Lots of questions for my 24x36 detached garage. Location FL.

Astross89 · Jun 22, 2018

Sorry ahead of time for all my questions. I'm building a 24x36 detached garage about 100ft away from the house. I'm about to start the electrical. Plan is 100amp 20 space breaker box. But only a 90amp service. Because of wire size.

1) I have a 150amp service to the house. Can I do 90amp to the detached?

2) I need to get power from the left side of the house(meter box) to the right side. I plan on going through the attic. I have no more room in my house breaker box. Can I exit out the main box where my 150amp breaker/meter is? See attached picture.

3) once I exit the box. What wire type? Ser/mhf? For 90amp I would assume 2-2-2-4?

4) do I need to run conduit in the attic?

5) once I go through the attic and exit on the right side of the house. What do I put over here? Is this where I put a disconnect or the 90amp breaker? Is there anything I can add incase I add a pool and need power?

6) leaving the house I will bury the cable all the way to the garage. I will put it in conduit. Again what wire? Ser/mhf? Size? 2-2-2-4 still?

7) once I get to the garage. Is this where the 90amp breaker or a disconnect goes?

8) I would assume I need two grounding rods at the entrance to the garage?

Now that their is power to the breaker box. I added a picture of my layout. Hopefully it can get big enough to see.

9) do the 20a 120v outlets have to be gfci? If so. Gfci breaker or outlet?

10) size wire? 12-2

11) next. The two 50a 240v outlets. Small welder and compressor. One is 60feet away. The other is 3 feet. Size wire. 6/2?

12) not on my layout. I'm adding a 30amp plug on the outside of the shop for my Rv. Does this need to be gfci? 60 ft away. Size wire? 10/2?

13) 16 sams led lights going up. I planned on 2 switches. 8 per switch. Is that alright?

I think that's it. Any suggestions is greatful. Thank you.

Stuart in MN · Jun 22, 2018

You should say where you live, at least what state (assuming you're in the US.) The electric codes and requirements can vary.

Astross89 · Jun 22, 2018

Stuart in MN said:
You should say where you live, at least what state (assuming you're in the US.) The electric codes and requirements can vary.

In the title I did. I should have in the description.

State: Florida
County: Brevard

sberry · Jun 23, 2018

Small welders only require 10 wire and newer ones may only need 30A service. They still use a 50A plug and can run on up to 50A. The comp may need a different breaker depending on model.
Most,, all but 250A migs can run from 10/50A just fine, I usually put a 30 for them on home outlets but it can be done either way for 200 compacts. In today's world most equipment in small garages can run 10 wire, if using cable a 5hp comp could require an 8.

Platonic Solid · Jun 23, 2018

Astross89 said:
24x36 detached garage ...
13) 16 sams led lights going up. I planned on 2 switches. 8 per switch. Is that alright?

Depends on ceiling height, fixture mounting height, wall/ceiling finish, purpose of space, age/visual acuity of occupants, specific fixture (Sams is a retailer not a fixture manufacturer).

m32825 · Jun 23, 2018

SER in the attic. You don't need conduit, but you do need to protect it if it is close to an access or runs through an accessible area. You need something rated for wet conditions between house and garage, you can use XHHW for that.

You want a lot of current a long way from the main breaker panel. When picking wire size you need to take into account voltage drop as well. At that distance you may need to go up in size to reduce voltage drop.

Are you thinking copper, or aluminum? Check prices for both and you will be thinking aluminum. If you were thinking copper, you're going to need bigger wires with aluminum.

-- Carl

pattenp · Jun 23, 2018

Astross89 said:
Sorry ahead of time for all my questions. I'm building a 24x36 detached garage about 100ft away from the house. I'm about to start the electrical. Plan is 100amp 20 space breaker box. But only a 90amp service. Because of wire size.

1) I have a 150amp service to the house. Can I do 90amp to the detached?
In most cases yes. You don't want the total max amperage in use at one time to exceed 150A.

