Electric Overhead Heater Fire

[Travis Lavallee]

I remembered a recent news story dealing with several fires up here from these forced air electric heaters and found this:

http://www.csagroup.org/product_reca...nguage=english

Just another possibility to consider.

[Leo Vogel]

Maybe this is my problem. I was looking at the receptacles (outlets) used by my electrician when he wired my 220v circuits. They are 30A RV OUTLET Leviton Model: 7313. * UL listed for copper or aluminum conductors * Heavy gauge double wire copper alloy contacts for maximum conductivity * Color coded terminals for easy identification and fast wiring * All mounting hardware included * Flush mount receptacle for recreational vehicles * 125 volt 60 Hz AC only * 2 pole, 3 wire grounding.

Problem?

[Rod Sheridan]

Maybe this is my problem. I was looking at the receptacles (outlets) used by my electrician when he wired my 220v circuits. They are 30A RV OUTLET Leviton Model: 7313. * UL listed for copper or aluminum conductors * Heavy gauge double wire copper alloy contacts for maximum conductivity * Color coded terminals for easy identification and fast wiring * All mounting hardware included * Flush mount receptacle for recreational vehicles * 125 volt 60 Hz AC only * 2 pole, 3 wire grounding.

Problem?

Although he's dumb for using a 120 volt receptacle on a 240 volt circuit, that wouldn't be the cause of the overheating.

It's a really stupid manoeuvre however since you could have plugged a 120 volt appliance into it. He must have made up the cord on your heater as well since it wouldn't fit a 120V receptacle.

Regards, Rod.

[Jason Beam]

Although he's dumb for using a 120 volt receptacle on a 240 volt circuit, that wouldn't be the cause of the overheating.

It's a really stupid manoeuvre however since you could have plugged a 120 volt appliance into it. He must have made up the cord on your heater as well since it wouldn't fit a 120V receptacle.

Regards, Rod.

+1 - I don't think I'd be using that electrician anymore, myself. That was clearly a bad call on his part. Given this information, I wouldn't be surprised if he had a loose wire in your box, either, causing your fire.

[Kerry Wright]

Power (watts) = I (amps) x E (volts)

If the receptacle is rated for 30 amps at 125v, the maximum power rating of that receptacle is 3750 watts. By comparison a 30 amp 220 volt receptacle can handle twice that amount, 7500 watts. The 5000 watt heater seriously overloaded the receptacle and more than likely caused the fire.

Your electrician was at fault. At the very least a call to your state licensing board is in order.

[Bernie May]

Those of us with correctly wired 220V electric heaters in our shops collectively breathed a sigh of relief learning your electrician used a 120 V outlet. You had all of us worried about losing all of our tools.
-bernie

[Leo Vogel]

Bernie - sorry for the worry. I am happy knowing what caused the fire. Looking at the male plug, I'm sure it was a combination of a loose fitting wire and the 125v outlet (thanks Kerry for the formula). I was really lucky. That little heater ran many a day without anyone in the shop to catch a fire. Needless to say, I lost all confidence in my electrician. Thanks everyone and check those connections!

[Rod Sheridan]

Power (watts) = I (amps) x E (volts)

If the receptacle is rated for 30 amps at 125v, the maximum power rating of that receptacle is 3750 watts. By comparison a 30 amp 220 volt receptacle can handle twice that amount, 7500 watts. The 5000 watt heater seriously overloaded the receptacle and more than likely caused the fire.

Your electrician was at fault. At the very least a call to your state licensing board is in order.

Incorrect, there is no wattage rating on a receptacle, which was rated for the current drawn by the heater.

It was dangerous however to use a 120 volt receptacle on the circuit since you could plug a 120V appliance into it by accident.

Regards, Rod.

[Rick Moyer]

My PM2000 is wired to a 20-amp breaker - the installed cord was not intended for a 30-amp breaker. you may have one with a larger motor.

This illustrates an important issue that has come up before and is always drowned out by the "breaker is designed to protect the wire in the wall" posts.

Many fires occur because the line sets to the equipment are not designed to handle the amps from either the equipment or the suppling breaker if some problem should arise. This situation can easily occur when a cord is replaced or when a cord or plug needs to be supplied on equipment not furnished initially.

