Grant Boilerhouse boiler thermostat etc

Hi all,

My boiler is a Grant Engineering Boilerhouse boiler and the thermostat has no temperature figures on it. The dial is like a volume control - a curved arrow getting wider. There are moulded line marks on the dial and the dial housing at about 50%. The boiler is a condensing boiler. Are the moulded markings the point it starts operating as a condensing boiler?

At that 50% level and even at the bare minimum my hot water is extremely hot, dangerously hot really. When the boiler is not firing and the the thermostat is moved to a higher temp, the boiler does fire so the thermostat is working.Do I need a hot water thermostat ?

The heating system was installed in the early 1970s but the boiler was installed about 6 years ago. Part of the system is gunmetal and other parts is copper. The hot water cylinder has a valve which allows hot water from the heating to be used as bathe water if required.

From time to time there is air in the hot water taps more in the bathrooms rather in the kitchen. Currently when a zone pump comes on there is a noise that sounds like ball bearings rolling through the radiator pipework / cylinder pipework.Turning down the zone thermostat a tad lower and then back to just above the click a few times the noise quientens but changes tone to what sounds trapped air being squeezed out. There is an air release thingy (copper cup shaped thing with a sealed cap but with a small screwable valve cap) which is opened to almost the highest point.

I also need to have my boiler running for heat to have hot water so on hot days my rads are hot too.

What are my options to deal with these prbblems?

any help, advice etc welcome

regards all