Quote:
Originally Posted by Dalmatiansoap
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.
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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.