by plumbbob »
Sat Feb 13, 2010 4:26 pm
First you have to discount a frost stat is not over riding the heating controls and firing the boiler even when the programmer is in the off position.
If this is not the case, it may be the three way valve if fitted may be jamming and keeping the heat on. Another possibility is incorrect wiring or even a faulty room stat.
The trouble is, unless you know a little about heating systems, because of the number of possibilities, it may be difficult to nail down the problem.