of, the main panel. You're better served to install a main breaker panel. It simply offers better protection during maintenance, or other work within the panel.
For example. If you turn off the feeder breaker in the main panel, and start working in the secondary panel. Somebody could easily come along, and flip on the feeder breaker. Since you can't keep an eye on the breaker, you can never be sure the panel will be dead. (unless of course you're using a lockout like you should).
If the secondary panel is in a separate building or structure, then you either need a main breaker, a main disconnect, or the ability to disconnect all ungrounded conductors within 6 or less hand moves.
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Best Answer
Please install a bigger box!!!
Your box definitely should exceed minimums in this area: Number of spaces. Listen, there's always a future project, there's always another load. The out-of-pocket cost for a larger panel is very small (especially when you consider other factors, as we're about to). But the regrets and unnecessary expense when you run out of spaces is a rather expensive affair.
As such we very strongly recommend you wildly oversize your panels. You need 8 spaces? Consider nothing less than 24 spaces. All of our panels here have plenty of extra space (except an 8-space Pushmatic that's a nightmare) and that's the way we like it. I myself would go 30-space.
I mean "space" not "circuit" - you see a lot of 20 space/40 circuit panels - that's only a 20-space.
You wouldn't drive 85 mph on 85 mph-rated tires, would you?
Suppose you lived in Nevada where posted limits are 80 mph. Yeah, you'll want the 115 or 130 mph tires I think :)
The same applies to service panel amp ratings. You wouldn't run 60A on a 60A box, would you? Of course not, you want some safety headroom. So 125A or even 200A is perfectly reasonable. It's a "limit" thing, not a "mandatory match" thing.
This also ties into the "spaces" problem because I gather you were feeling stifled with only 8 spaces. As well you should! You are at liberty to get as large a panel as you want.
You need a main breaker there!
To be more precise, you need a main disconnect switch. But the cheapest most practical way to get that is to use a box with a main breaker.
Now I happen to know none of the 8-space panels on the market include a main breaker. So setting up one of those "straight" would be a code violation. If there are 6 or fewer throws, "no main breaker" can be legal, but never with 8.
You might skate by the "Rule of Six" if two of your breakers are 2-pole. However that "paints you into a corner" of being unable to add a seventh throw in the future. And you know you will!
Voltage drop - yikes
Obviously, voltage drop will be a big problem. At 2 AWG wire and 48A draw (figuring for 80% of your 60A breaker that you seem happy with), your voltage drop will be 7.04%, which is high even by my standards.
That would not be acceptable in Canada or in a Tim Horton's restaurant. In Canada you'd be required to use 4/0 AL wire, which is ridiculous in my opinion, eh?
I haven't priced 600' of that stuff but I'm sure I will not like the price.
By the way, if you aren't in Canada, you are allowed to breaker the feed breaker for whatever the wire limits are, e.g. 90A for #2 aluminum.
Transformers!
Like I say, I haven't priced the fat wire, but it may be worth looking at transformers for the long haul. The wire is good for 600V (and 600V transformers are readily available in Canada), but around the States 480V is more likely to be findable cheap used. If you're buying new transformers then price 600V.
In this case, you use 2 transformers back to back, 480V-jumpered primaries facing each other. This steps up the transmission voltage to 480V. Now, the wire gets a lot thinner (for the same voltage drop).
If you do it Canada-style, holding voltage drop to a firm 3% at 80% of rated current, then #4 aluminum will suffice, eh? From 4/0 down to #4, that's the power of transformers for 'ya! If you don't mind that 7% drop from your original proposal, are you sitting down? #8 aluminum or #10 copper gets it home.
So transformers let you drop 6-8 numerical sizes. More if they are 600V transformers.
However, I would recommend #6 aluminum at that point, giving a very acceptable 4.29% drop at 48A practical draw (80% of breaker trip).
You probably won't push the wire to its thermal limits. The reason is the transformers are a limiting factor also. I'm imagining you get 15 KVA transformers which will limit you to 60A@240V total throughput and you'd have to breaker for that at the supply side to protect the transformer. You might get a better deal on used 25 KVA transformers, which would let you got 100A @ 240V. If that's the plan, a bump to #4 Al wire might be called for.
Obviously transformers are not free, but they make the wire a lot thinner, so you have to crunch the numbers and see what you get.