Garage sub-panel. 100a? 200a? How about 125a?

[plowhog]

I am putting in a detached garage and current plans are to set a 100a electric subpanel. It will connect to a 400a subpanel at the house. (Existing 200a panel presently being upgraded to 400a.) In the thread about my garage, many here advised to upgrade the garage subpanel to a 200a model, for just a "small increase in wire cost."

I asked my electrician about this. He said "don't do it." According to him, if I put a 200a subpanel in the garage, it would require using the "big breaker" slot at the top of the 400a panel. Using that "big breaker" slot in the 400a panel would then limit the 400a panel servicing the house to only 200a. To meet code I need more than 200a for the house.

He did say there is sort-of a happy medium. He said I could set a 125a panel in the garage instead of a 100a. With that config, it uses a regular breaker in the 400a panel which doesn't limit the house amperage in the same way. But I get a little extra "oomph" of power to the garage.

I'm new to this. Does that make sense?

 

[Deere Dude]

All I know is I put in a 100 amp service in my garage and works fine. A 100 amp breaker from the main house was simple.

But, it all depends on your usage at one time. I have a 50 amp plug for my welder, a bunch of 20 amps outlets for shop tools, a 30 amp for my camper, a 220 volt for an AC.

The thing is, I never run a drill press and weld at the same time. I am the only one running power equipment in the garage. The only two things that may take place at one time are the welder and the battery charger for the camper.

A 100 amp with a dozen spots for breakers will work fine, unless you have a few people working in there welding and using another high amp draw tool at the same time.

 

[jaxs]

Ask the electrician about burying wire capiable of 200 amps and installing the largest breaker that will fit "small breaker slot". That leave's the 200 amp option open should code change later and meanwhile cause less voltage drop to garage.

 

[RNeumann]

I am putting in a detached garage and current plans are to set a 100a electric subpanel. It will connect to a 400a subpanel at the house. (Existing 200a panel presently being upgraded to 400a.) In the thread about my garage, many here advised to upgrade the garage subpanel to a 200a model, for just a "small increase in wire cost."

I asked my electrician about this. He said "don't do it." According to him, if I put a 200a subpanel in the garage, it would require using the "big breaker" slot at the top of the 400a panel. Using that "big breaker" slot in the 400a panel would then limit the 400a panel servicing the house to only 200a. To meet code I need more than 200a for the house.

He did say there is sort-of a happy medium. He said I could set a 125a panel in the garage instead of a 100a. With that config, it uses a regular breaker in the 400a panel which doesn't limit the house amperage in the same way. But I get a little extra "oomph" of power to the garage.

I'm new to this. Does that make sense?

Not everyone was suggesting a 200a subpanel in the shop. Glad your electrician is bringing you back to a more reasonable amperage. 200a amps of 120v (100a breaker and feed) is more than enough.

 

[Stimw]

You don't say what you plan to run in the building. ??
At my last property I had a 200 amp main and I ran electric to a 40' X 50' shop. I put in a 100 amp panel and used the building for a business.
In 18 years I only had the 100 amp main trip once and that was when I was welding and a friend was using my Plasma cutter with the 5 hp air compressor going also.

 

[2458n]

That is good to see your electrician is working to keep you up to code, and up on power. Money well spent.

 

[Industrial Toys]

That sound insane! A 200 amp garage panel. Used to be, whole farms had 60 amp service. People usually think they need more then they do, as they don't usually use several heavy loads at once.

 

[plowhog]

My motor home draws close to 50 amps with everything running, which can happen on a hot day (3 a/c units, residential refrigerator, etc.) I designed a 2nd exterior/outdoor 50a hookup so our friends can park their motorhome adjacent to the garage when they visit.

For freeze protection, there are four ceiling mounted qmark heaters. Those are 220v/5kw each, not sure how that equates to amps.

I also have a 220v compressor (not sure of amps,) electric water heater (30a), car lift (30a), 2nd interior RV hookup (30a), 220V linear amplifier (not purchased yet,) and ceiling fans. Plus lights, plugs, etc.

Of course not all things would run at once. The motorhome a/c is high draw, but it would never be running at the same time as the high draw qmark heaters.

 

[jaxs]

My motor home draws close to 50 amps with everything running, which can happen on a hot day (3 a/c units, residential refrigerator, etc.) I designed a 2nd exterior/outdoor 50a hookup so our friends can park their motorhome adjacent to the garage when they visit.

For freeze protection, there are four ceiling mounted qmark heaters. Those are 220v/5kw each, not sure how that equates to amps.

I also have a 220v compressor (not sure of amps,) electric water heater (30a), car lift (30a), 2nd interior RV hookup (30a), 220V linear amplifier (not purchased yet,) and ceiling fans. Plus lights, plugs, etc.

Of course not all things would run at once. The motorhome a/c is high draw, but it would never be running at the same time as the high draw qmark heaters.

The spare amps doesn't sound insane to me. I say go for it.

 

[truckdiagnostics]

Put 200 amp in the shop or at least make sure you have the option! You may not use it but what about if you have to sell it. what will the next owner going to do. Things change if you don't have to 200 amp and you need it what are you going to do. will you be able to add more latter. I thought I would never use the 200 amps I have, I have the panel maxed out. I run a 50 amp powder coat oven, welder, 5hp compressor and lift. with only two in the shop, it is not hard to be using all those things at once. Then there is the lights, well pump and plasma cutter. it does not take much and adds up fast.

