Thread: Siemens Box Blowing main breaker

Lately we have had much rain in Colorado (about twice the previous totals for up to now) Well one of my past customers has been blowing his main breaker in a Siemens box installed on the outside of the home. The service is underground so the rain has to be causing his problem. Has anyone seen this kind of thing especially in your more wet climates and is there any solution?Most of the electricians I have talked to just like a scratch golfer when a putt goes the wrong way.

Thanks
Blain

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Did you open the box? Was there any moisture inside it?

Most of the electricians I have talked to just like a scratch golfer when a putt goes the wrong way.

huh??

Originally Posted by Blain Plantz

Lately we have had much rain in Colorado (about twice the previous totals for up to now) Well one of my past customers has been blowing his main breaker in a Siemens box installed on the outside of the home. The service is underground so the rain has to be causing his problem. Has anyone seen this kind of thing especially in your more wet climates and is there any solution?Most of the electricians I have talked to just like a scratch golfer when a putt goes the wrong way.

Thanks
Blain

Is it wet inside the panel box?

Are the "water tight" connections remaining "Water Tight"?

Have they replaced the breaker?

Is the back of the box sealed (with silicone or caulk) to the wall that it is attached on?

I have seen water flow up into a panel through the underground conduit. Although, I don't think that this would likely trip the main as it would just flow back out the bottom of the box. It does keep the interior of the panel damp and this could cause problems.

thanks Scott everything is yes except the sealing. Are you suggesting that the box should be sealed to the exterior of the home? In Colorado they like a space between the 2 for cooling purposes I am told.

Brandon I left out the word look but my point was they get a I don't understand you and i am not going to look. Yes the box is moist inside like it has been rained on and water is getting in through the dead front. Though it should not be, the panel is latched there are no unusual bends or spaces.

The enclosure must be rated for use outdoors, i.e., 'rain tight'.

The enclosure must NOT be sealed to the wall behind it, it must have the designed and built-in 1/4" standoff air space between the back of the enclosure and the wall.

All 'raintight' connections to the enclosure should be 'rain tight'.

The underground service lateral *is required to be sealed* where it penetrates into the enclosure.

As for the feeders, do they go down and into the ground? If so, that conduit riser also *is required to be sealed* where it penetrates into the enclosure.

If the feeders are in a conduit going into the ground, are the feeder conductors of the insulation intended to be allowed to be in water? Underground conduits *are not watertight* and *it is assumed that water will enter them and collect in them*, thus the proper underground rated insulation conductor must be used. Otherwise you could be getting leakage through the insulation, and that leakage could be tripping the main.

First thing I would recommend is to check the current at the panel with a clamp-on ammeter, then check the current at the feeders at the service disconnect (make sure to keep track of which phase gives what reading) - the reading at the panel and the reading at the load side of the main disconnect *should be exactly the same* - otherwise you have some leakage currents going on between conductors.

Then check the current reading at the service entrance conductors (coming out of the service lateral or the meter), that too *should be exactly the same* - otherwise you have some leakage currents going on between conductors.

Any leakage between conductors on the line side (the power company side) will not show up in the main disconnect, so that would not cause the main to trip.

Curious as to 'how close' the use is to the size of the main disconnect - usually the use is not much as compared to the rating size.

I would first start with, recommend someone check, those current readings. You might find that they have a 150 amp main, are drawing 70 amps at the panel, yet are pulling 145 amps at the main disconnect ... that would not be good.

Originally Posted by Blain Plantz

thanks Scott everything is yes except the sealing. Are you suggesting that the box should be sealed to the exterior of the home? In Colorado they like a space between the 2 for cooling purposes I am told.

Brandon I left out the word look but my point was they get a I don't understand you and i am not going to look. Yes the box is moist inside like it has been rained on and water is getting in through the dead front. Though it should not be, the panel is latched there are no unusual bends or spaces.

As Jerry stated, you don't want it sealed to the wall. The reason is not really for cooling but more for water drainage and air flow.

Originally Posted by Scott Patterson

The reason is not really for cooling but more for water drainage and air flow.

"Cooling" has nothing to do with it.

The reason for the air space is, as Scott stated above, for water drainage and air flow, and water drainage is actually a by-product of the air flow reason.

With no air flow, condensation will form on the back of the enclosure against the wall (or even spaced out from the wall with no air circulation). That condensation will cause corrosion and corrode the back the enclosure out.

When you leave that 1/4" gap for air flow, you are also leaving a 1/4" gap from which water can gravity drain down and out.

From a cooling standpoint, surface-to-surface contact would create a heat sink effect and "cooling" would actually be better than with that 1/4" air gap.

