Add subpanel?

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Old 08-13-17, 01:59 PM
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Add subpanel?

I would like to add a kitchenette with small cooktop, maybe a microwave, and small fridge in the basement.

[edit for clarity] Unfortunately my main panel is full and anyway too far away to run a new line without ripping open several walls (i.e. I don't want to address a new line to the old panel)...but...

I have a 50AMP wire that passes by the area in the basement I am working on. Right now it terminates at a plug outdoors that I use to power the house (backwards) with a generator in emergencies. Don't need any help with that.

What I am thinking is that I will put some sort of switch and then a small subpanel on that line. Regular operations it would go to the kitchenette and have separate circuits for the cooktop (20A), MW, and one for a few plugs. The current breaker in the main panel is 50A GFCI.

In emergency power situations I would switch the circuit to the outdoor plug and go back to the old system, cutting off the kitchenette completely.

Any thoughts on this plan? Any recommendations on what to get as far as a switch and subpanel, or am I way off track?

Access is easy as the finished area getting the upgrade backs up to a open wall in the unfinished section, with all the wires out in the open. I have done a fair amount of wiring but mostly plugs and lights (finishing the basement with successful inspection), not appliances.
 

Last edited by orca15; 08-13-17 at 03:27 PM. Reason: clarity on adding new circuit
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Old 08-13-17, 02:36 PM
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Right now it terminates at a plug outdoors that I use to power the house (backwards) with a generator in emergencies. Don't need any help with that.
Do you mean an inlet? A receptacle would be dangerous.
What I am thinking is that I will put some sort of switch and then a small subpanel on that line.
Does your panel take tandems? What is the make and model number of your panel?
 
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Old 08-13-17, 03:22 PM
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Thanks for the reply. Answers:

1) Don't need any help with the current termination of the 50A line. I am willing to get rid of the current termination (generator input) but only as a last resort.

2) The current main panel is Square D series S01 (circa 2004) but is far, far away from where I want to put the sub-panel, and running any new line from the old panel to this area is impractical for several reasons (without major work). I want to address only the question at hand, which is "is it feasible to splice into a rarely used 50A circuit, add a switch and sub-panel, and service a kitchenette, while maintaining the ability to cut off the kitchenette and use the circuit as before." Unless you have some idea how to use a tandem CB and the existing wires to service two terminations, which I can't imagine, I think that question is off-track.
 
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Old 08-13-17, 05:07 PM
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Don't need any help with the current termination of the 50A line.
We look for any unsafe conditions. The term "plug" does not apply as you used it that and your reluctance to discuss what you have raises red flags. If you have an inlet not a receptacle why not just say so.

The line to the generator if properly installed disconnects the power to the panel when it is connected to the panel.The line to the generator should have an interlock that prevents the breaker for the 50 amp being on unless the main breaker for the house panel is off or it has a transfer switch which again means power to the main breaker is turned off when it is connected to the panel.
 

Last edited by Tolyn Ironhand; 08-13-17 at 06:43 PM. Reason: added a "d"
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Old 08-13-17, 05:21 PM
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As Ray said the generator input to the main panel should be set up such that when it's being used it locks out the POCO power to your home. This can't be done if you do what you are proposing because when the circuit is providing power to the kitchenette it would have to be on while the incoming power is on. You wouldn't have any way to block out incoming power when you were on your generator, this creates a very dangerous situation for those working to restore power.

In order to comply with code requirements you are going to have to run a new circuit to the kitchenette or to the generator.
 
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Old 08-13-17, 06:59 PM
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or am I way off track?
Yes, you are off track. I know of no switch or equipment that can do what you propose safely. Plus the wires going to the "plug" will not be long enough to make the terminations that would be required in a panel or transfer switch.

The best you could do is eliminate the emergency line and use that to power your sub panel, if there are 4 wires.
 
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Old 08-14-17, 08:07 AM
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The termination of the 50A line is a large pull out switch (cutoff? same as what is by the AC units) that was used for a spa, but no longer used for that. The generator input is a theoretical use, You all have convinced me not to use it. I will run an extension cord up to my refrigerator. I only meant I don't need to worry about that right now because it is something I was going to deal with later. Didn't mean to raise "red flags"--I was just trying to use shorthand for a future project but obviously got us anchored. Sorry. The point is I would like to keep that circuit available because it is in a handy location.

