Was that a joke or are you implying leaving a portable electric heater in the room would leave it susceptible to freezing over in winter?
I'm not sure if you are being serious H, but ajrobb's joke was about the condensate freezing on a hyperthetical condensing boiler heating your house. The electric heater will be in your new cabin at the bottom of your garden is it not?
I did think it was a joke but I was also confused.
Makes sense now, but no worries, our relatively new combination boiler is doing fine so the house has nothing to worry about haha. And yes, any electric heater would be in reference to the gardenhouse