Junction boxes for appliances?

lesp

As part of my kitchen remodel, I will be running new dedicated circuits to the following hard wired appliances:
- dishwasher
- disposal
- cooktop
- vent hood
- wall oven

My question is what type of boxes should be used - metal or plastic? If metal, should they be installed flush or surface mounted? All the sheetrock is down, so I would prefer to go flush mount unless there is a reason not to.

I have seen some examples where the Romex just sticks out of the drywall and is spliced directly into the appliance (on a dishwasher, disposal, or vent hood). Is it to code to have the NM cable running unprotected like that outside of the wall?

Please share any pictures you have -- it helps so much! Thanks in advance.

sirsparksalot

If you have access to inside the walls (sheetrock down), there's no reason not to flush mount them. Plastic or steel, it doesn't matter.

It depends, but generally, I don't think it's a violation unless the Romex is running unprotected in an area that can cause damage to it. Running it short lengths to a diswasher is not all that uncommon, but if I had a choice, I'd hard wire it via a juction box, flush mounted in the wall. Don't forget that the jbox has to always be accessible.

lesp

Thanks for your response, Sirsparksalot. I was hoping to get plastic boxes, but I couldn't find matching covers with a knockout on the front. I'm assuming this is what is needed for connecting the whip from the appliance if the box is flush mounted? Thanks for pointing me towards the right materials!

Jim Port

You need to use metallic boxes if the appliance has a metallic whip.

314.3 Nonmetallic Boxes.

nonmetallic sheaths, flexible cords, and nonmetallic raceways.

__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.

lesp

Thanks for the code reference, Jim. I have been going over the code check book but it can only hit the high points of the NEC!

So here is what I have so far for my electrical plan:

-> 50A cooktop w/whip - 32 cu.in. metal box (fill calc = 31.5)
-> 40A wall oven w/whip - 24 cu.in. metal box (fill calc = 23.5)
For the fill calculation, I assumed no device since there is no switch or receptacle, just wire nuts and cable in the box. Is this correct?

-> 30A dryer w/with 4-prong receptacle like this one:
http://www.leviton.com/OA_HTML/ibeCC...minisite=10026
I'm assuming this will fit in a regular 2-gang plastic box - correct? And what do you use as a cover plate?

-> vent hood: Romex direct to appliance terminal box.
BUT the mfr instructions say that "the hood should be connected directly to the fused disconnect (or circuit breaker) box through flexible armored cable or flexible metallic conduit." Do they seriously want me to run armored cable all the way back to the breaker? Or just to a metal junction box in the wall right behind the hood?

-> dishwasher: mfr gives option of direct wire or using a power supply cord. Is there a reason to do one vs. the other?

Thanks for all your help as I get all these details sorted out!

lesp

I have had no luck tracking down the right combination of junction box and cover plate for doing a flush mount install for the wall oven and cooktop. Why does this seem so much more complicated than the wiring itself??

The 4" square junction boxes have the attachment bracket aligned with the face of the box itself (rather than set back). I could add a mud ring but can't find one that has just a knockout for connecting the armored whip from the appliance.

I'm hoping someone can explain what parts are needed for a code-compliant flush mount junction box. Thanks in advance!

Speedy Petey

Thing is, there are literally dozens of types of 4"sq boxes. There is no list of parts needed. We just use what is right for each particular application.
Home centers have only a fraction of what is available.

If there is room behind an appliance, such as a range, oven, cooktop, etc., I rarely flush mount the box.

electures

Surface mount the box to the wall behind the oven. As for the cook top, the same mothod will work.

Jim Port

What voltage problems are you talking about being caused by metal boxes? How would the box material cause this problem?

Metal boxes have been used for years without problems and are needed with metallic wiring methods like conduit.

__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.

lesp

I am shopping at an electric supply house (not a big box), but I need to be able to specify the right part.

Per Sirsparksalot's recommendation, I would like to recess the junction boxes for the wall oven and cooktop, since the sheetrock is down. Since both appliances have a metal clad whip, I know (thank you Jim Port) that I need a metal box.

To do a recessed installation, what kind of 4" box do you use? What kind of cover? I picture would be great if anyone has one. TIA

sirsparksalot

lesp, my recommendation relied on asthetics only, and my anal retentivness. There's really no reason to disregard the pros' (of whom, I'm NOT) advice.

But, if you want to flush mount it, a simple 4x4 Metal Box. It will nail into a stud.

lesp

Sirsparksalot, I don't think any of the pro's have said not to do a recessed install. I too, like the aesthetics better of a recessed box.

So do you just take a regular 4" square box (without a bracket) and attach it through the back to a horizontal nailer between the studs? I'm assuming you would position the box face ~1/2" in front of the stud so that it will be flush when the sheetrock is added. Then finish it off with a cover plate with a knockout to accept the connector for attaching the MC appliance whip?

Please let me know if I have the parts and process right for doing this to code. Thanks so much!

sirsparksalot

I don't know of a cover plate that has a hole in it to attach a cable. The box I linked to has NM cable clamps, but for MC, you would just use one of the side knockouts.

lesp

Oh no, now I'm confused again. If the junction box is recessed behind the sheetrock, how do you use one of the side knockouts? With the box mounted flush, it seems like the only option for connecting the appliance whip is via the cover plate. Am I missing something here? Thanks again for all the guidance!

jbfan

That is one way, but I would buy a deep 1900 box with a side mount.
This allows you to screw the box to the stud from the top and bottom of the bracket.
You can find a blank cover with a 1/2" ko for the whip to attach to.

Don't forget to bond the box with the ground wire.

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