Newbie - problems with 2/3 way valve

JM2

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Retired in:- Nottinghamshire
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Hello all.

Bit long but I want to include everything.

Whilst heating system *appears* to be working okay my motorised valve isn't happy if HW & CH demanded together. It continues to click every 2-3 seconds - surely this isn't right. Or is it ??

It switches across to CH is that's all that is req'd. Works on HW as req'd. On both seems to do both. Small plastic lever moves okay when operated electrically. If on HW I can move it manually to CH too and it starts to warm the rads - it returns to HW as expected.

I can't tell the model of the valve as tight for space and faces into a wall! I don't even know if it is a true 3-way or just a 2-way valve. It has a 4-core plus earth cable at the junction box nearby.

System is older style boiler (Elan xxx), micro-proc controller, hot tank, pump & valve, tank stat and room stat. As fitted/programmed it does not run CH without HW enabled. If both are demanded, both work but when HW is warm enough it does shut down before CH resumes on its own.

I'm sure unrelated but a while ago we had 2 long power cuts and the controller gave me grief as the internal battery died and getting into the controller was something of a challenge (nearly used the hammer). All better now (though must change that battery still) but I have been 'in there'.

Small (70k) pic of the airing cupboard pipework is at http://www.hiddengems.btinternet.co.uk/hosting/heating1.jpg is anyone can clarify my unknowns. Not tackled the current wiring diagram yet ! Other than I seem to have a change-over type tank stat which surprised me.
 
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Your system appears to be a 'Y' plan using a 3port mid position valve.
The cable will most likely have wires coloured white, grey, orange as well as blue (neutral) and green/yellow (earth).
The valve is driven forward by a spring return motor starting from the HW position.
The room stat powers the white wire which powers the motor up to mid position when a micro switch is triggered.
If CH only was selected and in demand the grey wire (connected to the same micro switch) would be live and it would take over from the white to power the motor forward to the CH position.
When both HW and CH are selected and in demand the valve moves to the mid position but in this case the grey is not live so it can't move any further.
What happens here is that a pcb produces a modified voltage which is not strong enough to drive the motor forward, but strong enough to stop it returning to HW position.
I think in your case this modified voltage is not there, so it does drop back a fraction. The micro switch is triggered and the white wire being live sends it forward again and the whole process is repeated.
All this takes place with very little movement at mid position and what you hear is the micro switch making and breaking the contacts.

When CH and HW are selected and both are in demand and the valve takes up the mid position, it only stays there until one of the demands is satisfied. Usually that will be HW. This is where your change over type stat operates. It diverts the power going to boiler to the grey wire of the valve, and its the grey that powers the motor over the second half of the range.
You may not realize it but this closes down the boiler for a second, until the valve has moved and a second micro switch the powers to the boiler through the orange wire and it re-lights.
 
Sounds well described - thanks.

So you doubt the 3-way is faulty.

Which line would you expect the hold/modified voltage to be on? (white?)

I've start drawing the wiring at the w/end; certainly grey/white/orange/grn-yel, I can't remember if blue was there or not.

I thought all these were mains up or off lines, hadn't realised might be modified, so could indeed be boiler PCB. However, following my trials with the heating programmer unit (potterton e2001?) might I have broken something there I wonder.

The wiring in my house was unfinished by monkeys, I am still finding problems many years later. Indeed, whilst looking at the pump/valve/stat wiring the 'orange' fell out - thought I'd cracked it but alas it only fell out because I was there). That said I believe this is a new fault (not that I've ever played with that valve before).
 
Both micro switches are like two way switches (two sets of contacts) but not both wired the same.
Sw A has 1 input from white wire(from room stat)and
1 input from grey wire , which comes from two sources ie cylinder stat when satisfied, or if HW is not switched and therefore cylinder stat is non active it comes from programmer HW OFF terminal.
There is just 1 output to motor, so when switch is operated it toggles from white wire to grey wire. What happens depends on the state of the grey wire.
If live it takes over from the white and valve continues, if not the modified holding voltage comes into play.
SwB has 1 input, again from the white wire (but has two outputs)
!st output is to a small pcb (not the boiler pcb) which produces the modified holding voltage.This is fed to the output terminal of SwA. The wire going direct into the motor carries both the 230v ac and the holding voltage. When the 230v ac is dropped it leaves the holding voltage, but as stated above it all depends on the state of the grey.
If the grey is live and the valve moves on, the SwB is triggered and it diverts the power from the pcb(no longer required) to the other output terminal which is the orange wire to light the boiler.
Whenever there is a 'load' (motor) there has to be a neutral (blue).
To me, If the valve/quadrant/motor has moved to mid position and it's not receiving the holding voltage it can't stay still, it cant'go forward(no live grey) Spring wants to return valve/quadrant/motor so it drops back towards rest position, but micro switch toggles over to white wire which is still live so its driven forward again. That to me would explain the clicking every 2 or 3 secs.
The pcb itself may not be at fault, cause I had a problem with everything working OK except bad contacts on micro switch meant no output on ogange wire.
 
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Sorry I was there up to a point.

Is this PCB in the motorised valve or somewhere I've not spotted yet?

I've drawn my wiring out here http://www.hiddengems.btinternet.co.uk/hosting/heating2.jpg but didn't prove the earths and noted one of the STAT wires a N (I think I meant to write B blue).

