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Old 10-16-2009, 08:19 AM   #1
Maverick2002
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Default space heater plug ... getting hot

I have one of those Holmes space heater air blowers (~1200watt on high). I noticed after a bit of usage the prongs on the plug get really hot - as in I can barely touch them. Is there some faulty wiring somewhere? I also have a radiant (oil based) space heater which doesn't exhibit the same problems. Thanks!
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Old 10-16-2009, 08:22 AM   #2
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Default space heater plug ... getting hot

high wattage devices often do that, my elcheapo vacuum does that dont think its wiring...
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Old 10-16-2009, 08:41 AM   #3
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Default space heater plug ... getting hot

Are the prongs dirty or flattened ( less contact between prong and socket )?
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Old 10-16-2009, 08:50 AM   #4
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Default space heater plug ... getting hot

When you plug it in is it a tight fit or is it an outlet that is kind of loose from years of use ? Loose outlets cause higher resistance.
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Old 10-16-2009, 08:50 AM   #5
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Default space heater plug ... getting hot

If your socket is worn out even a perfect plug will be a problem with high draw devices. Try the other side of the socket, if no change and the plug looks good you might swap out the socket.
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Old 10-16-2009, 08:51 AM   #6
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Default space heater plug ... getting hot

It's normal, but it wouldn't hurt to take an emery board to the prongs.
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Old 10-16-2009, 09:08 AM   #7
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Default space heater plug ... getting hot

Heat definitely means poor connection, and his much (too hot to touch) is too much. Check all these.
1. Appearance of the prongs on the plug. If they are dirty / corroded, clean off with sandpaper, fingernail emery board, of just a knife to scrape clean.
2. Condition of the outlet. If the plug feels loose in it, it is worn out and needs replacement. Likewise, if you look into it and it appears dirty back in there, it may need replacement. As a test, plug into another outlet and see if it runs much cooler.
3. This CAN be a poor connection between the wires and the plug blades inside the molded plug body. Only solution to that is to cut off the plug and replace it with a new one.
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Old 10-16-2009, 09:21 AM   #8
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Default space heater plug ... getting hot

Prongs are clean, socket looks fine. I'll try it another socket. However, I used this same heater in my previous residence and the same thing was happening, so it's probably not the socket.

Also, while the oil-based DeLonghi heater also had some slight heat on the prongs (it's about 1200watts on full blast as well), it was nowhere near as bad as this.
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Old 10-16-2009, 09:23 AM   #9
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Default space heater plug ... getting hot

be careful with those, I had one of those and it melted my cord and scorched my plug.... luckily I was there and smelled it or it probably would have caused a fire. Now i just throw on more clothes...
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Old 10-16-2009, 09:42 AM   #10
Maverick2002
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Default space heater plug ... getting hot

Is it just the fact that it's a cheapo heater (cost me $30 or $40 I think) or is that a characteristic of the coil/fan blower models in general?
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Old 10-16-2009, 09:49 AM   #11
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Default space heater plug ... getting hot

have you checked for recalls?
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Old 10-16-2009, 11:43 AM   #12
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Default space heater plug ... getting hot

Maybe it's also a bad connection inside the plug itself, resulting in all the current passing through a relatively thin segment of wire?


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Old 10-16-2009, 11:56 AM   #13
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Default space heater plug ... getting hot

What's the wire guage on the plug? Is it a heavy duty 3 prong or one of those cheapo ones? May be worth changing out the cord with a higher guage one. I'd personally find some 12 or 14 (12 prefered but 14 will do) and a heavy duty extension cord 3 prong plug.
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Old 10-16-2009, 11:59 AM   #14
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Default space heater plug ... getting hot

1200W = 10A draw from your outlet. That's a lot of current. Any of the above are good, but a lower-power heater would reduce the current draw and reduce the possibility of this kind of problem.
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Old 10-27-2015, 12:22 PM   #15
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Default Space heater way too hot at plug

