how many amp draw ?

[Fix_It]

its -5 at the house this morning ..and i keep popping my gfi outlet ..

i bought a brand new heavy winter rated 10/3 cord thinking the old one was shot .. still popping i have a brand new winter kit on the dodge and factory blanket battery heaters ...

when its 20 * it dont pop only 5* or colder ?

i have no idea why ..any suggestions

[Bulldog]

If it kicks the breaker immediately when you plug it in, your engine block heater may be shorted out. I've seen them short out where the electrical cord (the one that comes with the heater) plugs into the element at the block. Or one of your battery blankets might be bad.

Try unplugging some of the heaters from the junction block on the vehicle to isolate the bad circuit. Troubleshoot from there. One one truck, I got two bad block heaters in a row. Ford replaced them under warranty.

[Bulldog]

when its 20 * it dont pop only 5* or colder ?



Sorry didn't see this info the first time. A block heater is only about 850 watts, so about 7 amps. The battery heaters are only about 60 watts, so 1 amp for the pair. You shouldn't be kicking the breaker unless there is more draw on the same circuit. I would still isolate the different heaters on the truck and see if you can find one bad.

[78calico]

If you don't find a bad heater, plug something else in and see if it pops. Use a drill or something with a motor that will pull about 10 amps or so. Ive seen many GFI's go bad when used in outdoor conditions and the more they trip the weaker they get. It gets pretty annoying working with GFI's on a construction site but they're a necessary evil.

[93hummer]

I know some breakers are 15 out in town, most of the ones on Fort Wianwright are 20. To figure out your current draw, us ethis formula: Current (I) equals Power (P)divided by Voltage (E)

I=P/E

You have two of the 3 variables already, for a 20 amp breaker on 110 volts, you cannot exceed 2200 watts of power total, so add up the watt ratings of all your heaters, battery blankes, etc and see if the total comes in over 2200. Breakers do get old and weak ad it may pop at say 2100. If you are using a 15 amp breaker, then it would be 1650 watts.

[akdsmer]

This is a pretty common problem. I use a small extension cord with the neutral cut in two and the other two wirer seperated. I plug it in, run it through my meter with alligator clips and watch the current flow. Over 50mA will usually pop the GFI breaker. Next I use my inductive amp clamp to read total current flow when it's first plugged in and as it warms up. If the total current is near the limit of your breaker (It certainly shouldn't be unless there is a lower resistance in one of the heaters), fix the current draw culprit. If it isn't close to the limit, replace the GFI breaker. It can be cold related, you will flow more current through the cold heaters until they warm up. For example, you can plug them all in when it's 5* and only pull 8 amps with a 10mS spike of 10 amps or so, when it colder, you can pull 10 amps with a 10mS spike over 15A. You really have to be on the edge for that to occur, or a weak breaker.

[akdsmer]

There is some good information, I'm moving this to the tech forum.

For those that don't want to break-down watts to amps:

The following are actual dynamic amperage readings of these components-assume some variability!

L'il buddy interior heater.... 5.2A
Suzuki clamp-on heater..... 2.6A
400W block heater........... 3.6A
600W block heater........... 4.9A
750W block heater........... 5.8A
250W Oil pan heater......... 1.2A
100W oil pan heater.......... .8A
75W oil pan heater.......... .7A
60W batteru heater.......... .6A

Your typical 4/6 3 heater system (400W block heater, 75W Oil pan heater and 60W battery heater) would pull ~5A

Your typical 8 cyl with 4 heaters (600W BH, 2 75W heaters for oil and tranny and 60W Battery heater) would pull ~ 7A

Obviously if you are plugging in 2 vehicles with 4 heaters (not including an interior heater) you will be very close to the 15A breaker limit, but singularly not even close.

Here is the set-up I use to check the heater circuit. It uses a small extension cord with the insulation removed so that I can clamp around either the black or white wires to read circuit current. The green wire is cut so that I can look for amperage (milliamps usually) on the ground, which will trip the GFI breaker (somewhere around 40-50mA from the few that I have seen do that). The 2 steps:

1) Check heater current total. It should add up like the examples above. Notice this says .863A (A/C). The conversion is 100mV=1A so this is 8.6A.

http://www.arcticoffroad.com/forum/gallery/files/3/0/3/blockheater002.jpg

2) Check milliamps (after checking thru 15A circuit first) to ensure they are near 0. Anywhere near 40mA will trip the GFI breaker.
http://www.arcticoffroad.com/forum/gallery/files/3/0/3/blockheater003.jpg

Playing with this to get the pictures, I found a Van with 2 cords: A 750W block heater. (5.7 Amps) and another cord with 1.2A. That was typical of an engine/tranny pan heater, but this was one cord. I followed the cord, it split into two, but both pan heaters were 250W (which equals about 1.2A each) I then placed my hand on each to see which one wasn't working. :)

Keep in mind, if you aren't tripping circuit breakers, you simply need to make sure each heater is getting hot/warm. You can use a infared temperature gun to verify that or if you have a scan tool, check the engine temperature pid.

[AKMark]

Unless you have a diesel running two 750W block heaters, two 100W oil pan heaters, a 75W trans pan heater, and two 60W battery blankets. That's what my 85 was running anyway.

[Fix_It]

Unless you have a diesel running two 750W block heaters, two 100W oil pan heaters, a 75W trans pan heater, and two 60W battery blankets. That's what my 85 was running anyway.

I don't know what my Cummins grids run at, but it does have 2 of everything that i know of .. and my taco runs a block heater, battery blanket and tranny pad .. so i must be real close-then add the decreased resistance for the cold, and I must be maxing the gfi out ..

Thanks for the info Kelly, good stuff ...

[93hummer]

Here is an OHM's law calculator. http://ourworld.compuserve.com/homepages/Bill_Bowden/ohmslaw.htm

Basically add up the wattage rating of each of your devices, the total for a 15 amp circuit is 1800 watts, the max for a 20 amp circuit is 2400 watts. I run a 900W buddy heater, 2 amp trickle charger, and a 650 watt block heater on my Hummer and it doesn't trip breakers. My suburban has 2 block heaters, a buddy heater and a 2 amp battery charger and it doesn't trip breakers either. The circuits on fort wainwright are 20 amp.

try getting rid of your battery blankets and running a 2 amp trickle charger instead, it will cut about 58 watts out of your load and it your engine will start much better with a charger than a blanket.