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Old 10-01-2011, 10:26 PM   #1
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Detached Garage electrical wiring


I will be running electric to my garage from my home pannel which is 200 amps. I already bought some stuff for this last year but I have changed my plans and im not sure if the stuff I bought will still work so please let me know.

what I bought last year :
125 amp sub pannel(8 spaces, 16 circuts) for the garage and a 30amp double throw breaker that was going to go in the pannel in my house to power the whole garage.

I rencently decided that I will be using electric heat in the garage that will require 2 240 outlets for 2 of these type of heaters http://www.amazon.com/NewAir-Electri...521559&sr=8-12
I also want to have a 240 for a welder or something that may need a 240. So 3 240 outlets and in the winter 2 of them will be active when I want to run the heaters.

I dont have much electrical knowledge but my uncle who build my house will be instaling everything. I just want to make sure I have everything in advanced. I will be taking a home depot run tomaro if I figure out everything I need.

So here are my questions.
Is the 30 amp double throw enough amps for my garage and my plans or do I need more? If so what should I get? Same goes for the sub pannel I got. Is it big enough?

My next question is what main wire do I need to run from my house to the garage? I already have the pvc tubing the wire will go in.

Thanks guys hope you can clear this up.

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Old 10-01-2011, 10:47 PM   #2
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Detached Garage electrical wiring


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Originally Posted by wonderd View Post
Is the 30 amp double throw enough amps for my garage and my plans or do I need more? If so what should I get? Same goes for the sub pannel I got. Is it big enough?

My next question is what main wire do I need to run from my house to the garage? I already have the pvc tubing the wire will go in....
Short answer is: NO.

30 Amps is not nearly enough juice. EACH of those heaters will require their own 30 Amp circuit. Then there is the welder: 50 Amp circuit. Plus the lighting and other outlets!

You may need a 100 Amp feeder for your connected loads. That would be #1 XHHW aluminum, or #3 THHN copper conductors. Don't forget the ground wire!

I'd go with (2)#3 THHN copper for the hots, #4 neutral and a #8 ground.

You will also need a disconnecting means at the garage -- a 100 Amp main breaker is sufficient for this. I'd swap that panel for a main breaker type -- it will be cheaper than backfeeding a 100 Amp breaker and installing the required hold-down kit.

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Old 10-01-2011, 11:09 PM   #3
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Detached Garage electrical wiring


Okay so if I wanted all of that I would need a 100 amp breaker comming from my house box

I have a question though. I never really understood double throws does a 30 amp double throw really mean its 60 amps?

Also will the heaters need a double throw 30 or single? Not sure what is the difference between a single and a double throw.

Last edited by wonderd; 10-01-2011 at 11:17 PM.
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Old 10-02-2011, 12:26 AM   #4
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Detached Garage electrical wiring


There really is not such thing as a double throw breaker. From your descriptions here, I believe you are thinking about a double-pole breaker.

No, a double-pole 30 Amp breaker does not mean you have 60 Amps. You have 30 Amps .... at 240 Volts. Most of your items are 240 Volt loads in any case.

You will need more than 3 times that capacity with your connected loads.

There will be other considerations you have to deal with (in no particular order):

Conduit size, length of run, and number of elbows, etc.
Grounding at the separate building (2 ground rods, or other suitable grounds)
Permits, inspections, etc.
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Old 10-02-2011, 01:01 AM   #5
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okay yea after reading I have a little better understanding. There will be 6 elbows, those I already have as well.

So from my thinking I will need 2 double poll 100 amp breakers. 1 at the house box and 1 at the garage box. Then the other breakers will run off that.

So tell me what you think about this

2 double poll 100 amp breakers

2 heaters- 2 double poll 30 amp breakers

1 welder outlet double poll 50 amp

1 double poll 20 amp for outlets around the garage, this should be enough for my craftsman compressor and other tools I may use in the future?

15 or 20 amp single poll for the lights? I have 4 10ft 2 bulb florecent fixtures (8 bulbs altogether) may add more fixtures in the future, is it a good idea for my 2 garage door motors also go on this circuit?

Last edited by wonderd; 10-02-2011 at 01:04 AM.
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Old 10-02-2011, 01:49 AM   #6
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Detached Garage electrical wiring


What brand name breaker you have on your exsting panel ?

