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miguelito3218 · Jun 22, 2009, 08:36 PM

Hi there. I haven't been on this forum in over two years, but I remember how useful it was when I was adding a bathroom and figured I'd give it a try for a problem I'm having with my main breaker.

I have a 150A square D service panel (non-homelite) and over the past 3 or 4 days, my main has tripped a few times. Each time, I let it sit for a bit, and reset it, and it will be good for anywhere from 8 hours to a couple of days. This started about about a couple months ago, with it tripping every few weeks..

Lately, its been ripping hot in Florida (106!) and my panel is in the garage and I figured the extreme heat did not help the tripping situation. Anyway, I removed the cover, and tightened the main lugs (3/8" allen key). I got a good 3/4 turn out of one of the legs. I thought that was the cause for sure, but about 10 hours later it tripped again (this morning). I reset it again this morning, and the a/c has been running non-stop all day and its held up well.

I don't think the panel is overloaded since when its been like this for about 5-7 years with no problems.

I'm thinking I have a bad main breaker, caused by the loose main wire, causing it to overheat and eventually wear out. The main breaker continues hot to the touch, but has not tripped in over 12 hours. Could there be a bad connection to the bus from the main breaker? Also, can a loose connection in the meter pan manifest itself in the main breaker?

Right now, I'm thinking I may replace the main breaker after I have the power company removes my meter (I'll also have them double check the live lugs in the meter pan while they are at it). What is a good lubricant to use on the main lugs to prevent oxidation and loosening?

Thanks in advance for any suggestions offered!

tkrussell · Jun 23, 2009, 02:56 AM

Loose connections do cause heat, that migrates into the breaker mechanism and weaken springs. Heat also damages the contacts creating more heat even if the external connections are tight.

So you may not have any other choice but to replace the breaker.

If you have aluminum wire, it will need anti-oxidant lube, a popular brand name is Penetrox, among many others. Nothing stops loosening other than periodic inspection and maintenance. The connections need to be torqued tightened to proper values, these values will be listed on a label on the breaker and with the manufacturers datasheet. Do not overtighten any connection, esp aluminum.

There is a "lube" for copper wire, but is rarely used.

miguelito3218 · Jun 23, 2009, 09:29 PM

Thanks so much TK. I don't have aluminum wiring, so no problem there.

My principle "symptom" is that the main 150 amp breaker gets very hot, and yet the regular breakers don't. Does that sound like a main breaker problem?

Also, can something with my central a/c or water heater or other circuit cause the main to heat up and eventually trip? Can a loose connection inside my meter pan cause the main to heat up inside my circuit panel? Thanks again for the advice.

tkrussell · Jun 24, 2009, 02:40 AM

Yes a loose connection in the meter can make the breaker hot, but the wires between both would be hot also.

Any load can make the breaker hot if the breaker is defective or has loose line or load connections.

The main breaker should not be hot in any case. This needs to get checked, it will not get better on it's own. Someday it will fail completely, usually after 5 PM on a Friday.

miguelito3218 · Jun 24, 2009, 07:21 AM

Thanks again. I'm going to tackle it this weekend. I noted I turned off my hot water heater last night at the breaker, and I woke up this morning and the main breaker was cool. I did this because I noticed that at least twice, I was in the shower when the main tripped.

The water heater is new, about a year or so old. I don't have the specs in front me right now, but its not more than 50 gallon electric water heater. If I recall correctly, its on a 30 amp breaker, and run with 10/2 wire. What could go wrong with the water heater to cause a main to trip?

tkrussell · Jun 24, 2009, 11:25 AM

You losing site of the issue. There is probably no problem with the water heater, the problem is at the main breaker, either due to being defective, or a loose connection.

Any appliance can be enough load to create heat at a loose connection or a bad breaker.

I had a loose nut on the load side busbar of a 200 amp breaker create enough heat to trip the CB with only 20 amps of load on it.

How do you plan to tackle this?
Change the main breaker?
Has the power company been scheduled to pull the meter? If not who will pull the meter? It needs to be pulled to de-energize the feeder conductors to the main breaker?

Many utilities, not all, require that only THEY pull a meter. If you plan on doing it, use extreme caution, and do at your own risk. Be sure to have someone with CPR training available, have a working phone ready to call 911, and have your life insurance payments current.

miguelito3218 · Jun 25, 2009, 10:18 PM

Thanks again, TK. The electric co. will come pull the meter, I've had them do it once before when I had to move my breaker panel about 1 ft to the left. Anyway, I had the water heater off all day, and the main breaker still got hot and tripped, so your point is well taken. The last thing I want to do is to turn the A/C off overnight, and leave the water heater on, and see if it still heats up.

Now, hypothetically, *in the event* that the main breaker does not get hot with both the inside and outside a/c units turned off, is there a *possibility* that something with the a/c is causing the main breaker to heat up and trip, *other than a loose connection somewhere, or defective main*?

tkrussell · Jun 26, 2009, 12:40 PM

No individual load, or even a combination of loads running at the same time, should in no way ever cause a Main Breaker to get hot, as long as the breaker is not defective and/or there are loose connections.

jcdpk · May 17, 2010, 04:57 PM

You must understand that breakers will trip on thermo which means that either high current (which causes heat) or high resistance through bad connection will cause the breaker to trip it is the heat that trips the breaker lever whether the heat is through high current or its created by a bad connection its still heat. I have seen this happen many times through bad connections, while I have tighten them and clean the connection off both the wire and terminals and still trip when I reenergize the breaker again. I would use a thermo imager (IR) it would show a little change but most of the time I would just change out the breaker with no more further problem. So in short, if the connections are clean off and the screws are tighten and still the breaker trips then have the breaker change out by a licence electrician or if you are up to the job but take extreme cautions as was mention in the above note.

jcdpk · May 17, 2010, 04:57 PM

You must understand that breakers will trip on thermo which means that either high current (which causes heat) or high resistance through bad connection will cause the breaker to trip it is the heat that trips the breaker lever whether the heat is through high current or its created by a bad connection its still heat. I have seen this happen many times through bad connections, while I have tighten them and clean the connection off both the wire and terminals and still trip when I reenergize the breaker again. I would use a thermo imager (IR) it would show a little change but most of the time I would just change out the breaker with no more further problem. So in short, if the connections are clean off and the screws are tighten and still the breaker trips then have the breaker change out by a licence electrician or if you are up to the job but take extreme cautions as was mention in the above note.

jcdpk · May 17, 2010, 04:57 PM

You must understand that breakers will trip on thermo which means that either high current (which causes heat) or high resistance through bad connection will cause the breaker to trip it is the heat that trips the breaker lever whether the heat is through high current or its created by a bad connection its still heat. I have seen this happen many times through bad connections, while I have tighten them and clean the connection off both the wire and terminals and still trip when I reenergize the breaker again. I would use a thermo imager (IR) it would show a little change but most of the time I would just change out the breaker with no more further problem. So in short, if the connections are clean off and the screws are tighten and still the breaker trips then have the breaker change out by a licence electrician or if you are up to the job but take extreme cautions as was mention in the above note.

Missouri Bound · May 17, 2010, 06:37 PM

Two things... did you tighten those lugs live? Pretty risky if you did. And have you put an ammeter on the main feeders?

TWN75 · Aug 19, 2010, 02:34 PM

In side the main breaker are contacts when you turn off the main under load you dirty up those contacts that's wher the heat is genorated. I found one like this today .I allways recommend that you turn off all smaller breakers first before the main this will save the contacts revers the process when restoring power. Im a licenced electrician out of the chicago aria