2) I need to get power from the left side of the house(meter box) to the right side. I plan on going through the attic. I have no more room in my house breaker box. Can I exit out the main box where my 150amp breaker/meter is? See attached picture.Yes as long as there is an open space to add a second breaker. This is where you'd add a 90A breaker. I do see open knockouts below main breaker.

3) once I exit the box. What wire type? Ser/mhf? For 90amp I would assume 2-2-2-4?You can use SER for inside and outside where above ground. Installs like Romex. MHF needs to be in conduit where inside and exposed above ground. Can be direct buried but can be placed in conduit under ground.

4) do I need to run conduit in the attic? Not if using SER and is not subject to damage.

5) once I go through the attic and exit on the right side of the house. What do I put over here? Is this where I put a disconnect or the 90amp breaker? Is there anything I can add incase I add a pool and need power? If you plan to split off another circuit at this point you will need a small sub-panel at that point, can be a main lug with no main disconnect breaker and needs to be rated at 100A. Feed to garage will continue from there using another 90A or smaller breaker.

6) leaving the house I will bury the cable all the way to the garage. I will put it in conduit. Again what wire? Ser/mhf? Size? 2-2-2-4 still? If using MHF it can be direct bury or you can use XHHW as mentioned but will need to be in conduit the whole run panel to panel. You need to use #2 aluminum from house to garage if wanting 90A at garage

7) once I get to the garage. Is this where the 90amp breaker or a disconnect goes? You can use a 100A main breaker panel in the garage and this serves as the disconnect at the garage. 90A breaker is used as the feeding breaker in the main house panel.

8) I would assume I need two grounding rods at the entrance to the garage? Place 2 rods 6ft apart from each other using #6 bare copper for the electrode conductor connected to the garage sub-panel.

Now that their is power to the breaker box. I added a picture of my layout. Hopefully it can get big enough to see.

9) do the 20a 120v outlets have to be gfci? If so. Gfci breaker or outlet?All 120V outlets in garage need to be GFCI protected. Use GFCI outlet to protect downstream outlets. Cheaper than GFCI breaker.

10) size wire? 12-2 20A circuit needs #12

11) next. The two 50a 240v outlets. Small welder and compressor. One is 60feet away. The other is 3 feet. Size wire. 6/2?For general purpose 50A outlet you need 6/2. Compressors with motors over 3HP need to be hardwired.

12) not on my layout. I'm adding a 30amp plug on the outside of the shop for my Rv. Does this need to be gfci? 60 ft away. Size wire? 10/2?10/2 is good for 30A 240V, if 120V is needed you need to use 10/3, no GFCI needed.

13) 16 sams led lights going up. I planned on 2 switches. 8 per switch. Is that alright? No problem with the number of switched groups as long as the total amp load of the lights don't exceed 80% of the circuit size (example 20A = 16A max load).

I think that's it. Any suggestions is greatful. Thank you.

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Astross89 · Jun 23, 2018

pattenp said:
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Thank you so much. And everyone else.

New question. If I use ser in the attic. When I exit the house and hit the new sub panel. Can I switch to mhf there?

pattenp · Jun 23, 2018

Astross89 said:
Thank you so much. And everyone else.

New question. If I use ser in the attic. When I exit the house and hit the new sub panel. Can I switch to mhf there?

Yes, that would be a good point to switch. You may want to reread my post as I added several bits after I posted it and may not have seen those parts when you read. The MHF coming out of the panel to the ground will need to be in conduit until bottom of trench. Direct bury wire need to have 24" of cover, in conduit it needs 18" of cover. If using 2-2-2-4 use 2" conduit, but no smaller than 1.5".

Astross89 · Jun 23, 2018

Great information. Thank you so much. please subscribe just in case I have a couple more questions when I start wiring it up next week.

Astross89 · Jun 25, 2018

Shopping list. Just want to make sure I'm ordering the correct stuff.

