Hot water...when only the heating has been on

Cardew

owain.davies wrote: »

This doesn't sound like a fault as much as the system working normally! I presume you have a hot water tank and as such you have a three-way valve controlling the direction of flow. The normal situation for these is that they have only two positions - (1) On for hot water only (2) on for hot water and heating. This is because the hot water heating loop through the tank is relatively small and therefore heating the extra is at minimal additional power compared to sending it to all the radiators through the house. You can get valves with a third position to shut it off, but in terms of additional cost, it should be minimal, presuming that your hot water tank isn't some enormous size.Personally at most houses i've ever lived in this has been the case and i've generally only activated the 'hot water' control for the summer when i didn't want heating, as the heating alsways provides more than adequate hot water.

I have seen a system such as you describe, but then the control to switch on the CH also operates the HW control i.e. it is physically not possible to set CH on and HW off.

However I suggest the the vast majority of CH systems have a 3 port valve that allows CH on and HW off - (every house I have lived in).

If your system was normal, then a tank stat could not be used, the HW would eventually get up to the same temperature as that in the CH system - which can be 85C and a serious danger of scalding.

If I am away during the winter I set my CH to come on twice a day(TRVs on low) - I don't want to heat HW.