100a main to 100A sub?

[MrPink]

So I had an electrician come out today for a quote on putting in the sub-panel for my garage. I was blown away by what he had said. 10k total cost, because they would have to update the main panel to 200A to even support the sub. I have read and have been told by other electricians that a 100A main can feed a 100A sub. Is this correct? I won't be using the total of 100A in the sub all the time, 30-50a 220v for a dedicated heater(only used in winter and only on while I am out there), 20a for my air compressor, 30a 220v for welder, 20a for the outlets, and 15a for lighting. Am I crazy to think that this can be pulled off well under 10k? Or do I absolutely have to upgrade to 200a service?

 

[wyliesdiesels]

Well was a load calc done on your main service? its possible your main service is maxed out(doubt it unless the house is all electric and large) but absent of a load calc, no way to know for sure.

what electric loads do you have in the house?

 

[Fasthotrod]

Technically, no... but as WD mentioned, what you really 'need' depends on the load calcs. It also depends on the physical size of your existing main panel, and if you have a space available for a breaker to feed your sub-panel. The cost is dependent on your location, as wages vary from one location to the next. Current supply chain issues have caused an increase in costs for materials as well, so don't be too surprised if it's higher than normal, or what you may have expected.

To answer your question, the NEC allows you to have sub-panels rated the same as the main. So for instance, if you had a 100A main breaker in your main panel, then installed a 100A breaker in that panel to feed your sub-panel, and had a 100A breaker as the main disconnect in your sub-panel, it's okay by Code.

Because the breakers are all in series, the Main breaker would be the one that had the most current flowing through it, and would likely trip first before your 100A feed to the sub-panel, or trip the 100A in the sub-panel. If there were some random fault in the sub-panel, then it's a race to see which breaker will trip first. (Because there is not proper breaker coordination, but that's another topic for another time.)

If I am not mistaken, you could technically feed a 200A sub-panel from a 100A Main panel... but with the understanding that the 200A breaker is not going to provide you with circuit protection and will simply be used as a disconnect. Protection of the conductors would be based on the Main breaker, or the feeder breaker.

If you have done the load calculations and know how much power your system draws, it may work out just fine.

Depending on the condition of the existing panel, its age, and availability of parts, replacing your existing Main panel might be the only option available to him. (Breakers to be used in your existing panel must be UL Listed for use in your panel. If they are not, he cannot install them per Code.) Without knowing all of the details of the project, I can't tell if the person that quoted the job is doing it right, or price gouging you. The devil is in the details, so they say.

Hope this helps.

Mark

 

[MrPink]

I don't believe it is overloaded and no a load calc was done, here is pictures of my main. The one labeled window air unit has my work computer plugged in. we got rid of the window air unit. And the one labeled "hot tub" is for our jet tub in the bathroom.

 

[MrPink]

Technically, no... but as WD mentioned, what you really 'need' depends on the load calcs. It also depends on the physical size of your existing main panel, and if you have a space available for a breaker to feed your sub-panel. The cost is dependent on your location, as wages vary from one location to the next. Current supply chain issues have caused an increase in costs for materials as well, so don't be too surprised if it's higher than normal, or what you may have expected.

To answer your question, the NEC allows you to have sub-panels rated the same as the main. So for instance, if you had a 100A main breaker in your main panel, then installed a 100A breaker in that panel to feed your sub-panel, and had a 100A breaker as the main disconnect in your sub-panel, it's okay by Code.

Because the breakers are all in series, the Main breaker would be the one that had the most current flowing through it, and would likely trip first before your 100A feed to the sub-panel, or trip the 100A in the sub-panel. If there were some random fault in the sub-panel, then it's a race to see which breaker will trip first. (Because there is not proper breaker coordination, but that's another topic for another time.)

If I am not mistaken, you could technically feed a 200A sub-panel from a 100A Main panel... but with the understanding that the 200A breaker is not going to provide you with circuit protection and will simply be used as a disconnect. Protection of the conductors would be based on the Main breaker, or the feeder breaker.