I had a house at the lower end of a long street that sat below the curb line with under ground Service. The Elc. panel was on the out side of the garage that had a suspended concrete salb floor. the main service came up from the sub-structure under the garage and extended into the garage wall. the plywood under this concrete slab was infected with fungus with water stains all around the service from the underground conduit. at some point there was a opening in that underground conduit. when it would rain the water would fill up the underground conduit and flood out the service box.

I have only found this condition 2 times in 30 years.

Not a common thing in Calif.

Best

Ron

Originally Posted by Ron Bibler

at some point there was a opening in that underground conduit. when it would rain the water would fill up the underground conduit and flood out the service box.

Ron,

Provided the proper conductors were used, that would not matter.

I would be no different than running the conductors themselves underground and not in conduit, which is allowed - provided the conductor insulation was rated for that ... and those same conductors (rated for direct burial) are the only type allowed to be in a raceway which goes underground - because it is "presumed and expected" that the raceway (conduit) is going to be filled with water.

Originally Posted by Jerry Peck

Ron,

Provided the proper conductors were used, that would not matter.

I would be no different than running the conductors themselves underground and not in conduit, which is allowed - provided the conductor insulation was rated for that ... and those same conductors (rated for direct burial) are the only type allowed to be in a raceway which goes underground - because it is "presumed and expected" that the raceway (conduit) is going to be filled with water.

Good point Jerry.

The problem that this home had was not the under ground areas. it was the fact the the water was coming out of the conduit like a garden hose
with a lot of force. this was due to the long down hill run and that the house was below the street. but at some point the county installed a section incorrect and rain water was able to get into the conduit. The damage to the garage floor & supports and framing was due to this excessive moisture from the conduit. to the tune of $ 8,000.00

Best

Ron

Wht would a short in the underground service kick out a main breaker in a panel? I can see where it would blow the PC fuse but i see no reason it would kick out a main breaker.

Originally Posted by James Duffin

Wht would a short in the underground service kick out a main breaker in a panel? I can see where it would blow the PC fuse but i see no reason it would kick out a main breaker.

James,

It wouldn't.

Not sure where you got that from in the above ... me? Another post?

You are referring to "service entrance conductors", in one post above I also referred to feeders (though separately from service entrance conductors) in an underground raceway, and, yes, if those were not the correct insulation and leakage between conductors occurred, that could trip the main - but only from the feeders, not from the service entrance conductors.

The first poster stated

"The service is underground so the rain has to be causing his problem."

My comment had nothing to do with you..

Mythbusters did a show some time back with a dog taking a wee wee on a hot ELC Wire. The dog did not get an electrical shock. That was a good show.

Best

Ron

lets get back to basics. Water is not nearly as good a conductor as some people think. You may well be able to completely fill the service panel and never trip the main. I would start looking for a ground fault. It is not unusual for the main to trip before a branch breaker has a chance to. I have seen many instances of a realativly small short circuit to trip the main. (Happened last week when one of my guys pinched a 12 guage wire under the panel support clamp. It blew a 2500 amp main.)

peter@certifiedinfrared.com

Certified Infrared | Infrared Thermography, Inspection, electrical, mechanical, New York, New Jersey

What Peter says is true based on my experience...

In my previous life I worked at a place that had several steam boilers in basements. The service for most of these buildings was in these boiler rooms.

We had one that flooded about three times a year through the old coal chutes. (I was not in charge of coal chutes.)

The service panels were flooded under 4' of water about 20 times while I was there. We always dried out the breakers, fuses, and motors with no problems. Once in a while we would loose a motor due to bearing failure.

Originally Posted by Peter Plein

lets get back to basics. Water is not nearly as good a conductor as some people think. You may well be able to completely fill the service panel and never trip the main.

I have used that fact in several demonstrations I've done over the years, such as the time I filled a 5 gallon bucket with water, connected wires to a keyless lampholder, installed a 100 watt lamp, dropped it all down into the bucket of water, then turned the lamp on - no sparks, no sizzling water, etc.

Originally Posted by James Duffin

We had one that flooded about three times a year through the old coal chutes. (I was not in charge of coal chutes.)

The service panels were flooded under 4' of water about 20 times while I was there. We always dried out the breakers, fuses, and motors with no problems. Once in a while we would loose a motor due to bearing failure.

James,

You were fortunate. Water does definitely degrade electrical connections, electrical equipment, etc., including electrical insulation.

That is not to say that you will have failures, but after just one flood all of that should have been removed and replaced with new, the cause of the flood corrected (your job or not), should there ever have been a problem due to stray currents, arcs, shocks, electrocution, whatever, there would have been no justifying having left those items in place.