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Author Topic: Condensation in Electrical Vault  (Read 2615 times)

Frank Koenig

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Condensation in Electrical Vault
« on: January 20, 2016, 11:34:18 pm »

This is not sound related and only somewhat electrical but, if you'll indulge me, I expect this crowd, especially those involved in nasty stadium installs and the like, may have some good ideas.

In the concrete floor of my unheated barn I have a 2 x 3 x ~1.5 ft. deep pit, which I had built as a secure location for telemetry, alarm, UPS, and communication bits. It has a 1.5 in. recessed locking steel cover and embedded conduits running off to various places around the building. It also has a drain to daylight so that it doesn't fill up with water in the event of a flooded floor (the electronics live on a raised plywood platform). I did consider condensation when I designed it but wishfully thought that the heat generated by the gear inside (some tens of watts) would be sufficient to keep the relative humidity below 100%. Well I was wrong. I went to open it the other day to find the contents thoroughly soaked. I think water droplets hanging on the underside of the steel cover rained down the moment I started to remove it. Whatever the source, I have problem.

I really don't want to resort to heaters and fans as they make noise and present a continuous power draw. I'm thinking along the lines of painting the inside of the pit with an epoxy concrete floor paint and insulating the outside of the lid with 1 in. of polyisocyanurate foam. This would put the layer of least permeability (the steel plate) on the "warm" side, as is done in exterior building walls in cold climates. But what a pain. Any thoughts are welcome. Thanks.

Best,

--Frank
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frank kayser

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Re: Condensation in Electrical Vault
« Reply #1 on: January 21, 2016, 06:46:57 am »

This is not sound related and only somewhat electrical but, if you'll indulge me, I expect this crowd, especially those involved in nasty stadium installs and the like, may have some good ideas.

In the concrete floor of my unheated barn I have a 2 x 3 x ~1.5 ft. deep pit, which I had built as a secure location for telemetry, alarm, UPS, and communication bits. It has a 1.5 in. recessed locking steel cover and embedded conduits running off to various places around the building. It also has a drain to daylight so that it doesn't fill up with water in the event of a flooded floor (the electronics live on a raised plywood platform). I did consider condensation when I designed it but wishfully thought that the heat generated by the gear inside (some tens of watts) would be sufficient to keep the relative humidity below 100%. Well I was wrong. I went to open it the other day to find the contents thoroughly soaked. I think water droplets hanging on the underside of the steel cover rained down the moment I started to remove it. Whatever the source, I have problem.

I really don't want to resort to heaters and fans as they make noise and present a continuous power draw. I'm thinking along the lines of painting the inside of the pit with an epoxy concrete floor paint and insulating the outside of the lid with 1 in. of polyisocyanurate foam. This would put the layer of least permeability (the steel plate) on the "warm" side, as is done in exterior building walls in cold climates. But what a pain. Any thoughts are welcome. Thanks.

Best,

--Frank
Even with epoxy paint, I'd be worried about moisture under the paint that will just make the paint bond fail.
Ideally, one would want to seal the outside of the bunker just like a basement - waterproofer, membrane, etc,  Given your description, that's not a possibility.
using some rigid foam insulation, you may be able to insulate the inside walls and floors over a plastic vapor barrier with the wet side with access to the daylight drain.
You may end up being stuck using a full-time dehumidifier in addition to other mitigation.


frank
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Stephen Swaffer

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Re: Condensation in Electrical Vault
« Reply #2 on: January 22, 2016, 12:11:42 am »

Well, if you have a drain to daylight, perhaps just some ventilation in the steel lid to allow air flow?  Let convection do the work.
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Steve Swaffer

Craig Hauber

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Re: Condensation in Electrical Vault
« Reply #3 on: January 24, 2016, 08:12:09 pm »

This is not sound related and only somewhat electrical but, if you'll indulge me, I expect this crowd, especially those involved in nasty stadium installs and the like, may have some good ideas.

