Will this work? 200 amp sub panel to 200 amp subpanel

[reader2580]

I currently have a detached garage with a 200 amp panel fed by a 70 amp feed from my house. I ran a 2" conduit when I did this in 2017.

I am planning to build a large garage for a motorhome. Can I replace the wire from the house to the current garage with a size rated for 200 amps and then run wire from the current garage panel to a 200 amp panel in the new garage?

I tried searching here and I gave up after looking through a half dozen pages of results. At the house the garage feed is tapped into the wires coming from the meter and bypass the house panel. This was done because I have solar on the garage. Is the feed from the house to garage considered a service so I can get by with 2/0 copper for 200 amp, or do I need 3/0 copper?

 

[wyliesdiesels]

So the current detached garage feeder is tapped straight off the service entrance from the meter meaning no disconnect?

 

[reader2580]

So the current detached garage feeder is tapped straight off the service entrance from the meter meaning no disconnect?

Yes. I never even thought to question it and the inspector passed it. This is becoming more and more common for solar installations since some of the installations are bigger than a 200 amp panel is rated for.

This was done by a licensed electrician who only does solar, not me.

 

[reader2580]

So the current detached garage feeder is tapped straight off the service entrance from the meter meaning no disconnect?

I did a few minutes of research. This is allowed in 705.12(A) of the NEC. Electrical production sources may be connected on the supply side of the service entrance disconnect.

The question might be is it legal to power the detached garage from this supply side tap? The solar is all on the detached garage so if the solar and the feed to the garage were run separately then the rule that a detached structure cannot have two sources of power would be violated.

My main question is still can I run power from the subpanel in one detached structure to the subpanel in another detached structure? I don't have room near the house to run another 2" conduit from the house panel to the new structure. I barely got the current 2" conduit to clear the gas line, electric line, and every other thing buried in that area.

 

[wyliesdiesels]

I wasnt questioning the legality of it. Just wanted to make sure I understood the setup.

Yes of course you can connect a subpanel to a subpanel.

That has been discussed on this site numerous times.

You wont find anything about that in the NEC because code is permissive.

 

[theoldwizard1]

I am planning to build a large garage for a motorhome. Can I replace the wire from the house to the current garage with a size rated for 200 amps and then run wire from the current garage panel to a 200 amp panel in the new garage?

That is a HUGE amount of power for a garage that is basically only going to house a motorhome ! Besides the 50A connection for the to motorhome, what else is going to be in that second garage ?

(IMHO, you are going to spend a lot of money for no good reason.)

 

[reader2580]

That is a HUGE amount of power for a garage that is basically only going to house a motorhome ! Besides the 50A connection for the to motorhome, what else is going to be in that second garage ?

No, I probably don't need 200 amps. I was just thinking that since I have a 200 amp capable load center in the garage that I might as well just go to 200 amp wire while I was at it. House to current garage is 75 feet of wire. The distance from current garage to new garage will probably be 40 to 50 feet of wire.

I am currently at 70 amps to my current garage. I will probably want to upgrade that to 100 to 150 amps to cover both buildings.

The motorhome garage will also be used as a shop, but nothing more energy intensive than a table saw and welder most likely. If I can afford it at some point I will add heat and air conditioning.

 

[reader2580]

I wasnt questioning the legality of it. Just wanted to make sure I understood the setup.

Yes of course you can connect a subpanel to a subpanel.

Sorry, I was thinking you were questioning why I did a supply side tap before the service disconnect.

 

[wyliesdiesels]

No, I probably don't need 200 amps. I was just thinking that since I have a 200 amp capable load center in the garage that I might as well just go to 200 amp wire while I was at it. House to current garage is 75 feet of wire. The distance from current garage to new garage will probably be 40 to 50 feet of wire.

I am currently at 70 amps to my current garage. I will probably want to upgrade that to 100 to 150 amps to cover both buildings.

The motorhome garage will also be used as a shop, but nothing more energy intensive than a table saw and welder most likely. If I can afford it at some point I will add heat and air conditioning.

You're putting the cart before the horse.

bigger is not always better in this situation.

Do a load calc first.

As the wizard pointed out, the power you want is way overkill.

If all that will be in there is a stored unused motorhome running a battery charger(?) and a table saw or welder, then no need for even 100a. The motorhome will not use the full current of the 50a outlet. If you wont be running the AC or any appliances inside of it and its just gonna be stored there, you could probably get by with a 120v outlet and an adapter for shore power....

