Heating still heats water even when off??

[zelig33]

Hi - I wonder if anyone would be able to advise?

My mum has an 8yr old Glowworm Space Saver 40B MKII boiler with Honeywell Control GC NO 41 315 88 - and this has 3 settings as per norm - 1 for Heating 1 for Hot Water and 1 for both.
Even when she has just the Heating on and the Hot Water off the water is red hot and you can hear it bubbling all night.

Any ideas before I book an engineer? all suggestions most welcome

Many thanks

Zelig33

 

[Boilerman2]

Although the control can be set to HEAT only, many older systems especially those with GRAVITY PRIMARIES CANNOT actually provide HEAT only whenever the boiler fires the HOT WATER will be heated, it is my guess that this is the case with your system