Everything else sounds spot on.
Do I need to measure the voltages/check live at these points during various demands or not be able to tell.

If the mini-PCB and SWa and SWb (are these the c/o microswitches?) are all in the valve unit should I get that changed as a complete unit ?
 
Yes the pcb is in the actuator head of the valve along with the two micro switches. There are a couple of cams on the quadrant so it triggers the first switch at mid position and the second one a little further on.
As far as I know most actuator heads are removable and can be replaced.

Regarding the wiring of the system, think of 3 wires (ignoring earths and neutrals at this stage)leaving the programmer from HW ON......HW OFF...and CH ON

The wires can't be wired direct and a terminal box will be used.

HW ON wire will go to the common on the cylinder stat.
then wire from cylinder stat (not satisfied terminal) to boiler/pump
Also wire from cylinder stat (satisfied terminal) to the grey wire of valve.
This is what drives the valve on from mid position when HW is satisfied.

HW OFF wire will go join the grey mentioned above. This is required to drive valve forward when HW has not been turned on.

CH ON wire will go to room stat and from room stat to the white wire of valve.

Note: It's the cyinder stat that powers the boiler for HW and HW/CH but for CH only power comes from the valves orange wire. Of course the orange will be joined up with wire from cylinder stat so the boiler can operate from both sources.
The wires from HW ON and HW OFF can't both be live at the same time.
If you use the search facility for 3port valve you'll find lots of information
Hope it helps
 
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Very helpful indeed, many thanks.

Decided a microswitch contact or maybe one of the resistors has failed. Looks identical to the drayton mid position valve (says lifestyle on it). Unfortunately I can't get the cover off in situ as no room (even drilled the wood above to release the retainer screw!) - older type, no quick release.

So it'll have to be replaced complete & draining the system (aghh).

Anyone recommended in the Newark on Trent area ? ....

PS. Didn't see anything else on the Grey (HW OFF) just the hw stat (satisfied?).
 
Regarding the two wires (1) from HW OFF terminal and (2) from satisfied terminal of cylinder stat.
They could be joined to the grey in the terminal box, or (1) above may be joined to (2) at the cylinder stat. which amounts to the same thing
Whichever way both are needed for the valve to operate correctly.
It does appear however that there has been quite a few reported on this site that the wire from HW OFF has been omitted
 
Can you see my revised diagram here please http://www.hiddengems.btinternet.co.uk/hosting/heating2.jpg

grey connects only with g/y (poor choice) of tank stat.

My programmer is set so that I can't have CH only - I think there's a hidden switch inside that does this - perhaps they've skimpt on a wire run.

Does this affect my fault?

Away at weekend but must trace these back at the programmer/Room stat I don't see why I've Y-R linked unless cable1 Y is CH ON and cable 2 goes back downstairs to the rm stat.
 
regarding your diagram. The HW ON side is OK although 'green/yellow' could be mistaken for 'earth' and 'blue' could be mistaken for 'neutral'.(not the best choice of colours)

As you know the 'grey' is only showing one feed from the cylinder stat. so is the HW OFF wire missing, or does it join it at the stat.

As you realize the 'red' from cable 2 is linked to 'yellow' from cable 1 and these need tracing to find source.

The one that puzzles me is the 'red' from cable3 that joins the 'orange'. The boiler/pump already has provision from both the cylinder stat and valve, so this should not be there.

This 'red' can't be the missing HW OFF wire. because it would be live when HW is OFF and boiler would never shut down, so this also needs investigating
 
Hope no one mind these posts;

Yes, Y/Gn very poor choice for switched live - not my wiring/colour scheme/efforts.

Traced out the rest tonight. Took me by surprise - I'd DL'd manuals, diagrams etc for the options. Opened up the programmer to find little wiring. They've been cheating big time here (some years ago I expect).
I've updated http://www.hiddengems.btinternet.co.uk/hosting/heating2.png

No HW OFF as thought - it works with HW being locked on, fair enough doesn't cause problems selection wise. So long as that isn't the cause of the failure. I'd hoped to rewire a blue (N) off to act as HW OFF but alas nothing spare.

The loop back is to the room stat.

The Red from Orange is the boiler! The boiler doesn't connect into the programmer as expected.

I must add, I'd never have designed a control system that uses the sensors to do the work - looking at my diagram the boiler feed goes round the house/s to get fired, no wonder I suffer from clicks, pops and bangs on the radios.

Before I get this mid-p valve changed (needs draining) can you check this odd wiring scheme is not the cause please, ie. HW & CH demand should still hold the valve mid-way. I'm happy to find this is just a straight failure (micro-switch or component) as the valve unit will be about 18-20 years old but seems daft to replace it if the scheme is at fault.
 
Just looked at your revised diagram.
Seems correct to me, except for the HW OFF wire.
You'll still get CH providing HW has been selected.
If HW is satisfied CH will receive the full flow of water.
If HW has not been satisfied then the flow will be shared.
Just means if you selected CH only valve would move to mid position and no further (due to no HW OFF) and of course boiler would not light from cylinder stat (no HW) or valve.(not far enough to trigger micro switch).

If the small pcb in the actuator head is faulty or its not receiving power through the micro switch (dirty contacts) then the quadrant can't be held in equilibrium. Momentum will take it forward a little, but with nothing to hold it, it will drop back and receive 230v from the white again which will result in a continuos clicking of contacts
 

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