Panel rusted / corroded & breakers failing

stevekem

In an old house of mine (that my brother now owns) I installed a new 100 amp service about 11 years ago, which was inspected. This was my first service install so take it easy on me, it's not pretty

So about 5 years go by without any problems then main breaker failed (lights began dimming, main breaker buzzing). During replacement we noted rust stains and corrosion on breaker and bus bar. We cleaned up buss (I know your suppose to replace buss at signs of corrosion) and changed breaker.

About 3 years later the branch breakers started failing and we noted lots of rust at bottom of panel and severe corrosion on bus bar. The corrosion is so bad on bus that we are unable to remove at least 1 breaker as it is seized onto bus.

The service entry cable comes into basement about 2 feet above ground level on outside and is duct sealed thoroughly at entrance hole. Once it enters basement, it immediately raises 6" higher and proceeds to the right and down into panel. This gives it a drip loop.

Panel is mounted on a piece of plywood hanging about 1-2" off of foundation wall.

We have never seen any kind of moisture in or panel entire time.

HVAC duct is about 2 feet away.

Basement floor is dirt.

At this point I'm going to change out panel again, but before I do I have a few questions.

1. Any ideas on where the moisture would be coming from? Can it be from being so close to foundation wall and HVAC duct being close causing condensation build up in panel?

2. Would it be wise to add 2x4 frame behind plywood and insulation with R-13 fiberglass? Acceptable code wise?

3. Can the existing meter base SE cable, ground wire and rods be re-used as long as they meet current code requirements?

stickboy1375

Time for a replacement, & fix the water issue, most likely at the weather head.

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stevekem

So your thinking the water is traveling through the jacket of the SE cable from the weatherhead into the meter base and through the next SE cable to the panel?

stickboy1375

only way to know is open up the meter and check for the same damage... you would be amazed at what water can do though.

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stevekem

Ok, cool I will keep that in mind...

If this is not what is causing the water issue, can everything else (other than panel and breakers) be re-used if in good shape?

Is it against code to install insulation behind the plywood backer?

rjniles

Basement dirt floor. Suspect moisture/condensation.

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AllanJ

Run a dehumidifier in that space. You would be surprised at the amount of condensate you collect.

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AandPDan

Happened to me when I bought my house.

The water came in via the weatherhead, into the meter base, followed the neutral connector down into the main panel.

Don't be surprised to find corrosion in the meter base too.

Now it's all in conduit from the weatherhead down. Just like it should be.

stevekem

What size conduit should I use between weather head and meter base for #2 AL SE Cable on a 100 amp service?

I can use SE cable in conduit for service entrance correct or do I have to use THWN?

If I use conduit from meter base thru foundation into basement (instead of exposed SE Cable), do I terminate the conduit (not connected to panel) with a male threaded adapter w/insulating bushing or do I have to run conduit into panel if conduit is being used?

Jim Port

Conduit needs to be continuous between boxes.

SE cable is not typically run in conduit.

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Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.

stevekem

Thanks Jim...

So would it be fine to run conduit between the weather head and meter base but run SE cable from the meter base to the panel?

What size THWN in CU and AL should I use for 100 amp service (between weather head and meter base)? I do not understand the temperature ratings fully yet so these got me confused when trying to size my wire...

Jim Port

For sizing service conductors that serve the entire load of the house you can use Table 310.15

Table 310.15(B)(7) Conductor Types and Sizes for
120/240-Volt, 3-Wire, Single-Phase Dwelling Services and
Feeders. Conductor Types RHH, RHW, RHW-2, THHN,
THHW, THW, THW-2, THWN, THWN-2, XHHW,
XHHW-2, SE, USE, USE-2

100 amp copper #4, AL #2

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Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.

stevekem

Thanks again Jim...

Is it acceptable to put Noalox or DiElectric Grease on the bus bar tabs before putting the new main/branch breakers in?

I wasn't sure if this was within code or not?

jbfan

Not that it matters since you are planning to replace the panel, but the top leg on the main breaker has been overheating.

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stevekem

Would that be from the bus bar being corroded?

Would it help to put Noalox on all bus bar stubs during panel change? Maybe hoping this will prevent future corrosion issues if we can't get the moisture level down to an acceptable level. Is this allowed?