Sub panel for attached garage

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Old 12-07-19, 04:15 PM
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Sub panel for attached garage

I want to put a sub panel in my attached garage. 50 foot run from 200 amp main panel. It will power a heater rated at 36/42 amp, outlet for chest freezer and refrigerator. 1 outside outlet. And possibly the two lines that already run out there. 1 for lights and 1 for outlets (15 and 20 amp breakers now). What size breaker at main panel and what size and type of wire is needed. Thx
 

Last edited by Kjv42; 12-07-19 at 05:24 PM.
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Old 12-07-19, 04:50 PM
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If the wire can be run without being buried within insulation I would use aluminum 2-2-2-4 SER and use a 90A feeding breaker. If the SER will be within insulation then drop the breaker back to 80A.
 
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Old 12-07-19, 05:05 PM
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Is that a 120 volt or 240 volt heater?
 
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Old 12-07-19, 05:28 PM
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Heater is 240 volt. Unit will be about 10 feet from sub panel. Thx
 
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Old 12-07-19, 09:13 PM
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He said the garage is attached. No problem with more than one feed.

60 amp is too small. The heater is using that all up. 100 amp is the next size up I see at HD.
 
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Old 12-08-19, 06:49 AM
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100A will give you better headroom, so use 1-1-1-3 AL SER. Same issue if run within insulation, need to drop back to 90A breaker. In insulation you use 60deg C rating, not in insulation you use 75deg C rating which is 100A.
 
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Old 12-08-19, 07:07 AM
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Thx pattenp. I will be running from the main up and through the basement ceiling joists, then out through the house/garage wall. Then along the garage sill plate 6 feet and up to the sub. Along the sill I plan on running through conduit. Then either up through conduit, or into drywall and up to flush mount sub. With this should I go 80 or 90 amp breaker at the main? 2-2-2-4 al ser? 100 amp sub? What breaker for 240 heater 36/42 amp draw. My city goes by NEC 2009. Any other suggestions will be greatly appreciated. Thx. Additional info. Is pvc ok for conduit and the sub panel will be on a external wall. Id like to go with 2-2-2-4 as it is easier to find here.
 

Last edited by Kjv42; 12-08-19 at 08:22 AM. Reason: Additional info
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Old 12-08-19, 10:22 AM
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As long as the 2-2-2-4 Al SER is not running within insulation I see no reason not to go the max with a 90A feeding breaker in the main panel. SER is installed just like NM-b (Romex). Conduit can be used where needed for protection were the SER may be subject to damage. A sub with a 100A main breaker is best even though you could use a 100A main lug panel. The 100A main breaker only serves as a disconnect since the feeding 90A breaker provides the overload/short circuit protection. For the heater check and see if the manufacturer suggest a circuit size. Based on the high amps of 42 I would use Cu # 6-2 NM-b with a 60A breaker. PVC conduit is fine. Use Sch80 PVC if the conduit is subject to getting whacked. Also use conduit large enough to easily pull cable through. You may be looking at using at least 1.5" or even 2" conduit.
 
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