You will have to buy 16 or 20 space panel avce main breaker it cheaper than just buy two - 100 amp duex pole beakers { they are 45 + Euros each }

For le heaters yes two breakers for each one { duex pole breakers }

Welder useally 50 amp duex pole breaker

For air compressour typically 20 amp 240 volt { 20 amp duex pole breaker } will work fine this useage.

For general circuits you may want to split at least two 120 volt GFCI protected circuits for lights you can use either 15 or 20 amp however the conductor size will trump it so if you have #14 it have to use only 15 amp breaker while #12 can use either way.

For the Garage door openers I genrally run it seperated circuit however it have to be GFCI protected.

Merci,
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Old 10-02-2011, 01:58 AM   #7
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not to sure what he said maybe if you agree kbsparky you can elaborate

I was thinking of something along the lines of this http://www.lowes.com/pd_214802-76863...1&facetInfo=GE
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Old 10-02-2011, 02:03 AM   #8
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okay yea after reading I have a little better understanding. There will be 6 elbows, those I already have as well....
You are allowed a maximum of (4) 90 degree elbows in any one run of conduit. Please describe what your "elbows" are ...
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Old 10-02-2011, 02:13 AM   #9
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I have uploaded a picture, the box to the right it comming from the house, but the way the land runs I have to step it down.
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Detached Garage electrical wiring-elbows.png  
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Old 10-02-2011, 02:14 AM   #10
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not to sure what he said maybe if you agree kbsparky you can elaborate

I was thinking of something along the lines of this http://www.lowes.com/pd_214802-76863...1&facetInfo=GE
If you want the 100 amp subpanel the best size for bang of your bucks is typically 16 or 20 space panel so you have more than engough room to add few extra circuits.

The 12 space panel IMO it may be ok but check the price differnce between the two { both 12 and 16 or 20 space verison } and I did count the numbers of poles requirement you listed and you will run out of space fast so the 16 or 20 space verison work better for your purpose.

Merci,
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Old 10-02-2011, 02:16 AM   #11
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Detached Garage electrical wiring


The picture you posted that is underground run ?? if so try rearrange to get under 4 - 90 ells the fewer it get more easier to pull it.

Some case you can use couple 45'ers that will really help a bit.

Merci.
Marc
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Old 10-02-2011, 02:17 AM   #12
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I understand that but i wasent sure what you meant by "You will have to buy 16 or 20 space panel avce main breaker it cheaper than just buy two - 100 amp duex pole beakers "
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Old 10-02-2011, 02:21 AM   #13
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Originally Posted by frenchelectrican View Post
The picture you posted that is underground run ?? if so try rearrange to get under 4 - 90 ells the fewer it get more easier to pull it.

Some case you can use couple 45'ers that will really help a bit.

Merci.
Marc
In my situation its not possible to have under 4. I have to use 6. starting from the left the first 90 will run along the foundation of the house then it will have to run between 2 concrete slabs (so we dont have to trip over a pvc tube when walking) then it has to step down again to be level with the ground the garage is on. Then there will need to be a 90 at the garage to go up the wall
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Old 10-02-2011, 02:22 AM   #14
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Originally Posted by wonderd View Post
I understand that but i wasent sure what you meant by "You will have to buy 16 or 20 space panel avce main breaker it cheaper than just buy two - 100 amp duex pole beakers "
Let me reword it for you .,,

You have to buy 16 or 20 space panel with main breaker then buy a subpanel without main breaker and use two - 100 amp breaker { one use for backfeed main breaker purpose } due the cost of two pole 100 amp breaker are not really cheap btw.

So a factory installed main breaker like 16 or 20 space panel is cheaper than try to buy two main breakers { if I did recall they run about 40 Euros ( bucks ) each }

Also if you get one with main breaker included get the ground bussbar kit as well for your subpanel purpose due most of them will not included so they typically run about 5 to 10 Euros for it.

Merci.
Marc
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Old 10-02-2011, 08:31 AM   #15
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As was already pointed out you can only have 360 degrees of bends between pull points. You need to change your conduit run. You will get hoarse cursing if you try to pull with the current setup.

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