Another Motorised Valve / Cold Rad Problem?

[Illmatic]

Hi hopefully someone can help me out a bit here. I've had a search and done a bit of reading up on the subject, but need to ask a few specifics so here we go.

I think I have a problem with the motorised valve on my central heating which is causing the downstairs radiators to stay cold when the hot water is on.
Before I dive in and get a replacement, I would like a bit of advice / confirmation.

My motorised valve is a 3 port Honeywell with the number F4-9511, and it currently (mis)behaves as follows:
The only time I see the lever on the motorised valve move is when (with CH and HW off on the boiler controller) I push it over fully to the open position, then turn the HW on. The lever moves straight away to around the middle position. After this has happened, it stays there, regardless of whether CH, HW or both are on.

If I turn CH on with it in this middle position, the downstairs radiator is cold.

If with both CH and HW on, I then move the lever to the open position, it stays there, and the rad heats up.

I can also get the rad to warm up by turning off the HW. The lever still doesn't move from wherever I position it, but it doesn't seem to matter where it is, the rad still warms up if CH is on and HW off.

The lever never moves towards the open end, unless I put it there.

Hopefully someone's still with me...

As the boiler control only allows me to set the timer for both HW and CH together, I obviously would like the rad to be warm, whilst also heating the water, which is how it always used to work.

Does this sound like a faulty motor unit (which is what I leaning to), or something else? Are there any other diagnostic tests I can do? Pretty sure the pump is working, as I can hear it, and as I say, it is possible to get heat into the rad - just not with the hot water on.

And one more thing, if it is the motor unit, could someone point me in the direction of a suitable replacement, as I can't seem to find one with a matching part number.

If any more info is needed, I'll try and provide it. Thanks in advance!

 

[seco services]

forget the lever on the end doesn't have nothing to do with what the position of the valve is. only there for means of opening the valve when filling the system.

with hw/ch on rads cold
with ch on only rads hot.

sounds like the cylinder is starving it.

As the boiler control only allows me to set the timer for both HW and CH together

so how did you turn only the water off ? and have ch on.

 

[Illmatic]

forget the lever on the end doesn't have nothing to do with what the position of the valve is. only there for means of opening the valve when filling the system.

with hw/ch on rads cold
with ch on only rads hot.

sounds like the cylinder is starving it.

As the boiler control only allows me to set the timer for both HW and CH together

so how did you turn only the water off ? and have ch on.

Ok this is news to me, from what I had read I thought you could change the valve position by moving the lever.

with hw/ch on rads cold
with ch on only rads hot.
is basically correct, although I thought I could get it to heat by moving the lever to open position!

Regarding the boiler controls, prob didn't explain very well. I can individually turn them on and off manually, but there's only one timer - you can't have the heating come on at one time and the water at another.

 

[seco services]

the valve at its relaxed position is hw port open heating closed.

if you fill the system from empty you push lever across and the valve will go into mid position (both ports open) then lets the water circulate and air out.

the lever will only open the valve to mid position. it won't fully open valve to heating open hw closed.

have you a gate valve on the cylinder return ?

 

[Illmatic]

Ok thanks that makes sense.

There is no other valve between the motor valve and the cylinder - just a branch off that goes up to a bleed screw.

There is a valve on the pipe that goes in at the bottom of the cylinder - is this the cylinder return?

Apologies for my lack of familiarity with this - I'm learning fast though!

 

[seco services]

yes thats the cylinder return.
count the amount of turns it takes to open fully or to close.

 

[MANDATE]

