question about electrical circuit - what's going on?

[Lee]

I bought a space heater for my girls to use in their bathroom - my wife and i also use one in our bathroom in the morning.
If both heaters are turned on at the same time, the circuit breaker trips from an overload and the power goes out in my bathroom, but not the girl's bathroom.  if they are on seperate circuits, how does their heater overload the circuit to my bathroom?  I'm cornfused.

[Nick1911]

Weird.  I have a theory that involves voltage drop and ohms law, but it seems implausible.  Tagged for interest!

[wmenorr67]

Try it with just the one in your room on and see what happens.

[280plus]

Weird.  I have a theory that involves voltage drop and ohms law, but it seems implausible.  Tagged for interest!

Are you sure your last name isn't Tesla there Nikolai? lol...

Try changing the breaker that keeps popping. Something in my gut tells me it's weak but don't ask me to explain or prove why. If the breaker is a 15 amp DO NOT increase the amp rating to 20 please! Unless you like smoke and flames in your house.

GENERALLY those heaters draw 15 amps. 1500 watts = 15 amps (the ohms law Nikolai was talking about) 1000 watts = 10 amps. Get it? So if there is a 15 amp breaker on either circuit chances are they are maxed when the heaters are running and on the verge of popping. Possibly with both running you are drawing the voltage down a bit which might be enough to trip the weaker of the two breakers. Just a semi educated guess. Kind of sounds like what Nick might be alluding to? Having an ammeter and measuring these currents would be helpful.

[Lee]

Try it with just the one in your room on and see what happens.

I tried that.  We've had our heater in the bathroom for two years, with no issues.  
The pattern is pretty defined now -wife get's in the shower at 6 am - daughter turns on her little heater at 6:05 >>> wife SCREAMS my name and announces that the power went out - while daughter is merrily singing in the shower with lights and heater on.  I turn off the heater and head to the basement to flip the breaker.
I don't know diddly about wiring, but I'm wondering if this might be connected to the way they tied several of the circuit to GFI's.  I think I have 3 GFI's in the house and it's always a mystery to me when one of them trips. No GFI tripping in this case -just the one breaker.
  

[Azrael256]

Nick, you're probably spot-on if you're thinking that I think you are.

Lee, is the run from the breaker to your daughter's bathroom shorter than the one to yours, heavier wire, or much newer?  It's either that, or a weak breaker (or some horrible wiring fault).

"Separate circuit" is misleading.  The outlets are protected by separate overcurrent devices, but the whole house is no more than three circuits.  Even then, it's still just one, but at a different scale.

[Lee]

Lee, is the run from the breaker to your daughter's bathroom shorter than the one to yours, heavier wire, or much newer?

It is shorter.  Not newer, but could be heavier (don't know).  The weak breaker might be the answer.  Thanks for the replies.

[geronimotwo]

bad breaker?  perhaps corrosion on the main buss bars?  do you hear any buzzing, or arcing in the main panel ?(particularly when you are running your heater)  do any of the breakers feel warm?

[Brad Johnson]

Some homes have both bathrooms wired on a common circuit.  I found that out at a cousin's house.  The power was out in her master bath.  It ended up being a tripped GFCI in the second (hall) bath.

Brad

[AJ Dual]

Also, is it possible that the outlet your daughter uses is tied to the bathroom circuit, but the rest of her room isn't?

My house has had a couple of haphazard electrifications done since the 1930's when it was first built, and subsequently remodeled into a duplex, then back to a single-family. I have many runs where rooms share common walls etc. on the same circuit as the people running wires made shortcuts.

[Brad Johnson]

If you want to trace out the wiring in your house bird dogs (circuit detectors) are relatively inexpensive.  They're also darned handy to have around on occasion.

Brad

[Lee]

Are they called Bird Dogs? 
Kinda funny, the first video I pulled up on breaker replacement has 2 ....bird dogs.  Not sure they helped much though.
http://www.5min.com/Video/How-to-Replace-a-Circuit-Breaker-57208272

[280plus]

didn't watch the vid but if you happen to have a GE screw in type setup most of us guys wrap electrical tape around the shaft of the screwdriver we're going to use and just leave the tip uninsulated. 

