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I am planning to install some convenience receptacles in the deck area. I will use a PVC conduit, and it will run at the bottom/side of the joist and beams. I am not sure if I will use THHN or Romex inside the conduit. The total number of single boxes with dual receptacles will be 6 or 7. One of them will be used for a 4CF outside refrigerator which, the manufacturer specs for 1 Amp normal operation. I am planning to use a 20 Amps breaker.

The questions:

  1. I suppose to make holes in the Junction box to accommodate IN/OUT. Is there a code for how many holes the box can have? For example, if 2 or more holes can be made on the same side of the junction box, what will be the minimum distance between each other?

  2. If I decide to use the THHN wire, once the PVC conduit reaches the inside of the house, can I transition to Romex, or do I need to continue to use PVC up to the breaker box? And how will I be doing the transition? A junction box?

  3. Metal boxes require to use of a wire clamp. Do I need to use a "CLAMP" with PVC no matter the wire I am using?

BTW, I am planning to have the work inspected.

Thank you

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If I decide to use the THHN wire, once the PVC conduit reaches the inside of the house, can I transition to Romex, or do I need to continue to use PVC up to the breaker box? And how will I be doing the transition? A junction box?

Definitely use THHN. Actually THWN, but wire is commonly dual rated THHN/THWN. You can't use Romex because it isn't rated for outdoor == wet usage.

Any junction box used for transition must remain accessible - i.e., it can have a standard screwed on cover plate but it can't be covered with drywall.

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    I ended up getting a metallic box (Drawn Handy Box, Bracket, and Raised Ground). It will be attached against a joist in the basement. One knockout is fitted with PVC conduit fitting (male terminal adapter) and the other with Non-Metallic Twin Screw Clamp. I guess this is the best way. Any comment? Jul 24 at 14:27
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You use an adapter fitting to transition from an indoor box to a PVC conduit

You are correct that you need to use a junction box at the point where you transition from NM to PVC, but there's more than one way to skin this cat. This can be done at an indoor box, with a LB conduit body fitting connected to a male adapter via a stub of conduit, and that adapter lock-nutted to the box. It can also be done using an outdoor box, but that can be problematic for water damage to the NM cable unless you use UF for the last indoor run instead of NM. Finally, you can use PVC, or even ENT (aka "smurf tube"), for the indoor run, continuing the THHN in conduit all the way to the breaker box, or even a convenient transition point indoors.

However, since you're dealing with wires in conduit, there's no need for any sort of clamp or other strain-relief fitting since the conduit handles all the mechanical forces exerted on the wiring method.

Don't get boxed out!

The other issue with your plan, though, is that "holes in boxes" is generally not how weatherproof boxes are used. You can do it with PVC boxes and box adapter fittings along with a healthy supply of couplings, but that is going to be more time consuming and expensive than simply using PVC FS and FD boxes that have molded-in hubs in the correct places for your conduits to enter and exit. This also handles any concerns about minimum hole-to-hole spacings.

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  • See the first comment regarding transition. Using Romex for the indoor section is easier to handle than using a conduit. Regarding the box. I need a PVC waterproof box that is similar to this: ___________ To above deck | |------------- from home -----------------| | |__________|------------- to the deck (receptacles) It will be installed vertically. I purchased a PVC junction box 4x4 and drilled the necessary holes. Used fittings and used cement to glue them. ..... Jul 24 at 15:02
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As for as "holes in the junction boxes" your best bet is to use PVC boxes similar to the one shown below. They have the molded holes already installed and come in a variety of configurations. enter image description here

You will also need some covers that are weatherproof when plugs are installed or not similar to the one shown below. enter image description here

You'll need GFCI protection so you might want to consider a GFCI breaker or individual GFCI outlet and utilize the load terminals

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  • Thank you for the inputs. For sure I will use the water Jul 24 at 14:30
  • Thank you for the inputs. For sure I will use the waterproof cover for each receptacle. I will search for a box similar to the picture you provide but with an additional molded hole. ___________ To above deck | |------------- from home -----------------------| | |__________|------------- to the deck (receptacles) It will be installed vertically Jul 24 at 14:53

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