Main Panel Condensation

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Old 04-21-08, 07:35 AM
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Main Panel Condensation

I am looking to buy a new house and in the inspection we noted some moisture in the main panel. Its not soaked, just what appears to me to be some condensation buildup but I can't figure out from where. Long story short I am going to go back and look at it today and get some ideas about things while we negotiate on the house and I want some ideas of what could be causing this.

My fancy drawings here show the setup of the house. The panel is in an unfinished part of the basement. I removed the access plate where the elbow is outside and it was dry as a bone in there so I don't think its rain water coming from the meter. The main service lines also apeared dry and the main breaker wasn't wet or corroded so I don't think its coming in under the insulation of the wires.

Could air be coming in and causing the condensation? Any ideas on what to look for in particular when I am there today and what can be done about it?

I'm not new to electrical work, but I am not up on construction code and obviously don't know what causes condensation in a panel. So any tips short of "hire an electrician" would be greatly appriciated. Right now I am trying to get a rough idea of what is going and and what needs to be done to it before I pay someone to come in as I am hoping to convince the current owner to fix it on his dime.



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Old 04-21-08, 07:54 AM
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As you may know condensation happens when a cold metal box is exposed to warmer moisture laden air. That said you need to find out why the air is humid (moisture laden). Is there an open sump pit nearby? Does the dryer vent into this area? Any open drains that have water in them? Is there any places where outside air can enter this space? Does the area have any ventilation in it so the air can move? Find and cure the humidity problem and the condensation will disappear.
 
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Old 04-21-08, 08:05 AM
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Good response. Thanks.

The day we looked at it, it was about 55 or 60 in the house. The current owner hasn't lived there all winter and it was about 70 outside, it just hasn't been warm enough at night to heat up the house, plus the basement will be the last thing to warm up I suppose. They had the heat on just high enough keep the chill off I suppose.

The way the basement is finished is that on this one wall of the basement instead of taking the drywall/insulation/vapor barrior all the way to the concrete like they did everywhere else and just having the panel access via the finished room they left a 2 foot gap and put a door on it. The sump pump is on the other side fo the basment and there wasn't anything obvious venting here, but I'll look again. This area is not tied into the ventilation system and there are no wall vents or anything allowing it to get air from the other room, just when you open the door.

I wondered about putting a dehumidifier in there or connecting it to the ventilation system or just putting vents in the door to this room if that would help.
 
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Old 04-21-08, 08:39 AM
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Originally Posted by Dave.H View Post
The current owner hasn't lived there all winter and it was about 70 outside, it just hasn't been warm enough at night to heat up the house, plus the basement will be the last thing to warm up I suppose.
This could be it. If the condensation is just a one-time thing, then it's not really a problem, but it is important to make sure that it hasn't been going on a while.

Continuous condensation will corrode the bus bars in the panel which requires a full panel replacement ($) before it catches fire. Signs of an ongoing problem would be rust on the panel box or white colored buildup on any of the bus bars or wire connections.

If the service drop wires have a drip loop and a weatherhead on the conduit mast, then you probably aren't getting any leaking down the wires. Another spot to check out is the threaded hub on the top of the meter box; the seal on that hub could be rotten which may be leaking water into the pipe. Just visually inspect the meter area; don't open the meter box without the power company present.

I would try to put some duct seal in the LB access where the conduit turns into the wall. It's basically a sealant clay-like material you can pack into the conduit around the wires to block airflow. You should be able to find some in the electrical aisle of the hardware or home center.
 
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Old 04-21-08, 01:19 PM
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Well I went back at lunch today and looked around. There is a significant temperature difference between that room and the rest of the basement. There is zero ventilation to that room other than a small gap in the bottom of the door, but we all know heat rises.

What I found interesting is that there were some signs of moisture (surface) rust on the outside of the panel and on all the staples and nails in this area. There is some buildup begining on the bus bars but due to the location of the other areas that show signs of moisture there is no way its a water leak anywhere, it has to be humidy/condensation.

I am going to start by putting some vents in the wall to tie this room into the rest of the house and keep an eye on it. Maybe even put the dehumidifier in that room. I'll look into sealing off the conduit from the access outside as you suggested.

I needed to put a new panel in the house anyway as this one only has one space availible and there are only a couple outlets in the garage and no 220 in the garage so I need a larger panel anyway. This was going to be a later project but it looks like it just got bumped to the top of my list. I'll wire the garage later but as soon as we close on the house I'll put some vents in or leave the door open for now and get the power company to pull the meter so I can swap the panel.

Thanks!

Originally Posted by ibpooks View Post
This could be it. If the condensation is just a one-time thing, then it's not really a problem, but it is important to make sure that it hasn't been going on a while.

Continuous condensation will corrode the bus bars in the panel which requires a full panel replacement ($) before it catches fire. Signs of an ongoing problem would be rust on the panel box or white colored buildup on any of the bus bars or wire connections.

If the service drop wires have a drip loop and a weatherhead on the conduit mast, then you probably aren't getting any leaking down the wires. Another spot to check out is the threaded hub on the top of the meter box; the seal on that hub could be rotten which may be leaking water into the pipe. Just visually inspect the meter area; don't open the meter box without the power company present.

I would try to put some duct seal in the LB access where the conduit turns into the wall. It's basically a sealant clay-like material you can pack into the conduit around the wires to block airflow. You should be able to find some in the electrical aisle of the hardware or home center.
 
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