[Cob] Cob: electrical

[Dorothy Bothne]

There's been quite a stir concerning my comments regarding heat transfer in the electrical conduits buried in cob,  I forwarded Darel's comments (listed below phil's response) to my electrical design engineer friend, and here was his response.
From: "Phil" 

To: "Dorothy Bothne" 
Subject: RE: Re: Cob: electrical
Date: Tue, 16 Sep 2003 17:19:37 -0500

Dorothy:  there may be some merit to his argument (he seems mighty intelligent - except for his spelling (reminds me of Gilmo)).  I still feel the open conduit is going to allow heat to be released from convection.  Never-the-less, the main reason for using conduit (raceways) is to provide flexibility.  You can rough-in with "the tube" and decide later exactly what you want to do with the wiring.  You always have the option of adding or changing wire size in the future.  It seems especially important when you are talking about structural walls like cob.  The gyp-board covered frame walls in the interior are a different story though - although, why not do the same thing all over?
 
PDG

 


"D.J. Henman" <henman at it.to-be.co.jp> wrote: Date: Tue, 16 Sep 2003 11:58:35 +0900
From: "D.J. Henman" 
To: Dorothy Bothne , Coblist 
Subject: Re: Cob: electrical

Air is as I previously mentioned not going to help. It will be the 
aluminum casing conducting out to the recepticles and out to the 
surrounding cob. The figure of 9,600 times faster is a mater of 
record and can be verified by looking at the conductivity factor for air 
verus aluminum. If you wanted you could also try to find a 
conductivity factor for dry packed dense soil and compare it to air. 
I am sure that your electrician is good as what he does, but, having 
air inside would not help dissipate heat and you are not going to force 
blow air through the conduit to make any difference.

Having air between wires is a difference matter, in this case you using 
it as an insulation keeping them disconnected and avoiding conduction. 

It will not remove as much as the conduction to the cob. Give us your 
real data and I will show you.

What factor are you using for cob's thermal conductivity? The heat 
is conducting though metal which transfers heat 9,600 times faster than 
air. The surface area of the whole length of the conduit will be 
dissipating heat into the cob. 

And secondly, you shouldn't be having a heat problem in the first place.

So if you disagree with this give use your cob conductivity factor. I 
have the factors for aluminum and air.

Darel





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