120 Volt System

[richard5933]

Those ones with the internal screw clamp are very good and I would choose that over crimp lugs. Not sure what the ratings you're likely to see are. 15a of course but the better ones could be 20, could be 30. I'd go for the higher ones if there isn't a good reason not to. The breaker is there only to protect the wiring and the outlet. That's the entire extent of it's job. If the outlet is rated higher than the breaker that's just an extra safety margin, same as if the wire is heavier than it has to be. Good for peace of mind. Plus if needed later it allows the freedom to install a heavier breaker. Good example: Did a little remodeling in the kitchen which included an outlet strip, and the only circuit readily available was 14 gage wire on a 20 amp breaker. Turns out when you turn on a crock pot and an air fryer it's too much. IF the wiring had been 12 gage it would be a simple matter to switch to a 30a breaker and a 30a outlet to plug the power strips into but to run a new wire is not so simple.

Jim

20-amp outlets have one straight slot and one T-shaped slot. One prong on the plug is turned sideways on a 20-amp plug, and the T-shaped outlet slot allows either a 'regular' plug or a 20-amp plug to be used. Very few household appliances will require a true 20-amp outlet aside from some very large window a/c units and perhaps a counter-top oven. More common in commercial kitchens or industrial settings.

I'd say that it's pretty common to find regular 15-amp outlets in most homes on the 20-amp circuits, which is perfectly acceptable. Very rarely will you find a device which needs the 20-amp outlet, even less likely on a bus.

Not sure what you're talking about with a 30-amp outlet. Most everything I've ever seen for 30 amps is totally different and not capable of accepting a 'regular' plug found on most household appliances.

[dtcerrato]

THHN wire is extremely robust with superior insulation that lasts a lifetime. Ours was installed in our diy conversion in 1979 and is of the same condition today as it was when installed. We even used 10 through 6 gauge THHN for portions of the 12V wiring & has held up better than any of the TW of SJO cords - especially in the engine house - just for the record 

[chessie4905]

if you think that receptacles in kitchen area may have two high draw items plugged in at the same time, you have a couple choices. Run different receptacles in that area on separate circuit, or snap off the side jumper in those receptacles and run upper half of receptacles on one circuit, and lower half on different circuit. Not positive if latter is ok with code though. Whatever you do, use all heavy duty 20 amp ones. They secure plugs tighter than the lesser ones due to heavier components.

[richard5933]

The heavier duty outlets which grip plugs tightly can be found in 15-amp and 20-amp versions. You're looking for outlets designed for commercial applications as opposed to residential ones. The 'contractor grade' outlets are usually the bargain bin option and of the lower quality - they are designed to build fast and cheap.

[dtcerrato]

Codes differ greatly in different locations. I would be comfortable running two circuits to one duplex outlet with a removed side jumper as long as there is a caution lable inside that J-Box that states the outlet is fed by two circuit breakers with their numbers. We remove side jumpers where we want one of the duplex receptacles switched - as our. aux. air compressor is plugged into and energized from the driver seat if needed - among others in the bus & on the home front...

[Jim Blackwood]

I was just trying to point out that it may not be all that easy to run additional wires if you need to on down the road. In which case you can often get by if you ran the heavier wire in the first place. And the breaker is there to protect the wire and the outlet. So if you plan on using 20a breakers you'd better not be using 15a outlets. You could overload the outlets and the breaker would never know. That's a recipe for a fire.

Jim

[richard5933]

I was just trying to point out that it may not be all that easy to run additional wires if you need to on down the road. In which case you can often get by if you ran the heavier wire in the first place. And the breaker is there to protect the wire and the outlet. So if you plan on using 20a breakers you'd better not be using 15a outlets. You could overload the outlets and the breaker would never know. That's a recipe for a fire.

Jim

Yes and no...

Any appliance which requires a 20-amp breaker is going to have one of the prongs on the plug turned sideways. Unlikely you'll be using an appliance like that on the bus, and you won't get that plugged into a 15-amp outlet.

