Monocoat on EMT

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motodiva

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Hello,We have an ongoing discussion in the jobshack, and I was hoping for some more opinions. We installed miles of EMT in the ceiling before ALOT of monocoat (spray-on fireproofing) was applied. We pre-installed it to keep from disturbing it and so we wouldn't have to work in the nasty stuff. However, many of our pipes have been coated, in some places up to 2" thick all the way around.
Does this stuff affect the ampacity of the wires being that they won't cool as well with this as insulation? Any advice would be appreciated, this is more of a theoretical discussion, since the work is done and the AHJ doesn't seem to mind.
This is a very common occurance around here, and I've never heard of any inspection problems.
Thanks!
 
Re: Monocoat on EMT

My thermal conductivity chart indicates that still air is the poorest medium for dissipating heat.

Air is .024, glass is .8

I think that anything around the conduit will dissipate heat better than air.
 
Re: Monocoat on EMT

Well, since this is a theoretical discussion, I'll disagree with Bennie (in a good natured way of coarse :) ). I don't duspute his facts (I'm sure still air is a very poor conductor of heat), but with his conclusion. The problem with free air is that when affected by heat it doesn't stay still for long. It sets up convection currents and transports heat in that way. I think the reason insulation works, is that it traps small quantities of air so that it has to stay still. If I had to go out into some calm subzero air, I'd rather wear some nice warm clothes than... well.. air :D .

More seriously, since the purpose of the fireproofing is to protect the structural steel from heat, it must have some pretty good insulating value. If air works better, somebody could get rich by setting up a company to fireproof structural steel by spraying it with air :D
 
Re: Monocoat on EMT

eprice: You very well can be correct. I don't have the thermal conductivity rate for monocote.

I am using the thermal heat flow numbers from "Physics" by Halliday and Resnick. 3rd Edition.

Interesting that silver has the highest thermal conductivity.

Thermal conductivity follows DC resistance of a material.
 
Re: Monocoat on EMT

You have affected the ampacity of the conductor.
the thermal resistance of the conduit + the new
momoccoat + air is the total thermal resistance.
If you can locate the thermal resistance of the monocoat we might be able to caculate the ampacity of the conductor.
 
Re: Monocoat on EMT

I hate working around monocoat fireproofing, put your stuff up early and your boxes are buried, go late and you own repair of damage to the monocoat.

Back to the question, would it really make a difference?

Think of all the wiring methods in walls and ceilings surrounded by insulation, fiberglass, blown in cellulose or now spay in foam.

If you are using the ampacity tables, (instead of engineering supervision) and have already applied the ambient temp. correction if needed and derated for more than 3 wires in a raceway if appropriate, IMO you are all set.
 
scraped off monocoat

scraped off monocoat

Any -building- inspectors out there? An electrican removed monocoat to attach beam clamps, 4 by 4" boxes, etc. The building inspector turned down the entire job because of the small patches of coat removed to attach elec. goodies. THe elec. inspector had no problem since the penetrations were sealed. Does anyone know of an elec. code prohibiting the fireproofing? --Should the bldg. inspector overlook those attachment areas?
 
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bill@nkapc said:
Should the bldg. inspector overlook those attachment areas?
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No, that is a building inspectors job to ensure the fire proofing meets code.

Those spots must be re-coated to maintain the fire resistance rating.

BTW....four years between postings in single thread is a new one for me. :)
 
iwire said:
BTW....four years between postings in single thread is a new one for me. :)
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Sometimes I'm a dope. I didn't look at the date and was wondering why we heard from Bennie again.
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iwire said:
BTW....four years between postings in single thread is a new one for me. :)
Click to expand...

And I thought George had a slow ISP connection:D
 
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