Thorn Apolo Boiler - System Problem

[JCCHunter]

Thorn Apolo Boiler - System Problem

On low stat setting everything is working fine, pump running & radiators heating satisfactorily.

On high stat setting the burner ignites normally and the full flame comes up, the pump appears to be running satisfactorily but radiators are not heating up.

I would welcome any thoughts as to what exactly may be the problem?

My initial guess is that the high stat may be faulty, but then I would not expect the burner to come fully on?

 

[twgas]

How long does it stay on when set to high, the heat has to be going somewhere.

 

[JCCHunter]

How long does it stay on when set to high, the heat has to be going somewhere.

Mick,

Thanks very much for your reply.

I should have mentioned that the heating system has two modes of operation, namely;

1.Heating the water in the domestic hot water storage tank only

2.Heating the domestic hot water tank and also the wall mounted radiators (6 in total).

It is in the second mode, on high stat that the radiators are not heating up.
Perhaps the heat is being dissipated through domestic hot water storage tank?

I guess in this case there will be solenoid operated valves, which may further complicate the issue.

I don’t have a schematic diagram to hand so I will need to carry out a visual check on the heating system, when I am next in Edinburgh.

 

[twgas]

Am I right in thinking that you are saying;
If both CH and HW are calling (on at timer AND appropriate thermostat) the boiler only works if its 'stat is on low, doesn't work on high.

 

[mysteryman]

If that is the case, check the wiring around the high thermostat, and the 'stat itself. I had one where a wire was broken inside the insulation, giving exactly this problem.