We need to keep the power on.

November 25, 2008 6:09 PM

How do I keep the GFI from tripping?

Winter is here. This time of year, we plug in an outdoor heating pad for a feral cat and a bird bath heater. The circuit is on a GFI. As long as only the heating pad is plugged in, there are no problems. When we plug in the heating pad and the bird bath heater, the GFI trips.

The GFI circuit is wired to an indoor electrical outlet, into which we plug a light fixture and a computer. The circuit trips even if we unplug everything from the indoor circuit. We have replaced the extension cord and the bird bath heater, so we are reasonably sure they aren't the problem. In the summer, the outlet is used for outdoor lighting, which works just fine. Could just the bird bath heater and the heating pad draw enough power to trip the circuit breaker? If not, what's going on here?

posted by clarkstonian to home & garden (21 comments total)

Could just the bird bath heater and the heating pad draw enough power to trip the circuit breaker?

It would depend on its rating. It's completely plausible if it's only a 20 amp circuit.

Look, the breaker is saying "It hurts when you do that." So don't do that.

I would guess that the bird bath heater is the big villain here. Drain that sucker and unplug it.
posted by Class Goat at 6:17 PM on November 25, 2008

I think part of your problem might be that heaters cycle on and off. If both cycle on at the same time, they could draw enough power to trip a GFI. I'd move the heaters to separate circuits.
posted by kuujjuarapik at 6:38 PM on November 25, 2008

You could have a short in the bird bath. Usually the GFI continuously tripping is a sign that something is wrong. Could be a bad GFI.
posted by jeffamaphone at 6:40 PM on November 25, 2008

I don't think it's a short in the bird bath heater. It's brand new. The old one did the same thing. That's why we replaced both the heater and the (outdoor rated) extension cord. We have the plug off the ground and protected. The cycling together makes sense.

Can an electrician put in a heavy-duty circuit so that this won't happen?
posted by clarkstonian at 6:47 PM on November 25, 2008

I doubt seriously that anything is bad. Electric heaters are really pretty high load, especially ones designed to keep water from freezing. They're also ON or OFF, no "ISH" about it. Of course, it could be a faulty wiring job, in which case one of the $4 plug in circuit testers from Lowe's will light up LED's to show you what's wrong. They're handy anyway.

We've got brand new, perfect wiring in our house. Torchiere + p4 computer + heater = fine. Torchier + p4 computer + heater + say, a plug in personal satisfaction machine = tripped breaker.

It's interesting to me that you put a plug-in, outside heater for a feral cat, and it's also interesting to me that the feral cat's heater is in general proximity to a birdbath that you want to stay liquid. Is this your cheap way of feeding the cat?
posted by TomMelee at 6:49 PM on November 25, 2008 [1 favorite has favorites]

On preview---yea, it can be updated, BUT I really think you're looking at an entirely new circuit, and if you're gonna do that you might as well get a few waterproof boxes and put 3 or so on the outside of your house. You DON'T want a 30 or 40 amp circuit when you're trying to protect sensitive electronics like computers, surge protectors be damned.
posted by TomMelee at 6:52 PM on November 25, 2008

No, the water heater and the heating pad aren't in close proximity. One is on the patio, and one is in the yard. We take care of the cat because she quit eating the birds when we started feeding her & keeping her warm (other cats are a different story). We need to provide fresh water for her and for the birds - but they share.

The computer isn't normally plugged into that circuit, but it was today - thanks for the warning.

We can put in a whole new circuit, I think. We need to have an electrician come in the next month anyway, so if it can be done, we'll do it. Thanks for the input.
posted by clarkstonian at 7:01 PM on November 25, 2008

Wait, is it the GFCI or the breaker that's tripping? If it's the GFCI, then you know there's a ground fault. It wouldn't be tripping otherwise. The GFCI has nothing to do with how much power's being drawn; that's the breaker's job. I would agree that it could be a bad GFCI.
posted by kindall at 7:15 PM on November 25, 2008

kindall, I think he has the GFI that is built into the breaker, not the outlet type. And it's tripping from being overloaded. not shorted.
posted by lee at 7:27 PM on November 25, 2008

Ideally it trips on a ground fault, but it can also trip on overloads, such as when heavy load devices kick on, especially together. More info. and More info. They'll flip on surges for heaters especially. We had them at the last place I worked. When the heaters would first flip on and draw heavy loads, they'd flip every time.
posted by TomMelee at 7:27 PM on November 25, 2008

heaters use lots of electricity. i hesitate to use the coffeemaker and microwave at the same time. bird bath heater and heating pad together is lots of draw. either use 2 circuits for them or leave one off.

sorry, birds.

could be a bad wire or outlet as well. if it's only the gfci tripping, i'd start looking at that part of it. do you use a weatherproof box?
posted by KenManiac at 7:48 PM on November 25, 2008

If it is an outlet based GFI just replace it to see if that is the problem. If you can wire it yourself this is a sub $10 potential fix. If that doesn't work then it is likely worth having an electrician out to make sure you don't have a dangerous ground fault.
posted by caddis at 8:06 PM on November 25, 2008

Could just the bird bath heater and the heating pad draw enough power to trip the circuit breaker?

