Can I make my own fixture box?

[wahzoo]

I'm doing a home-brew low voltage lighting system that requires a box that's 26"W x 56"H x 5"D. I can't find any off-the-shelf enclosures that are even close to these dimemsions.

Would it be out of the question to fabricate my own? I'm not new to metalworking. Provided it was 14 gauge, good workmanship, primed and finished, would it still get rejected because it's not NEMA rated or UL listed, etc?

Granted this isn't a breaker box, but it does have 120V circuits running through it.

If the 2002 NEC addresses this please give me the chapter and verse.

More detail if needed:

The box will contain relays which will accept low voltage signals and

120V (of branch circuits) for input. The 120V output of each relay then goes thru conduit it's respective light. The signal and power will be separated by the required barriers in the box and with separate runs of conduit.

I'm using this message to prepare for asking my electrical inspector. I don't want to bug him with amature questions.

Square D makes some breaker boxes that approach the right dimensions, but the catalog says the boxes are not available separately.

--wahzoo

[HeatMan]

Just curious, have you checked at the electrical supply houses? Most can get some custom made if you need one.

[wahzoo]

Thanks. Didn't know that sort of service was available. Still, if it's $400+ dollars, I'll gladly make my own, if allowed.

[zxcvbob]

It might be cheaper and easier to get a 200A main-lug panel and gut it. (Main lug because you don't need and don't wanna pay for a 200A breaker) You might can even find one surplus or at a metal recycler.

Another good thing about using a panel enclosure is it will have lots of knockouts for your conduits.

Best regards, Bob

[Childfree Scott]

Is there some reason why it has to metal? I mean isn't wood going to be much easier to work with?

[SQLit]

How did you decide on the dimensions? Is the box surface or flush mount? Inside or outside? The NEC says that junction boxes are to be listed for the purpose.

company is not cheap. Very solid products

You going to put relays that generate heat into a closed box. This could be a recipe for disaster over time. Anything that generates heat should be vented. Especially if it is in a wall.

I have drilled 1" holes on the top sides and bottoms of cans for ventilation. You can buy a round screen and screw them on to prevent entry. Never put vent holes on the top. Water is everywhere and it will find its way into the worst places when least expected.

The size your talking about should really have a hinged cover. No one wants to pick up and put on that big of a cover. I used to buy handles for new electrical services and install them One guy would place the cover and the other would put in the screws. If your determined to not use a piano hinge. Then be sure to install studs 2 at the top and 2 on the lower sides. That way you can place the cover alone. All the rest of the fasteners can be pan head screws.

Last suggestion, put a pan in the back so you will not be drilling and screwing into the back of the can. Hang it on studs and then you can install the can, pull the wire, and do the wiring on the kitchen table.... just kidding.

program may help you decide on what if any ventilation you will need. It is actually set up for sizing air conditioners.

[Chris Lewis]

According to wahzoo :

If you can't find one already made/approved that'll do, it don't matter whether you make it or have it made, it still needs to be "approved" for electrical code purposes.

[I'm assuming you can't design this in a way to take it "outside of the NEC mandate" - eg: making it a plug-connected device. If you were able to do that, you can do anything you want as long as you don't "sell it" (at least in Canada that is)]

Just gutting, say, a 200A panel box won't work because it's not approved for the purpose you're putting it to.

I'm not familiar with US electrical code in this area, but I'm sure they have allowances for this sort of thing.

In Canada (which have considerably stricter rules about approvals than the US) there's an "out" for things that aren't CSA (or now UL) approved.

You get an "approved authority" to approve it. In Ontario, for example, you can get someone from Ontario Hydro (the power utility, now subdivided into several component entities) to come and "approve" a device for CSA/CEC purposes for $75. There are several other organizations also certified to do this.

Many years ago we were importing some computer gear for resale. It wasn't yet clear whether it would be worth CSA-approving the units. So we had Ontario Hydro come in and "unit approve" for $75 each.

This isn't an "amateur" question. Ask the inspector about how to go about this.

Do take into consideration "design criteria" mentioned by others here. Eg: venting and doors.

[Chris Lewis]

According to zxcvbob :

It's not "listed for the purpose". This doesn't help.

[feemail]

To save money on my house I took small cardboard boxes from the hardware store and used them instead of electrical boxes. They were free and saved me about $2 on each outlet. I even saved more when I used some scrap speaker wire that I got when the tv store closed. I used that to wire most of the house. It all worked real well, and would still be working today if the damn house had not burnt down.

