Block heater... melted extension cord

[NotMatt]

So what's going on here... block heater on my 96 powerstroke has been working fine up until this morning. Went out there and the plug was almost too hot to touch, it melted a big hole in the plug on the extension cord, the block heater plug itself is charred a bit as well. This is a 15 amp "outdoor" extension cord, plugged into a 20 amp circuit. It's the only thing on the circuit. Should I ditch the 15 amp cord and upgrade to a heavier duty (12 gauge) cord with "20 amp" heavy duty ends?

I'm assuming it melted the 15 amp cord because it was just trying to draw too much power through it from the 20 amp circuit... but can the block heater alone really pull that many amps by itself? The wiring is good, this is the only outlet on the circuit (it's a dedicated GFI outlet on the patio that was used for a spa or hot tub by the previous owner of my house)

How many amps/watts do these heaters usually draw? The plug has always been a little warm to the touch after being plugged in all night, but never like this.

It appears the heater was still working even with the plug melted pretty good, as the coolant was plenty warm when I started her up this morning.

 

[CHOP SHOP]

Is the cord on the heater bigger then you extension cord? The ex cord should be atleast a size larger then the heater.

Is the plug in end chared up/black on the prongs? Any bad connection will make heat too.

 

[JOOP]

It didn't trip the circuit??

Sounds like you got a short, but it should of tripped the circuit. Try a bigger cord I guess.

 

[NotMatt]

Is the cord on the heater bigger then you extension cord? The ex cord should be atleast a size larger then the heater.

Is the plug in end chared up/black on the prongs? Any bad connection will make heat too.

Well, the wiring on the block heater seems to be similarly sized, but I suppose it could be rated higher than the cord. I specifically remember looking at the rating on this cord as being "15 amp" when I bought it though, as I purchased it specifically for plugging the block heater in on my old Dodge. You have a good point though, the terminals on the plug on the Ford are dirty and corroded, that may have been the issue... just a bad connection that created a bunch of heat. The plug on the truck is missing the cover that should go over it to keep the elements out, so I guess I will have to pay more attention to keeping it clean.

The circuit itself is good, grounded and it trips when overloaded... I think the problem is that it didn't trip because the cord was only 15 amp rated and melted first.

 

[JOOP]

Well you need to take in consideration that it worked before then all of a sudden it melted the cord.. Possible dirty terminals, but I would check everything out just to be safe.

 

[Binder]

Sounds like you need a thicker cord and probably a new GFI.

 

[Grommit327]

How long is the cord? That plays a part in it too. If I remember right the block heaters that I have seen only have a 15A plug on them. If it was 20A one prong would be turned sideways. I wouldn't think that heater should be pulling that many amps though

If the cord is UL listed and you're concerned about the construction of it shoot me a PM and I'll get you in touch with the right people to get it looked at

 

[Binder]

I've been told that block heater is 1500 watts FWIW.
1500W at 110 volts should be about 14 amps....

 

[zukkev]

Mine did the same thing a little while ago, but didn't burn a hole---the truck end of the plug on the cord was corroded, and the plug on the truck itself---cleaned up the truck plug; went to a different ext cord that was clean; used dialectric grease to coat everything & keep it sealed; no more problem with the cord end getting hot...:awesomework: See the tip would be the location of the heat---> if the heat is concentrated at the plug, look at the connection issue. If the whole ext cord is hot, you're drawing alot of amps----> look for a short somewhere....Most block heaters I've tested run at about 1.5 to 3 amps, not alot...I will test mine in the next day or two, as my amp clamp is at work...:awesomework: Will post up the info...And the next NEW block heater I install I will record the test results and post up.:awesomework:

 

[jeepermc]

You might think about replacing the cord on the truck too as well as the extension cord....The block heater will pull some decent power.

Is the cost of a new cord worth burning the truck to the ground and possibly what's next to it?

 

[JOOP]

I've been told that block heater is 1500 watts FWIW.
1500W at 110 volts should be about 14 amps....

That explains my electric bill

 

[Binder]

That explains my electric bill

You're not one of those guys that leaves it on all night are you?:haha::flipoff:
Major waste of electricity. Get a timer and turn it on for about 3 hours before you start the truck. It will only get so hot and that's it! How warm the truck was when you plugged it in makes no diference as it's 1500 watts cold or hot.....:awesomework:

 

[JOOP]

You're not one of those guys that leaves it on all night are you?:haha::flipoff:
Major waste of electricity. Get a timer and turn it on for about 3 hours before you start the truck. It will only get so hot and that's it! How warm the truck was when you plugged it in makes no diference as it's 1500 watts cold or hot.....:awesomework:

YES

 

[NotMatt]

Lowes sells a device that plugs in inline that will tell you how many watts or amps a device is using... it's 30 bucks, I'm just too cheap to buy it.

I'd be interested in what you find out Kevin. This is the first winter I've had this truck, and also the first winter I've been in this old house with electric heat and crappy insulation. My last power bill was $223, but I'm not sure how much of that is due to simply leaving the truck plugged in all the time vs. my juice used to heat the house when it was really cold in December.

Tonight I will be replacing the extension cord with a heavier duty one with new ends, cleaning the plug on the truck and using some dielectric grease on the connection. My timer is rated at 1200 watts... it was the highest rated "outdoor" one I could find. Hope it's enough.

 

[JOOP]

My electric bill in the winter is usually about $250. But we have a lot of electronics and 5 computers.

 

[zukkev]

I'll let ya know Matt....FWIW, we didn't notice much of a jump in our bill during the winter months, not enough for me to not plug my truck in!
And Rick is right on the timer thingy-but I will say this; I've gotten up at 3:30 am to plug my truck in after forgetting to that night, and when going out to start it that morning, it didn't seem to start as easy or as warm as when I leave it plugged in all night; not to mention the windshield is all but thawed when left plugged in all night...take it FWIW...:awesomework: