Only getting heat to radiators when there is demand for hot.

[Fwapp]

Hi Guys,

I'd appreciate your help in trying to solve my problem.

About a month ago, we woke up to no heat from the radiators. I moved the lever on the 3 way valve, and got some for the morning. When I investigated further i found the following.

When there is call for heating, with no HW, the 3 way does not move to the correct posistion, and will move back to the home posistion, when moved manually.

When there is call for heating AND HW, the 3 way will move to the heating/HW posistion. However, if the HW cylinder stat is satisfied, the pump will turn off immediatley, with valve in the heating/HW posistion.

I replaced the 3 way yesterday, and the problem is the same (now have a spare 3 way!).

The overall control (Landis Steafa programmer, honeywell turn dial analog room stat, honeywell cylinder stat, Thorn apollo 40 boiler) has been in place for about 7 years, apart from the boiler which has been in for about 15. Pump over run is connected.

My question is, what do you think the problem is, and how would you prove it? I feel it may be the programmer, but would like to prove it out first. I do have a radio room stat (Danfoss RX3) I could install but do not think that would benefit at the moment. Any help would be warmley received, and being an electrical guy, have no problem with that side of things.

 

[corgiman]

what part of the "3 way" did you change?

 

[Fwapp]

The entire unit, motor and valve, as a wholesale replacment.

 

[corgiman]

what make of valve is it?

 

[Fwapp]

Hi,

Went from a Landis MAV322 to a Horstmann Z322XL

Fault was the same on both valves, the Landis one having worked OK for the previous 7 years.

 

[corgiman]

I am not sure of the colours on that one but check that you have 240v on the central heating demand wire.

 

[Fwapp]

Hi,

Have 230v at the central heating demand wire, and the valve moves to the correct posistion. The pump is not brought on though. The pump runs if HW is demanded. I think the pump is brought on via the Boiler (A thorn Apollo 40b)

 

[gas4you]

Have you got 230V on the orange wire coming out of it?.

Don't know this Horstmann in particular but some 3 way valves need 2 lives to them to shift the valve into ch mode.

I would check the timer again