In the concrete floor of my unheated barn I have a 2 x 3 x ~1.5 ft. deep pit, which I had built as a secure location for telemetry, alarm, UPS, and communication bits. It has a 1.5 in. recessed locking steel cover and embedded conduits running off to various places around the building. It also has a drain to daylight so that it doesn't fill up with water in the event of a flooded floor (the electronics live on a raised plywood platform). I did consider condensation when I designed it but wishfully thought that the heat generated by the gear inside (some tens of watts) would be sufficient to keep the relative humidity below 100%. Well I was wrong. I went to open it the other day to find the contents thoroughly soaked. I think water droplets hanging on the underside of the steel cover rained down the moment I started to remove it. Whatever the source, I have problem.

I really don't want to resort to heaters and fans as they make noise and present a continuous power draw. I'm thinking along the lines of painting the inside of the pit with an epoxy concrete floor paint and insulating the outside of the lid with 1 in. of polyisocyanurate foam. This would put the layer of least permeability (the steel plate) on the "warm" side, as is done in exterior building walls in cold climates. But what a pain. Any thoughts are welcome. Thanks.

Best,

--Frank
lightbulbs! (-normal incandescent ones.) 
Use as many as you need to keep the surfaces just above condensation temp.  I prefer multiples of smaller wattage ones as they last longer and if one goes you still have others running.
I have a cctv, internet equipment and music gear in an insulated rack in my unheated quonset and it takes 3 100W to keep it above freezing in there when it drops below -30.  (They sell a cube-tap type gadget at the hardware stores around here that turn on an outlet at around 34 and shut it off at 40 for running heat-tape on water pipes -I just use it for those bulbs -probably way too cold for your application!)
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Frank Koenig

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Re: Condensation in Electrical Vault
« Reply #4 on: January 25, 2016, 01:28:40 pm »

Thank you all for the replies. I think I'll try to box in the vault with some low permeability material, such as corrugated-core polypropylene sheet, and insulate the lid. If that doesn't do it I guess heaters (light bulbs, etc.) are the next step. Explicit ventilation -- there is some leakage as is -- would require cutting a hole in the lid and I'd rather avoid that. We'll see. Best, --Frank 
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John Roberts {JR}

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Re: Condensation in Electrical Vault
« Reply #5 on: January 25, 2016, 02:05:55 pm »

Thank you all for the replies. I think I'll try to box in the vault with some low permeability material, such as corrugated-core polypropylene sheet, and insulate the lid. If that doesn't do it I guess heaters (light bulbs, etc.) are the next step. Explicit ventilation -- there is some leakage as is -- would require cutting a hole in the lid and I'd rather avoid that. We'll see. Best, --Frank
I actually have some incandescent lamps (3x60W) with a dimmer mounted under my computer desk as a variable leg warmer. It works like a champ... but. I just checked and one lamp is already burned out.  :o

For your electrical vault can you just use some of the electrical pipe heating tape, perhaps wrapped around conduit and major metal parts? I think they even have thermostats but more to prevent freezing than condensation.

You might be able to install a small baseboard hearer with thermostat... I have a 1kW unit in my bedroom that works fine, you can probably use a smaller cheaper electric heater. Modern programmable thermostats steal power from the load and are < $100. but you don't even need programmable so even cheaper for set and forget thermostats.

I am not aware of a smart dew point thermostat but here is a good link to a dew point calculator http://www.dpcalc.org/ So you can probably figure out some temperature based on anticipated RH.

If unsure of RH you can buy cheap RH meters (<$10 at Walmart) that log temp and RH over 24 hours..

You're smart enough to figure out a thermostat temp setting from that data.

JR
 
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Frank Koenig

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Re: Condensation in Electrical Vault
« Reply #6 on: January 26, 2016, 01:30:03 pm »

For your electrical vault can you just use some of the electrical pipe heating tape, perhaps wrapped around conduit and major metal parts? I think they even have thermostats but more to prevent freezing than condensation.

