I doubt that it's any sort of immediate safety hazard, but I would be
concerned that the bending of the embedded wires around the wires of the
grid could ultimately lead to cracks that could become hot-spots.

Some of the heat will be conducted away in the metal, which will effect the
heating of your seedlings. My guess is that the "10-20 degree" rise in the
uncontrolled mat is determined by the overall resistance of the wiring in
the mat coupled with how fast the heat is taken out. Dana's idea about
insulation under it obviously means more is pumped up toward the plants.

--

Ray Barkalow First Rays Orchids
http://www.firstrays.com
Secure Online Ordering & Lots of Free Info!


"Elpaninaro" wrote in message
...
Good evening all,

The Paph flasks are now in compot and going great! And my seedling mat
finally
arrived yesterday to keep the plants warm.

I never thought much of it at the time, but now I realize that I was about
to
place this mat directly on the metal grid shelving of my indoor growing
set up.

Is this asking for trouble? Do any of you who recommended this mat use it
on
metal? If so, should I take any steps to keep the metal separate from the
mat-
ie a rubber mat or perhaps some bath towels?

Also wondering if you guys leave this plugged in 24-7. For now just to be
safe
I am tempted to use at night only, and perhaps also buy the regulator that
is
optional. The ad said 10-20 degrees over ambient temp so I had assumed it
was
adjustable. Granted there will be plastic trays holding the plants, but I
am
concerned about things getting too warm.

Thanks for any thoughts!

Tom.

PS- To all the sanderianum growers out there- just tonight ordered my
flasks of
that and Sam's latest PEOY. I will keep good records and pics (delivery
expected in 3-4 weeks after a few big shows are completed) and look
forward to
hearing further on everyone's results.