W-plan pump run on

[Basher]

Not sure this is the exact correct model, but likely similar
Mains from the FCU connects to the boiler at one block.
There is a separate connection block to accommodate a live (out) supply to eg thermostat , a switched live (in) from eg thermostat, a neutral etc etc as below simple example.

Ls is live supply (out). Lr is switched live (control in)

So the Boiler L in the diagram above (post #34 yellow and grey wires) should actually be Lr in the boiler. Hopefully it is like that already.

 

[davidwf]

Again thanks for the prompt replies.....I will check I all out when i next go over ......and will of course report back 😁

 

[davidwf]

right.....having gone through all the connections it appears that on the cylinder stat, C & 1 were reversed....the stat is actually marked 1,2,3 rather that C,1,2 which might explain it
I have corrected this and re-drawn the actual installation as it is, I also fitted a new Drayton home battery operated programmable thermostat just to eliminate that
When I tried it yesterday it all seemed OK but was later advised that after the water had been on the rads were still getting hot at the top - suggesting a short run rather than being on all the time
The diverter valve is new and moves and seals OK

 

[Basher]

As far as I can see, the only difference the reversal of C and 1 would make, is that the diverter valve would be permanently powered once the cylinder stat is satisfied, irrespective of whether timer is on or off.
Having corrected the C/1 swap, the diverter is no longer powered once the timer is off.
So I hope residual boiler heat won't now be continually pumped around the rads as before, but it seems there's still something of that effect?

Well done for finding that wiring feature!

 

[davidwf]

yes....but if the diverter valve IS / WAS being held open that would explain the residual heat around the rads whilst the pump was over-running......it is only a small house with small rads
I will do another check in case I have missed something but, with it operating as it should, there's no way the residual heat CAN circulate around the rads is there.......unless the pump pressure is keeping the valve open but that is unlikely
"feature" indeed 🙄

 

[Basher]

yes....but if the diverter valve IS / WAS being held open that would explain the residual heat around the rads whilst the pump was over-running......it is only a small house with small rads

Yes absolutely!

I will do another check in case I have missed something but, with it operating as it should, there's no way the residual heat CAN circulate around the rads is there.......unless the pump pressure is keeping the valve open but that is unlikely
"feature" indeed 🙄

I don't think you've missed anything! Now the diverter should return to hot water position when the programmer/thermostat are off, so hopefully no spurious heating any longer 🏅.
I was just slightly surprised by the report that rads were still getting hot at the top after water heating, as the diverter surely shouldn't operate if heating isn't called for 🤔

 

[davidwf]

So was I 😅......it is possible that I have mis-wired it again as even I got confused with the C/1/2 and 1/2/3 labelling and have also swapped the colours around to try and simplify (!!!!) things

 

[John.g]

So was I 😅......it is possible that I have mis-wired it again as even I got confused with the C/1/2 and 1/2/3 labelling and have also swapped the colours around to try and simplify (!!!!) things

What is the cylinder stat exact make and model?.

Did you do the basic test of feeling pipe A (should be cold/cool) when HW calling and boiler firing and should remain cold/cool on pump overrun.

 

[davidwf]

not sure of exact make but it had the terminals marked 1-2-3 .... looks identical to this one (attached)
....yes, at least whilst the HW was on the pipe seemed to remain cool
will check again when I can get over there....again 🙄

 

[Basher]

Someone got confused when writing the instructions!🤔🤪

 

[davidwf]

I wondered about that...... but I think the printed version is correct....
so C & 1 are connected when it is calling for heat i.e. when the water temp is lower than the set point
when it is satisfied contacts C & 2 will connect as per my diagrams
...it all depends on what they are calling normal.... in my opinion, normal is whan everything is satisfied co normally open would be C & 1

 

[John.g]

I wondered about that...... but I think the printed version is correct....
so C & 1 are connected when it is calling for heat i.e. when the water temp is lower than the set point

Looks that way to me, so, in the installed stat. 1&2, (where 1 is "C" & 2 is "1") are made when the water temp is < the SP, I would turn up the stat fully and check for continuity between 1&2.

when it is satisfied contacts C & 2 will connect as per my diagrams
...it all depends on what they are calling normal.... in my opinion, normal is whan everything is satisfied co normally open would be C & 1

then turn the stat fully down and check for continuity between 1&3.

Also check that pipe A remains cold on the pump overrun, if so, the only other explaination I can think of is some form of reverse circulation.

 

[davidwf]

Apologies again for the delay in response.......I have been pretty much laid up for 8 weeks with sciatic pain 🙄 but its finally easing.....