Now the feed to the first subpanel MAY need to be upgraded depending on tools used, number of people AND the load calc....

Sorry, I was thinking you were questioning why I did a supply side tap before the service disconnect.

NOPE. I'm well aware of outside taps and the rules (very minimal) regarding them.

 

[reader2580]

A big part of my problem is I don't really know how much load I will have in my new garage. Initially I could probably get by with a single 20 amp circuit for the garage door opener and a few lights. Over time I hope to add insulation, HVAC, and then move some stationary power tools out there. It could take years, if ever, to get enough money together for the insulation and HVAC.

The primary reason I put in a new conduit to my current garage was for my solar. I couldn't hardly run solar on a three wire connection to a crappy load center with no ground at all.

The three things in my current garage that take higher amounts of power are a welder, a 10,000 watt heater, and a compressor.

 

[nadogail]

Please tell me if I do not understand your question.

I think you are asking if you can put 200 Amp conductors (really fat wires)in a conduit that has 70 Amp conductors.

Is that your question?

My answer is it depends on the size of the existing conduit.

 

[reader2580]

Please tell me if I do not understand your question.

I think you are asking if you can put 200 Amp conductors (really fat wires)in a conduit that has 70 Amp conductors.

Is that your question?

My answer is it depends on the size of the existing conduit.

No, I think I didn't phrase things properly. My real question was if I can run power from one detached structure to another detached structure? The answer to that appears to be yes.

The 3 AWG wires for the 70 amp would be pulled out and replaced with larger cables. Conduit is 2". At the time I wasn't going to be allowed to build another building on my property so I thought 70 amp was plenty.

It sounds like something more in the 100 amp range will be enough compared to doing 200 amp.

 

[nadogail]

If the existing conductors in the 2" conduit are not copper, you may want to consider replacing them with copper.

 

[reader2580]

The existing conductors are copper.

 

[sberry]

3 copper will carry 100 that distance. You will not have 100 continuous load. Doesn't matter how much you got its how much is running at once.
Since its now in place, now working and nothing is going to change and changes are in the distant future do what you got to do now and run another 100A panel to the new and it wont be any more work to upgrade the rest if and when its needed. If the wire in place is in good shape and modern why mess with it and park more copper in it today that wont work any better. Get power to it so it can be used, in 10 years if you need more fix it.
Moving stuff from garage 1 to garage 2 doesn't change the load on the feeder to garage 1 but I have wired a couple 3 dozen small garages, a couple of them busy like this, 5 hp air and an air conditioner and never trip up a 60,,,,, never.
Falcon on this forum has a bunch of stuff, runs it on 70 with room to spare, never a trip. The goal isn't to see how much you can use or how much it can possibly use but to provide adequate service. A modern welder now runs on from 16A to 25A service, a 5 hp air is 23 run, good sized air cond on 20 service, big ones on 30 and that isn't their run.

 

[sberry]

I have a couple panel to panel to panel hookups. Got a service with 15 panels on it, maybe more.

 

[reader2580]

Sorry, I was incorrect on the wire size. It is 4 AWG, not 3 AWG. Good for 85 amps at 75C or 70 amps at 60C.

I have stuff in my basement shop that will end up in that shop if I add HVAC so it isn't just stuff moving from my existing garage. I suppose I could just stick with 70 amp to start and replace all the wire later if I need to go bigger.

 

[dcg9381]

I have a dual feed situation (from the meter) using correct lugs. My meter splits to 2 x 200A panels. It's legal and a "supported configuration" from my power company. I'm rated to 320A total amp service.

The solar is all on the detached garage so if the solar and the feed to the garage were run separately then the rule that a detached structure cannot have two sources of power would be violated.

My guess is that you don't understand how solar works - the misconception is very understandable. I also have 6KW of solar on the garage side. Typical grid-feed PV situations - the solar is not a separate source. The inverter will shut down as soon as the grid shuts down, as required by NEC, as such, it's not a source.. There are a very few installs that have "stand alone" power available at the inverter or feed a bank of batteries, but these circuits are isolated and not tied in.

Note, you cannot tie in a generator with solar. Just FYI.

My main question is still can I run power from the subpanel in one detached structure to the subpanel in another detached structure?

