Convert a disconnect to panel?

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Old 07-31-19, 02:50 AM
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Convert a disconnect to panel?

About 25 years ago I built a solid log cabin with 200amp service. The load center is on an interior wall and there is a 200amp disconnect just below the meter outside (so the load center is really acting like a subpanel).

I am going to add solar power and was going to do that through a subpanel as I don't have room on my primary load center. My original plan was to mount a 100amp subpanel outside and tie it to my main load center (i.e. 100amp subpanel off of the 200amp subpanel).

Then I had this epiphany; why not convert my disconnect to a small 200amp subpanel then run both my main 200amp load center and the 100amp subpanel off of what was previously a disconnect? this would be a whole lot easier than trying to access my 200amp load center that is buried in an interior wall in the cetner of the house.

There must be some problem with this logic as I can't find a 200amp circuit breaker for any of the standard panels on the internet.

So, is there a way to run both my 200amp primary load center and new 100amp subpanel off of my disconnect and if so, how?

Thanks
 
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Old 07-31-19, 05:41 AM
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There are two ways to accomplish this. The first is to leave the meter as-is, and replace the 200A disconnect with a 200A main panel. That new panel will then have a breaker for your solar system and a breaker for the indoor panel. There are 200A circuit breakers, but they usually have different frame sizes. For example in the Siemens line you would use a QN2200 or QN2200R breaker which takes up 4 spaces (two full rows).

The other way to accomplish this would be to replace both the meter and the disconnect with a CSED (combined service entrance device), which is a meter and main panel all in one box. This option also allows you to feed 200A into the building and install whatever breakers you need for the solar system.

In either case, the first breaker after the meter is always the building "main panel", which will make your interior panel a subpanel. It may require some rewiring in that panel to feed it with a four wire feeder and separate grounds and neutrals if that isn't already done in the current configuration.
 
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Old 07-31-19, 08:40 AM
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Thanks for the input.

I think I am just going to try and replace the disconnect with a similar (physically) sized load center.
I am going to be dependent on the power company coming out to pull the meter so I can work and I think just replacing the panel will happen faster with less down time (as compared to replacing both with a combined panel).

Since I posted I did find a Square D 200 amp breaker; I just need to make sure I have the right box.

Luckily, I left some "slack" on the line from the disconnect to the inside panel so I have should be able to work with what I have already pulled.

Also, I surprised myself (I was working full time and doing this on the weekend; in a fog) that I actually grounded the system appropriately so the inside panel is set up as a subpanel with the neutral/ground unbonded and separate ground.

This will also give me a chance to move that sewer system connection (installed by the water company with these dracula-like taps on my main feed lines) to a breaker which I suspect is a safer install.

Thanks for the input.

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Old 08-01-19, 09:42 AM
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I am going to be dependent on the power company coming out to pull the meter so I can work and I think just replacing the panel will happen faster with less down time (as compared to replacing both with a combined panel).

Don't forget that in most areas a wiring approval from the electrical inspector is required before the power company can reconnect your service or install a meter after your work is completed.
 
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Old 08-01-19, 06:39 PM
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Yes, I've talked with the power company inspector today who has agreed in principle with what I am planning.
He said he would come out, do my disconnect, check out what I am doing and reconnect when done.
This is a rural area and if I understand correctly the power company does the inspections and there isn't a separate entity.

I'm trying to getting everything I need together so I can get it done quickly.
I assume I used 4/0-4/0-4/0-2/0 AL SER for my feed (I remember it was SER, AL, and very hard to work with!).
I can get a Square D Ground Lug that accepts 2/0 but how do I connect my 4/0 neutral to the bus? I can't find a SD 4/0 lug. I don't think the neutral bar can handle 4/0.

Also, is it best to install the 200amp Branch Breaker at the top of the panel? I assume getting it closer to the service feed will reduce resistance through the bus. Or is that negligible?

Thanks for your input.
 
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Old 08-02-19, 05:15 AM
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Square D lug #LK225AN will do what you need for the neutral. The breaker does not have to be near the top. It's best to position it where ever you get the most working space and bend radius for the #4/0. Sometimes going up and around is a better option than straight to the breaker. Use some Noalox paste on the aluminum wire terminations to inhibit corrosion.
 
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Old 08-02-19, 07:13 AM
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This is a rural area and if I understand correctly the power company does the inspections and there isn't a separate entity.

There are quite a few rural areas with no AHJ that operate just as you describe, the power company inspects the service just to be sure it is safe. Why not look for a 200 amp main breaker loadcenter with feed-thru lugs so you don't have to buy a 200 amp branch breaker to feed the inside panel? Just feed it from the feed-thru lugs. You shouldn't have to buy any separate lugs this way either. Then, install the 100 amp breaker for the new subpanel.
 
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Old 08-02-19, 07:59 AM
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Thanks for the lug part number - I hadn't found that on my previous searches.
I was going to use the LK100AN for the 2/0 ground but that is only rated for 100amp so I guess I should use the LK225AN even though it will fit in the LK100AN?

I will look into the feed through lugs option. The 200amp Branch Breaker is as expensive as a whole 200amp panel so that option might be easier and less expensive. I'm in Square D territory - do you have a preferred brand?
 
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Old 08-02-19, 10:45 AM
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You can use the smaller lug for the ground wire. I considered recommending a feed-through panel, however I think this might be a complication with your intention to add solar supply to the panel. I'm not 100% sure that it is required, but I'm leaning towards it being necessary once the solar is online. The reason is that you could theoretically have 200A coming in from the power company, 30A coming from the solar and therefore have an overload of 230A on the feeder.