So I would still like to maintain that circuit in case I ever need it again. I am not sure why it is impossible to put a switch in. The kitchenette is only going to be used when we have guests, so why can't I choose when it is powered up? And when I am talking about the pre-sub-panel switch, I really mean something that takes power in and sends it one way (old termination) or the other (sub-panel to kitchenette) but not both. In my amateur mind this seemed like a reasonable thing I could buy, I was imagining something that looked like the safety switches you see in a shop with a big handle...but instead of OFF/ON it would be CIRCUIT 1/CIRCUIT 2. Sounds like that isn't possible? Something like this 60 Amp 240-Volt Non-Fused Indoor General-Duty Double-Throw Safety Switch?

As far as the wires go, my plan was to cut the wire in the basement, run it to the switch, then splice enough back in to re-complete the circuit. Is there something special about 50A wire that would keep me from doing that? Obviously I would use a proper splice, whatever that needs to be (haven't looked yet).
 

Last edited by orca15; 08-14-17 at 09:15 AM. Reason: Clarity
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Old 08-14-17, 09:02 AM
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I am not sure why it is impossible to put a switch in.
Because if it is correctly connected to the main panel for use to carry power from a generator the line is DEAD when there is power to the main breaker. Any line used for a generator must have a method that automatically disconnects the main breaker from power to house when the generator line is connected to the breaker box.

You can use it assuming there are four wires. You will need to abandon the outside portion. You will NOT be able to use it for a generator. Are there four wires? What gauge?
 
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Old 08-14-17, 09:50 AM
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OK let's completely give up on the generator idea. It was just something I was considering for the future. Easy to install one of those automatic transfer switches up by the main panel when I get there and put the generator near the garage by the main panel. So...right now there is no generator, no automatic transfer switch, just a 50A existing breaker with a wire through the basement to the outdoors for a spa. Again, sorry I got us tied up with the whole generator thing.

yes four wires.

Focusing on the sub-panel, and some sort of mechanical (not automatic) switch like the one I quoted, what is the issue? Why abandon that circuit if I am willing to swap power between it and the kitchenette if ever needed?

So my proposal would be

Main--->double throw switch-->

-->subpanel (or)
\-->outdoor terminator

All four wire, all 50A wire. I'll check on the gauge but it's quite thick and professionally wired as 50A for the spa.

[added] and thanks for all the help!
 
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Old 08-14-17, 10:06 AM
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In case it is not clear, I am pushing back on abandoning the extra (albeit unused) 50A circuit coming out of the (proposed) switch because some of this work is going to get closed in when I do some planned finishing to the basement. Not sure if I will ever need it, but there is also possibility that I will add some high amp workshop equipment someday and the ability to switch off the rarely used kitchenette and power something else is just an option I really don't want to abandon unless necessary. I can't tell you how hard getting from there to my main panel is...I'd have to tear open half the house.

Maybe the best way to imagine this is in its possible future state:

existing 50A CB at the main, existing 50A wire, to a (new) manual double throw switch, to two different sub-panels. One for kitchenette, one for workshop. Both rarely used, no need to power both simultaneously, only one can be on at a time via double throw switch.
 
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Old 08-14-17, 11:06 AM
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Why the switch? The first subpanel can feed the second. No switch needed.
 
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Old 08-14-17, 01:39 PM
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Why the switch? The first subpanel can feed the second. No switch needed.
Because both subpanels would be fed by a single 50 A wire and would both have many (30-50A) of load possible. Just the kitchenette has 20A cooktop, 15A fridge, and a few lights and plugs. I suppose I could do what you are suggesting and just let the main panel 50A CB do it's job but my suggestion seems safer (to me) ensuring the load would never get past 50. Am I missing something?
 
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Old 08-14-17, 01:49 PM
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Am I missing something?
Yes. Count up the total amp ratings on all the circuit breakers in your main panel and compare that to the main circuit breaker. Most of the time the sum of all the branch CBs is far more than the rating of the main CB but the main does not trip because not every circuit is using the rated amperage. In my home I have over 900 amperes of circuit breakers but only a 200 ampere main. Doubtful if the full load ever surpasses 100 amperes and that would only be in winter when I might have both of the electric heaters in the garage running.

In other words, when you are using the kitchen you most likely will not be using the workshop and vice versa. Save the cost of the switch (literally hundreds of dollars) and the second sub-panel.
 
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Old 08-14-17, 02:21 PM
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OK, If the 50A CB on the main would protect the 50A wire going to the basement add-on sub-panel, (and I guess that's sort of the whole point!) then that is a reasonable solution. It never occurred to me to put more than 50A of stuff in the sub-panel but as you say, there is really no chance of everything running at once.

So the configuration I think we are talking about is

Main-->50A CB-->50A existing wire-->Sub-panel--> many circuits (20A cooktop, 2x20A workshop, 15A microwave, 15A mini-fridge and some plugs).

