the project I am working at is in dekalb county ill,,the question is,,we are not allowed to use 20 amp recepticals ,even on a 20 amp cercut>what is the logic behind this?

On a 15A circuit, you cannot use 20A receptacles, as it is a code violation.
On a 20A circuit with more than one receptacle, you can use 15A receptacles and save money over buying 20A receptacles if you like (or the engineer's specification require).
So it may be just financial.

Using 20 amp receptacles is generally allowed per code pretty much anywhere else, so I don't think it's an NEC issue. Could it be that someone at the local jurisdiction is trying to enforce something that he/she is mistaken about?

Radar

My suspicion is that the AHJ is trying to make sure a full 20 amp load isn't plugged into a single outlet, i.e. 80% maximum loading allowed on a 20 amp outlet is 16 amps (unless all components are rated to operate at 100%).

To be honest, I don't think I've ever seen an electrical product with a true 20 amp connector.

They're usually on high-powered 110 volt domestic air conditioners. That's where I've seen NEMA 5-20 plugs.

Of course those are usually plugged into dedicated 20 amp circuits.

Bingo.

Maybe that right there is their problem. If the receptacles are 20 amp rated, then 2 of them would/could draw 40 amps, 3 would/could be 60 amps, etc. Ya never know.

Radar that is not really an issue. Anyone could plug 2 1440w heaters into a 5-15 duplex. That's why we have 240.4(D)

[This message has been edited by gfretwell (edited 01-07-2006).]

True enough - that wasn't really a serious comment. Besides, I'm trying to figure why a jurisdiction would not allow 20 amp receptacles on a 20 amp circuit. Seems to me like a similar bit of short sighted reasoning is the most likely answer.

If ya' got 20 amp wire and 20 amp breaker, why not a 20 amp receptacle?

Sounds like a waste of money to put the 20 amp stuff in if you're going to slow it down with a smaller receptacle.

Following the 80% circuit loading direction...

Perhaps the intent is get #10 wire and a 25A CB behind the 20A receptacle?

Gosh, if you aren't allowed to install 20 amp receptacles, how do you wire for a 20 amp AC with a 20 amp cord end?

I'd ask the inspection division to quote the code or local ordinance to you. Perhaps it is just folklore

The 80% on #14, 12 and 10 wire is handled by 240.4(D).

more info,,all the kitchen ,dinning room outlets are fed for 20 amp, with 15 amp recepticals.the ac is fed from the pannel to the outside disconect ,no need for a seperate outlet. the bath gfci's are all fed for 20 amp with 15 amp recepticals the rest of the house is all 15 amp unless there is an upgrade on somthing "like a wirlpool or a 220 outlet in the laundry or somthing like that.

That is not exactly what the NEC requires.

First lets think about a circuit with only one single 20 amp receptacle outlet connected to it.

That single 20 amp receptacle could be loaded 100%, the breaker feeding that receptacle could be loaded 100% for up to 3 hours or forever if it was 100% rated.

Now lets think of a circuit with two or more 20 amp receptacle outlets connected to it.

In this circuit we could plug in two or more items that total 20 amps and that 20 amps of load could again run 3 hours or forever with a 100% rated breaker.

The only time 80% comes into play is here.


So in a circuit with multiple outlets the total load can exceed 80% of the circuit rating but not at one particular receptacle.