[Ron]

Hopefully the two circuits aren't sharing the same common (neutral) going back to the panel. In Chicagoland most wiring is in metal conduit, so this bad practice is often employed on spare rooms or add on rooms in older houses.

Replace the tripping breaker, if it trips again I suggest NOT using it for a space heater.

[birdman]

Are you sure your last name isn't Tesla there Nikolai? lol...

Try changing the breaker that keeps popping. Something in my gut tells me it's weak but don't ask me to explain or prove why. If the breaker is a 15 amp DO NOT increase the amp rating to 20 please! Unless you like smoke and flames in your house.

GENERALLY those heaters draw 15 amps. 1500 watts = 15 amps (the ohms law Nikolai was talking about) 1000 watts = 10 amps. Get it? So if there is a 15 amp breaker on either circuit chances are they are maxed when the heaters are running and on the verge of popping. Possibly with both running you are drawing the voltage down a bit which might be enough to trip the weaker of the two breakers. Just a semi educated guess. Kind of sounds like what Nick might be alluding to? Having an ammeter and measuring these currents would be helpful.

Actually, given that single phase mains voltage is 120vac (rms), 1500W is 12.5A and 1000W is 8.33A. 

[280plus]

yea, I know, I stick to the "rule of thumb" just because I'm not that smart. 

[Jim147]

I would swap out the breaker. And check for loose wires. At the breaker or the outlet. If the outlet is getting worn, plug fits loose, it can cause a lot of heat also.

jim

[Hawkmoon]

Do the heaters have lower settings? Most of the ones I've seen -- even inexpensive ones -- are dual element. You can use 600 watts, 900 watts, or both together for 1500 watts. If they have multiple settings, just tell the ladies to run 'em at 900 watts instead of full-tilt.

[birdman]

yea, I know, I stick to the "rule of thumb" just because I'm not that smart. 

It's a good (meaning its inaccuracy is conservative) rule of thumb. 

[K Frame]

"Hopefully the two circuits aren't sharing the same common (neutral) going back to the panel."

Oddly enough I had the same thought this morning.

But wouldn't that still tend to trip both breakers?

[Ron]

It's just difficult to say what is going on without knowing voltages, current draw and even disconnecting wires and checking continuity.

Jim's recommendation to check all the connections at outlets and in the panel is the first thing that should be done. Getting the circuits traced is a good idea before using them for high current devices going forward.

[CNYCacher]

I bought a space heater for my girls to use in their bathroom - my wife and i also use one in our bathroom in the morning.
If both heaters are turned on at the same time, the circuit breaker trips from an overload and the power goes out in my bathroom, but not the girl's bathroom.  if they are on seperate circuits, how does their heater overload the circuit to my bathroom?  I'm cornfused.

Did anyone verify that while the lights were off in bathroom A, the heater was still running in bathroom B?  The simplest explanation is that one of the outlets in bathroom B is on the same circuit as the lights and outlets in bathroom A

Hopefully the two circuits aren't sharing the same common (neutral) going back to the panel.

If the hots are on opposite legs, which is the only application where sharing a neutral is acceptable, this is not a concern.

But wouldn't that still tend to trip both breakers?

Nope.

[K Frame]

"Nope."


And the reason for that would be..........?

[Hawkmoon]

Did anyone verify that while the lights were off in bathroom A, the heater was still running in bathroom B?  The simplest explanation is that one of the outlets in bathroom B is on the same circuit as the lights and outlets in bathroom A

Post number five:

The pattern is pretty defined now -wife get's in the shower at 6 am - daughter turns on her little heater at 6:05 >>> wife SCREAMS my name and announces that the power went out - while daughter is merrily singing in the shower with lights and heater on.  I turn off the heater and head to the basement to flip the breaker.

[Ron]

Is it just the lights in the bathroom that go dead? Or is it the lights and outlet(s)?

"If the hots are on opposite legs, which is the only application where sharing a neutral is acceptable, this is not a concern."

Hmmm, not so sure about that myself. Isn't current, current, regardless which leg is being used in the panel? If the neutral is 14 gauge and you have two circuits using it, pulling at their max of 15 amps, how can the single #14 wire be acceptable?