Basic Run to Detached Garage

[gnidaer]

Greetings all. I've read through a lot of threads here and couldn’t find exactly my case, so here goes:

Sending wiring to a single-car detached garage.

I plan to go from a 20A breaker in the house panel, then use NM-B 12/2 (12-guage 3-wire) through the underground PVC conduit which was just laid.

In the garage, I will have a junction box (not a breaker panel) which will feed 4 lines: 1) GFCI Receptacles, 2) Light switch (1 or 2 bulbs), 3) Garage Door Opener, 4) Light switch for external light.

Distance from house panel to junction box: 65'.

Here is the map:
House panel->-----(38ft)---->8 inch brick wall--->LB connector ---->underground 1.75" conduit 27ft-------->LB Connector ----->Junction box

Notice the plan is to go straight from the house panel to the garage junction box (no intermediate splices). I plan to use indoor Romex for the entire run as it is never exposed to weather.

1. Do I have to use 4-wire? Somewhere I read that you need to run 4-wire to the garage. I have no plans for 220V/240V usage.
2. Can I use a junction box or do I have to install a breaker panel?

-g

 

[EOC_Jason]

Because of distance, I'm pretty sure you need a breaker panel for safety reasons. It doesn't need a main though.

Just a single 20A circuit to a garage seems kind of pushing it. It's better to have a little extra capacity now then to have to re-pull wire and re-do things later.

I would put lights on one circuit, maybe the garage door too. Plugs on their own circuit.

 

[pattenp]

If running a single 120V circuit then 4 wires are not needed. My advice is to run 3 w/G in case you decide in the future you need 240V. The big thing is you cannot use NM-B in conduit under ground. NM-B is not suited for wet locations. You need to use UF cable or individual wires rated as THHN/THWN. And it's best to use a small panel for disconnect.

 

[dipper]

If you have conduit underground, you don't want to run romex, you want to run THHN.
Water can and will get into that conduit.

I think you can have a single circuit feeding a garage (it might be two, not sure offhand) after that you get into running a sub panel.

plenty of info here:
http://www.selfhelpandmore.com/home-wiring-usa/accessory-structures-to-dwellings/wiring-a-detached-garage-2002.php

 

[bmcdowell40]

I would definitely run 2 circuits in this case, 1 for the garage door and lights and 1 for your receptacles. You can run 4 runs of #12 THHN: 2 Hots (1 for each circuit), 1 neutral and 1 ground. The neutral and grounds can be shared between the 2 circuits.

With this setup, you can get away without a sub-panel; I'm not sure if its OK per code but it will work.

 

[pattenp]

Just an FYI, technically THHN in it self is not suited for wet locations. The wire also has to carry the THWN rating to be suited for wet locations.

 

[IONH]

Just an FYI, technically THHN in it self is not suited for wet locations. The wire also has to carry the THWN rating to be suited for wet locations.

That is great information to know. I've seen THHN and THWN thrown around numerous times in various threads seemingly interchangeably but never knew the difference. Thank you pattenp.

Can THHN be used inside houses then? If THHN has individual conductors, I would assume it would need to be located in conduit.

 

[pattenp]

You can not have more than one circuit/feed to an outbuilding. Your example of running 4 conductors is not running 2 circuits. 2 circuits would be 2 individual runs off of 2 separate breakers in the main panel which is not allowed. Running 4 conductors would be a 240 volt feed using a double pole breaker in the main panel. Giving you the ability to split into 120V circuits.

I would definitely run 2 circuits in this case, 1 for the garage door and lights and 1 for your receptacles. You can run 4 runs of #12 THHN: 2 Hots (1 for each circuit), 1 neutral and 1 ground. The neutral and grounds can be shared between the 2 circuits.

With this setup, you can get away without a sub-panel; I'm not sure if its OK per code but it will work.

 

[pattenp]

THHN is suited for dry locations only. Individual THHN or THWN wires need to be in conduit. Wire such as NM-B is a cable assembly and does not need to be in conduit. NM-B wire is THHN rated.

That is great information to know. I've seen THHN and THWN thrown around numerous times in various threads seemingly interchangeably but never knew the difference. Thank you pattenp.

Can THHN be used inside houses then? If THHN has individual conductors, I would assume it would need to be located in conduit.

 

[IONH]

Romex would be considered NM-B then.

 

[pattenp]

Yes. Romex is a brand name.

Romex would be considered NM-B then.

 

[IONH]

Yes. Romex is a brand name.

Understood. Thanks.