My Block heater cord on my 03 Excursion 7.3 has an end that was replaced by the PO.

It also trips my garage GFI outlets, but when I run the cord into my house, and plug it into a 15 amp outlet/ protected by a 20 amp circuit breaker, it holds.

From what I have read about heater cord fires, this worries me. Should I go ahead and order a complete replacement OEM cord, and is there a way to tell if my heater element is still ok?

Thanks! Let avoid a

 

Usually, the cord and not the element is the culprit. I'd get a new one asap and go from there.

 

cool, I've got a new cord ordered and on its way.

 

Time for my annual reminder that you can get cords at the IH dealer for a lot less, and also online. Last I knew, Ford's price for a cord was pretty breathtaking.

To me, the OE cord clip (next to the heater itself) is a fire waiting to start. The newer cord has a screw-down bezel that is much better engineered. CHECK YOUR CORDS!

 

Here's a small glut of info.

My E99 had an original. It popped everything I plugged into including a dedicated 20 amp non GFI breaker.

I replaced the block heater after I inspected the element and wire.

If you do replace your heater and continue popping your GFI's then you have 1 of these issues.

1. The source power breaker to your GFI is weak.
2. Your plugging into a GFI that has too much draw from lighting and other shared members on the same leg.
3. Faulty GFI (they do go bad)
4. Your length of extension cord is too long or the gauge of that cord is overwhelmed.

Here's a quick rundown:

A longer cord will draw more CURRENT in AMPS but not more watts (power is expressed in watts) Because a longer conductor (wire) has more resistance (the force that tends to block the flow of power). Power (measured in watts consumed by any electrical device) is expressed in Ohm's law as

P = E x I which means

watts = volts x amps

Your watts quantity will always be what the electrical device is demanding. A 1000 watt Block heater will try to pull in 1000 watts of power no matter what the length of the cord. With a shorter cord with little resistance your voltage will be 120 volts. So your amps will be about 8.333 amps (1000 watts divided by 120 volts = 8.333 volts.)

However, if you use a 200 foot extension cord, the extra resistance might reduce the voltage to only 100 . So, in order to transmit 1000 watts to the appliance, the current would go up to 10 amps (1000 watts divided by 100 = 10 amps).

However, using more amps tends to heat up the wire and as the wire heats up the resistance also goes up so you are choking off the amp draw even more and reducing the voltage even more. The result is that the appliance or other device (light bulb, hair dryer, etc) will actually be getting less of the wattage it needs, but you would still see the 1000 watts being drawn by the cord and appliance if you had a meter at the source. It's just that a lot of that power is being lost to the resistance and heating BEFORE it gets to your appliance. The result of this is strain on the appliance, which can burn out an element, also dangerous overheating of the cord, which can cause a fire.

So, your current draw (amps) goes up with a longer cord but NOT your power consumption (watts.)

Ideally: For safety, 12 Gauge wiring, 20 amp dedicated breaker, 12 Gauge extension cord. Also for safety, If you have a detached garage, that would be my choice to plug into.

Denny

 

The only thing about this statement is that the power consumption seen by the breaker is increased with the added load of the cord. The resistance added by the cord that causes the voltage drop is drawing power when used in the circuit with the heater.

Agreed. A constant resistive load such as a heater needs to have wiring capable of staying cool at that load. One could argue that if your plugging in because it's cold out, then the cord should cool just fine. However, any part of the cord run inside, pinched by a door, etc. would have increased heat. IMO, not worth it.

As Denny said, GFCI's do go bad. The ones in my garage are very twitchy and they are only 9 years old. If you stare at them sternly, they trip. After you install your new cord, see if it still trips the GFCI. If so, I would replace it. I would not run a cord outside on a non-GFCI protected circuit.

 

Probably nothing to do with this problem, but all it takes to trip the GFCI I use on my truck is a poor connection at the truck along with wet weather. Dry it off, plug it in good and the problem goes away.

And yeah, GFCIs are a pain.

 

The tolerance on GFCI's is only 5mA (.005A) difference between the hot and the neutral, anything more than that and it trips. Resistive loads, like our block heaters, are not usually the issue, More so the actual connections, check your cord (try a different one if you can) and check the connections at the heater itself.

 

You have a blocker on the way, so let's see what we see. Just so I know I told you. Be as safe as you can if you have family in your home.

Everything is first, the trucks last.

Denny

 

That said my .02 on why it trips:

1. cord problem
2. block heater corroded thru and coolant leaking onto element

 

GFCI's and block heaters don't have a good history of working well together.

An electrician gave me his theory which could be bogus, the heating element draws enough current in a loop that it creates a small Magnetic induced electrical charge to the truck.... Just enough to play havoc with a GFCIs outlet?

Does that sound like a possible explanation or just writing something off he couldn't explain?

 

I am experienced licensed electrician in both industrial and residential applications. I have been an electrician for over 20 years. This sounds like someone trying to explain something without enough knowledge. As said above, they measure the line current going to and from the hot/neutral. If the receptacle is not seeing the same load on both sides of the circuit, it assumes a problem and trips. The history of them not playing well together comes down to wet plugs, faulty wiring, faulty components, undersized GFCI. If all the equipment is in good shape, the resistive load of the heating element will not trip the GFCI.

 

I don't know if I explained it correctly but he wasn't talking about line current or the resistive load, it was the magnetic induced current to the ground wire from the heating element that was tripping the GFCI's?

 

The GFCI monitors just the line current, not the ground. You can even add them to ungrounded circuits and they will still function.

 

Haven't researched them enough to understand exactly how they work . Guess what I'll be researching tomorrow, I love learning new stuff!