If you have done the load calculations and know how much power your system draws, it may work out just fine.

Depending on the condition of the existing panel, its age, and availability of parts, replacing your existing Main panel might be the only option available to him. (Breakers to be used in your existing panel must be UL Listed for use in your panel. If they are not, he cannot install them per Code.) Without knowing all of the details of the project, I can't tell if the person that quoted the job is doing it right, or price gouging you. The devil is in the details, so they say.

Hope this helps.

Mark

100A sub panel into a garage which is 20ft from the main panel. But the location I want the sub panel on is on an interior wall that separates the enclosed porch and my garage. so it would be 40-50ft of 100A rated wire to feed a panel which will have what i listed in the 1st post.

 

[theoldwizard1]

Most garage shops can easily be feed from a 60A breaker in the main. With 60A you may not be able to run the heart, welder AND compressor all at the same time. Pick 2 and shut the third one off.

 

[mike93lx]

You have a 20a 120v hot tub? Never seen one of those.

IMO, you have lots of capacity remaining. Call in a new electrician.

 

[MrPink]

You have a 20a 120v hot tub? Never seen one of those.

IMO, you have lots of capacity remaining. Call in a new electrician.

its a jetted tub in our bathroom

 

[mike93lx]

its a jetted tub in our bathroom

Ah, makes sense then

 

[wyliesdiesels]

I don't believe it is overloaded and no a load calc was done, here is pictures of my main. The one labeled window air unit has my work computer plugged in. we got rid of the window air unit. And the one labeled "hot tub" is for our jet tub in the bathroom.

I think you meant to say that a load calc WASNT done.

If thats the case then the electrician is talkong out of his ***. Get a new one

You dont have much load on that service at all.

Whats with the 30a range? Never seen a range circuit that small. Theyre either 40a or 50a...

 

[sparky 1971]

It wouldn't bother me to feed a 100 amp sub off of that panel if it were mine. The existing panel may not be listed for a 100 amp breaker though, in which case, whatever it's listed for would probably be sufficient since it's going to be at least a 60. (It should say on the door somewhere.) If there is concern, run a separate circuit for the heater at the same time the wire for the sub is pulled.

As far as the price to upgrade to 200 amp, that may not be out of line. One city and another county here require to house to be updated whenever a panel is changed. A single story house with an unfinished basement starts around $10,000, and that's on the less expensive side of things.

 

[u2slow]

Go with the 100A panel, but run it off 50-60A wire and breaker in the main.

Or, if you figure you will eventually go to 200A service, put in the 100A feeder now on the smaller breaker.

You panel probably says 70A max branch breaker on the decal.

 

[MrPink]

I think you meant to say that a load calc WASNT done.

If thats the case then the electrician is talkong out of his ***. Get a new one

You dont have much load on that service at all.

Whats with the 30a range? Never seen a range circuit that small. Theyre either 40a or 50a...

It's a double 30 amp breaker same with the dryer.

I figured as much that he was talking out of his ***. He listened to where I wanted the panel but nothing else.

It wouldn't bother me to feed a 100 amp sub off of that panel if it were mine. The existing panel may not be listed for a 100 amp breaker though, in which case, whatever it's listed for would probably be sufficient since it's going to be at least a 60. (It should say on the door somewhere.) If there is concern, run a separate circuit for the heater at the same time the wire for the sub is pulled.

As far as the price to upgrade to 200 amp, that may not be out of line. One city and another county here require to house to be updated whenever a panel is changed. A single story house with an unfinished basement starts around $10,000, and that's on the less expensive side of things.

The house is on a 4.5ft crawl space, the main box is in the kitchen. So no basement, who ever updated the panel from the orig 60a to the current 100a panel did the exterior wiring all sorts of funky. I have 0 need for 200A service. My house is small(900sq ft), if we do any upgrades it will be minimal extra load on the panel if any. We want to get rid of the jetted tub in our bathroom and go with a regular one. As well as going with a gas range instead of the electric. No additions, no extra anything.

 

[theoldwizard1]

Go with the 100A panel, but run it off 50-60A wire and breaker in the main.