Ser wire.

https://www.wireandcableyourway.com/2-3-4-ground-ser-aluminum-building-wire.html

Mhf wire

https://www.wireandcableyourway.com/2-2-2-4-aluminum-mobile-home-feeder-cable.html

6/2 wire

https://www.wireandcableyourway.com/6-2-w-g-nm-b-wire-black.html

Breaker box in garage. Any brand better?

https://www.homedepot.com/p/Square-...th-Cover-Value-Pack-HOM2040M100PCVP/204836397

Or

https://www.homedepot.com/p/GE-Powe...-Main-Breaker-Value-Kit-TM2010CCU2K/100115205

Or

https://m.lowes.com/pd/Eaton-Type-B...p-Main-Breaker-Load-Center-Value-Pack/3027588

Main leg for right side of house. Ser wire entrance and mhf exit to the shop

https://www.amazon.com/dp/B00002N7N4/?tag=atomicindus08-20

pattenp · Jun 25, 2018

Looks good to me. For the sub panel of the panels you listed I'd go with the Square-D Homeline.

Astross89 · Jun 27, 2018

Sorry for the extra questions. Just been ordering stuff. I changed up the box on the right hand side because of breaker type. I want to make sure this box and breaker is what I need.

This is where the Ser wire exits the house into this box and switchs to mhf wire to be buried to the detached garage. I want to make sure this is the right box and breaker? Both wires 2-2-2-4 size

Box

https://www.amazon.com/gp/aw/d/B00002N7N6#Ask

90 am breaker

https://www.amazon.com/dp/B000UE6BLI/?tag=atomicindus08-20

75gmck25 · Jun 27, 2018

You can make the transition from SER to MHF in a standard plastic or metal junction box, but it needs to be sized correctly. The box size requirement for larger than 4AWG wire is based on the size of the conduit entering/leaving the box, and whether its a straight pull through box, angle pull, or a splice. You will have a splice.

For example, if you have 2" conduit, I believe you need a 12"x12" box (2"x 6). This web site has an explanation for calculating the size of a splice box http://www.ecmweb.com/code-basics/sizing-junction-boxes.

When I did a similar installation I ran SER to an exterior wall and installed the junction box on the inside of the wall. Then I drilled a hole through the wall and box, and connected conduit to the box for the MHF run. The MHF in 2" conduit ran through the wall, down to 18" below ground and then through a trench to the garage, and then back up to sub-panel in the garage. I bought special splices for the 2-2-2-4 AL wire from an online supplier. You should use Schedule 80 conduit if its in an area subject to damage, but its not readily available from the big box stores. Many folks just use schedule 40.

In your links to breaker boxes you have one for the Square-D Homeline and another for the Square-D QO panel, and the 90 amp breaker is for a QO panel. QO is considered to be a better quality Square-D panel, and the price difference is not very much. Homeline is the budget Square-D home panel, often sold with a starter set of breakers.

If you don't need the full 90 amps right now, you can also put a cheaper (and easier to find) 60 amp breaker in the main panel. There is no code violation with using a smaller breaker in the main panel.

Bruce

wyliesdiesels · Jun 27, 2018

OP- whats the HP rating on the comp motor?

theoldwizard1 · Jun 30, 2018

Unless you are going to have buddies bring their welders over for a party a 1 man garage can get by on 60A even with A/C ! If you get a plasma cutter, which requires air from your compressor, you might have turn off the air while the torch and compressor are in use.

Astross89 · Jun 30, 2018

90 AMP was not that much more for me to do over the cost of 60 amp. Plus I might have some pool equipment coming off of it at some point.

My next question is when I come out of the ground with 2 inch conduit. What's the best way for the connections to go through the metal wall of the steel building. If I'm correct I don't need an outside junction box with a disconnect. Correct?. That's on the house outside wall with a 90 am breaker. Plus the inside breaker box has a 100-amp breaker that acts as a disconnect also . I should be able to run the conduit straight through the wall or some type of fitting?

Something like the attachment?

Lots of questions for my 24x36 detached garage. Location FL.

Astross89

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