Window AC fire hazard

[GG]

Hello. I have an apt. complex where each apt. has a 120V AC window unit with a name plate of 12 amps. Each AC unit has a #14 wire cord that is plugged into a 15A duplex receptacle that is on a 15A dedicated circuit. Problem is 1 of them I serviced today had melted the hot side of the receptacle and the male cord prong. It looked as though a fire could have easily started. I replaced the receptacle and the cord, but I dont think thats good enough. Do any of you think that placing a GFCI or an AFCI receptacle in place of the 15A duplex would be a better way to prevent this from overheating again and melting the receptacle and cord? The breaker never tripped and its a QO115 Square D.

 

[roger]

Re: Window AC fire hazard

GG, if not already installed, I would use a commercial or industrial grade receptacle for these units.

Residential receptacles just don't have the guts to handle this border line load IMO.

Roger

 

[bphgravity]

Re: Window AC fire hazard

The air conditioners should already have integral LCDI or AFCI protection. (440.65)

I don't think either of these devices would provide any protection against what you are describing.

 

[hurk27]

Re: Window AC fire hazard

I see this allot with any high amperage appliance. What happens is over time the open receptacle starts getting a little corrosion on the contacts where the plug makes contact with it. this sets up a resistance between the connection point and unlike most appliances that are plugged in and unplug on a fairly regular routine most window air units get plugged in a left that way for the summer or longer. when this happens the contact points don't get wiped off and with the resistance of the connection it starts heating up then this even causes more resistance Lost and more heat until you have a melt down. This is why it is good to unplug and replug in appliances that don't get moved much. AFCI's can only help if the heat causes a line to neutral short or a line to ground fault. A series heating (glowing fault) can not be detected as of yet.

 

[redfish]

Re: Window AC fire hazard

hurk27, that makes a lot of sense. I'll always remember that, thanks.

 

[physis]

Re: Window AC fire hazard

I don't disagree with Wayne because what he says is true. But I agree with Roger that an industrial receptacle should be used.

A long time ago I installed a new receptacle that was used for a space heater. These people were pretty getto and who knows what they were doing but in a couple months the brand new shiny, I admit it, "cheap" receptacle was seriously burnt up. These people continually wiggling it to make the heater come on again I'm sure didn't help much.

But even though all the UL approvals or whatever I haven't used a 50? Home Depot receptacle anywhere I knew there'd be a heavy load since. No more problems like that that?I know of since either.

 

[GG]

Re: Window AC fire hazard

The circuit is 15 amps. Do they even make a commercial grade 15 amp receptacle. I have only seen these commercial grade receptacles in 20 amps, so Table 210.21(B)(3) would prevent me from using a 20 amp recep. on a 15 amp ckt.

 

[hurk27]

Re: Window AC fire hazard

Not if it is a single receptacle.
210.21(B)(1) only says a single receptacle cant be rated less than the branch circuit. and 210.21(B)(3) is only for two or more receptacles like a duplex which is two receptacles.
So using a single 20 amp receptacle on a 15 amp circuit is allowed.

 

[infinity]

Re: Window AC fire hazard

Hurk,

what about 210.21(B)(2) which states that "a receptacle shall not supply a total cord and plug load in excess of the maximum specified in table 210.21(B)(2)", which lists a 20 amp receptacle as only being permissible on a 20 amp circuit. A 20 amp single receptacle on a 15 amp circuit would permit the connection of a maximum load above the 12 amps permitted on a 15 amp circuit in table 210.21(B)(2).

 

[roger]

Re: Window AC fire hazard

Infinity, 210.21(B)2 is for where two or more receptacles or outlets are connected to a branch circuit, see the paragraph before the table.

Roger

 

[infinity]

Re: Window AC fire hazard

Roger,

After reading it again I would agree with you. It's somewhat confusing because it seems to go against logic. I can't have a 15 amp single receptacle on a 20 amp circuit even though the receptacle will limit the load to something with a 15 amp attachment plug. But I can put a 20 amp single receptacle on a 15 amp circuit and plug in a load that is 16 amps.

The part I found confusing is in the second part of the sentence in 210.21(B)(2) it uses the term "a receptacle" which is one receptacle. But including the first part of the sentence "two or more" this section seems to refer to a duplex or more receptacles and not a single receptacle.

 

[peter d]

Re: Window AC fire hazard

Originally posted by infinity:
But I can put a 20 amp single receptacle on a 15 amp circuit and plug in a load that is 16 amps.

Can you? I know this one has been argued before but I can't remember the code reference for it. Anybody??

 

[infinity]

Re: Window AC fire hazard

Peter the basic argument here is that in 210.21 (B)(1) it says that a single receptacle on an individual branch circuit must have a rating not less than that of the branch circuit. It says "not less" so it could be larger, therefore you could have a 15 amp circuit with a 20 single receptacle.

 

[peter d]

Re: Window AC fire hazard

Thanks infinity. Now I remember. That was definitely one that was hard to accept when it was being debated but I have no problem accepting it now.

 

[physis]

Re: Window AC fire hazard

Edit : Never Mind, I was wrong.

Table 210.21(B)(3), what am I, crazy?

[ July 08, 2005, 06:02 PM: Message edited by: physis ]

 

[hurk27]

Re: Window AC fire hazard

infinity

A 20 amp single receptacle on a 15 amp circuit would permit the connection of a maximum load above the 12 amps permitted on a 15 amp circuit in table 210.21(B)(2).

Even with the table aside, The receptacle is not what limits the circuits to a certain load, This is what the breaker does.
Edit to add that also the circuit conductors

[ July 08, 2005, 08:20 PM: Message edited by: hurk27 ]

 

[stud696981]

Re: Window AC fire hazard

It's been my experience in most of these cases the receptacle is either worn out and doesn't make a good connection anymore or it was just a junk receptacle to begin with.

 

[amptech]

Re: Window AC fire hazard

You can use a spec grade 15A receptacle and some idiot will find a way to abuse it. I wired a church addition a few weeks ago and used all P&S spec grade duplex receptacles. The GC called me last week and said there were 2 receptacles that looked to be melted. I went back to the job and sure enough they were both black around the neutral slot and melted. After further investigation I solved this mystery. The guys installing the sprinkler system had a power threader with a 20A cord cap on it. They had an old, ragged 16/3 SO cord with a 20A female cord cap and a 15A male to make a cheater cord to plug their threader in to my 15A duplexes. One guy admitted they had tripped the breaker several times while threading 2" pipe. All of their equipment looked like worn out junk waiting for the opportunity to bite someone really good. You can make it idiot resistant but not idiot proof.

 

[physis]

Re: Window AC fire hazard

Now I gotta take exception to you looking down your nose at old machine tools. I only wish we had that kind a quality anymore. A lot of that stuff was built 100 over instead of 10% under like things today. That's why it's still out there puttin' threads on pipes.

I'm kind of just being funny but it's also true. I know the receptacle might have been pushed "a little" hard. But which is still working? the receptacle or the threader? I'll bet the receptacles that were made when that threader was built would be proud to supply it power for it year after year.

I'm stickin' up for the threader. The receptale is what failed.

 

[peter d]

Re: Window AC fire hazard

Sam, I'll take the modern nylon devices over the old bakelite ones any day of the week. You can still get "old fashioned quality" stuff; you just have to pay more for it.