As a practical matter however that is never going to happen at a log cabin in the woods, so a feed through panel is a reasonable compromise if you wanted to go that way.
 
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Old 08-02-19, 04:24 PM
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Thanks for spending so much time on this.

To help me understand, you are saying that if (for instance) the Solar was generating 30amps and the subpanel was pulling 200amps that could create a situation where the subpanel is being exposed to 230amps thus exceeding the breaker/rating?

And a feed-through panel would help avoid that situation by feeding the subpanel directly from the service feed?
 
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Old 08-04-19, 07:03 PM
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Actually, I think I understand. The concern is exceeding the bus amperage capacity, not the breakers.
would a feed-through avoid that or still possibly exceeding the bus rating?

at this point, I think Iím just going to create a PV only sub panel off of my new, main panel.
 
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Old 08-05-19, 05:31 AM
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A feed through panel only has a 200A main breaker on the incoming side from the power company. It then just has an extra set of lugs that allow you to feed the 200A out to a subpanel without the expensive 200A branch breaker. Essentially both the main panel and the subpanel share the 200A main breaker.

This is no problem when both panels and the feeder between them is rated for 200A. However when you add solar into the mix, you have the potential to inject more amps after the main breaker. In theory you could have 200A coming in from the power company, 30A coming in from the solar inverter and therefore 230A going into the house panel.

As a practical matter this is a tremendous amount of power that will not happen in a modest residence. As a code matter I think the 200A branch breaker is required and a feed through panel is not allowed as it is technically possible to exceed 200A on the subpanel feeder. Given that you are in an area with loose inspection requirements in my opinion (and as recommended by Joe above) it would be OK to choose the non-code option of a feed through panel to save the $200 if you wanted to.
 
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Old 08-08-19, 07:52 AM
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I've confirmed what I am planning on doing with the inspector at the utility company who handles their solar installations. He approves my swapping out the disconnect with a new 200 amp outdoor panel, running my interior panel off of a 200 amp branch breaker, and having a separate PV-only panel that ties into the new exterior panel but he is requesting a mechanical disconnect between the PV panel and main panel, not just breakers.

I'm trying to find an affordable disconnect that is rated for at least 70 amps as I may eventually add that capacity (actually max 55 amps x 125%) to my system. Any suggestions? I can only seem to find 60 amp disconnects locally/affordably.
 
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Old 08-09-19, 05:56 AM
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Unfortunately no. There is a massive price jump between 60A air conditioner disconnects ($10) and 100A disconnects that will probably be over $100. The search terms you'll want to use are 100A, non-fused, 2-pole and 3R (outdoor rating).

The disconnect shouldn't need the +125% rating unless he specifically told you to get one that large. Ask him if a 60A A/C disconnect is OK.
 
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Old 08-15-19, 04:39 PM
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Well, I did my panel swap and install over the last two days. Had it inspected today by an elderly inspector whom seemed uninterested in engaging in discussions around bus capacity, why I was setting it up the way I was, etc. His primary concern appeared to be centered around my primary and sub panel grounding (which was correct). So got his stamp of approval. As I mentioned before, the utility solar experts only concern was that I have a mechanical disconnect, not just a breaker for the PV panel.

On another issue, I had the water/sewer rep come out and convinced him to let me redo the work they did several years ago. It not only looked sloppy but they didnít cement any of their conduit connections (even the buried ones) and has 12g wire on a 30amp breaker. Pisses me off that they get away with doing a crappy job.
 
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Old 08-16-19, 05:12 AM
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12g wire on a 30amp breaker
That could be OK for a dedicated pump circuit depending on the motor size.
 
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Old 08-16-19, 05:54 PM
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Ok. I was wrong.
Do I ground my disconnect? Iím using a 60amp AC unit box with lugs for the two hots and a neutral bar. Do I have to ground the box itself?
 
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Old 08-17-19, 07:35 AM
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I think the answer to the above is "yes" that I need to bond the disconnect box to ground, but which ground, the supply side or subpanel side? And do I need to put a small lug bar into the box to accomplish this?

Thanks.
 
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Old 08-17-19, 08:09 AM
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All grounds are tied together always.
Bonding ground to neutral is different issue.
 
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Old 08-17-19, 08:38 AM
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It is quite possible that the #12 and the 30 amp breaker is correct. Motor loads are sized using different rules.
 
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Old 08-17-19, 12:16 PM
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My disconnect switch (GE TNA60R1CP) doesn't have any type of a ground lug (just a neutral pass-through lug) so I bough a small lug bar that I will bolt to the case. I assume that would be acceptable.
 
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Old 08-19-19, 05:06 AM
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Yes a bar or screw mounted to the disconnect box is acceptable grounding.
 
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Old 08-19-19, 05:18 AM
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Thanks. This box has a pass through lug that I assume is for Neutral but it is not insulated from the metal disconnect box.
The disconnect box is attached to the subpanel with a metal nipple.
I assume that will create a bond between Neutral and Ground at the subpanel level which I don't want, correct?
Can I just "pass" the Neutral through the disconnect? without attaching it to the lugs/box?
 
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Old 08-19-19, 05:23 AM
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Yes that would be preferred to pass the neutral through and use the lug for ground instead. Leave a loop of neutral wire so it can be cut and spliced if you need to in the future.
 
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