Great suggestion. Sorry for the blind spot.

[added] I assume the above would meet code for having those appliances on "a separate circuit?" That part is new to me, having only dealt with non-kitchen wiring before. Also, should I keep the GFI 50A CB (yellow pushbutton) in the main or use a regular CB? Seems like the existing GFI would cover the whole kitchenette, right?
 
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Old 08-14-17, 02:25 PM
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Sorry for the blind spot.
Nothing to be sorry for, it is a common misconception.

I wish you well, my friend.
 
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Old 08-14-17, 02:34 PM
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Before we go further please describe the wires to the basement. Is it 6-3 NM-b (AKA Romex) or are they individual conductors in conduit. If #6 copper THHN/THWN then you could increase the breaker to 60 amps.
 
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Old 08-14-17, 02:53 PM
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Not separate conductors in a conduit, at least as I understand that question. It is four wires in a sheath. Says "Type NM-B AWG 6-3 with AWG 10 Ground."

When the sheath is cut away it is a B-W-Red plus bare ground (all solid) with the gauges per the above.
 
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Old 08-15-17, 04:58 AM
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So that is cable and is good for 50 amps. Use a 100 amp either main lug or main breaker panel to give you plenty of spaces. Sometimes a main breaker panel kit with several branch circuit breakers is cheaper than a main lug with no breakers. Either can be used since it is in the same structure so if you want go by price.
 
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Old 08-17-17, 12:05 PM
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Thanks for all your help. Went by the county inspector's office this week and they had no issue with the 100A subpanel on the 50A line, with the 50A CB up on the main.

[edit] Was unfamiliar with a "lug" but I get it now. No main disconnect/breaker so I would have to use the one at the main panel. Will likely use a breaker even if more $$ just for convenience.[/edit]

Did raise the question of whether I should leave the 50A CB as GFCI up on the main panel, or make it a regular CB and put GFCI CBs in the subpanel. We decided to just leave it and test the circuits at the end and see what happens, but appreciate any thoughts on:

Would you leave a subpanel, which will have at least a couple of GFCI CBs on it, being fed by a GFCI CB or swap to a regular CB?

They couldn't really point to any code issues. We did hypothesize that there may be more nuisance trips.

Also, I will likely put a 50A CB in the subpanel and reconnect the rest of the original circuit (to the spa outdoor location) just in case I ever want to use it or tap into it for a workshop device as discussed. Any thoughts? Perhaps I will just swap the main 50A GFCI CB with a regular then move the old one to the new subpanel as this "spare" circuit and solve both problems.

Again thanks so much for helping get my head wrapped around the very simple solution.
 

Last edited by orca15; 08-17-17 at 12:38 PM.
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Old 08-17-17, 12:34 PM
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I am not familiar with a "lug," is it just like a main but with no overall CB?
Yes.
Did raise the question of whether I should leave the 50A CB as GFCI up on the main panel, or make it a regular CB
No, best to change to non GFCI and use GFCI receptacles or breakers if protection is needed.
Would you leave a subpanel, which will have at least a couple of GFCI CBs on it, being fed by a GFCI CB or swap to a regular CB?
One GFCI feeding a second GFCI is not recommended. It can sometimes cause a problem and makes troubleshooting more difficult.
 
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Old 05-09-18, 08:04 AM
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OP Here-

Just wanted to let folks know that your help was fundamental in completing the installation successfully. I replaced the original (unused outdoor Spa) 50A GFCI on the main with a standard breaker. I installed a 100A lug for the kitchenette, cut the existing 50A wire and ran it to the lug, then out of the lug on a GFCI to a point where I spliced it back in to the old wire. SO I have the lug on a 50A standard breaker and the old line on a 50A GFCI, should I ever reinstall the hot tub (very unlikely!).

Main--> 50CB --> 6-3NM --> 100A lug --> 50A GFCI --> 6-3NM -->Unused spa terminus.

100A lug --> small cooktop, fridge, small appliance, microwave, and workshop circuits.

The 100A lug has been flawless running the kitchenette and even gave me an extra 20A circuit for the workshop (which gets used infinitely more than the spare kitchen).

Everything done to code, passed inspection, and buttoned up. Mother-in-law now using the new basement suite, and happy to have her own fridge and coffeemaker, etc.

Thanks all!
 

Last edited by orca15; 05-09-18 at 08:21 AM.
  #22  
Old 05-09-18, 09:54 AM
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Great job. Just minor terminology correction. That is main lug panel. "Lug" alone has a different meaning.
 
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