Thanks for the info, gr5.
I want to go to 140-150degC because I am trying to print with POM.
If I use a bed temperature of 105-110deg C, using adhesion sheets,
the POM warps and lifts of the bed at the edges.
The POM prints OK at a nozzle temp. of 225degC.
I already have an enclosure.
i.e. I don't need to alter the firmware (I think), but I need the supplemental heater .
So, its not really a problem with printing POM, but the problem
is insufficient heat to the bed.