I just bought one new myself very similar setup. Mine will regulate voltage fine until the heating element gets to certain temperature than it will jump up to full voltage even with the potentiometer is it lowest setting, 70-80 volts sometimes. I find this frustrating and i was wondering if anyone had any potential ideas? It does do it until running for several minute and temperature is high. Any help would be appreciated

New unit, just bought, I would ask the manufacturer about the problem and I would not do anything which may void any warranty. It sounds like a problem for the seller or manufacturer to resolve.

Just My Take....
Ron

 

That is why I asked a question and said to take a look. If it i new and under warranty that is one thing. The heater suddenly jumping to max is strange. It does sound a bit like a short circuit happening because of expansion, which should not happen.