Those pipe heating tapes come in a self-regulating version that is interesting. I use some on, what else, pipes. They're a Raychem product that uses some magic material between the wires that has a huge step in its resistivity as a function of temperature. I'm guessing it's some polymer with a high thermal coefficient of expansion that's loaded with conductive particles, or something like that. Probably the same stuff that's in those self resetting fuses I've seen show up as tweeter protectors in some (large, expensive) speakers. A great suggestion in any case, if I need to heat this thing.

I'm still hoping for a passive solution and one that doesn't cause everything to overheat in the summer when the ambient in the barn can get to 100 F. Nothing is simple.

Best,

--Frank

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Jeff Robinson

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Re: Condensation in Electrical Vault
« Reply #7 on: January 26, 2016, 04:10:45 pm »

Those pipe heating tapes come in a self-regulating version that is interesting. I use some on, what else, pipes. They're a Raychem product that uses some magic material between the wires that has a huge step in its resistivity as a function of temperature. I'm guessing it's some polymer with a high thermal coefficient of expansion that's loaded with conductive particles, or something like that. Probably the same stuff that's in those self resetting fuses I've seen show up as tweeter protectors in some (large, expensive) speakers. A great suggestion in any case, if I need to heat this thing.

I'm still hoping for a passive solution and one that doesn't cause everything to overheat in the summer when the ambient in the barn can get to 100 F. Nothing is simple.

Best,

--Frank
http://www.pentairprotect.com/SearchDisplay?categoryId=3074457345616682668&searchTerm=HEATER&storeId=715838534&catalogId=3074457345616676718&langId=-1&pageSize=12&beginIndex=0&sType=SimpleSearch&resultCatEntryType=2&showResultsPage=true&searchSource=Q&pageView=
OR
http://www.pentairprotect.com/en/hoffman/Product-Enclosure-Cooling-Heating-Cooling-Heating-Accessories/Electronic-Hygrotherm
Hoffman offers solid state heaters (no fans) and hygrostats/hygrotherms.

Kooltronic likely has similar for less $.
http://www.kooltronic.com/ea-ksehk-ptc.aspx
http://www.kooltronic.com/ea-hygrostats.aspx
http://www.kooltronic.com/ea-electronic-hygrotherm.aspx

http://www.grainger.com/product/DAYTON-Humidistat-46D473
http://www.grainger.com/search?nls=3&ssf=3&searchQuery=heater#nav=search%2Fecatalog%2FN-%2FNtt-heater%3F_%3D1453842324445%26nls%3D3%26ssf%3D3%26sst%3Dsubset%26ts_optout%3Dfalse
Graingers is likely cheaper.

HTH,

Jeff Robinson
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Stephen Swaffer

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Re: Condensation in Electrical Vault
« Reply #8 on: January 26, 2016, 06:07:58 pm »

Those pipe heating tapes come in a self-regulating version that is interesting. I use some on, what else, pipes. They're a Raychem product that uses some magic material between the wires that has a huge step in its resistivity as a function of temperature. I'm guessing it's some polymer with a high thermal coefficient of expansion that's loaded with conductive particles, or something like that. Probably the same stuff that's in those self resetting fuses I've seen show up as tweeter protectors in some (large, expensive) speakers. A great suggestion in any case, if I need to heat this thing.

I'm still hoping for a passive solution and one that doesn't cause everything to overheat in the summer when the ambient in the barn can get to 100 F. Nothing is simple.

Best,

--Frank

The contractor I was subcontracting for did not win the bid, but a few years ago I quoted a bunch of the self regulating stuff for a freezer floor.  My understanding is that is won't heat above its design temp-I think you can put it on a stat, too-but I like the fact that it does not rely on a mechanical or electronic device other than its own characteristics-seems less likely to fail.  I would think it a reasonable low maintenance solution.
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Steve Swaffer

ProSoundWeb Community

Re: Condensation in Electrical Vault
« Reply #8 on: January 26, 2016, 06:07:58 pm »


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