The valve on the cylinder return is basically like a lockshied on your radiators.
When the 3port valve is in the mid position water is going to both CH and HW. Water will always take the easiest route it can and the CH side will offer more resistance so it will be easier for it to go through the cylinder coil, So it is a matter of balancing the two sides. If the valve is open too much, you get less through the radiators, especially those further away from the pump.
If yours is a mid position valve and you have both CH and HW selected together, it does not mean the valve remains in the mid position. It only stays there until one of the modes is satisfied and then moves to fully close the valve on the satisfied side and fully open the other side.
In practice the HW will most likely be the first to be satisfied, so the valve will move across to CH.
These 3 port mid position valves do sometimes give problems.
They rely on two different sources of power supply to get the valve fully from HW to CH. One supply gets the valve to mid way and the second supply takes over to move the valve to CH.
You can see a problem with 1st supply or motor will not get valve to mid way. A problem with 2nd supply will not get valve away from mid way to CH.
Sometimes the valve moves exactly as it should, but due to faulty microswitch it fails to provide the power to light boiler.
This baffles people who don't fully understand the valves operation, especally when the boiler gives no trouble when HW only is selected.
This being due to the fact that power in these circumstances comes fro the cylinder stat and not the mid position valve.
You will see many claim they can only get CH when HW is also on, can't get CH only and it's usually a valve related problem

 

[Agile]

The valve on the cylinder return is basically like a lockshied on your radiators.

Well it is if its NOT the cold feed to the cylinder!

The OP can test for that by turning ot OFF ( fully clockwise of course ! ) and then seeing if it stops any flow from the HW tap.

If not then its the lockshield as suggested.

Intitial setting for this is fully closed and them open ONE turn.

Tony.

 

[Homesafe]

cylinder stat. could be faulty and not energising the valve to close to heating, and if it's and old tired pump.....

system dirt is also a factor.

 

[Illmatic]

Thank you all for your replies.
I will check the cylinder return valve tonight when I get home to see how open it is, and also whether when it's off it stops flow to the hot tap.

It looked like I might need a special too to adjust the valve? Does that sound familiar? Sure I can find something to turn it with though!

Is there a way I can test the cylinder stat. to see if that is faulty?

 

[MANDATE]

I think so far all we have to go off is the statement.
(a)With HW/CH on rads cold
(b)With CH on only rads hot.
(c)With HW only not mentioned
If (b) is correct, it means the room stat is ok, it means the valve moves to mid point, it means the valve moves further to CH and it means the microswitch is ok for the boiler to light.
With respect to (a) the cylinder stat provides the power to light boiler, until the HW is satisfied. Without knowing about HW only, it could be any of a few problems.
Is power going to the stat from programmer?
Is the power going across the stat from input to 'not satified terminal?
If boiler operates for (c) ignore these two questions
Is there a wire from satisfied terminal of the stat to the 'grey' wire of valve
When HW is satisfied and stat diverts power to 'satisfied terminal', is the 'grey' mentioned live.
The 'grey' wire has to be fed from two sources. One is the cylinder stat, but what if HW is not on? Another wire comes from the programmers HW OFF terminal.(this wire must be there to get CH only) So regardless there is power from one of sources to the grey to drive the motor when HW is either satisfied or not on.

 

[Illmatic]

I think so far all we have to go off is the statement.
(a)With HW/CH on rads cold
(b)With CH on only rads hot.
(c)With HW only not mentioned
If (b) is correct, it means the room stat is ok, it means the valve moves to mid point, it means the valve moves further to CH and it means the microswitch is ok for the boiler to light.
With respect to (a) the cylinder stat provides the power to light boiler, until the HW is satisfied. Without knowing about HW only, it could be any of a few problems.
Is power going to the stat from programmer?
Is the power going across the stat from input to 'not satified terminal?
If boiler operates for (c) ignore these two questions
Is there a wire from satisfied terminal of the stat to the 'grey' wire of valve
When HW is satisfied and stat diverts power to 'satisfied terminal', is the 'grey' mentioned live.
The 'grey' wire has to be fed from two sources. One is the cylinder stat, but what if HW is not on? Another wire comes from the programmers HW OFF terminal.(this wire must be there to get CH only) So regardless there is power from one of sources to the grey to drive the motor when HW is either satisfied or not on.

Hello, thanks for taking the time to reply. Sorry for not responding sooner, work gets in the way of my amateur plumbing.

Right to answer (c) above, with HW only on, boiler runs, rads downstairs are cold, upstairs lukewarm.

The wiring to the stat appears to be as follows:
Brown Wire (Stat) connected to Orange (Valve) and Red (unknown)
Black/White Wire (Stat) connected to Yellow (unknown)
Blue (Stat) connected to Grey (Valve) and Blue (Programmer?)