From my garage panel, I have 3 additional parallel sub-panels that are 50-60A each.
Check out "Siemens Talon" -they are exactly what you want for an RV setup (50A, 30A, and 20A connections) with a few extra breakers and they're about $150. I use one inside the building for an RV, one or the north side for an RV, and one on the south side for an RV.... Just in case RV friends show up. You can't beat them for the price, already wired, include breakers.

There is an eventual limit of how many sub-panels / disconnects are allowed.. but a sub-sub-panel is certainly ok.

70A is probably more than enough for a shop and a 50A RV connection. A 50A RV connection, even running dual ACs, you're won't hit 50% capacity.. I regularly run a hot tub, residential refrigerator, RV water heater, 2 RV ACs, 2 ductless split units (4 tons total), and a bunch of misc during the heat of summer all on a 90A feed. Note, the solar WILL add to your available capacity at the panel it's tied into, when producing - it reduces the line load.

PM me if you want details or suggestions.

 

[reader2580]

My understanding is code does not allow two power sources to to a detached structure. Meaning I could not run one circuit from my house to my garage for the solar and a separate circuit from the house to the garage to feed the rest of the garage.

I am well aware of solar shutting down during a power outage.

 

[dcg9381]

> My understanding is code does not allow two power sources to to a detached structure

This is true. It's worth noting that there are exclusions to this general rule (not that apply here) per NEC.


> Meaning I could not run one circuit from my house to my garage for the solar and a separate circuit from the house to the garage to feed the rest of the garage.

I understand what you're asking. As you can't draw power from solar circuit through an outlet and the array cannot energize the building, etc - this *MAY* be allowed. It's not really a "power source" and if you shut down power to the garage, everything is dead (except the array, which is outside). To be honest, I'm not 100% sure and it might be interpretive.. I know that the rule exists so that if you shut down the "main" to a building that there are no secondary "surprise" circuits that stay hot in the building.

If you wanted to do it this way, I'd feed the garage from the house and run the solar array into the panel in the garage... It accomplishes the same thing, probably costs less than two runs to the house.

I'm not sure why you need to feed solar back to the house unless you have separate meters for the house and for the garage. With a single meter, it doesn't matter where the solar feeds from because it's essentially net metering at the meter...


The other benefit of having the array tied to the shop is that it supplements the available power. My shop is only on a 90A feed, but I've got another 30A of solar (at peak) - so 120A available, depending on conditions...

I've attached a simplified diagram of what I've got going on, which sounds similar.

No insult intended on indicating that PV shuts down when the grid does..

 

[reader2580]

I understand what you're asking. As you can't draw power from solar circuit through an outlet and the array cannot energize the building, etc - this *MAY* be allowed. It's not really a "power source" and if you shut down power to the garage, everything is dead (except the array, which is outside). To be honest, I'm not 100% sure and it might be interpretive.. I know that the rule exists so that if you shut down the "main" to a building that there are no secondary "surprise" circuits that stay hot in the building.

If you wanted to do it this way, I'd feed the garage from the house and run the solar array into the panel in the garage... It accomplishes the same thing, probably costs less than two runs to the house.

All of my solar power is already fed through the garage panel and back to the house.

The reason I was thinking I would like to have separate feeds is for sub-metering for an electric car for off-peak rates. I was thinking the power company would want the second meter at the house and I didn't want to pay the peak rates for my new garage if I add HVAC.

I talked to the engineer at the power co-op today and he said I can put the second meter on whichever garage will house my future electric car. That means that only the power going to the electric car charger would go through that meter with the high peak rates.

 

[dcg9381]

All of my solar power is already fed through the garage panel and back to the house.

Got it.

My take is that the solar is not a "source" for the purpose of NEC. It's not supplying power to the garage. Check with your PoCo engineer.

The reason I was thinking I would like to have separate feeds is for sub-metering for an electric car for off-peak rates. I was thinking the power company would want the second meter at the house and I didn't want to pay the peak rates for my new garage if I add HVAC.

Around here, just having a meter connection is $20/mo with zero power usage. If a 2nd meter is free, I get it.. Otherwise the cost of that meter may wash.

I don't quite get the off peak deal. I assume you want to charge the car nights/evenings when rates are low?
HVAC the garage, you're producing solar during peak rates and using power during peak rates. Your solar production is most valuable when rates are high.

I'm not quite on the same page, but I hope I've been helpful.