Hot water but no heating

[FrancesMillar]

Hi all, I have a ideal icos boiler, 10 years old but new computer 18 months ago. Al been working fine. This morning I discovered I had hot water but no heating. Have checked thermostat is high enough and timer correctly set. Green light is reading 0 so no error messages and c when hot water is on. But boiler does not fire when I put heating only on. Have read about valves that can get stuck on water only but if this was the case would the boiler still light? Also any advice would be appreciated as to cost. Should I just get out a local engineer or take out a BG scheme if likely to be v expensive? Many thanks for reading.

 

[stem]

You don't give any details of your plumbing / heating system, but if you have a Y-Plan system with a 3 Port motorised valve that looks something like this:

[GALLERY=media, 21163]Untitled by stem posted 1 Apr 2010 at 3:54 PM[/GALLERY]

Then symptoms you describe would fit failure of the motorised valve's motor. Normally the valve sits in the hot water only position. When heating is required the motor winds it across to the heating position. If the motor has failed it won't move to the heating position, so no heating.

The hot water cylinder thermostat switches on the boiler when heating up of the hot water cylinder is required, so yes the boiler will light and heat the hot water.

On the other hand, if you have an S-Plan system with 2 x 2-Port valves something like this:

[GALLERY=media, 20994]Untitled by stem posted 26 Mar 2010 at 10:00 AM[/GALLERY]

Then, just the Heating valve may have failed and the hot water one is OK.

If the boiler is heating the hot water cylinder OK, then the boiler is working. The fault is elsewhere.