Block heater trips breaker

JMarchant · Jan 13, 2018

Hi - I have a John Deere 301A with a block heater. Sometimes it will heat the block without problems but most of the time it trips the breaker within 10 seconds or so. The heater has about a 6' cord and I'm using a heavy duty 8' extension cord. Do you think the cord is the problem? I was thinking about installing a new receptacle so I could plug the heater in directly - do you think that would help? Thanks

marchanna · Jan 13, 2018

I shouldn稚 trip. The more powerful block heaters are 1500w which is about the same as a hairdryer. More than likely though, yours is 400w. Have you checked to see what else is on the circuit?

jeff9366 · Jan 13, 2018

Breakers deteriorate over years. How old is your wiring?
Most home circuits are 15 amps, so a 1,500 watt load is near max with a NEW breaker. Start up surge requires more power than later run.

If you install a new, more convenient receptacle be sure to include a GFI so you do not electrocute yourself.

marchanna · Jan 13, 2018

1500 Watts is 12.5amps on a 120v circuit, so that in and of itself won稚 likely trip it, but it doesn稚 leave a lot of room for anything else to run a 15amp circuit. But like I said, you probably have a 400w heater which is only 3.3 amps.

dieselcrawler · Jan 13, 2018

Try plugging in another high-wattage item, like a hair dryer, and see if it still trips. Try plugging in block heater to a different circuit, and see if the different circuit trips... isolate the issue using the process of elimination.

marchanna · Jan 13, 2018

I would start by plugging it into another circuit. Preferably one with a gfi. If it pops the breaker then the circuit is overloaded. If it pops the gfi then there is a short in the heater and/or it痴 power cable.

4get gto · Jan 13, 2018

You might able to check the resistance in the heater element. Higher reading probably tells you it not good. I would think it's going bad.

JMarchant · Jan 13, 2018

Thanks everyone,
The wiring is new and this is a dedicated circuit. I tried a new 20amp breaker - no luck. I tried installing a different receptacle - no luck. When I plug in a 1750 W heat gun, it works fine. When the block heater causes the trip it takes 10s or so to happen which seems strange (if a short I would think it would trip immediately). The heater is new last spring. Very strange!

4get gto · Jan 13, 2018

Can you replace just the cord on the heater. Least that would rule that out.

crazyal · Jan 13, 2018

Is it a GFI breaker?

4get gto · Jan 13, 2018

crazyal said:
Is it a GFI breaker?

Crystal has a point. Heck I have a coffee pot that doesn't like a GFI.

JMarchant · Jan 13, 2018

It doesn't look easy to get into the heater to replace the cord. Yes the breaker is GFI. Maybe just time to buy a new heater?

yomax4 · Jan 13, 2018

I had the same issue on a newer 20 amp circuit. Even drove to my neighbors new shop. same thing. We pulled my heater out of the hose and the element was just hanging there. Installed a new heater and all is well.

marchanna · Jan 13, 2018

JMarchant said:
It doesn't look easy to get into the heater to replace the cord. Yes the breaker is GFI. Maybe just time to buy a new heater?

It sounds like the heater or the cord is your problem. You should be able to replace either individually. The cord can crack or split causing a trip, or the resistance wire can burn through to the outer tube also causing a trip.

JMarchant · Jan 13, 2018

I agree - thanks to all!

Doofy · Jan 13, 2018

marchanna said:
I would start by plugging it into another circuit. Preferably one with a gfi. If it pops the breaker then the circuit is overloaded. If it pops the gfi then there is a short in the heater and/or it痴 power cable.

Now that sounds Genius. Never thought to troubleshoot that way.

My Gym · Jan 14, 2018

Loose connections on outlets and circuit breakers can cause breakers to trip. Arc fault protection. All it takes is someone not tighten a connection. Since he replaced outlet and breaker, not the problem. Most likely problem is that the heater warms up, expands and and shorts out. It will test good with a meter and will only fail when it heats up. Replace the heater.

CincyFlyer · Jan 14, 2018

marchanna said:
I would start by plugging it into another circuit. Preferably one with a gfi. If it pops the breaker then the circuit is overloaded. If it pops the gfi then there is a short in the heater and/or it痴 power cable.

Actually, if it pops the GFCI then there is a ground fault. A short will pop the breaker.

marchanna · Jan 14, 2018

A small short that is insufficient to pop the breaker will trip the GFI. That could be a short to neutral or a fault to ground because the gfi monitors the load across hot to neutral and trips if there is a variance. These are super sensitive and will trip before a breaker will.

So yes, I agree you are correct, but the real world dynamics of how they work allow you to investigate as I stated.