I have been a little paranoid ever since reading the thread about the FTE member losing his PSD due to fire. possibly caused by the block heater.

I did some testing with my A/C voltage plug in meter I use for my TT.

I plug my truck in using a newer 25' 12-3 lighted contractor grade drop cord, plugged into a exterior GFCI duplex plug with cover.

When I plug the meter to the end of the drop cord it reads -120 volts

When I plug the drop cord to my trucks block heater, then plug the meter in the same duplex plug it reads 113 volts, still in the Green safe zone.



I'm I ok with the voltage at 113 volts all night ? or is that to low ?

Would it make much different if I use a 10-3 drop cord ?

I'm I just being to paranoid. my biggest fear is fire.

I have a Marino plug in my bumper.

Here is a pic of the meter I used to check the voltage with.

 

Bump to the top.

 

Not sure Mark. In the bump spirit I will just say that the cord I use to plug mine in is far inferior to what the truck has from it's plug to the heater. My theory is that my extension cord will fail first and melt down causing the breaker to trip. I could be wrong. Subscribing.

 

Mike,

That's not a bad idea! I too have been concerned about a fire and loss of my beloved truck.

 

Thanks Les, but not so fast, I am sure a smart electrical guy will be along to point out the fallacies of my idea but hey, that is what I do.

 

I pluged mine in once this year and that fire thread wasn't posted yet but it got me thinking too. Not sure on the numbers you posted Mark, never took a look but I used just your regular ole extension cord, outdoor cord that is. No GFI but might put one in now, subscribing..

 

Well I'm no electrical expert, but do know these fires usually are starting due to high resistance in the wire. GFIC circuits can't limit current, that's the fuses job. I'm not even sure making an extension cord with a breaker at the truck end would fit the bill.

When the small strands of wire break, you loose capacity to "flow" current. So the situation is the current is traveling down a 50 lane highway, then suddenly there's only 10 lanes, but it can't slow down, so it "squeezes" through the 10 lane, causing a lot of "friction" (read heat)... then continues on to the element in the block. So as far as the electrical circuit, there is no "fault" technically. This "friction" heat is exactly how the element is designed to work to begin with... difference is, the HEAT is an expected by-product at the element, not along the length of the wire.

The wire jacket is rated for a certain amount of volts and amps, meaning it will survive a certain amount of heat, but once that amount is to high, you start melting things, then, when the materials flash point is reached.... you have a FIRE! More than likely the wire's jacket would have to melt away, and two of the leads touch, before the breaker would trip (over current.)

Pardon the non technical description, mostly from experience, I am NO electrician. My philosophy is to go to BIG, keep the resistance as low as possible in the extension. The smallest extension cord I have is 12/3... My favorite, 50' 10/3, I can run anything off that.

 

Just use a gauge that stays cool. You want heat the coolant and not the air between the outlet and truck.

14 would be as high of number to use but preferring a 12 gauge if not 10.

 

CPUNeck...Nicely put. And correct.

The insulation on the cord, be it the extension cord or the cord to the block heater will melt and trigger the circuit breaker when the exposed wires cross....however, depending on where the fault is at, by the time this happens, the damage could only be starting. Even with 12volts, if you cross a couple of 12g wires, one + and one -, you will see just how fast they will start glowing red. That much heat can start something else on fire before the circuit breaker is tripped. Just be sure that your cords are in good condition and you should be ok....although that is no guarantee that the element itself doesn't have a problem, but it does make the cord one less thing to worry about.

 

I've been heating the air and will continue. When something melts I want it outside my truck. So when I feel that my extension cord is a bit warm, I don't care as the truck cord is not.

Now on the other hand if my truck cord is failing even my inferior cord will not prevent this. Maybe we need to consider a proper fire resistant wrap for the length of that cord. Any ideas on this since my method clearly just makes me feel good.

 

From an engineering stand point, seems the proper "fix" or "safe guard" would be a thermistor probably just aft of the receptical on the truck wired into a relay that powers the circuit. Figure out the "limit" temperature, get the thermistor rated at that, and your done. This way if the wire starts getting to hot, the circuit would be shut down.

Now, who's an engineer?

 

This is beginning to sound like the story of the $600.00 toilet seat. Just make sure the supplied wire and plug are in good shape, use a proper extension cord and transfer your worries elsewhere, there are hundreds of thousands of block heaters, working without issue, all over the world.

 

I think we need Gene in on this one..Where are yaa Gene??

 

The block heater short cord at the block on the tractor is 33 years old. It seems over time the cord can have a few wires to break and over time that can increase resistance therefore heat.

Over heating power cords should short out if they start to burn tripping the breaker reducing the heat. Keeping the block and under hood space clean would make a fire very hard to start due to lack of fuel.

 

My thoughts exactly. Just how big can this fire get?