Could someone plug two 15-amp appliances into a duplex outlet and overload a 15-amp breaker? Sure, but it would also blow a 20-amp breaker.

Check out nearly any residential kitchen in the US which has been wired in the past few decades, and you're likely to see only 15-amp outlets installed on 20-amp circuits.

[dtcerrato]

A 15A rated outlet won't even get the least bit warm on a 20A CB let alone catch fire!
The beauty of ridged metallic conduit & steel J-Boxes is total containment of fire, explosion, etc.

[Jim Blackwood]

I'll still maintain that the ratings are there for a reason. Fortunately there is a safety factor built in, but that is for the end user's safety, not the convenience of the builder. A duplex outlet is easily capable of being overloaded. Very easy to plug in two devices that each draw 10a. And I know you've all seen and even occasionally used those multi-plug adapters of various sorts. The best preventative is multiple outlets each with their own feed but you can never know exactly where you want them after until you've been living in it for awhile, and then needs change.

Under ideal conditions a 15a outlet will handle 20a, at least for awhile. But conditions will always deteriorate. Ever live in a 30 year old house where the cords won't stay plugged into the outlets? I have. All it takes is one poor connection. Resistance in an electrical circuit creates heat. Heat generally makes connections worse, with cascading effect. Maybe you notice the blackened plug or outlet, maybe you don't but the next stage is open flame. Why take a chance on that when for another buck you can completely avoid it? 15a outlets are for builders, not owners.

Oh, and those 15a outlets on a 20a circuit? Those are daisy chained together. Again, for the convenience of the builder. Install the extra wires. Make it safe. If your bus burns down it'll do it in about 5 minutes flat.

Jim

[richard5933]

Aside from everything else, one major reason I will always install 15-amp outlets on a 20-amp circuit is because I don't want anyone actually plugging a 20-amp appliance into one. Great way to limit the circuits to devices of less than 15-amp draw.

Double checking myself on this, in my re-reading of the code online it does appear that this is allowed in the US, and it also seems that the 15a outlets are rated for a 20a passthrough, meaning that the internals are the same on both 15a and 20a outlets, the difference being the face. One will allow insertion of a 20a plug and one will not.

There are only two outlets in my house with 20-amp receptacles in them - both installed with single receptacle outlets, both next to a window, each on their own circuit, and each intended to run a large window a/c unit.

[sledhead]

WOW 
r codes must be more strict than yours

15 anp outlet = 14 g wire = 15 amp breaker

20 amp outlet = 12 g wire = 20 amp breaker

and if they look they will give you sh%t if they see the larger wire used than needed

4 the coach just use 12 g wire and 20 amp outlet's & breakers , it's not very much more $$
than no worries

[richard5933]

WOW 
r codes must be more strict than yours

15 anp outlet = 14 g wire = 15 amp breaker

20 amp outlet = 12 g wire = 20 amp breaker

and if they look they will give you sh%t if they see the larger wire used than needed

4 the coach just use 12 g wire and 20 amp outlet's & breakers , it's not very much more $$
than no worries

Best I could tell the only difference was that we're allowed to put 15-amp outlets on a 20-amp breaker/circuit. You guys are not. Not sure why the difference - perhaps at one time the 15-amp outlets didn't carry a 20-amp passthrough rating like now.

[sledhead]

that could be

when I see the 20 amp outlet I think of a 20 amp breaker

but most times I think it is just keeping the inspector happy and they all have there little querks

[richard5933]

that could be

but most times I think it is just keeping the inspector happy and they all have there little querks

Boy howdy, do they. My old shop building had old-school 240v 3-phase. The particulars of the system were odd, and very few electricians knew how to work with it. Just my luck the inspector was also the instructor for the certification class for this system. Good and bad - he was able to teach my electrician a few things, but he definitely had his quirks about how he like to have things done including a specific way to label things. Was really glad to get that project approved, and it only took a few inspections to get there.

[usbusin]

If someone will point me in the right direction, I'll post a picture of a receptacle where the screw was not real tight. Picture is on my computer.
Thanks