Difference between revisions of "Talk:Taking electricity outside"
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more here: http://www.psihq.com/iread/ufergrnd.htm | more here: http://www.psihq.com/iread/ufergrnd.htm | ||
[[User:NT|NT]] 22:45, 7 June 2007 (BST) | [[User:NT|NT]] 22:45, 7 June 2007 (BST) | ||
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+ | I posted a question on the group on this, it will be interesting to see what is said. | ||
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+ | A couple of points to note is that the ufer earth does require the slab to have both high moisture content and rebar. Most floor slabs will have a couple of inches of dry screed, isolated from the sub base by a DPC membrane among other things. | ||
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+ | --[[User:John Rumm|John Rumm]] 23:45, 7 June 2007 (BST) |
Revision as of 22:45, 7 June 2007
concrete resistance
"A concrete floor in a garage that has no extraneous metal parts in contact with earth and no other services like water pipes entering the building will offer a good isolation from earth,"
Experience with ufer earthing seems to indicate the opposite. NT 23:26, 4 June 2007 (BST)
Not been able to find much on this. Normal practice in new builds seems to suggest that a concrete floor is considered to pose no risk with a PME installation. Ufer earthing also seems to depend on quite a high rebar content in the foundation slab.
The conductivity of concrete also seems hard to pin down - but it is influenced by its moisture content. I have seen figures of 25K ohm / cm - which if true would place more than enough impedance in the earth reference to make this a non issue.
I might post another invitation to comment on the group since the first one seemed to generate somewhat less than the normal level of response.
--John Rumm 11:17, 7 June 2007 (BST)
Some comments on Ufer concrete earth resistance:
"When structural steel is bonded to the earth electrode system, the results can be quite dramatic. The author participated in one mountain-top project where the measured resistance-to-earth of a 20-rod, building earth electrode system — prior to bonding to foundation steel — was 150 ohms. After bonding foundation steel to the earth electrode system (all below grade), the resistance-to-earth was 1.0 ohm"
more here: http://www.psihq.com/iread/ufergrnd.htm NT 22:45, 7 June 2007 (BST)
I posted a question on the group on this, it will be interesting to see what is said.
A couple of points to note is that the ufer earth does require the slab to have both high moisture content and rebar. Most floor slabs will have a couple of inches of dry screed, isolated from the sub base by a DPC membrane among other things.
--John Rumm 23:45, 7 June 2007 (BST)