Panel Configuration

[barnee]

I have a 200 amp 30 space/30 circuit main breaker panel with 40 circuits in it (tandems) in my house. Its QO panel.

I'm also in permit phase for my new detached garage so I need to cure my overloaded panel when I reconfigure my electric.

My plan is to put a subpanel next to my main panel in my house and move at least 10 circuits over to fix my main panel issue. I want to set this subpanel up to have an interlock and back feed it with a remote portable generator plug (50A). The circuits I move over will be the ones that I would want to be able to selectively use on emergency power.

Now to my question, I also need to run 100 amps to a new panel in a detached garage. Is it better to feed it from the original 200 amp main breaker panel or from this new subpanel? The answer to this will dictate how many circuits to move and what size subpanel I need

Trying to get the best plan figured out before getting electrical quotes. Thanks for your input.

 

[rockwithjason]

If you are using the sub as a generator backed panel then you can only move those circuits to the sub that will be backed up. The garage sub feed should come from the main panel.

When you say the existing panel is over loaded do you mean you have too much load on the panel or do yoi mean that there are no more spaces left? That is an important distinction. If the existing panel has too much load on it then you must upgrade the existing service. If its just full then you have more options

 

[barnee]

The house subpanel will not be a full generator backup panel since the back feed will only be 50 amps and fed by a portable generator. I've seen manual interlock kits for sub panels (to isolate from the main panel) where you basically shut off all sub panel circuits, start the generator, and only turn on the circuits you want to feed.

As far as my issue with the main panel, its only supposed to have 30 circuits and I have 40 and its really crowded (and likely not code). When I add up my final loads including the new panel in the detached garage I may find out that my incoming service is insufficient. That's part of the scope for the electric bids I get and it will change this configuration.

 

[JimRB]

Overloaded to me means that you have too many amps. A breaker panel filled with no spare breaker space is a different story and a different word. You could have 2,000 amps of breakers but only pull a 100 amps of power during your high activity times. My house could run the HVAC and water heater at the same time for 50 amps of load. If I am in the garage I could have a 120v air compressor or welder running on a 20 amp circuit. The fridge could start up or the clothes dryer. It is unlikely that I draw more than a 100 amps at once. Far from being overloaded.

The QO 30/40 panel is designed for those skinny double breakers and is code.http://www.homedepot.com/p/Square-D...-with-Cover-Value-Pack-QO3040M200VP/202523118

 

[CNGsaves]

Might as well tell GJ Sparky's everything now . . .
. . . .
a) Electrical loads now in house (ie is it all electric . . .what appliances ??)
b) Planned electrical loads in garage ??
c) PICTURES of panel now . . . . Cover On . . . and . . . Cover Off

If it were me, I'd put interlock on the main panel so you would be 100% in charge of what items you want to run in case of outage. Just move easy stuff to tag-a-long sub panel like lighting and outlet circuits.

 

[Speedy Petey]

Now to my question, I also need to run 100 amps to a new panel in a detached garage. Is it better to feed it from the original 200 amp main breaker panel or from this new subpanel? The answer to this will dictate how many circuits to move and what size subpanel I need

May I ask why you need 100A to the garage???
Will it be a commercial shop, with several people working at the same time?
Do you have a large commercial welder?
Will you be running large kilns for pottery?

It is pretty rare that any residential garage or shop would need over 50/60A.

I would install a 20 space sub-panel in the house, then run the garage panel off the main.

 

[barnee]

Didn't really want this heading into a "is my service size large enough" discussion since I don't have the data compiled to be able to figure this out. I think its a 50/50 chance that I will need a larger service since the "big power" in my house is two Heat Pumps with electric backup heat, well pump, sewage pump and sump pump (all 1/2 HP single pole), two refrigerators, range, dryer and the usual lights and receptacles.

The garage will have two mini split systems with heat, lift, compressor, refrigerator, fans, electric heater and the usual lights and receptacles but I want to provide capacity for larger shop tools in case I get a new hobby or the next guy has larger needs.

 

[manwithtools]

Nothing wrong with supplying the shop with 100 amps, I think most folks will ask the "do you need it" question to help save money. Depending on the distance to the garage, the increased wire cost can add up between a 60 amp and 100 amp circuit.

The other concern is (that you have already identified): if you really need 100 amps at the shop, then is your incoming service big enough to provide 100 to the shop and 100 (or whatever you may need) to the house?

Only way to answer all those questions with a load calculation as you probably know. To answer your orginal question, I'd add a 20 space sub-panel and move your generator circuits to that. Feed that sub-panel and your new garage sub-panel from the newly freed up space in the original main panel. This allows easy isolation of the new 20 space sub-panel to feed it with a generator when the need arises.

