Plastic or metal electrical boxes?

[Mace Canute]

grsthegreat, I used to work in the cellulose plant at Port Alice, BC many years ago. IIRC, the big chipper had a 2000 HP electric motor and the small chipper just a 1000 HP motor. One time both chippers took on a maximum sized log at the same time and I think the chipper blades must have been ready to be sharpened because one of the chippers stalled out. (FYI Highest paid worker in the whole place was the guy who sharpened the blades) Anyways, the electrical room that housed the panels that fed both motors was ancient and so was the equipment and when that much current draw hit it simultaneously, it couldn't interrupt it for whatever reason. Should have, but didn't. Probably blew the connectors apart and started a huge arc flash. The resulting electrical fire burnt the cr*p out of that room! It looked like you poured 100 gallons of gas in there and burned it. Very impressive!

 

[clemsonfor]

Metal boxes absolutely need to be grounded. The old wiring didn't have the ground wire so the outlets didn't have provisions for the ground prong - just hot and neutral and since there was no ground conductor in the wiring, the metal boxes at that time wouldn't have a provision to connect the ground wire to them. You absolutely can not expect a metal box to ground through the house! The house is absolutely NOT a conductor! A plastic box is non conductive. It does not need to be grounded, just the receptacle ground lug needs to be connected to the ground wire.
Electricity does not take the path of least resistance, it takes the paths of all resistances. Every path is in parallel and the amount of current that flows depends on the individual resistance of each path.
I don't think I have ever seen such dangerous statements concerning house wiring as yours are.

Sorry for ill advised comments. I dont mean to say that you dont need to ground anything, just what i thought? What i thought is wrong. But i do connect all my ground wires so thats not an issue on metal or plastic. I do notice when i replace fixtures in my house that the grounds are folded back on the lights.

 

[Code54]

Anyone use the gray surface mount boxes that Lowes and Home Depot sells? I was thinking of using them in a pole building we are putting up?

 

[2manyrocks]

I sometimes use those gray boxes.

It's hard to generalize about plastic boxes because some are flimsy and some are okay. You have to look at what you're getting.

My locally owned supply store seems to have a better deal on better boxes than the big box stores.

One comment on the spiral drywall saws--I tried cutting some outlets in drywall with one of those harbor freight multifunction tools. It's not as fast as the spiral saw, but much less dusty and I could cut a cleaner line with it. So for any rennovation work where I'm installing a box in existing drywall, I'm using the multifunction tool to make the cut.

 

[JB4310]

Metal boxes only, never use plastic, had nothing but trouble with plastic.

Except outdoors, have used the HD gray plastic, also had trouble especialy with the device screws Now outdoors I use the painted metal boxes

JB.

 

[grsthegreat]

grsthegreat, I used to work in the cellulose plant at Port Alice, BC many years ago. IIRC, the big chipper had a 2000 HP electric motor and the small chipper just a 1000 HP motor. One time both chippers took on a maximum sized log at the same time and I think the chipper blades must have been ready to be sharpened because one of the chippers stalled out. (FYI Highest paid worker in the whole place was the guy who sharpened the blades) Anyways, the electrical room that housed the panels that fed both motors was ancient and so was the equipment and when that much current draw hit it simultaneously, it couldn't interrupt it for whatever reason. Should have, but didn't. Probably blew the connectors apart and started a huge arc flash. The resulting electrical fire burnt the cr*p out of that room! It looked like you poured 100 gallons of gas in there and burned it. Very impressive!

those large electrical panels are beautiful looking, and extremely deadly.

years ago, while working on a 6000 amp panel, we had all the flash protection in place, all the blast shields, hot gloves, etc. One of the guys managed to drop a socket off of the snap-on ratchet, it shouldn't have fallen off, but did. there was a HUGE bang and flash. when we could all hear again, we went to look for damage to gear. no damage, and no socket. it completely denigrated. nothing left. nada.

it was amazing.

i hate working on live panels, but you CANT shut down a hospital.

 

[grsthegreat]

Anyone use the gray surface mount boxes that Lowes and Home Depot sells? I was thinking of using them in a pole building we are putting up?

not sure of the codes up your way, but the nat elect code requires, and most states also require, all wires from ground level up to 8 feet be enclosed in conduit (pvc pipe is ok, schedule 80) and the use of metal boxes for shops UNLESS the walls are finished. If you leave the walls exposed, you need pipe. best to check your local codes first, so you dont have an issue if you sell your place.
if the walls are finished, then wire the same as a house.

 

[clemsonfor]

hmm, that has homeowner repair written all over it.

ive found some old work where someone ran a ground to some water pipe. absolutely useless. the ground HAS to run all the way back to the point of origin to allow stray voltage to make it back to the breaker and trip it.

that is one ugly picture there. In the old days, before wire nuts. people crimped the wires together and taped them.

I thought the way that you were supposed to retrofit the old 2 wire romex to ground each outlet was to run a seperate ground wire for each outlet to a groundrod under the house. I swear i read or was told that. May be wrong to, again. By me saying this im not saying i would ever do it or that it was right, but isint the pipe the same thing? This obviously is not right as it will electrify all the drains and faucets.

 

[clemsonfor]

I sometimes use those gray boxes.

It's hard to generalize about plastic boxes because some are flimsy and some are okay. You have to look at what you're getting.

My locally owned supply store seems to have a better deal on better boxes than the big box stores.

One comment on the spiral drywall saws--I tried cutting some outlets in drywall with one of those harbor freight multifunction tools. It's not as fast as the spiral saw, but much less dusty and I could cut a cleaner line with it. So for any rennovation work where I'm installing a box in existing drywall, I'm using the multifunction tool to make the cut.

I can buy romex cheaper at the eletic supply house here in town, cheaper than lowes. I needed about 40 ft of 8/2 wire and lowes was something a little more than a $1/ft and the supply house was like $.35-.50/ft. I think its cause since CU is a commodity the supply house moves more and maybe bought that lot when the price was down and Lowes bought a container full when the price was high. That and they prolly dont move that much 8/2 wire.

 

[QRTRHRS]

Anyone use the gray surface mount boxes that Lowes and Home Depot sells? I was thinking of using them in a pole building we are putting up?

If you are talking about the Carlon brand, I have used a lot of Carlon products in my horse barns.

I prefer plastic over EMT in a horse barn because I have seen rust issues with EMT due to high moisture levels.

I always cut about a quarter inch or so off the two mounting screws on duplex outlets and switches because they bottom out and strip the plastic boxes out.

Get a product catalog from which ever box manufacturer you use. The big box stores have limited space and don't have half the options that an electrical supply outlet would. Though, I have found some exceptions. For instance, this one shop I frequented would only special order slip conduit fittings in smaller sizes if I bought a whole box. Only needing a few, I found them at Home Depot.

Re: plastic boxes in the house. Stupid first year apprentices, take the time to fasten the boxes square to the studs and set to the correct depth. PS, you can find rectangular plastic shims in varying thickness's to fix this issue so your outlets/switches are flush. You may have to adjust on the belt sander.