Back Boiler Not Heating Water But Heating Rads

[foresttemple]

Hi Guys, I've got a woodburning stove with a back boiler that I cant quite figure out. Last year it was heating the water but not the radiators, and this year its heating the radiators and not the water. Does anybody have any ideas? Its a fairly old installation, I'm guessing from the 80s ish, in a 70s house in the highlands of scotland.

There is a gas boiler, which is currently switched off, and an array of pumps and thermostats. Theres a thermostat next to the gas boiler, one in the hallway, one on a pipe beside the water tank in the attic, and one on the water tank itself. Theres a pump downstairs beside the stove, which is running. And one in the attic near the hot water tank which is switched on but not running. There seems to be a honeywell valve near the attic pump which switches between auto and manual, but neither seem to make a difference. There is a header tank in the loft space above the hot water tank (with water) and a smaller tank near to it (which i havent checked the level of). When the immersion heater is on it only heats a small portion of the water tank capacity. Perhaps this means there is an airlock? Any other ideas. The stove is absolutely belting out heat and it has worked in the past heating both the radiators and hot water so i'm confused (which is nothing new).

Cheers!

 

[Deleted member 120897]

Looks like you have a 3 port valve, but this may be part of the gas boiler installation? If it’s part of the whole installation then this might be failing.

 

[foresttemple]

Looks like you have a 3 port valve, but this may be part of the gas boiler installation? If it’s part of the whole installation then this might be failing.

I'm really not sure unfortunately. Is the 3 port valve the grey Honeywell box? That box seems to heat up when the back boiler is heating. There are two positions on an actuator switch; "auto" and "manual". When i switch to manual i can hear some water glug through but not much else seems to happen

 

[Deleted member 120897]

I'm really not sure unfortunately. Is the 3 port valve the grey Honeywell box? That box seems to heat up when the back boiler is heating. There are two positions on an actuator switch; "auto" and "manual". When i switch to manual i can hear some water glug through but not much else seems to happen

Yes the Honeywell box. Manual won’t do anything on that valve, it’s for filling the system, not a bypass for the microswitch. If that heats up when the back boiler is in operation then it’s likely that this does the hot water too.

 

[foresttemple]

Yes the Honeywell box. Manual won’t do anything on that valve, it’s for filling the system, not a bypass for the microswitch. If that heats up when the back boiler is in operation then it’s likely that this does the hot water too.

Great, that sounds like good news. Any ideas on how i can switch from heating the rads to heating the water in the tank?

 

[Deleted member 120897]

You could try turning it off on the fused connection unit, which may trigger the valve to return back to hot water position. If that doesn’t work you’ll likely need a whole new valve, as yours doesn’t have a dimple on the metal box, which usually means it’s not serviceable without draining it down.

 

[foresttemple]

You could try turning it off on the fused connection unit, which may trigger the valve to return back to hot water position. If that doesn’t work you’ll likely need a whole new valve, as yours doesn’t have a dimple on the metal box, which usually means it’s not serviceable without draining it down.

That sounds like a good plan, I'll give that a bash. Thanks!