100 amp Breaker tripping, 75 amp water heater?
Posted on | December 12, 2011 | 4 Comments
Hi – I have one of these on a dedicated line (old central heater unit) which now serves a 75 amp tankless water water heater and nothing else. 6 gauge wire. It is tripping after about 5 minutes running at 57-60 amps according to my clamp meter. But it has pulled more amps than that without tripping so it seems to be a time function. Breaker gets quite hot at the terminal screw end. Does this sound like a worn-out breaker or some other problem? Thank you if you have time to reply, Jeff
Thank you for the replies. I was guessing at the wire gauge from online pics, the wire is from an old installation, over 20 years old. The wire is 7 strands (about 12 ga ea) and with insulation measures 3/8 inch in diameter which puts it between 2 and 4 gauge per an online source I have since found.
The wire is Building Wire- Type THW PVC Insulation, 600V from some faint stampings on the insulation.
It originally powered an attic furnace and blower.
Power runs direct into a 100 amp cutoff beneath the meter and gives no other service.
We are rural so a quick jaunt to the hardware store is impractical today to verify size.
The tankless heater is brand new and per their spec requirements: Required the installation of “one circuit of 80 amps or 1 circuits of 60 amp and # 6 wire”. (their language) which is confusing to me.
Please note the clamp meter gave me amp reading ranges from <40 amps to >85 amps as the unit’ build-in circuit breakers monitored the current. The 100 amp break
LOOKS LIKE ALL MY ADDITIONAL DETAILS DIDN’T POST:
The 100 amp breaker tripped while showing a reading of 57 – 60 amp currents.
I have not yet removed the breaker from the box, by the time I got to that point, the temp outside at the box was near 105, and i was getting a bit weary.
Choices:
1. Replace with a 75 amp breaker if there is one to fit
or
2 Replace the entire cut-off box and breaker with another brand.
Note this does not run through my 100 amp household service which is served by smaller gauge wire and runs 3 window units, microwave, stove/oven and TV/Computers with no problems in 16 years.
Thank you for your patience with my question, and I do have a thick skin (grin) Jeff
(Run is about 70 feet, I disconnected from the obsolete attic unit and ran under the house, there may be 10′ of excess length which could be cut.”
The questionable breaker is a FEDERAL PACIFIC Stab-Lok FPE 2P 100 Amp Type NA BREAKER,
I found a new one online for about $250 which sounds ridiculous, used in the $35-$90 range.
I also found several less-than-complimentary reviews of these FP breakers.
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4 Responses to “100 amp Breaker tripping, 75 amp water heater?”
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December 12th, 2011 @ 9:45 am
sounds like a worn out breaker, could be a problem with the electrode rods in the water heater, but I think you would see small pieces of gunk in your water/ screen filters on you faucets.
Try swapping out a breaker from somewhere else in the box, if possible, If that fixes it go buy a new breaker
December 12th, 2011 @ 10:30 am
Yes, bad breaker on the side that is getting hot. Replace the item and inspect the wiring while you do it, it may be grounded do to a section of melted insulation. Also apply some conductive paste to the conductor when you install the new breaker.
December 12th, 2011 @ 10:37 am
2nd edit,
Apply the $250 towards replacing the FPE equipment. What you read on line is just the “tip of the iceberg”. FPE Really IS a Safety hazard. Even brand new breakers can (and do) fail to operate correctly. And a used one? “Forget about it” Once again, that’s the way it is. If I could I would replace FPE panels all day long as a Public Service.
If money is tight at this time, may I suggest you replace the just the panel that feeds the Water Heater. This will eliminate the possibility that the breaker is bad and may not cost much (if any) more than a replacement breaker. Then as soon as possible do the rest.
The 70′ run is OK, but if you don’t need the extra length go ahead and remove it. May not make any difference, but it can’t hurt.
OH, it just occurred to me, Disconnect the wire at both ends. Use a good quality Ohm meter to read resistance from each leg to ground, There is the slight possibility of a nick in the wire (where a staple is holding it) and current is bleeding to ground.
Best of luck!
Edit:
First of all I would like to apologize for having been harsh. Terribly sorry about that.
Your description brought back a memory of a service call where the home owner did his own electrical work that resulted in a fire.
Now then, moving on.
It would appear that the wire size is sufficient. Now I would look at the wire to the “100 amp cutoff”.
Is it large enough for the load?
Are the connections “green” with corrosion?
Is the breaker making good contact with the Buss Bar?
Are all connections good and tight?
IF “yes” to all of the above then it is entirely possible the breaker is at fault.
If you still have troubles try calling the manufacture for support. They might know something I don’t.
Best of luck to you sir!
#6 wire is not rated anywhere near 100 amps, so there’s your first problem.
Second, having #6 wire on a 100 amp breaker is just BEGGING for a FIRE. I’m absolutely serious.
So, the first thing you have to do is install the correct size wire.
Then the correct size breaker.
What did the Manufactures Specifications call for? (The i n s t r uc t i o n s)
And why on earth didn’t the installer follow them?!
Sorry , but that’s the way it is.
Another thing to know, (and I’m not trying to insult you) Insurance Company’s are real good at identifying fires caused by improper wiring. Something to think about.
Please, please, please correct this situation Pronto!
Sincerely,
December 12th, 2011 @ 10:40 am
Yes, high resistance it causing something to heat up in the breaker. It should be fine once you replace it.