Subpanel question
#1
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Subpanel question
I have 150A service in my house, and a 100A breaker in the house's panel that feeds the garage. The garage has a 100A panel (one of the cheap $20 6 position boxes with no main disconnect). This panel currently has a breaker for lights, 2 breakers for outlets on a tandem breaker, and a 30A 240 breaker for a compressor. I have 2 spaces left. I'm wanting to put another 100A breaker in the remaining space and place another one of the same panels by the furnace to power it.
The question is can I put a 100A breaker in a 100A panel to feed a subpanel? The lights and outlets breakers are barely pulling a load as it is. My other option is to replace the panel in the garage with a full sized 100A panel, but I'm trying to save about $80.
Thanks
Greg
The question is can I put a 100A breaker in a 100A panel to feed a subpanel? The lights and outlets breakers are barely pulling a load as it is. My other option is to replace the panel in the garage with a full sized 100A panel, but I'm trying to save about $80.
Thanks
Greg
#3
Read the label on the 100A garage panel. Look for stab rating and feed through lug kit. These determine your answer.
Stab - the piece of metal formed from the power bus that the breaker slides onto. Abutting left and right breakers slide onto the same stab. The sum of those two breakers cannot exceed the stab rating.
Feed through lugs are cheaper and more durable than 100A breakers. They attach at the ends of the power buses.
If this is an attached garage then a junction in the wires just ahead of the breaker is possible.
Stab - the piece of metal formed from the power bus that the breaker slides onto. Abutting left and right breakers slide onto the same stab. The sum of those two breakers cannot exceed the stab rating.
Feed through lugs are cheaper and more durable than 100A breakers. They attach at the ends of the power buses.
If this is an attached garage then a junction in the wires just ahead of the breaker is possible.
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I'd prefer to feed through this panel onto the next panel. The description on Square D's website says "Feed Through Lugs: Yes", although there is only one lug for each hot bar and one lug for the neutral. Not sure how I'd attach a second set of wires to the bus bars. The panel is a Square D HOM612L100SCP.
[ATTACH=CONFIG]21485[/ATTACH]
[ATTACH=CONFIG]21485[/ATTACH]
#5
You do not need a 100 amp sub panel to feed a furnace. One circuit should be enough. Is the furnace gas fired or is this actually part of a heat pump?
#6
If saving money is the goal you would install one 20A breaker & a few feet of 12ga cable to the furnace rather than a 100A breaker, + 6ga. wire + the lug panel + a 20A breaker + a short length of 12ga cable to the furnace.
There must be more to the story?
There must be more to the story?
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I haven't got the furnace yet. I'm looking for a residential electric furnace, hoping to get one off a jobsite within the month. Probably somewhere between a 15kw and 20kw unit. I will need a 15A circuit for the blower and control panel. Then depending on the unit, I could need several double pole breakers, depending on how many elements are in the furnace.
I live in the middle of nowhere. No natural gas, heatpump wont work because I need my garage heated in very cold weather, and electricity is cheaper than propane or oil (at least in my area). So resistance electric heat is my best, cheapest option.
BTW the main house is heated with a woodburner only (so no worry about overloading the main with two electric furnaces running simultaneously)
Thanks again.
I live in the middle of nowhere. No natural gas, heatpump wont work because I need my garage heated in very cold weather, and electricity is cheaper than propane or oil (at least in my area). So resistance electric heat is my best, cheapest option.
BTW the main house is heated with a woodburner only (so no worry about overloading the main with two electric furnaces running simultaneously)
Thanks again.
#8
With thoughts of adding that kind of load you might be looking at a service upgrade.
I would keep large loads like that in your service panel, not a sub panel, especially with other loads.
I would keep large loads like that in your service panel, not a sub panel, especially with other loads.
#9
You still haven't told me if this is an attached garage. I need to know.
Really!? Far out. Get the feed thru lugs kit and it will be obvious how they attach.
My guess is you take the wire capture screw out of the lug, which exposes the screw that holds the lug on. It's usually a torx or allen head. Then you replace the lug with a double lug.
x2 with pcboss/service upgrade. At the very least you need a residential load calculation and a sub panel load calculation.
The description on Square D's website says "Feed Through Lugs: Yes"
Not sure how I'd attach a second set of wires to the bus bars.
x2 with pcboss/service upgrade. At the very least you need a residential load calculation and a sub panel load calculation.
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It's a detached garage, appx 100 ft from the house.
I know I'm going to be very close with only 150A service total, and only 100A feeding the garage. I'm trying to make due with what I've got though, and depending on the furnace I get, I might be able to rewire to eliminate one of the stages, thus saving power. If everything was on at once, I can definitely see needing more power. However, I understand I would have to switch the heat off to fill the compressor tanks or use a welder. I'm not worried about that, really.
So i can't put the furnace in the service panel because I'm too far away from the house. My options at this time seem to be to feed through the current subpanel in the garage and place another subpanel next to the furnace. Or, replace the current subpanel with a 100A panel with plenty of spaces. The first option is MUCH cheaper ($20 box vs $80 box, short runs from breakers to furnace, I already have extra 100A wire to install new box)
Thanks
Greg
I know I'm going to be very close with only 150A service total, and only 100A feeding the garage. I'm trying to make due with what I've got though, and depending on the furnace I get, I might be able to rewire to eliminate one of the stages, thus saving power. If everything was on at once, I can definitely see needing more power. However, I understand I would have to switch the heat off to fill the compressor tanks or use a welder. I'm not worried about that, really.
So i can't put the furnace in the service panel because I'm too far away from the house. My options at this time seem to be to feed through the current subpanel in the garage and place another subpanel next to the furnace. Or, replace the current subpanel with a 100A panel with plenty of spaces. The first option is MUCH cheaper ($20 box vs $80 box, short runs from breakers to furnace, I already have extra 100A wire to install new box)
Thanks
Greg
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Yeah I know. I'm actually shooting for around 15kw.
I know having the heat on will almost max out the 100A panel. As I said I'll shut the heat off to run the compressor or welder. Other than those two things, the only other thing on the 100A panel is a few lights and a radio.
I know having the heat on will almost max out the 100A panel. As I said I'll shut the heat off to run the compressor or welder. Other than those two things, the only other thing on the 100A panel is a few lights and a radio.
#13
Probably somewhere between a 15kw and 20kw unit.
Most 20 KY furnaces are two circuit furnaces too; 2 - 60A circuits. A single circuit 20 KW furnace usually requires a 125A breaker.
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Sounds like ill be looking for a 15kw. The panel I have does not support a feed through lug so I plan on putting a 100a breaker in the existing panel, and put another 6 space panel next to the furnace.
Thanks.
Thanks.
#15
Sounds like ill be looking for a 15kw. The panel I have does not support a feed through lug so I plan on putting a 100a breaker in the existing panel, and put another 6 space panel next to the furnace.
I'm trying to save about $80.
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Another question is what size/type of cable will you be using for the 100' run? 100 amps on 2 gauge aluminum works out to 600 watts of loss.
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The 100A feed from the main panel to the garage is 2-2-2 aluminum. It's actually the 100a service wire that used to feed our single wide trailer. It's already installed and in the ground with a concrete pad and a deck on top of it... not too easy to fix that now.
I'm strongly considering a propane furnace instead.
I'm strongly considering a propane furnace instead.