Yes. Easily. Heating elements are power sucks, especially cheaper unregulated kinds.
posted by davejay at 12:38 AM on November 26, 2008

A GFCI breaker shouldn't (???) trip from current drawn through it. A GFCI breaker looks at the hot lead vs neutral (ground) lead and trips when there is an imballance between them. If your extension coard has been damaged, it could be letting a tiny amount of power through to the ground lead? Depending on how far away the bird bath is, could also be some sort of floating ground issue?

Try a different extension cord (preferably one of those heavy duty jobs).
posted by SirStan at 9:00 AM on November 26, 2008

Make sure you are using the largest, shortest extension cord you can. Heaters should always be on a heavy duty cord. I would plug any water based thing into an extension cord with it's own built-in GFCI.
posted by oneirodynia at 3:07 PM on November 26, 2008

GFCI tripping is unrelated to traditional breaker tripping. The mechanisms are completely different. They both get built into the same package sometimes, but it is important not to confuse the two things.

Bigger versions of a certain device will naturally have bigger effects. So, if a certain type of device happens to have a tendency to trip GFCIs, a big version of that device is naturally going to cause more tripping than a small version of the same thing. This has nothing to do with overloading the circuit though.

Maybe the bird bath heater has a high leakage to ground. Say it is a coil heater, and of course it is sitting directly in water that is more-or-less grounded. That could be a lot of capacitance to ground, relatively.
(well, I'm not certain that the coiling of the heating element makes any difference -- it makes the wire much longer, which means more surface area, but there are lots of other factors).

Try running the bird bath heater dry.. No wait, that might not be a good idea because of overheating. Try running the birdbath heater in a plastic/glass container sitting on a plastic stool. That should reduce the leakage current by quite a bit (as long as the water in the container has no direct access to ground -- if the heaters chassis is grounded, this experiment won't prove anything).

Anyway, all that aside.. If you want to be kind to wildlife, I recommend not running these heaters. While the heaters surely bring wildlife into your backyard, the waste is doing a lot of damage elsewhere.
posted by Chuckles at 6:01 PM on November 26, 2008

Also, please post the power rating of these two heaters. It will be printed on the devices, you just have to look for it.
posted by Chuckles at 6:03 PM on November 26, 2008

a big version of that device is naturally going to cause more tripping than a small version of the same thing.

And when I say this, I'm certainly not talking about physical size. I'm talking about big and small electrical loads. A 10W light bulb vs. a 300W light bulb, for example, which could easily come in exactly the same physical package!
posted by Chuckles at 6:06 PM on November 26, 2008

Alright, I'm not sure this whole bigger/smaller thing is making any sense at all :) D'oh! Take it as a rule of thumb, rather than a law of physics :P
posted by Chuckles at 6:45 PM on November 26, 2008

I'm gone for the holiday - I'll post the power rating on Sunday. Please check back.
posted by clarkstonian at 7:59 PM on November 26, 2008

Chuckles and Sirstan are giving you the best information from what I see, although most residential GFI Breakers have both Thermal Magnetic protection and Ground Fault protection.

Same as a regular breaker:
Thermal protects against long slow overloads (time versus current) so if you have too much load over a period of time the breaker trips

Magnetic function protects against sudden inrush of power which happens during a direct short or the starting of a large load (heater or motor)

These two functions are mechanical think heavy duty and rated for many circuit interuptions.

Ground Fault is as as Sirstan states, but is an additional mode of protection.
The sensitivity is either a 5ma or 30ma difference between load and ground, it is very little current.

This function is on a printed circuit board internal to the breaker, if your breaker has tripped multiple times there is a possibility of damage to the board and the tiny current sensor that measures the tiny current difference.

I would guess you have or had a small leak to ground which tripped the breaker and may after multiple trips now be damaged.

Check your load as Chuckles states, upgrade your cord as oneirodynia recommends then look to replacing this breaker

Good Luck
These kind of electrical problems can be tough to trace out
Be Safe
posted by Haujobbin at 3:36 PM on November 27, 2008