Radiators always heat up with HW

[scott1981]

After a bit of research this seems to be caused by the 3-way valve in the airing cupboard (it's a Honeywell 40003916-003). When I turn the controller to HW only both output from the 3-way valve heat up (which would explain why the rads get hot).

What I don't understand is the metal lever on the bottom of the valve, how is it meant to move, and can I manually move it to close off the CH side? I tried to move it and it seems free for the half towards "auto" but if I push it the other way it sounds like a servo is moving inside (it's harder to push).

At the moment I just want HW without the CH boiling the house!

 

[seco services]

Sounds like the ball is faulty or the port is full of crud stopping the ball fully closing the ch port.

No you can't move the lever to close the ch port
The lever opens the ch port and puts the valve in mid psition.

 

[Blagard]

Did your problem start after a period when the system was working properly or is this something that has always been happening and you are now trying to fix ?

 

[scott1981]

I really noticed it after we had the boiler replaced. Thinking about it the bathroom radiator used to get warm whenever the HW was on, but it was never an issue. I've called the company that did the boiler replacement and they're coming to look, they mentioned around £150 to replace the valve.

Is there any way to check the valve is getting the correct signals? When I turned the room thermostat up to activate the CH I couldn't hear anything moving from the valve - should I be able to?

 

[D_Hailsham]

Read How a mid-position valve works, which tells you how to diagnose faults with the valve.

The number you quoted is just the part number of the actuator - that's the box part, which is replaceable. The complete valve is known as a V4073A.

 

[scott1981]

Excellent reference - exactly what I failed to find before. Thanks.

Update: Took the cover off the actuator and gently "helped" the spring to close a bit with a screwdriver - it closed a few mm further than it would alone. For now it's fine, I'll see what happens in the winter when I need the CH.

 

[scott1981]

I had a bit of a further fiddle about and I'm confused. The guy who fitted the boiler came to look, told me the electrics were wired fine and it was the mid position valve that needed replacing.

However after a bit of researching I decided to check the valve was getting the correct signals. See photo below of my setup. First I checked the valve and it was working ok for the HW (live on orange, 0V on grey and white), but then it didn't seem to respond to any CH demand. The white wire was always at 0V with all combinations of room stat and programmer settings. This seems wrong?

Next I checked the programmer terminals, the one labelled HW ON switched between 0V and live with the programmer setting, but the CH ON one just stays at 0V no matter what I select on the programmer.

Does this mean the wiring is wrong somehow, or could a faulty valve cause this behaviour (by pulling the white wire to 0V somehow)? I don't want to try and argue against what the installer said without some confirmation or some other things to try.

Untitled

• scott1981
• 31 Aug 2011
• 1

 

[seco services]

One wire that's missing is the hw off in the programmer terminal block.

 

[scott1981]

The programmer doesn't allow the CH to be on without the HW, and the grey wire to the mid-pos valve is live when the cylinder stat is satisfied (assuming HW is on at the programmer), so I think this is ok?

Tonight I'm going to connect the white and grey from the valve to live and check it works as expected. If this is ok then I suspect the wiring under the boiler is incorrect somehow (the programmer is next to the boiler and all the wires go into a junction box).

 

[D_Hailsham]

The programmer doesn't allow the CH to be on without the HW,

Which programmer do you have (make and model no)?

If you don't know just post a pic.

 

[scott1981]

It's an RWB9 (branded as Landis and Staefa), whilst it looks like you can set CH by itself, the unit won't let you select CH without HW being on first.

I just wired up grey+white to live and it seemed to work as expected (boiler fired up and only CH side of the valve got hot). This seems like there is a wiring error downstairs, no?

 

[D_Hailsham]

It's an RWB9 (branded as Landis and Staefa), whilst it looks like you can set CH by itself, the unit won't let you select CH without HW being on first.

Remove the RWB9 from the backplate (loosen the two screws underneath).

Check the five small switches (dipswitches) on the back.

The first four determine whether you have two on/off periods a day or three. Number five switches between gravity (down) and full pumped (up).

It should be up for your system.

I just wired up grey+white to live and it seemed to work as expected (boiler fired up and only CH side of the valve got hot). This seems like there is a wiring error downstairs, no?

Yes!

There should be a wire from terminal 1 of the RWB9 to Programmer HW OFF in the Wiring Centre.

 

[scott1981]

Seems like I fixed it, when I looked in the junction box under the boiler there was a loose wire that had obviously come out of the connector block. When I traced it back it indeed came from the CH-ON terminal at the programmer. Connected it back up and works a treat. I guess when the installer pushed the junction box back up under the boiler it came out...

As for the RWB9, it is indeed set for a gravity fed system, but there are no spare wires to hook up an additional link between downstairs and upstairs for HW OFF signal. Could it have been gravity fed originally and upgraded at some point, and the installer not bothered to feed an extra wire through?

 

[D_Hailsham]

Seems like I fixed it, when I looked in the junction box under the boiler there was a loose wire that had obviously come out of the connector block. When I traced it back it indeed came from the CH-ON terminal at the programmer. Connected it back up and works a treat. I guess when the installer pushed the junction box back up under the boiler it came out.

Checking the wiring is always the first thing to do!

As for the RWB9, it is indeed set for a gravity fed system, but there are no spare wires to hook up an additional link between downstairs and upstairs for HW OFF signal. Could it have been gravity fed originally and upgraded at some point, and the installer not bothered to feed an extra wire through?

Sounds like a converted gravity system.

Either he didn't bother or he couldn't. Whichever it was, he should have informed you.

I would speak to him about all three faults: loose wire, missing wire, dipswitch setting, and see what his excuse is.

Have you changed the dipswitch to pumped?

 

[scott1981]

The system must have been converted before I bought the house, all we had done was the boiler replacement (the controller was exactly the same with the old boiler).

He's coming back to finish off an unrelated piece of work, I'll quiz him about the loose wire and general wiring then.