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Why is it the meter breakers burning out & not the breakers in the home's panel?

13K views 42 replies 12 participants last post by  MTN REMODEL LLC 
#1 ·
A mobile home park has groupings of the power company's meters (100 amp breakers immediately below the meters) installed on low profile-type billboards that are centrally located among the homes - this must be a familiar site to some of the pro's, I would think.

All the meter disconnects (I'm not a pro of course - just a relative newbie pretending I know the lingo) are 100 amps, and so go the main breakers in the homes' service panels.

Several electric furnaces have been installed in these homes without upgrading the service to 150 or 200 amps. Many of these homes with electric furnaces have clothes dryers, central air, 240v/4500w water heaters, as well as electric kitchen ranges.

So needless to say, overheated and eventually burned out 100A breakers (at the meters) are not uncommon in this park, and to my knowledge, the breakers at the meters are usually (possibly even always) the ones that eventually burn out; not the main breakers inside the home.

Usually, the main breaker in the home doesn't even trip when the home loses power (usually just one leg) due to the meter disconnect breaker tripping, which it'll do a time or two, then eventually fail entirely. More often than not (as opposed to the breaker failing only internally), the point that burns is one of the connection points (lugs?) where the breaker snaps into the box below the meter. In other words, these breakers at the meters snap in much like the service panel branch circuit breakers snap onto the bus bars.

My only question is, why is it always the breakers at the meters that burn up, instead of the main breakers in the home's service panel?
 
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#4 ·
I'm afraid I don't know what you mean exactly ("amp rating in the homes"), unless you're talking about the amp rating of the main breaker in the service panel, which is always 100 amps.

When you say "what size wire is feeding the main," I'm guessing you're talking about the cable from the meter to the main breaker in the service panel, but I don't know for sure. Sorry...
 
#6 ·
What is the size of the breaker in the mobile home, around my area they are usually 200 amp mains so they wont trip but if the trailer is being supplied by a 100 amp main or if the breakers are old or loose connections or corrosion at the meter panel that is where your problem is. A melt down is usually a bad connection or breaker, most breakers need to be cycled to make sure the contacts are not stuck and that they will actually disconnect the load
 
#8 · (Edited)
Breakers in the homes are 100 amps. Breakers at the meters on the outdoor pedestals are also 100 amps.

Since you've mentioned loose connections:
Maybe with the constant high current (clothes dryer, kitchen range, A/C, electric furnace) - higher than only a 100 amp circuit was meant to handle constantly I imagine, .... maybe the resulting constant heat wears the contact points prematurely (at least on one of the legs) in the box outside (the previously mentioned breaker connections where they snap onto the lugs of the box).

Then maybe it follows those connection points would overheat & loosen up prematurely? Those connection points would be the first weakest point encountered (from the meter toward the home) by all that higher than normal current (for a 100 amp circuit). Does that sound reasonable, or maybe I'm just being a little too imaginative?

I don't doubt that the breakers burning up prematurely is a result of more load than the 100 amp circuit was intended for, but just wondering why it's the meter disconnect breaker that burns up first, instead of the 100 main breaker in the home's panel.

Maybe I can get a pic posted today of the breaker snap-in connections in the box, if that would help any.
 
#11 ·
I don't doubt that the breakers burning up prematurely is a result of more load than the 100 amp circuit was intended for, but just wondering why it's the meter disconnect breaker that burns up first, instead of the 100 main breaker in the home's panel.

And I'm not saying your explanation for it couldn't be the reason (cause obviously I don't know), just wanted to reiterate my question for all just in case...
 
#12 ·
*I do repair work for several condominium and townhouse communities that have multi-gang electric meter sockets located outside with included main breakers. I have found that the outside main breakers have a higher rate of failure than those inside. These are not totally electric housing units. They have gas dryers, gas cooking and gas heat. I surmised that the failure is from being outside where the circuit breakers are subjected to temperature and humidity changes, insect and rodent infestation, and corrosion on the bus bar. I have discussed this with other electricians and they tended to agree that being outside was detrimental to the life of the circuit breaker. To my knowledge there is no circuit breaker that has an outdoor rating classification, so it is just normal circuit breakers being installed outside.

It sounds as though you may be running your main circuit breakers at or close to full load which may be a contributing factor. Those breakers will get warm with a full load and in the summer they will run warmer.

When you change a breaker, make sure that the bus bar is clean and not rough from arcing. You can use some fine sandpaper and maybe a small wire brush to clean it up. Make sure all connections are tight.
 
#13 · (Edited)
Thx Mr. Electrician~ Since I was getting this pic as you were replying, I'll go ahead and post it. Not defending it (No Siree), but the condition of this particular box is an exception. The bottom of the box is rusted away, thus the spider webs, etc, and I'm not involved in the actual replacement of these breakers outside, nor the boxes and/or their internal hardware (would've changed this box long ago).

