Central Heating Query

[ojread2]

Good Morning AB'ers

I had my radiator thermostats replaced last week on all but 1 of my radiators as they were not working to full potential. I returned from work to find the rads were all hot, very hot. Good, that means they now work but I got home from work at 18.15 and the heating guy had left at 13.30 and the heating wasn't switched on. The rads had been heated by hot water when the hot water was turned on.

I thought maybe this was just the system having been flushed through so I tested a couple of the rads on a different day and sure enough they became hot with only the hot water being turned on.

I have an appointment for him to come back but I wondered what it was he had done to make the system work this way? Could you run a system like this? Would it not be cheaper to run the rads this way? Is there any reason why I couldn't continue to run the rads using the hot water as it seems the rads stay hot for a long time after being filled with hot water?

TIA

[Steviegb]

If you have a normal system ( not a combi) you will probably have a 3 way valve or 2 divertor valves in your airing cupboard.This diverts your water so you can have either heating, hot water or both. There is a rubber ball inside this valve which can become worn, or if you have had your system flushed it could have some dirt on the seating allowing water to pass to your radiators,( when your water is heating up) even when they are turned off.Probably wants a new divertor valve.