Pump not working with CH

[confusedchippy]

Hoping this is a simple problem and im being stupid!!
Just replaced the mid position valve on my Y heating system, the old valve was getting stuck open. New valve seems fine, reconnected the wires as per the old valve (replaced honeywell for honeywell). when i turn on the HW everything works fine, pump runs ect. if i turn on the CH and the HW everything works fine, pump runs, rads get hot quickly and if i adjust the room stat down the new valve closes and opens when i turn it back up however if i turn the HW off the pump stops??? the room stat still controls the new valve ie it moves as i adjust the stat but no pump. turn the HW back on and the pump runs and everything works fine.
Any ideas?? to help a confused chippy, give me wood any day lol
bloody pumping's a black art i think!

 

[twgas]

did you change the complete valve or just the actuator (powerhead, as honey calls it)?

 

[confusedchippy]

i changes the whole valve head as well. im thinking maybe although i rewired it as the old one was maybe it was connected wrong when the system was fitted. We only moved in afew months ago so no idea whether it was always like this. I am right in thinking the pump should run with the CH?

 

[45yearsagasman]

Please answer the question:- did you just change the silver head or the COMPLETE valve which would have included the brass body and meant a drain down? If you just changed the head it may be that the old valve body has seized and not allowing valve to travel completely over, and that would prevent pump running on CH.

 

[confusedchippy]

Hi sorry answer didn't make much sense! I changed the complete valve, so brass body and silver box. The old valve had seized so only opening for HW. I reconnected the wires as they were before. Drained the system, refilled again and bleed the rads several times. Could it be the new valve is faulty?

 

[Agile]

If you did not make a mistake then it sounds as if it was wrongly wired in the beginning.

You should check the wiring against the Honeywell schematic.

Tony

 

[confusedchippy]

Cheers for the quick reply, I will double check my connections vim thinking I might rewire the whole airing cupboard anyway as it's rather a mess in there and valve, room stat, control box and feed for the immersion are all connected in one 1 1/4" pattress behind a fused switch for the immersion!! Too say it's rather tight is an under statement. Thanks again at least now I know I'm looking in the right direction
Cheers james

 

[MANDATE]

You would not be as confused if you understood how the valve worked. From what you have said It would seem the valve only moves to mid position and never goes to CH only or if it does go to CH only then it does not start pump/boiler.
If it's not moving beyond mid position, then there is no power on the 'grey' wire coming from the programmers HW OFF terminal. (wouldn't be the first time for wire to be missing)
If it does go to CH only power should leave the valve through the orange wire to fire up boiler/pump. So does 'orange' come'live' and is it connected boiler with other wire from cylinder stat.
First thing to establish with HW off put CH on valve should move first to mid position pause a second and move on to CH.

 

[Space cat]

-- if i turn the HW off the pump stops??? the room stat still controls the new valve ie it moves as i adjust the stat but no pump --

In a correctly wired circuit of this type, you need a demand for HW to power both the boiler and the pump. The valve rests in the HW only position until it gets a demand for CH. It then drives to the mid-position to allow boiler water through to the radiators. Meanwhile, the HW demand is still powering the boiler and pump.

When you want CH only, first of all, the valve must be driven to the mid-position. When it gets there - and only when it gets there - a No-HW demand from the controller (or cylinder stat) will drive it all the way over to the CH position. From what you describe, all of this is happening but maybe you've spotted a problem; with HW demand gone, how do you get the boiler and pump to run?

The answer is that the valve contains a switch that closes only when it reaches the CH only position. This is the one twgas and 45yearsagasman were thinking of, as in:

If you just changed the head it may be that the old valve body has seized and not allowing valve to travel completely over, and that would prevent pump running on CH.

That switch takes the CH demand - the one that got the valve to mid-position - and sends it to the boiler and pump. If you look at the wiring, you might think that this wire sends power from HW demand to the valve but it actually goes the other way. As long as No-HW holds the valve in the CH position, CH demand will control the boiler and pump. The valve doesn't need to move again until it gets a demand for HW.

In your case, something isn't right. For a start, you should not be getting the boiler without the pump. Indeed, some boilers control the pump themselves to provide a timed run-on after the gas goes off. The other things to check are (1) does that switch close and (2) where, if anywhere, does it send the power?

Edit: I see MANDATE just beat me to it.

 

[confusedchippy]

Hi, thank you that's very helpful. Sounds like I need to spend an hour with the multi meter when I get home.
The HW is working as it should, when just CH is turned on the valve does move past the mid position and allows water to enter the rads, if I turn the room stat down the valve closes and if I turn the room stat right up the valve opens again but the pump does not run? I connected all the wires from the new valve but not really sure what I connected them too as I just replaced the old wires. All the connections are made with choc boxes to blue, black and red wires?? Think I need to trace all wires back to work out what is what. So much for a simple swap job lol

 

[Space cat]

The HW is working as it should, when just CH is turned on the valve does move past the mid position and allows water to enter the rads, if I turn the room stat down the valve closes and if I turn the room stat right up the valve opens again but the pump does not run?

Well that's wrong for a start. Once the valve gets into the CH only position, it doesn't need to move again until the No-HW demand disappears. Turning the room stat up and down should only control the boiler and pump. I don't think it's getting to the CH only position; it's only getting to mid-position, which will give you hot radiators as long as you also have a demand for HW. To drive it all the way over, you need a No-HW demand. This is a real wire with volts on it, not just an absence of HW demand.. As MANDATE put it:

If it's not moving beyond mid position, then there is no power on the 'grey' wire coming from the programmers HW OFF terminal. (wouldn't be the first time for wire to be missing)

So there's your first test. Select HW OFF and look for power at the grey wire. There are three ways to do this: HW OFF at the controller, tank stat OFF or both. All three conditions should put power on that wire.

 

[confusedchippy]

Cheers will check that first, I'm thinking given the state of the wiring at the moment it might be as easy to start again and rewire the whole airing cupboard. Really wanted to just check it is not working before I spend all day in there only to find I was barking up the wrong tree! Wonder if I could build a wooden pump and valve, at least then I'd know what was going on lol

 

[confusedchippy]

Right just got home and checked my new valve, as space cat said the valve is only moving to the mid position. with only the CH turned on i can still push the manual lever about 2mm further, when i do this the pump starts up as it should. Im guessing the wire that moves the valve to the CH position is not connected to where it should be!!
Sorry everyone should have checked that to start with, go on plumber's take the mic out of a confused chippy lol

 

[confusedchippy]

Just looked at the wiring again, I connected like for like when I changed the valve and didnt really pay any attention the where the wires went. The Grey wire from the valve which I belive to be the CH one is connected to the earth from the pump??? guessing it has never worked.
Now just have to workout which one of the many blue wires to connect it too, time for the multi meter I think

 

[MANDATE]

blue wires are neutral which come after a electrical 'load'.
The 'grey' wire should be connected to two sources.
First is the satisfied terminal of the cylinder stat, so when HW satisfied it powers the grey instead of the boiler. Of course this means nothing if HW is not on.
Second source is the HW OFF terminal on programmer, so if HW is not on it still powers the 'grey'