Space Heater Basics: Am I missing something?

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BMacky

Senior Member
Location
Foster City, CA
I went to look at a problem with a space heater causing a circuit to trip. After reviewing all of the loads on the circuit, it was found that 3 bedrooms and 2 baths had all been placed on a single 15-amp circuit, receptacles AND lighting.

I did the calc for amperage drawn by this small, oscillating space heater, which was labeled 1650 watts, which is 13.75 amps at 120V. In the same space was a clock radio, and a cordless toothbrush recharging stand. Figuring the heater is used only at night, so it being the only active load on the circuit, I wonder why a mfr would engineer a product so close to the threshold of max amperage for a common-sized household convenience outlet circuit? I could put a clamp-on ammeter on this and see what the actual draw is, but still it seems like the math indicates that I am close to the breaker threshold for tripping anyway, so a slight variation upwards in current would be a reasonable cause for the breaker to trip.

It's possible there's a weak breaker or some other unknown load plugged into the circuit. Does anyone have any knowledge on this kind of situation? Could it be in-rush current when the heater kicks on after the breaker has had time to warm up a bit after several cycles on-off-on? The breaker is in the garage and the outlet is probably 30 feet away. I have not changed the breaker yet, but right now am trying to sort out the best possible solution for the customer, given both baths are on this circuit as well (I have already suggested dedicating 20-amp circuits for the outlets at the basins).

Any advice is appreciated.
 
480sparky

480sparky

Senior Member
Location
Iowegia
Did you happen to look at the instructions?

I'll bet it says something about the electrical requirements for the unit. Not that the HO cares about instructions, but a heater that draws 13? amps should be on it's own circuit, not a GP one.
 
Buck Parrish

Buck Parrish

Senior Member
Location
NC & IN
It may read in the small print the mfrg. reuqires a dedicated circuit.

I always tell my customers that these heaters can be a fire hazzard. Not because of it to close to clothes or turning over. But because of the over loading of wires in the walls. Through series wired outlets.
(Esspecially back stabbed outlets)

The circuit you are dealing with probably has a loose connection some where. And the wire is resiting the current flow. This causes heat and the house can burn down.
Your breaker may be weak. But chances are you need to add a new circuit.
And fine the problem that the heating may have caused in the walls.
 
J

jghrist

Senior Member
480sparky said:
Did you happen to look at the instructions?

I'll bet it says something about the electrical requirements for the unit. Not that the HO cares about instructions, but a heater that draws 13? amps should be on it's own circuit, not a GP one.
Click to expand...
1650 watt hair dryers are quite common. Do you recommend dedicated circuits for these?
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
BMacky said:
. . . I wonder why a mfr would engineer a product so close to the threshold of max amperage for a common-sized household convenience outlet circuit?
Click to expand...
Because they want to sell heaters. Who would buy a 500w unit when there's a 1500w unit next to it? They make the heater powerful enough to create useable heat.

Why don't they make ranges, clothes dryers, centra A/C's, etc., that run on GP circuits? Then we wouldn't have to install 200a services and major-appliance circuits.


Added: My point is that manufacturers make products designed to perform a certain job, and it's up to the end user and/or installer to supply the necessary power.

Mant window A/C's, for example, come with 15a plugs, because that's capable of supplying the required power. It's still up to us to supply the required individual circuit.
 
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Mr.MOD

Member
could it be that the listed watt is for heater part of unit (for btu conversion)
and the and oscilator and fan loads be putting it over the top?:rolleyes:
hair dryers need no btu conversion heaters may be a standard
i would suggest load amp test from a dedicated 20a circut so as not to stress the current circut.:wink:
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Is the heater rated for 125V?
While it is possible, it is extremely unlikely that you have a 'weak' breaker. The standards for this size breaker call for hundreds of operations at rated load.

Your only solution is to move the heater off of the existing circuit.
Remind them that extensions cords are not good option.
 
Rewire

Rewire

Senior Member
Location
Lake of the Ozarks
Remember that a breaker trips on heat so surrounding breakers can add heat to a breaker that is loaded close to capacity ,space heaters tend to run for extended periods so the breaker is never allowed time to cool.
 
76nemo

76nemo

Senior Member
Location
Ogdensburg, NY
BMacky said:
I went to look at a problem with a space heater causing a circuit to trip. After reviewing all of the loads on the circuit, it was found that 3 bedrooms and 2 baths had all been placed on a single 15-amp circuit, receptacles AND lighting.

I did the calc for amperage drawn by this small, oscillating space heater, which was labeled 1650 watts, which is 13.75 amps at 120V. In the same space was a clock radio, and a cordless toothbrush recharging stand. Figuring the heater is used only at night, so it being the only active load on the circuit, I wonder why a mfr would engineer a product so close to the threshold of max amperage for a common-sized household convenience outlet circuit? I could put a clamp-on ammeter on this and see what the actual draw is, but still it seems like the math indicates that I am close to the breaker threshold for tripping anyway, so a slight variation upwards in current would be a reasonable cause for the breaker to trip.

It's possible there's a weak breaker or some other unknown load plugged into the circuit. Does anyone have any knowledge on this kind of situation? Could it be in-rush current when the heater kicks on after the breaker has had time to warm up a bit after several cycles on-off-on? The breaker is in the garage and the outlet is probably 30 feet away. I have not changed the breaker yet, but right now am trying to sort out the best possible solution for the customer, given both baths are on this circuit as well (I have already suggested dedicating 20-amp circuits for the outlets at the basins).

Any advice is appreciated.
Click to expand...


Inrush current has nothing to due with this situation here. With the elements being purely resistive, the inrush that does occur is so fast the breaker won't hardly even recognize it.
 
Mr. Wizard

Mr. Wizard

Senior Member
Location
Texas
BMacky said:
I went to look at a problem with a space heater causing a circuit to trip. After reviewing all of the loads on the circuit, it was found that 3 bedrooms and 2 baths had all been placed on a single 15-amp circuit, receptacles AND lighting.

Any advice is appreciated.
Click to expand...

In my very own opinion, there seems to be more to worry about than the amp draw of a space heater. From what i gather, all plugs and lights share one 15 amp circuit? Why is the breaker not tripping from the other loads of the home? The panel has one breaker? :-? :-? :-?
 
brian john

brian john

Senior Member
Location
Leesburg, VA
But if you had daughters you'd be going nuts resetting the CB daily. Of course this can happen with a dedicated receptacle in any room in the house.
 
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