I have the exact same problem. I first replaced the whole HPN (high temp rated) line cord. It is 16 ga.,like the original. When it was still hot at the plug I replaced the plug I thought it might be a a bad crimp in the molded plug. I replaced the plug with a Hubble valise plug that has clamps to hold the wire. Still hot. I replaced the socket with a commercial grade socket with clamps for the wire. It is a very snug fit. Still getting very hot at the plug. The rest of the wire is just slightly warm. Obviously there is a high resistance contact somewhere but what's left? The wires to the socket and the plug are firmly clamped. I just tried the other side of the receptacle. It's no better. I measured 150 degrees off the cord, at the plug, with an IR thermometer. The plug body is discolored at the prongs. That sucker gets HOT!! My gut feeling is that it is bad socket contact but what can I try that I have not already done short of going to a 30 or 50AMP twist lock receptacle and plug?
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Old 10-27-2015, 12:47 PM   #16
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Quote:
Originally Posted by 6PTsocket View Post
I have the exact same problem. I first replaced the whole HPN (high temp rated) line cord. It is 16 ga.,like the original. When it was still hot at the plug I replaced the plug I thought it might be a a bad crimp in the molded plug. I replaced the plug with a Hubble valise plug that has clamps to hold the wire. Still hot. I replaced the socket with a commercial grade socket with clamps for the wire. It is a very snug fit. Still getting very hot at the plug. The rest of the wire is just slightly warm. Obviously there is a high resistance contact somewhere but what's left? The wires to the socket and the plug are firmly clamped. I just tried the other side of the receptacle. It's no better. I measured 150 degrees off the cord, at the plug, with an IR thermometer. The plug body is discolored at the prongs. That sucker gets HOT!! My gut feeling is that it is bad socket contact but what can I try that I have not already done short of going to a 30 or 50AMP twist lock receptacle and plug?
Is hard wiring out of the question? If so, I would try a 20 amp twist lock, or heavier cord.
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Old 10-27-2015, 01:07 PM   #17
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has anyone checked if there is a problem with the heater and its drawing more than 10 amps? my volt draws 12 on the 110 v charge cord. i used a commercial grade outlet and the stock plug and have had no trouble at all.

measure the current draw.

i would use nothing less than 12 gauge cord on something like that.
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Old 10-27-2015, 01:16 PM   #18
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Could be the heating coils. Over time I bet they draw more current. Have you ever seen one where eventually they will glow red? Come to think about it there may be a sticker or in the manual that says you might want to replace the space heater after so long. Not sure.

And props to an old as thread revival.

Here's some interesting information. http://energyboomer.typepad.com/ener...e-heaters.html
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Old 10-27-2015, 03:02 PM   #19
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Most heaters on high are 1500W. That's close to 13A depending on your line voltage. They are not designed for continuous use. This power will make the line cord (HPN typ.) get warm to the touch. The blades on the power plug will be very warm to touch as well under long runs with this power draw. Also be aware that most receptacles employ series/parallel wiring so if you're plugging in to a receptacle at "the end" of the line, many other sockets - even if not in use - can be a cause of heating and reduced line voltage. A simple check with a forward looking infrared radiometer (FLIR) will reveal hot receptacles. Back wired ones are frequent offenders. Also, improperly terminated aluminum wiring will cause heating.

Heater coils on old units (bare nichrome ribbons or coils) on high settings could glow cherry red. Usually fan forced heaters with reduced airflow will have coils glowing brighter. They will burn out fairly quickly if left running like this. The mica insulators will also degrade faster and if the coil touches the chassis and shorts it will glow white hot and spark all nice and hopefully no one has put a penny under the fuse!

Ceramic heaters do not glow at all and should be kept free of dust and other debris. These types like the original Pelonis disc furnace had foam filters that needed to be cleaned.

They also had very high inrush current and could pull 25A or more for a few seconds when cold started. This would blow non slow blow fuses if the circuit was protected by them which was a pita.
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Old 10-27-2015, 03:22 PM   #20
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6PTsocket, your post says you've already done all the right things, and still the plug body gets very hot. Further, this happens if you plug it into a different outlet, right? Not just the other half of the same wall outlet - try it in a different outlet altogether.

Certainly 16 ga wire is sufficient for 1200 W heater. But tell us for sure: this thread was started by someone with a 1200 W unit, and you have not specified the watt rating of YOUR heater unit. The Hubble Valise plug is certainly a solid unit, too. Moreover, you say that the new wall outlet module is made with good wire clamps (screws?) and feels like a tight fit when you push the plug in.

That leaves not much to consider. You do say that the cord itself feels only slightly warm elsewhere, and hot just at the plug. You don't offer any comment on whether the outlet fitted into the wall mounting box is very hot - I'd expect it to be somewhat warm since it is in contact with the hot blades of the plug. But assuming the hottest things are the two plug blades, I would suspect again the connection between the cord wires and the blades, inside the Hubble body. Check that those are clean and tight.
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Old 10-28-2015, 07:12 PM   #21
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Quote:
Originally Posted by Rubycon View Post
Most heaters on high are 1500W. That's close to 13A depending on your line voltage. They are not designed for continuous use. This power will make the line cord (HPN typ.) get warm to the touch. The blades on the power plug will be very warm to touch as well under long runs with this power draw. Also be aware that most receptacles employ series/parallel wiring so if you're plugging in to a receptacle at "the end" of the line, many other sockets - even if not in use - can be a cause of heating and reduced line voltage. A simple check with a forward looking infrared radiometer (FLIR) will reveal hot receptacles. Back wired ones are frequent offenders. Also, improperly terminated aluminum wiring will cause heating.

