Boiler going off on hot water but ok for heating

[SteveGiles]

Hi, a little problem I am having - my Glow worm boiler (Ultracom 18kw) is fine on heating, but no hot water, the boiler goes off after a few minutes, then about 5 or more minutes later comes on, and the sequence repeats! There is no F code as in the manual,. so I am not sure what could be the cause?

I have bled all the radiators and checked the pump. Is there anything else causing this? Thanks for your help

 

[SteveGiles]

I have noticed on the display on the boiler that the temperature in hot water goes up very quickly then stops for a few seconds then goes up a bit again and then the flame symbol goes off. In heating this does not happen. Is there anything else I can check please?

 

[ljrgas]

hot cold hot cold????

is it a combi???

blocked plate....

 

[SteveGiles]

it is a boiler with a cylinder in the airing cupboard upstairs

 

[Armo74]

Could be a dodgy micro switch in the actuator on the valve. Need a bit more info on other system components.

 

[SteveGiles]

thanks for helping - I have just moved in. It looks a new(ish) Glow worm Ultracom hxi 18kw boiler - it feeds 7 radiators and a hot water tank in the airing cupbaord. The radiators heat up brilliantly in a short time. The hot water, fires up, pump runs, but the boiler gets to a temerature of 70 degrees, then stops, goes down a few degrees and then the flame symbol goes off. Then after a while it comes on for a short time again.

I have googled some information on it - and it says something about ranging the KW down and about it not being able to modulate enough. But I am not sure how to do this or if it would work! My hot water tank is standard, about 120 litres, not a large tank.

The pipe going in and coming out of the tank are both very hot and all air is out of the system.

There is a magnetic filter called TF1 above the boiler and this was also vented of air.

 

[DP]

Can you run CH by itself or does the HW channel also fire up when you ask for CH? Is the HW cylinder factory lagged or does it wear a red jacket or similar?

 

[hazetimesfive]

if the coil is hot then whats the problem exactly

 

[SteveGiles]

Hi

I can run heating by itself without hw coming on - the cylinder is pre lagged, not a jacket type.