sub panel, main breaker question

[Bill Dufour]

I will be installing a 200 amp subpanel in the shop. It will only be supplied by 50-70 amps or so. Can I use the existing 200 amp main breaker rather then buy a new lower amp one? To buy a main switch seems to cost more then a breaker does to fit the same panel location serving as a main disconnect.
Bill D

[Maurice Mcmurry]

For sub panels I have always used a main lug rather than a main breaker panel.

[Zachary Hoyt]

In my new workshop I used a used 100 amp panel from the house. I only had 50 amps feeding it. My electrical inspector told me to backfeed the panel through a 50 amp breaker and just leave the 100 amp breaker at the top in place but not connected. It may be different where you are, though.

[Tom M King]

The wire to that panel is protected by the properly sized breaker for the wire on the feed end. The main breaker in that panel just becomes a disconnect.

[Charlie Velasquez]

Yes, you can.
Done all the time.

Circuit breakers need to protect the wiring.
The wires feeding your sub will be protected by the breaker in your main.
The individual circuits in your ….

Never mind, I type too slowly.
I see Tom has already said this.

[glenn bradley]

Answers will be geographical. Consult the NEC; I believe we are currently complying with the 2022 edition in SoCal. These things are very easy to comply with once you know what version your state, county, and town are following. Deviations can result in insurance companies not paying if things go sideways.

[Jim Becker]

It will work fine as a disconnect (and it's nice you'll have one at the shop end...my shop disconnect is up at the house where the service splits), but I agree with Glenn that the local jurisdiction is where the final word lands.

[Bill Dufour]

Logically a over sized breaker is as good or better then a switch rated for even more amps before it fails. But logic does not always apply to rules.
Bill D

[Maurice Mcmurry]

Looking at the code, turns out mine with main lugs is in violation because it is in a detached building. It was inspected and passed. That is not surprising because our town voted in favor of not requiring the city engineer to have a degree in engineering.

[Charlie Velasquez]

Looking at the code, turns out mine with main lugs is in violation because it is in a detached building. It was inspected and passed. That is not surprising because our town voted in favor of not requiring the city engineer to have a degree in engineering.

Depends on year code you're area was using. The disconnect rule was started in the 2020 edition. Prior to that it was the rule of six. Must be able to disconnect power with no more than six throws.

[Jim Becker]

Yes, many jurisdictions remain on the 2017 (?) version of the NEC for their reference...mine included.

[Maurice Mcmurry]

Depends on year code you're area was using. The disconnect rule was started in the 2020 edition. Prior to that it was the rule of six. Must be able to disconnect power with no more than six throws.

OK! It was 2010 and I have 6 breakers. Good to know. Thank you Charlie.

[Charlie Velasquez]

OK! It was 2010 and I have 6 breakers. Good to know. Thank you Charlie.
Just as an aside, if you had had more than six breakers, and included several 120 volt circuits, you could bring it into compliance by getting approved handle ties and linking a couple of 120’s (or going to 240 volt breakers, one circuit on each leg).

You would maintain the over-current protection but have to put up with both circuits going off if either circuit trips a breaker.

[Bill Dufour]

In my new workshop I used a used 100 amp panel from the house. I only had 50 amps feeding it. My electrical inspector told me to backfeed the panel through a 50 amp breaker and just leave the 100 amp breaker at the top in place but not connected. It may be different where you are, though.
That seems like a poor idea. In an emergerncy a fire fighter would assume the top centered breaker, not in line with the lower ones was the main breaker.
Everyone knows the top most breaker is the main breaker without reading the old fadded labels..
Bill D

[Maurice Mcmurry]

That seems like a poor idea. In an emergerncy a fire fighter would assume the top centered breaker, not in line with the lower ones was the main breaker.
Everyone knows the top most breaker is the main breaker without reading the old fadded labels..
Bill D

I have used convertible panels. They come with "permanent" labels. Relying on labels will keep you compliant in most cases. In an emergency, in smoke, with a BA pack on, expecting a fire fighter to read the labels is asking a lot. I am wishing I had not gotten by with the rule of 6 back in 2010.

I have been trying to help my father in law sort our a failed inspection in Boston for over 30 years. A big, single function disconnect right inside the front door is required. We eventually received permission to use a shunt rather than rewire the entire main service. That was over 20 years ago. Eventually that work will have to be done. Now we are going to have to replace the entire service, under ground, out to the street, upgrading from 200 amps to 400 to meet the current requirements. I sure wish F.I.L. and his electrician had gotten this sorted out in 1987.