Heater coils on old units (bare nichrome ribbons or coils) on high settings could glow cherry red. Usually fan forced heaters with reduced airflow will have coils glowing brighter. They will burn out fairly quickly if left running like this. The mica insulators will also degrade faster and if the coil touches the chassis and shorts it will glow white hot and spark all nice and hopefully no one has put a penny under the fuse!

Ceramic heaters do not glow at all and should be kept free of dust and other debris. These types like the original Pelonis disc furnace had foam filters that needed to be cleaned.

They also had very high inrush current and could pull 25A or more for a few seconds when cold started. This would blow non slow blow fuses if the circuit was protected by them which was a pita.
Actually, plug in heaters are rated for continuous use, at least on the premise wiring branch circuit side. That is typically why they top out at 1500w. The NEC requires a branch breaker be sized 125% of the load for a continuous load. This is fudged a bit, but for a 1500w heater you would adjust the load to about 15.6 amps at 120v. Which is just a hair over the standard 15a branch circuits many homes still have for general purpose receptacles. This is also why home hair dryers can be as high as 2000 watts, as 20 amp branch circuits have been required in bathrooms for quite a while.

The problem lies in a cheaper manufacturer with either poor quality control of the cord/plug assembly, or just barely sizing the wire to meet voltage drop requirements. Any extra resistance in the branch wiring through splices or terminations exacerbate this problem.

I have used 2 heaters with heavy duty 3 prong plugs at 1500w for over a week straight and not had any plug warming, one was even on a 50' 12AWG extension cord. This was at a new construction site with 20amp branch breakers, and low ambient temps.

The topic of "backstabbed" receptacles is something debated on the electrical forum I frequent, but it is generally agreed that the builder grade receptacles with tiny fingers on the push-in rear connections should not be used by a professional electrician.

Everything else is good advice and spot on, although if people are still using a fuse box in a residential setting, then a plug-in heater is the least of their worries. Modern circuit breakers of course can handle inrush currents, as they have both a magnetic and thermal cutout.
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Old 10-28-2015, 08:35 PM   #22
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Isn't there something about circuits (15 amps, at least) only being rated for 80% of the total amperage for continuous use?

Regardless, given how often fires start due to space heaters, I'm surprised they're even allowed to run more than 1000W anymore.
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Old 10-28-2015, 09:35 PM   #23
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Quote:
Originally Posted by Imp View Post
Isn't there something about circuits (15 amps, at least) only being rated for 80% of the total amperage for continuous use?

Regardless, given how often fires start due to space heaters, I'm surprised they're even allowed to run more than 1000W anymore.
I had the same problem. Hot at the plug, socket, and even the wall around the socket was pretty warm.

Turned out to be the ends of the solid romex wires in the wall attached to the back of the socket.

They were making a poor connection, and had gotten so hot that they were brittle. When I pulled the outlet out of the box, one of them broke off easily. The ends did not look like normal copper wire anymore.

I cut the ends back until I had normal looking shiny copper wire, and re-did the connections, and that got rid of the high socket temps.
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Old 10-28-2015, 10:03 PM   #24
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OK, first off, this is a necro. But since we are still making intelligent responses I will contribute.




Quote:
Originally Posted by Imp View Post
Isn't there something about circuits (15 amps, at least) only being rated for 80% of the total amperage for continuous use?

Regardless, given how often fires start due to space heaters, I'm surprised they're even allowed to run more than 1000W anymore.

The wattage is not the issue. The main safety feature is how well designed the heater is.

I had one of those cheapo coil spring units and it almost burned the house down.








That style.

Those things are deathtraps, and should be outlawed. They arent safe even on the low setting.


Nowadays I prefer a ceramic heater, or oil. Much safer. Less likely to burn the house down, even at 1500 watts.
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Old 10-29-2015, 12:48 AM   #25
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Quote:
Originally Posted by shortylickens View Post
Those things are deathtraps, and should be outlawed. They arent safe even on the low setting.


Nowadays I prefer a ceramic heater, or oil. Much safer. Less likely to burn the house down, even at 1500 watts.
I used the oil ones as a kid. Parents said they were safer, slept with them right beside the bed.
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