Change of control unit – now CH not working no power to pump

[medina]

I’m running an old Gloworm back boiler which has operated without fault for the last 3 years (since I moved in to this house), the control unit used was a Landis and Gyr RWB2 which has a sliding on off switch for both CH and HW accompanied by a large rotating timer (which never worked, I just used to manually switch it on every day).

Recently so spruce the controls up I managed to get hold of a Siemens RWB9, which has an identical backing plate and wiring. I read the instructions, set the slides on the rear to programme ‘16’ which is pumped rather than gravity fed, and pushed the reset button as instructed.

At the same time I replaced the thermostat to a newer looking Honeywell unit.

The new control unit now lights up and you can hear and see it switching on for both CH and HW but on the CH setting it’s not telling the boiler or water pump to come on. HW is working fine. I have reread the instructions and found nothing which identifies why the CH is not working.

I’ve put an electric meter to the water pump to see if it’s getting power as I thought it might have packed up, but there is no power going to it.

Following this I put back the old Landis and Gyr control unit to see if the central heating would come back on. The result was no CH but only HW as per the new control unit.

Has any one got any ideas as to what to look at next?

Any advice would be welcome.

Many thanks.

 

[45yearsagasman]

Have you checked for 230v at the new thermostat when the CH is selected?
Do you actually have a fully pumped system and if so what other controls and valves do you have?

 

[twgas]

next thing is to tell us what type of system you have; fully pumped Y or S plan, gravity HW pumped CH, etc

 

[medina]

Have you checked for 230v at the new thermostat when the CH is selected?
Do you actually have a fully pumped system and if so what other controls and valves do you have?

Yep 230v at the thermostat, and yes its a fully pumped system. As far as Im aware there are no other controls which are present but there is an emersion tank upstairs, but I dont think that comes into paly with the CH not working.

Thanks

 

[medina]

next thing is to tell us what type of system you have; fully pumped Y or S plan, gravity HW pumped CH, etc

Hi, its a fully pumped system. Im affraid I dont not the difference between Y and S plan.

Thanks

 

[twgas]

Y plan has a 3 port valve

S plan has 2*2 ports

 

[mysteryman]

Try it with the selector set to 'gravity primaries' or 'ten position'. Whilst your radiators are pumped, the hot water primaries may be by gravity. This is not a 'fully pumped' system, and the timer needs to be set accordingly. Of course, I could be wrong in this, and there may be another fault...

 

[gavinda]

does the ch work when the hw is on, could be you are missing the 'off' wire from the clock and require the hw to be 'on' on the clock to allow the room thermostat to energise.

you should have connections on n,l,1,3 and 4 iirc.

plus earth

 

[gavinda]

Trolololololololol, trololololol