Need Advice Installing a Sub-Panel in the Garage

[superskaterxes]

Hey guys,

so ive recently started to build my garage workshop and i am going to need to add a 220V sub-panel. My current main panel is a 200A service with lots of empty space. I recently got rid of an electric dryer (30A breaker) and my electric stove (50A breaker) and switched over to gas. I also have 2 empty 30A breakers while the rest are filled with the house's normal lighting/plug loads.

Here is what i need to add:

A 230V air compressor which requires a 30A breaker
A 240V tig welder which requires a 30A breaker
A 220V automotive lift which requires a 25A breaker
several 120V receptacles (lets say 10 total receptacles on 2 separate breakers)


My HVAC unit also has a 60A sub-panel run to it from the main panel except there is only two 15A breakers inside of it (both only using 120V legs). One breaker is for the humidifier which i never use so that leaves a single 15A breaker fed from a 60A panel. Can this be shrunk down to a 30A sub-panel to leave more room for circuits in the garage?


So what size breaker and what size sub-panel do i need to add to my main panel to cover all of this? For the air compressor i am thinking of using the existing breaker/wiring from my stove (50A but can be shrunk to 30A) because i want the compressor to sit in the basement directly below where the stove used to be and there is plenty of slack in the wire for it.

I also dont need to run all of these items at the same time but i assume i should size the panel accordingly as if i were to. I also need to know what size wire to run to the garage. Its easily an 80 foot pull between the main panel and where i want to put the sub-panel so take that into consideration.

I do have some electrician friends but i want at least a decent idea of what im doing before i ask them to come over and help.


thanks in advance!

Read more: http://www.doityourself.com/forum/e...nstalling-sub-panel-garage.html#ixzz3AHyM6FoK

 

[Mustang51js]

Not sure I follow but just so you you know a 30 amp breaker takes up the same space in the panel as a 60 amp breaker. I would reuse any wire you can.

 

[wyliesdiesels]

Is the garage attached or detached? How many HP is the compressor?

 

[superskaterxes]

attached.

all wiring would be run inside the house and into the garage. The comp is a 5HP unit and the manual says to use a 30A breaker. Im pretty sure i can get away with 2-2-2-4 SER using a 125A sub panel with 100A breakers on either end (one in the main panel as a feeder and one for the sub panel main).

 

[wyliesdiesels]

attached.

all wiring would be run inside the house and into the garage. The comp is a 5HP unit and the manual says to use a 30A breaker. Im pretty sure i can get away with 2-2-2-4 SER using a 125A sub panel with 100A breakers on either end (one in the main panel as a feeder and one for the sub panel main).

If the compressor is a TRUE 5HP, which it sounds like it is, because the FLC of a 5HP motor is 28a, then it needs to be hard wire. Standard plugs/recepticles are rated @ a max of 3HP.

If the #2 SER is AL then it needs to be protected by a 90a breaker NOT 100a!

I would just put in a subpanel that way the branch circuit wiring is short! Also, your breakers are right there instead of being across the house!

 

[superskaterxes]

Why doesent the #2 SER fall into the 100A category? what does it take to be in the 90C column to make it 100A?

 

[offroadsteve]

You aren't allowed to use the 90C column for determining overall amp ratings because the connections at either end are only rated for 75C.

 

[wyliesdiesels]

Why doesent the #2 SER fall into the 100A category? what does it take to be in the 90C column to make it 100A?

90* c column is for derating purposes ONLY! I know of no devices that have a 90* c termination rating.

 

[superskaterxes]

so i guess my biggest issue is that i cant find a sub-panel around 100A that has a main breaker included or doesent cost $170+ just for the breaker itself. I need something with at least 12 spaces and around 100A main. 90A main is fine but you cant just buy a $30 90A breaker and pop it in the main because most panels require a molded case breaker for the main which is $$$$. Can someone link me to a good subpanel the suit this need?

i was originally look at this

http://www.lowes.com/ProductDisplay...catalogId=10051&productId=50085324&cId=detail

but clearly thats not gona work if i cant get away with the 100A 90C rating of the #2SER

 

[pattenp]

Cutting and pasting Lowes pages seems to not work. Look at item 39032. It's a 100A Homeline panel with main breaker.

The sub-panel can have a 100A main breaker. It's the feeding breaker in the main panel that needs to be no larger than a 90A. The 100A main in the sub-panel acts only as a disconnect.

 

[superskaterxes]

That looks like a good deal.

Do i need to worry about the SCCR of the panel?

 

[wyliesdiesels]

Your other option is a backfed main. U need a retention kit for it but unfortunately u loose 2 spaces in the panel.

 

[pattenp]

No, you don't need to be concerned with SCCR. The panels you'll be looking at are UL listed and are for primarily or solely residential use. If you want a better quality panel use Square-D QO or Cutler-Hammer CH panels. They will cost more.

.

That looks like a good deal.

Do i need to worry about the SCCR of the panel?

 

[Aceman]

Just a few questions:

Will the SER cable be installed in insulation?

How many feet will it be ran in insulation?

Roughly how long would the cable be overall?

Since you didn't list your location in your profile which NEC code cycle are you under?

 

[superskaterxes]

Just a few questions:

Will the SER cable be installed in insulation?

How many feet will it be ran in insulation?

Roughly how long would the cable be overall?

Since you didn't list your location in your profile which NEC code cycle are you under?

I suppose a few feet from the panel to the ceiling will be run inside the wall with insulation but the majority of the run (about 80-100 feet) will be run along the joists in the basement.

Im located in maryland (which should be in my profile ill have to check that)

 

[Aceman]

Based on the 2011 NEC, I'd say you'd be able to use #2 AL SER at it's 90 amp rating taking advantage of 310.15(A)2 which allows you to run SER cable through a feet of insulation without decreasing the cables overall ampacity.

 

[pattenp]

I believe Aceman asked the question about insulation because if SER is run within insulation it needs to be sized based on 60 degrees C instead of 75 degrees C. which would reduce the amp capacity from 90A to 75A. But since your run in insulation is only a few feet (I assume 3-4ft) of the 80 or so feet then the run in insulation is not a concern to reduce the amp capacity.

Edit: Aceman replied as I was typing.