The size of the "main" breaker in a sub-panel does NOT have to match the breaker that is feeding it ! It's primary purpose to be able to shut off the power inside the sub while you are working on it.

 

[MrPink]

I appreciate the input, guys. This is something I more than likely will do myself, with my best friend helping me. I know I can do it I was merely astounded by the cost figure of the company that came to give the quote.

 

[Terry D]

Is this a detached or attached garage. Defiantly get another bid. I would not loose any sleep adding a sub off your 100 amp panel. Like sparky said, find out what the max breaker can be in your main panel and go from there. You might not be able to have a 100 amp branch circuit out of that panel, so the electrician that gave you that price, knew that and figured in replacing the main service so you could have a full 100 amps out in the garage. See what the max breaker size is allowed for a branch circuit and get back with us

 

[mike93lx]

Also check breaker pricing. A 60a homeline is about 13 bucks. 70a to 100a are 3-4x that. Not deal breaker pricing, but worth considering when you evaluate what you need

 

[MrPink]

Is this a detached or attached garage. Defiantly get another bid. I would not loose any sleep adding a sub off your 100 amp panel. Like sparky said, find out what the max breaker can be in your main panel and go from there. You might not be able to have a 100 amp branch circuit out of that panel, so the electrician that gave you that price, knew that and figured in replacing the main service so you could have a full 100 amps out in the garage. See what the max breaker size is allowed for a branch circuit and get back with us

Detached, and if it is not listed on the cover label, where else would I find it?

 

[mike93lx]

Detached, and if it is not listed on the cover label, where else would I find it?

In the box

 

[pattenp]

Being a detached garage are you familiar with what type wire to use? And are you planning to bury the line to the garage and understand the requirements?

 

[Terry D]

Detached, and if it is not listed on the cover label, where else would I find it?

This is a newer panel, it should be on the label inside the door that you posted. I googled the model number, but yet have found info on this. If you are going to have electric heat out there, besides a minisplit, i would go with a 90 or 100 amp sub if your main panel allows it. The sub panel that you will be putting out there will be a least a 100 amp. Install 1 1/4 PVC conduit underground and use (3) #2 and (1) #6 aluminum XHHW's.. Some areas allow you to use #2 for 100 amp and some just 90 amps. you need to check with you local codes. Use a 100 amp main breaker panel in your garage. you could even use a 200 amp main breaker if more space is needed. the main breaker will serve as your disconnecting means. Even if your main panel now will only except a 70 amp max breaker, I would still do it this way, you will probably have to pigtail the 2 hots in your main panel to fit in the lugs of a smaller breaker. This way if you ever upgrade you existing 100 amp service to a 200 amp, all you would have to do is change the breaker feeding the sub to a larger one. Make sure to leave extra wire in your main panel so if you do up grade you have the extra length.

Guess I should have asked earlier, how far is the garage from the house. You might have to factor in voltage drop and go to a larger size wire.

 

[mike93lx]

The label on the cover is for the cover, not the enclosure and buss, same as my homeline setup

 

[MrPink]

This is a newer panel, it should be on the label inside the door that you posted. I googled the model number, but yet have found info on this. If you are going to have electric heat out there, besides a minisplit, i would go with a 90 or 100 amp sub if your main panel allows it. The sub panel that you will be putting out there will be a least a 100 amp. Install 1 1/4 PVC conduit underground and use (3) #2 and (1) #6 aluminum XHHW's.. Some areas allow you to use #2 for 100 amp and some just 90 amps. you need to check with you local codes. Use a 100 amp main breaker panel in your garage. you could even use a 200 amp main breaker if more space is needed. the main breaker will serve as your disconnecting means. Even if your main panel now will only except a 70 amp max breaker, I would still do it this way, you will probably have to pigtail the 2 hots in your main panel to fit in the lugs of a smaller breaker. This way if you ever upgrade you existing 100 amp service to a 200 amp, all you would have to do is change the breaker feeding the sub to a larger one. Make sure to leave extra wire in your main panel so if you do up grade you have the extra length.