 

[barnee]

I'm about half way don't with tracking down the information on my large power devices and then will get a load calc. done to verify service size.

If I do need a larger service then Ill have to re-evaluate. I'm going to go ahead and discuss this with the power company in case. My current outside disconnect is 225 amp and I'm not clear on how much of my "outside" equipment needs to be changed if this is needed (meter, conductor from transformer, etc).

 

[James-W]

When I built my garage I just had the power company run a new 200 amp service to the garage. I don't need a 200 amp service, but the power company ran the wire for free and the meter charge is the same each month whether it is a 100 amp service or a 200 amp service. So there was really no point in just getting the 100 amp service. The only extra cost was the panel itself.

Anyway, my whole point is that maybe you should consider just having a new service installed for the garage. Yes, there is a meter charge each month, but then you don't have to screw around changing things around in your main house service panel.

 

[md21722]

I had some land that had one service for the home and one for the barn. Since the barn wasn't a residence, commercial rates applied. Both the monthly service cost & per kWh costs are higher on commercial. I considered running a feeder from the main panel in the house and getting rid of the barn meter, but it was nice having dual 200A services on the property. Some friends of mine bought a house with a 200A service and upgraded it to 400A when they built their pole barn. They actually have the house as a sub panel off the pole barn, but the meter is on the house. They put their generator at the pole barn away from the house.

It sounds like you have some heavy loads, 60A x 2 for the HVAC backup heat, 50A for the range , 30A for the clothes dryer is 140A right there. 1/2HP motors intermittent use don't use much power.

Depending on the size of your air compressor(s) they may be larger loads than your garage HVAC or heat system. Remember electric motor wiring is sized differently than resistive loads. Per the NEC, a 5HP motor uses 28A, 7.5HP uses 40A, and 10HP uses 50A with wiring to 125% of those numbers.

Depending on your property a second service may be beneficial, or convert to propane/gas. If your power goes out in the dead of winter, it's going to take a very big generator to power electric heat. If you use gas heat, all you need to power is the blower & controls.

 

[James-W]

I had some land that had one service for the home and one for the barn. Since the barn wasn't a residence, commercial rates applied. Both the monthly service cost & per kWh costs are higher on commercial. I considered running a feeder from the main panel in the house and getting rid of the barn meter, but it was nice having dual 200A services on the property. Some friends of mine bought a house with a 200A service and upgraded it to 400A when they built their pole barn. They actually have the house as a sub panel off the pole barn, but the meter is on the house. They put their generator at the pole barn away from the house.

We don't have that here, I get charged the same rate as I do on the house. The only extra cost is the meter charge every month. Apparently different areas of the country have different rules for electrical services.

 

[Cmreschke]

To the op, your better off running your sub panel for garage from the main panel. Also the interlock kit in your sub at the house, don't forget that you will need a main breaker of some sort in that panel as well. This allows the interlock to feed only the sub panel.

 

[matt_i]

I think its worth a call to the utility - engineering. In general principles my experience is they are happy to sell you more amps/power and even provide their part of the wiring free of charge, if they are reasonably assured that they will recoup that investment down the line thru increased electron sales. They arrive at that confidence by a load study of circuits etc, so when you have a lot of electrical needs that are real & documented they may be able to help.

 

[dw1]

I had some land that had one service for the home and one for the barn. Since the barn wasn't a residence, commercial rates applied. Both the monthly service cost & per kWh costs are higher on commercial. I considered running a feeder from the main panel in the house and getting rid of the barn meter, but it was nice having dual 200A services on the property. Some friends of mine bought a house with a 200A service and upgraded it to 400A when they built their pole barn. They actually have the house as a sub panel off the pole barn, but the meter is on the house. They put their generator at the pole barn away from the house.

I put a 200 amp service in my pole barn, the bill is classified as "General Service/Single Phase and is .01 cent more per KWH, but the Basic/Meter service charge is $15 higher than my house (I live a mile down the road) This is the only power I have on the property at this time, a house is still to come.

 

[barnee]

My neighbor put in a pool/poolhouse and ran a separate service to it so its likely practical to do this, but I still need to rework my main breaker box regardless.

Sounds like having the garage feed come off the main is the way to go, so Ill move 12 circuits to have enough space. All the moved circuits will be plug and light circuits which will work well for my backup power needs since I'm not attempting to power HVAC. probably can get away with a 60 amp subpanel and then 100 amp for the garage.

Onto the load calc!