Central heating not automatically working (hot water ok)

[Steve Ruffles]

Hi all. I have an issue with the central heating not automatically coming on when thermostat kicks in.

Hot water seems to be fine and available when required. Central heating does work but only if I manually switch the lever on the actuator (Danfoss HSA3) to the central heating position, so I am assuming that the valve itself is ok and not stuck given that I can do that. Of course though if left there at central heating, it heats up the house and continues to do so well after temperature has been reached on thermostat (it did reach 29 degrees once before I switched the actuator back to hot water only, even though thermostat was set to 20).

I read up on a number of forums including this one that it could be the actuator at fault, so I replaced that with a new one (Danfoss HSA3) and wired that up matching what was previously in place (taking a photo on the camera before removing the old one). It seems that it didn't resolve that problem.

Any suggestions on what to check and look at next? Boiler is a Potterton Suprima and the hot water tank is a boilermate 3.

Any help appreciated. Cheers

 

[heatservice]

Have you checked the room thermostat has voltage when you select CH at the programmer ?

 

[Steve Ruffles]

Hi. I can see the light showing on the thermostat which goes from red to green based on temperatures (whether reached or below temperature set) so I presume that part is ok. I’ve checked as well the timer on the boiler and have switched that between timer mode and always on top.

 

[Steve Ruffles]

That’s supposed to say “too” not “top”

 

[Hot&Cold]

Could be a few reasons,could be the 3 port valve body partially seized,store/system sludged up,suprima boiler thermostat not set to maximum. Have a look on the boilermate ABC (its where you wired the actuator to) depending on version but has neons which light up when under different operating conditions.
one of the neon's indicates an external call for central heating,have a look in the installation manual to find the appropriate neon and the store temperature read out.
Iirc the manual has some fault finding tip's