HW only on, boiler running: Power on brown stat wire. Also power on Black/White stat wire. No power on Blue stat wire.

HW & CH Off: Power on Blue stat wire only

HW only on, but stat turned right down so boiler not running: Power on blue stat wire and also black/white stat wire.

This to me says things are as they should be with the HW - I am fully prepared to be corrected though!!

To answer other questions posed so far, the cylinder return valve was open 2.75 turns from fully closed. When fully closed water still flows from the hot tap.
I will set this to only 1 turn from open and see if this has an effect. The idea being it restricts the flow through the cylinder so more heat to the rads, yes? What would have changed on the system to need this adjustment?

Hopefully my answers can help with a diagnosis, as if the motorised valve is indeed functioning properly, I am at your mercy for suggestions of what else may be wrong.

Thanks all so far.

Edit - as an additional bit of info, when the HW is off and the CH on, boiler running, there is power on all 3 cylinder stat wires. Is this normal?

 

[MANDATE]

Have to agree it looks ok to me. Seems to be:

Stat input: from Prog HW ON....yellow ...joins black/white to feed stat.

Stat output (a) not satisfied condition, brown wire connects to red to light boiler. When HW not in use or satisfied, valve provides power through orange so it joins the brown and red.

Stat output(b) satisfied condition, power diverted so blue (stat) feeds the grey of valve. Also blue from programmer HW OFF joins these so the grey gets power from either stat or programmer.

regarding the three stat wires all showing live with CH on and HW off, is normal, its the blue from the HW OFF that feeds power back across the stat, but that power can't go anywhere to perform any function.
Am I right in thinking CH only selected (no problem)
HW only selected (no problem).
Problem occurs when both CH and HW are selected and when HW becomes satisfied valve fails to move to CH only.

 

[Illmatic]

That is right.
CH only = all rads hot
HW only = water hot, upstairs rads warm, downstairs cold
CH & HW = water hot, upstairs rads hot, downstairs cold
I'm not certain whether the valve is moving to CH only or not. I thought I would see the lever on the valve move, but apparently this is not the case.

I tried setting the cylinder return valve to one turn from closed, but no change.

Thinking about your explaination of the system, MANTDATE, I'm not sure I have seen the stat output go to satisfied without turning the stat right down. With it in its usual position (about 55deg) there always seems to be power on brown and black/white.

Could this mean that the cylinder stat is never changing to satisfied, so the valve never moves over to CH? Is this likely or even possible? As I say, it works when I turn it right down.

It may be that I haven't left it long enough to reach satisfied temp before I check power on the wires. Presumably if the boiler turns off that is HW satisfied? I will investigate more tonight.

Thanks.

 

[MANDATE]

That is right.
CH only = all rads hot
HW only = water hot, upstairs rads warm, downstairs cold
CH & HW = water hot, upstairs rads hot, downstairs cold
I'm not certain whether the valve is moving to CH only or not. I thought I would see the lever on the valve move, but apparently this is not the case.

You won't see the lever move. The motor dosn't move the lever, it leaves it behind. The lever is there to move the valve to mid position for filling purposes and to do that it has to move the motor and thats when you feel the resistance of the 'geared' motor which is also working against the return spring.

When the valve is required to move on from mid position, the valves grey wire has to be made 'live'. There are two situations to cater for.
(a) HW is not on. The HW bit of the programmer is like a two way switch. There is no live feed to the cylinder stat from HW ON terminal, but there is now live feed from HW OFF terminal, this is your blue leading to grey.
(b) The above wouldn't function if HW was ON, so the cylinder stat is also like two way switch, so when HW is satisfied power is diverted to the satisfied terminal where another blue wire provides the power.

Like Newgas suggested the cylinder stat could be at fault or poor connection on the blue wire, that is if the valve is not moving across.
Having said that, have you tried feeling the pipes 1ft either side of the
valve. If you select both HW and CH from cold both pipes should feel the same, then turn HW stat down. Valve should move to CH only and feeling the pipes again should show some difference.