central heating won't go above 15 degrees

melb

hi there had a worcester condensing boiler fitted in the summer. during the recent really cold spell we had the thormostat in the hall up to 20 degrees and it was clicking off at 15 degrees - ie it was only heating the house to a maximum of 15 degrees. at the same time the water seems to be constantly scalding hot even though it's only on for a couple of hours in the morning and we have bath washing-up cleaning etc each day. is there any way the boiler might have been wired up wrongly so that the emphasis is going to water rather than heating even though the water heater isn't switched on? we've only just noticed it but of course up til recently it wasn't that cold. temperature on water is set at 70 degrees thanks

gas4you

Anything is possible, but I would suspect a faulty motorised zone valve in your airing cupboard, assuming this is not a combi.

ormus

maybe a faulty thermostat. is it a wirless one?
if so, try changing the batteries.

ormus

ps
modern boilers have a priority system. the domestic hot water gets first choice.
CH comes second.

amcluesent

Would help to know if this was a combi or not. If not, it's a moments effort to put your hand on the output pipes from the pump and 3-way valve to check what's heating up when C/H is being called for.

melb

hi and many thanks for your replies. it's a condensing boiler. if hot water takes priority why does it seem to heat it when it must already be boiling hot as that's what seems to be happening. My OH has put his hand on the bit that is to do with the water heater (on the boiler - sorry not very sure of name) and it is cold when water heater is not switched on. haven't looked at hot water cyliner to see what's going on there byt maybe I should. thanks

melb

don't think it's a wireless thermostat - it's been there about 14 years and no access to be able to change batteries

gas4you

If you have a hot water cylinder then chances are it is not a combi.

Look for the motorised valve(s) in the airing cupboard. If a pressurised system, check the pressure is about 1.2-1.5 cold.

taffj

Might be a silly question but I can't see that anyone has asked the obvious. Are the radiators getting hot and how hot?

melb

yes the radiators are getting as hot as usual. the 70 degrees temperature is on the boiler

Rikki

My hall based thermostat won't go above 15 but the rooms in the house are a comfortable 18 to 20 degrees.
I wondered if this was the same problem for you? The thermostat being in a colder place so never getting up to 20.

70 is high for a water tank setting. Mine is at 50.