This box, as you can see, has had those connection lugs replaced not long ago (along with the breaker), and this home doesn't have an electric furnace either - just thought it might help to post a pic showing the usual point of burning. The arrow is almost always where the damage (burning) is found (one of those two legs).
 
#18 ·
One if the issues with nearly all meter gang setups is that that snap in breakers are a poor choice for being used as mains in outdoor panels. Since they are not bolted on to the bussing, there are several factors that can cause the breaker to slowly come loose and cause arcing which will damage the components.

One thing I would suggest looking at is where the meters are placed. Is there excess moisture, heat, freezing, or vibration that the meters are subjected to? Also, I assume aluminum wiring has been used to feed the trailers, has it been properly inspected and terminated? It is hard to see in that picture, but like someone said earlier, the left line side wire on that picture looks fishy.

If someone is just replacing the breakers, and ignoring damaged wire, it's no wonder you have issues all the time.



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#20 ·
JustPlum...... (I'm a GC...not an electrician... so just tossing out thoughts)

But, I'm not sure that every breaker has the exect same standards of when it trips....

I know they do not trip immediately at 100.001 amps.... there is tolerance in them.....in both time, amount of draw, and ambiant temp also I believe.
(I think they trip both on electromagetics and temp... not sure)

So maybe all the pedastel breakers are one make... or older... relative to the units breakers.... and there is basically a different tolerance that exists at the pedastels than generally in the units/homes.

Just guessing

Best
 
#21 ·
A quick and easy side note question: Does a partially blocked or heavily blocked air filter on an electric furnace increase its amp draw? There are usually no evaporator coils installed with the air handlers I see in this park. Just the mobile home electric furnace cabinet with a filter that slides into the top of it. Example pic attached. This one is actually a little taller than the ones I see.
Sorry about this post/question. I forgot where I was. Was working on an email message simultaneously and it was related to this thread about meter disconnects burning out before the main breakers in the home do. I'll ask a moderator to delete it.
 
#27 ·
The current that is the amps are the same through both breakers but the voltage is different. At the meter base it is likely 240volts but by the time it reaches the house the voltage has dropped. The voltage drop is the IR drop, the number of amps in the line x the resistance in ohms of the line. Same amps and less voltage means less power through the house breaker so the meter breaker kicks off first. Measure the voltage at both points and you will see the difference.
 
#28 ·
The current that is the amps are the same through both breakers but the voltage is different. At the meter base it is likely 240volts but by the time it reaches the house the voltage has dropped. The voltage drop is the IR drop, the number of amps in the line x the resistance in ohms of the line. Same amps and less voltage means less power through the house breaker so the meter breaker kicks off first. Measure the voltage at both points and you will see the difference.
Sorta where I was thinkng / wondering /questioning /trying to understand.

Guess I do not know how a breaker trips... (No guess... I don't know)

Can anyone explain...TIA

We tend to think it is a discrete measurement of amps that trips the breaker(as breakers are labeled in amps and that is what they are supposed to limit.)

But, you are saying (or implying) they are tripping as a function of power (or watts if you chooze).

I have heard on here that most breakers are tripped as a function of elecrtmagnetics and/or heat.

If breakers are somehow sensitive to different feed voltages (and we agree that line/feed voltages can easily vary by say 5% or more)... that would imply that the amps through them could vary by 5% or more before they trip...

Just a discussion.....
 
#34 ·
Thanks Oso.... I did read it... not sure I studied it.... but I have a better concept.

I wonder if the multi-gang breakers might just have different time curves for continuous loads (which is the OPs circumsttance) than those normally installed in the homes.
 
#38 ·
I wonder if the multi-gang breakers might just have different time curves for continuous loads (which is the OPs circumstance) than those normally installed in the homes.
It could be, but I doubt it. I think its a bad connection problem, not a tripping problem.

I think the problem is corrosion between the pedestal breaker contacts and the buss bar. If you look at the pic in post 13, the arrow of the problem area is the breaker contacts. Look at the amount of corrosion in the box. The lug/buss bars are new. How much corrosion was on the old lug/buss bars ?

A high resistance connection will generate a lot of heat. The thermal trip (bimetallic strip) registers heat from current passing through it. It does not see the heat of the contact area until it transfers by either radiation or conduction. So breakers are slow to trip (or fail to trip) with heat in the contact area.

The home panel is better protected than the pedestal panel, in fact it may be in a conditioned space. So corrosion is often less in the home panel, even if the home panel and pedestal are the same age.

Do you think that the pedestal box gets any inspections or maintenance before a problem happens ?

When the breaker failed (post 13 pic) they had a good opportunity to clean up the corrosion in the box, to prolong the life of it. Did they do it, NO. They just slapped the replacement parts in.
 
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