[Tom M King]

I changed an overhead 200 amp Service Entry on a rental house to a 400 amp underground. The power company charged me $1700 to run the wire 75 feet, and that was with me digging the trench. They did at least provide the meter base and hook it up, but the rest was up to me, including filling the ditch back in.

[Zachary Hoyt]

That seems like a poor idea. In an emergerncy a fire fighter would assume the top centered breaker, not in line with the lower ones was the main breaker.
Everyone knows the top most breaker is the main breaker without reading the old fadded labels..
Bill D

I would have preferred to use the existing 100 amp breaker as that would have saved me $20 or so to buy a breaker, but since he's the person in charge I did it how he said it had to be done. There is a meter main on the outside of the house that cuts power to everything after the meter, and I would think a firefighter would use that.

[Jim Becker]

Zachary, at least put some colored tape over that unused 100 amp breaker and a label that indicates it's not in use "just to be sure" there is never any misunderstanding. I agree that it's a potential hazard for first responders, contractors and future owners.

[Maurice Mcmurry]

I changed an overhead 200 amp Service Entry on a rental house to a 400 amp underground. The power company charged me $1700 to run the wire 75 feet, and that was with me digging the trench. They did at least provide the meter base and hook it up, but the rest was up to me, including filling the ditch back in.

My Father In laws estimate to have Pignatelli upgrade his service is over $20,000. That was a few years ago. It is a 3 family Owner occupied property.

[Tom M King]

I had to provide everything else. That was just for running the wire to the meter base.

[Maurice Mcmurry]

Tom, you certainly get stuff done! We met with the Rural Electric Engineer out at our little woodlot recently. They will bring in medium voltage and set a transformer, overhead or underground. 300 feet is included in the $2500.00 new service fee. I have to remove a lot of trees or provide a 5 foot deep trench. We are leaning towards underground.

[Tom M King]

Fortunately, we only need it to be 2' deep here. I had to rent a walk behind saw to cut the pavement, and a mini-excavator. I filled it back in with my tractor loader. They used the old transformer, but did have to set a new pole. I had to call them about four times to come back and take the old pole out. I wasn't there when they set the new pole and ran the wire.

I had most of the stuff in years of leftovers to change the boxes, but did have to buy the new box on the right.

The worst job was cutting the over 50 year old concrete footings to provide access for the wire to come up under the meter. No pictures of the finished job. This is somewhere in the process before I cut the footing.

sorry about another sideways picture. The box on the left is over the location of the original meter base.

The old overhead service was hanging too low for me to get a big excavator past the house to get down on our point. I need power down the hill too, so went underground and large enough to pull a couple of subpanels off this service. There will be a 200 amp subpanel 487' from this one, and another 60 amp one 300' past that one.

[Maurice Mcmurry]

I guess they want ours 5 feet beep because the wire will be 13,800 volts. It is recommended that we get county water at the same time and use an excavating contractor that the utility companies likes to work with (not my old 25 hp compact tractor and wobbly 3 point back hoe)

[Ronald Blue]

I had to provide everything else. That was just for running the wire to the meter base.

You do have some red dirt there Tom. Black as can be here. Cost me over $5K to have 400 amp service ran in. Bored all the way from the other side of the street 350 feet. I had to supply the meter base. Lever bypass with disconnect. That was another $800. They sat a transformer a few feet from the meter on the side of my shop building. Not sure what the voltage coming in is. Whatever the overhead is carrying out at the street. Only 2 or 2-1/2' deep.

[Tom M King]

Yes, good bricks are made around here. All you have to do is dig it out of the ground, mold them, and fire them.

[Maurice Mcmurry]

Yes, good bricks are made around here. All you have to do is dig it out of the ground, mold them, and fire them.

After seeing the Hallmark made for TV movie "The Last Brick-Maker" I can not pick up a brick without thinking about Red Clay and the places it comes from. We have blue-grey clay around central MO. It is great for making fire brick but lousy for holding up a house.

[Zachary Hoyt]

I was lucky when I had 200 amp service put in to the house here. I had to provide the meter main, the conduit mast up the side of the house with the wires to the top, and everything downstream from there, but the power company ran the new line from the pole to the top of the mast at no charge.

[Tom M King]

Our power company doesn't charge for overhead service entrance either, but the overheard wire went over the 15' wide access to our point, and it was too low to get any piece of heavy equipment under it. I needed to get rid of it.

[Jim Becker]

Local power company here doesn't charge for normal (reasonable) overhead installs, or for replacing meters, at least in my experience.