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Old 11-03-2009, 02:16 PM   #9 (permalink)
Richard
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Default Re: comparisons of heat mat costs and performance

Quote:
Originally Posted by Dalmatiansoap View Post
That is what i was reffering with watts/hour. More watts-less time needed, that why u use thermometers. True is that this sys needs more hardwork but in my opinion if U want to do something more proffesional than it is everthing clear. Heat mats are good and simplest solutions for areas that we dont use only for germinations and rooting.
With heating mats and cables, the first 5 minutes of operation uses nearly the same number of Coulombs (~watt x hours) as the first 20 minutes. This is why I am concerned about power density (watts per sq.ft.).

Following your suggestion I have found this efficient cable here in the U.S.: Gro-Quick 140' and 200' foot cables at 700 Watts and 1000 Watts. If I bury one in a shallow bed of horticultural sand it should be able to keep 18 flats (288 4-inch pots) warm enough for propagation. The 700 W system would be affordable to operate at 17 W / sq.ft.

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