Substrate heating

> From: Mike Bateman <vandi at well_com>
> I would like to hear some opinions or evidence on how substrate heating
> coils should function.

Dennerle suggests that the [low wattage] coils should be on a much as
possible.  They have a special controller that runs both the substrate
coils as well as an aux water heater.  The controller attempts to
maintain the water temp via the coils and only turns on the aux heater
if the water temp drops more than X degrees below the set point. 

I am doing the same thing as you are - the Ebo Jaeger is set just
below the UltraLife set point. 

I think the best circulation will occur if the coils are on as much as
possible.  Also, there is probably less stress on the plant roots if
the temp is relatively constant.