 

[Industrial Toys]

A 5KW heater is around 23 amps, depending on voltage.

A 200 amp service at 240 will give you just shy of 50,000 Watts. Good God!

I have a 200 amp service for the property, servicing 5 buildings AND electric HEAT! Plus water pump, heat, 220 pressure washers, compressors, hoists, plasma, welders, (all industrial stuff) 10 HP 600 volt Rotary Phase Converter and on and on.

 

[Code54]

How about separate service for the garage? I did a 200A separate service to my garage and it runs about $15 a month as an average. Never think twice about power and the way it worked out it was cheaper for me than coming from the house all the way to the shop.

 

[WM75Guy]

Can the meter base not supply 2 panels, one for the house and a panel to feed the detached garage? My 400 amp meter base has lugs to feed 2 panels. There is a short stub to a panel mounted beside the meter base that has a 175A breaker that feeds underground to the stables. The stables has it's own HVAC, washer/dryer, and hot water heater as well as lights and fans for the stalls. It also supplies the 4 1000W floodlights for the arena.

The other panel that feeds the house is 225A and is in the wall in the garage just behind the meter base. That panel only has 240V breakers. There is a 100A subpanel across the garage in my mechanical closet that feeds all the 120V circuits. It is on the house side of the garage so it saved having to run about 40' of extra wire for every 120V circuit, all 37 of them.

The shop is on it's own 200A meter base and panel.

 

[marchanna]

I have a second service panel in my garage the draws from the same meter, so yes it can be done. I have 200a in the house and 400a in the garage.

 

[medic0648]

My motor home draws close to 50 amps with everything running, which can happen on a hot day (3 a/c units, residential refrigerator, etc.) I designed a 2nd exterior/outdoor 50a hookup so our friends can park their motorhome adjacent to the garage when they visit.

For freeze protection, there are four ceiling mounted qmark heaters. Those are 220v/5kw each, not sure how that equates to amps.

I also have a 220v compressor (not sure of amps,) electric water heater (30a), car lift (30a), 2nd interior RV hookup (30a), 220V linear amplifier (not purchased yet,) and ceiling fans. Plus lights, plugs, etc.

Of course not all things would run at once. The motorhome a/c is high draw, but it would never be running at the same time as the high draw qmark heaters.

I hope those 4 heaters never run at the same time. 240/5000=20.8A. 240/20000=83.3A. You could run at most 2 of those heaters at 1 time on the 50A breaker for any extended amount of time.

 

[marchanna]

Yup. If theyæ±*e for freeze protection, I would make sure two of them are turned off, because the last thing you want is for for all four of them to turn on full power, which will absolutely pop the breaker. Then you will freeze up, defeating the whole purpose.

 

[tonyq60]

Put in the 200 amp panel...

We did so in our shop as home depot or lowes sells a 200 amp panel without a main breaker but with a handful of breakers for about 80 bucks...Back then.

We have smaller breaker feeding the panel but have dedicated circuits for each outlet and machine.

You use everything rated for 200 amp but use a 125 amp breaker to feed it.

You have plenty of room for dedicated circuits

 

[dstig1]

One item I keep seeing people miss on these threads is that the subpanel can be bigger than the breaker is rated for, just not the other way around. So you could mount a 200A subpanel being fed by a 125A breaker (unless you have some local code that won't allow it - NEC is fine with it). Now why would you want to do that? Breaker spaces! You can get up to 40 or 42 spaces in a 200A panel (the max allowed). If you run separate circuits for various tools like I did, you can start to fill up a 200A panel slots in a bigger shop (mine is 32x80'). I think I have 7 spaces left now after all the double pole 240V breakers and the various 120V single breakers for lights and regular outlets. For sure I need 3x 240v circuits to be safe - compressor, dust collector and a tool circuit as all 3 can be running at the same time, and sometimes do. The compressor and DC are on 40A breakers, and i also have a couple of 20A 240V outlet circuits around the shop so i can plug in as needed. I also have a thickness sander with it's own 30A circuit. Could I have consolidated them down a bit? Sure, but this made more sense to me for the long run.

So if you mount a 200A panel, down the road if you really do find you need the power, you can either pull bigger wire, or just swap the feeder breaker assuming you pulled big enough wire in the first place. I pulled a 200A panel for the shop and 200A for the house (new construction) off a 400A (320A actual) service. Didn't seem to make sense to do any less as the past has shown that electric use/need only grows with time. the house panel only has the ability to put in one more 120V breaker, if i use a doubled-up split breaker (by code). They fill up fast...

 

[Industrial Toys]

I have a few under powered panels. I don't need the current, but often need the higher number of circuits.

Around here, (and I used to work as an electrician) you only ever saw 400 amp single phase service in the largest of the largest homes.

 

[marchanna]

My house is serviced by a dedicated 13.8kV transformer. The utility technician told me that in town they use a transformer like that to service 10 homes. That leaves me open for as much expansion as I could ever need. I just have to make sure to keep the tree limbs clear because that current can jump close to a foot. I致e got about 250 volts at the panel, which is nice because it charges my electric car faster. The public chargers in town that are branched off of 3-phase are barely pushing 200 volts, and it takes forever to charge.