Guess I should have asked earlier, how far is the garage from the house. You might have to factor in voltage drop and go to a larger size wire.

20ft, the panel will be 32ft in total length away from the main panel.

 

[MrPink]

Being a detached garage are you familiar with what type wire to use? And are you planning to bury the line to the garage and understand the requirements?

Yes, yes and yes. it's going in 1.25" conduit, from house to garage. Using #2 wire.

 

[Terry D]

20ft, the panel will be 32ft in total length away from the main panel.

You wont have any concern with a voltage drop at that short of distance distance

 

[mike93lx]

Yes, yes and yes. it's going in 1.25" conduit, from house to garage. Using #2 wire.

Which #2 wire are you using.

 

[pattenp]

Which #2 wire are you using.

Exactly. #2 aluminum is 90A, #2 copper is 115A.

 

[Cruzan80]

From when I did my detached garage (longer run), it was 1/1/1/3 AL to get the full 100A, if I recall correctly. Cheaper to step up from #2 to #1 Al than pay for #2 copper.

 

[MrPink]

I have not decided yet on wire.

 

[u2slow]

Most Sq D QO breakers have rather large terminals for 40A on up. Dunno about Homeline.

 

[mike93lx]

I have not decided yet on wire.

#2 AL xhhw is great if you are doing conduit end to end.

 

[MrPink]

As of now(6pm EST) my Dad and his electrician co-worker(s) will be coming and upgrading the panel in house to 200A and installing my current 100A panel in my garage. for cost of materials, food and beer.

 

[wyliesdiesels]

As of now(6pm EST) my Dad and his electrician co-worker(s) will be coming and upgrading the panel in house to 200A and installing my current 100A panel in my garage. for cost of materials, food and beer.

um have you contacted the PoCo about this?

meter pan may only be rated for 100a.

and how will you disconnect the incoming unswitched power from the PoCo?

 

[mike93lx]

As of now(6pm EST) my Dad and his electrician co-worker(s) will be coming and upgrading the panel in house to 200A and installing my current 100A panel in my garage. for cost of materials, food and beer.

You can't just upgrade totally on your own, but something tells me you are being intentionally vague and/or you aren't interested in feedback, so good luck!

 

[u2slow]

Some 200A panels (like QO) have different size main breakers available from 100A-225A. That came in handy once....

 

[Terry D]

As of now(6pm EST) my Dad and his electrician co-worker(s) will be coming and upgrading the panel in house to 200A and installing my current 100A panel in my garage. for cost of materials, food and beer.

Your outside service most likely is only 100 amps. That needs to be upgraded also. Along with your grounding electrode conductor

 

[mike93lx]

Your outside service most likely is only 100 amps. That needs to be upgraded also. Along with your grounding electrode conductor

My last utility would change nothing when you "upgraded" from 100a to 200a service other than a new meter. You had to change the riser, pan, and feeder. All for the same connection to their grid

 

[Terry D]

My last utility would change nothing when you "upgraded" from 100a to 200a service other than a new meter. You had to change the riser, pan, and feeder. All for the same connection to their grid

That is how it is here, the customer is responsible after the utility's connection. So if it is a overhead service, thats everything after the parallel connectors. Underground its the meter and everything after. We use the same meter for 100 and 200 amp

 

[mike93lx]

That is how it is here, the customer is responsible after the utility's connection. So if it is a overhead service, thats everything after the parallel connectors. Underground its the meter and everything after. We use the same meter for 100 and 200 amp

I guess I was clarifying what "outside service" meant. The utility just needs to come pull the meter, or also disconnect the service at the pole/riser, depending on what is getting done. This is certainly not a "do whatever you want" kind of thing... Hope the OP figures that out

 

[sparky 1971]

If it gets upgraded to a 200 amp, under 2020 rules it will require an exterior disconnect. Since the easiest way is with a meter main, that may make it easier to run the 100 amp feeder to the garage. I suspect this isn't the case though. The friend will probably pull the meter, swap panels, and leave.