Just because you install a 30-amp plug on a device connected to a properly installed 30-amp circuit -- does not guarantee that the installation is safe - more is not better. This is why many european countries have fused plugs.

I apologize for the highjack, but I think we are learning something in this thread and I'd like some more info on this.
Correct me if I am wrong, but are you saying that all the wiring in a circuit from the breaker to the end tool/appliance must be equal? What about plugging a lamp cord (rather small generally) into a 20a circuit receptacle, or even a 15a receptacle for that matter. Lamp cords are usually only 18 gauge wire I think. I understand that a lamp is only going to draw a small amperage, but this is not unlike your analogy with a 20a table saw(cord) on a 30a circuitbreaker is it?
It is possible I am missing something. Thanks to whomever can enlighten us.

[Kerry Wright]

Rod,

First let me say, I don't want to get into a long winded debate.

I'll admit receptacles do not have a power rating, but they do have voltage and amperage ratings which can be used to figure out the power it is safely capable of handling. Some are rated for both 110 and 220 and the manufacture clearly states this. In this case the manufacture states "125V ONLY" (maximum capacity), which clearly brings in the question of the amount of power (watts) it can handle. You can't change the basic laws of electricity, where there is current flow, there is power consumption.

Respectfully
Kerry

[Kerry Wright]

Rick,

I believe Tom is just saying if you use a cord that is rated smaller than the load it is supplying, your asking for trouble. In other words, if you have a tool that requires 20A and you use a cord only rated for 10A

Now if you have the same 20A tool and a 20A cord, you can plug it into any circuit (as long at it's the same voltage) wired for at least, but not less than 20A.

[Carl Hunsinger]

Rod,
...I'll admit receptacles do not have a power rating, but they do have voltage and amperage ratings which can be used to figure out the power it is safely capable of handling. Some are rated for both 110 and 220 and the manufacture clearly states this. In this case the manufacture states "125V ONLY" (maximum capacity), which clearly brings in the question of the amount of power (watts) it can handle. You can't change the basic laws of electricity, where there is current flow, there is power consumption...

While it's true you can't change the basic laws of electricity, the thing to keep in mind is that a receptacle has very little voltage drop across it when it's supplying current to a load. And it's this voltage, and not the load voltage, that determines how hot the receptacle will get, for a given load current. Be it 250V or 125V rated, the important parameter, in regards to conductor heating, is the current rating of the receptacle. Although a receptacle wired to a 240V circuit may be delivering twice the power to the load, compared to a recepticle on a 120V circuit (delivering the same load current), the receptacle dissipates power according to P = Vdrop * Iload.

The voltage rating applies primarily to dielectric strength (i.e. arcover). Also, the voltage rating implies that the connector is mechanically consistent with similarly rated loads. In other words, a 125V/15A rated receptacle will mate with a 125V/15A plug.

Carl

[Rick Moyer]

My PM2000 is wired to a 20-amp breaker - the installed cord was not intended for a 30-amp breaker. you may have one with a larger motor.



Many fires occur because the line sets to the equipment are not designed to handle the amps from either the equipment or the suppling breaker if some problem should arise.

Rick,

I believe Tom is just saying if you use a cord that is rated smaller than the load it is supplying, your asking for trouble. In other words, if you have a tool that requires 20A and you use a cord only rated for 10A

Now if you have the same 20A tool and a 20A cord, you can plug it into any circuit (as long at it's the same voltage) wired for at least, but not less than 20A.

OK, Kerry, that makes sense. I was confused by the portion of Tom's post I quoted above. Maybe he meant what you said. I'll leave it at that. Don't want to get off the OP's topic.

[Matt Meiser]

Why on earth would he have used 30A RV outlets? They are actually kind of hard to find in my experience unless you buy them in a metal box with a cover similar to what they use at campgrounds. After the big blackout a few years ago I wanted to make a cord that plugged into my generator for the camper and ended up buying a "dogbone" and cutting the male end off and wiring on the proper plug.

On the other hand, they are intended to be plugged and unplugged regularly and have pretty big contacts. I doubt campgrounds are particularly good about maintaining them and I've never used one that seemed loose or heated up. Now regular 20A outlets--those I see loose and broken all the time.