Over loaded breakers not tripping ??

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Eric23

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Went to a customers house today who's existing 110v electric heaters weren't working. They were there when he bought the house 5 years ago and worked fine up until recently. Upon inspection the reason why they had stopped working was because the breaker had gone bad. I replaced the 20 amp breaker, turned it back on, and the heaters started working again. When I realized how many heaters were wired to the circuit I got confused because there are five 750 watt heaters wired to a 20 amp breaker with #12 wire pulling 33 amps through the circuit but for some reason the breaker is blowing and apparently this setup was working for years up until now ? Can someone explain why ?

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Eric23 said:
Went to a customers house today who's existing 110v electric heaters weren't working. They were there when he bought the house 5 years ago and worked fine up until recently. Upon inspection the reason why they had stopped working was because the breaker had gone bad. I replaced the 20 amp breaker, turned it back on, and the heaters started working again. When I realized how many heaters were wired to the circuit I got confused because there are five 750 watt heaters wired to a 20 amp breaker with #12 wire pulling 33 amps through the circuit but for some reason the breaker is blowing and apparently this setup was working for years up until now ? Can someone explain why ?

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chances are that not all of the heaters ran continuously so if even one was not running it was only 25 amps and most 20 amp breakers under most conditions will not trip at 25 A. Even at 33 A it may take quite some time to trip.

Or could have been a bad breaker.
 
petersonra said:
chances are that not all of the heaters ran continuously so if even one was not running it was only 25 amps and most 20 amp breakers under most conditions will not trip at 25 A. Even at 33 A it may take quite some time to trip.

Or could have been a bad breaker.
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All 5 heaters are on a single 110 thermostat that only goes up to 75 degrees. It warms up really fast so I'm sure they didn't run continuously for long amounts of time however I'm uncomfortable leaving it like this being the last person here.. it wouldn't be difficult to swap these out for 220 units and I would definitely sleep better knowing it's wired with #12... 17 amps on #12 vs 33 amps is big difference especially if the breaker isn't tripping even though it's brand new ...

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zog said:
How did you determine this?
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There was no power at the units or the thermostat and all breakers were in the on position. I took my meter and went to each one till I found one that had no voltage and tried to reset it but still got nothing. After that I took the breaker off and hooked up a toner to the circuit to verify that was the correct line which it was. I got a new breaker, energized the circuit and all the heaters started up

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Eric23 said:
There was no power at the units or the thermostat and all breakers were in the on position. I took my meter and went to each one till I found one that had no voltage and tried to reset it but still got nothing. After that I took the breaker off and hooked up a toner to the circuit to verify that was the correct line which it was. I got a new breaker, energized the circuit and all the heaters started up

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The breaker had no resistance to it it was just loose

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is the tstat a 2 pole unit?

if it bothers you a quick fix might be to wire several of the heaters in series with each other instead of in parallel.

maybe a parallel 3 branches with a single heater in one branch and two series heaters in the other two parallel branches.

That would give you about 1500 Watts and should not blow a 20A CB. Not sure what code provision this might violate, if any.

Or just disconnect a couple of them.

edited to correct math
 
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