------

[Tim or Marty Shephard]

I don't think so . I the phrase is "listed device" which your's would not be.

[volts500]

No. I've installed plenty of fabricated cabinets/boxes/troughs over the years never had the first one turned down by an inspector. The cabinets/boxes/troughs are usually built by local fabrication shops.

The NEC construction specifications for cabinets and metal boxes requires that they be metal (usually sheet steel), corrosion resistant, be at least

1.35mm (0.053 in.) thick, and be constructed so as to have ample strength.

Then build barriers between the the low volt and the high volt sides.

For cabinets (construction specifications): NEC (2002) Section 312.10 For metal boxes (construction specifications): NEC Section 314.40

Listing is only required for cabinets/boxes that don't meet the requirements stated above, such as the minimum thickness or using a material other than metal. It doesn't it hurt to run this by the inspector to get his approval, so you can fabricate the cabinet/box with confidence that it will be accepted.

[Paul Franklin]

Hoffman doesn't make them in that exact size, but you could gang two together with short large pipe nipples.

Look at:

HTH,

Paul

[wahzoo]

Yes, Chris also mentioned that. Where is that in my 2002 NEC? I was under the impression the non-listed, non-labeled, etc equipment could still be approved by the AHJ. You're saying he's not likely to approve?

[wahzoo]

It would, but the only wood in the whole house is the cabinetry and some in the furniture. You know the Terminix ad where they show a couple with a all-concrete house? I actually like that idea. Sick huh?

Also I'm using conduit everywhere, and that's going to mate better with a sheet metal box, not to even breech to subject of grounding.

To my suprise a wood box be approved. See NEC 312.10 C.

[volts500]

The NEC definition of "approved" is "accepted by the authority having jurisdiction", i.e., your local electrical inspector. I seriously doubt that an inspector would approve a wood cabinet (in my area anyway). Most will want to see a UL sticker for items that require approval. A _metal_ cabinet/box, OTOH, doesn't need approval if it is corrosion resistant, solidly constructed, and at least 1.35 (0.053 in.) thick sheet steel.

[wahzoo]

I require about 80 power relays in the box with enough space to make them accessible. I my latest drawing I have two colunns of 40 relays and they're stacked two deep. There's all sorts of allowance for spacing between the relays and wiring spacing in general as per NEC

312.10. BTW, the dims are now 72"H x 24"W x 7.25"D.

Is the box surface or flush mount?

Surface.

Inside.

The NEC says that junction boxes are to be listed for the

So this would be called a junction box? I thought of it as an auxillary box but that's NEMA parlance.

This company is not cheap. Very solid products

I didn't mention but these are "bistable impulse relays" (been around for years). What's cool about these is they accept a pulse from a cheap little momentary contact switch and switch state, but there's no holding current. They "latch" and stay that way until the next pulse. Each relay dissapates about 9W, but that's only for about 75 milliseconds while their switching.

They're an extremely rare item though. I looked for weeks on the internet for the 2 types that I found. I'll post the part numbers if you're interested.

Oh yeah, I'll definitely use piano hinge and weld it on, probably from Grainger.

Righto, everything is being mounted on a thick piece of phenolic or tempered masonite board. That board will be anchored to the box with (those long hex nuts, forget what that call them). Almost like a motherboard.

[HA HA Budys Here]

Isn't there a 42 circuit limit under NEC for ANY type of panel, box, pullbox, trough, etc???

[Chris Lewis]

According to HA HA Budys Here :

While it sounds like he's going to have several circuits feeding this beast, the numbers he's bandying about are relay counts, not circuit counts.

[Chris Lewis]

According to wahzoo :

Strictly on the basis that it's a "approved" panel box? No, he probably wouldn't approve on that alone.

This is implicit in the phrase "listed device". Devices are UL/CSA listed (approved) for very specific purposes. A 200A panel box is a, well, 200A panel box, not an enclosure for bazillions of relays. By using the box in a different way, the "listing" is invalidated, and it's not an approved device for the purpose.

This makes simple logical sense. UL/CSA tests devices for certain purposes, not others. The listing is only valid for those purposes, not others. Ie: UL/CSA approval of a 200A panel box is based upon a certain level of heat production by the contained breakers and wiring. Refilling the box with bazillions of relays completely invalidates the testing they did.