I have just re-checked EVERYTHING
The system IS wired as per my latest diagram in post #38
The cylinder stat operates correctly with continuity between C & 1 calling and C & 2 satisfied
The connector block wiring is all correct as per diagram
The diverter valve doesnt seem to be leaking or bleeding to the rads circuit in its' closed / normal position, it ONLY moves when the roomstat is calling for heat and returns to normal position when the roomstat is satisfied
The pipe from the diverter to the rads ONLY gets hot when it should
The pump overruns for approx 5 minutes during which time, with the roomstat satisfied, no heat (correctly) goes through the rads
With the HW satisfied and the roomstat calling, all the heat goes to the rads
With the roomstat calling, if I turn up the HW stat to calling the diverter valve closes and diverts all the heat to the HW
With the roomstat calling, if I turn it down to satisfied the diverter valve closes to its normal position (HW)

So, as far as I can see it is all physically, mechanically and electrically correct and functioning as it should......time, as they say will tell

 

[John.g]

Post #38 shows wire blue to C, brown to 1 and black to 2 (on the stat) but your stat is numbered 1,2&3? so what colour wires go to these numbers?.

 

[davidwf]

not sure why they have labelled it as normally closed.....it is closed whilst calling for heat, exactly as shown

 

[Basher]

not sure why they have labelled it as normally closed.....it is closed whilst calling for heat, exactly as shown

That is standard nomenclature. The contacts "normally closed" are connected when the thermostat is not doing anything, i.e. not hot.
When heat is applied, i.e. the system is activated to produce heat until the set point is reached, then the contacts will eventually open and the heating stops.
If you called them 'normally open', and you connected those contacts to the heating, nothing would happen!

Same with a relay. "Normally closed" means the unactivated state.
I was just brought up with this convention in electronics, and don't understand the issue!

 

[davidwf]

surely "normally" equates to satisfied - i.e. the water HAS heated up and no further action is needed....so in its' normal state it is satisfied .....the connections and make / break indications are correct, just the nomenclature is confusing
in a roomstat the contacts are normally (i.e. satisfied) open, closing when heat is required
we could probably argue and counter argue this until the cows come home.....😁

 

[davidwf]

the only other thing I can think of - but dont understand why - is that the 15mm bypass gate valve around the pump was open about 2 turns
As the system has no TRV's I have fully closed this now.....could it have possibly affected anything ?
I understand WHY it is provided on a system with TRV's but not in this installation........this is a W-plan system remember so surely as the diverter will be either HW or CH (or, if it ever gets stuck, somewhere in between as was the original issue) and with no TRV's fitted to any rads there is no need for a bypass valve / loop as the water will always have somewhere to circulate

 

[John.g]

This is similar to your one, I think the description might be less confusing if it just left out the "Normally" and describe it like on the EPH pipe/cylinder stat.

 

[John.g]

the only other thing I can think of - but dont understand why - is that the 15mm bypass gate valve around the pump was open about 2 turns
As the system has no TRV's I have fully closed this now.....could it have possibly affected anything ?
I understand WHY it is provided on a system with TRV's but not in this installation........this is a W-plan system remember so surely as the diverter will be either HW or CH (or, if it ever gets stuck, somewhere in between as was the original issue) and with no TRV's fitted to any rads there is no need for a bypass valve / loop as the water will always have somewhere to circulate

One could understand if the bypass was between the boiler flow and return because (on a Y plan anyway) a separate 2 port Motorized valve is supposed to be installed additionally on the cylinder coil because it fails shut whereas a MPV or Diverter valve will fail open to the cylinder.

 

[davidwf]

This is similar to your one, I think the description might be less confusing if it just left out the "Normally" and describe it like on the EPH pipe/cylinder stat.






View attachment 95025

thanks....
yes, so my diagram and wording is correct....c +1 calling, c+2 satisfied..... maybe just that wording would be simpler

 

[davidwf]

Well I dont know........having previously tested and fully confirmed correct operation I was confident it would be OK.....which it seems it has been for a while but yesterday I got "the call"........and sure enough the rads are getting hot when the HW is running and the wallstat is off 🤬 ...I have also replaced the wall stat for good measure.
The motorised valve appears to be operating as it should - I haven't removed the cover but the indicator lever seems to be moving correctly but the CH pipe is definitely getting hot.
Wondering now if it's worth doing it properly and converting to fully pumped Y plan .......I THINK it will only need re-wiring (and of course a new 3 way valve) and I would fit a programmer at the same time ..
the only thing I can think of is that the valve is sticking or is not sealing due to debris but the original water was clean and I drained and refilled it adding Fernox anyway..
..
....any better suggestions ?

 

[John.g]

Well I dont know........having previously tested and fully confirmed correct operation I was confident it would be OK.....which it seems it has been for a while but yesterday I got "the call"........and sure enough the rads are getting hot when the HW is running and the wallstat is off 🤬 ...I have also replaced the wall stat for good measure.
The motorised valve appears to be operating as it should - I haven't removed the cover but the indicator lever seems to be moving correctly but the CH pipe is definitely getting hot.
Wondering now if it's worth doing it properly and converting to fully pumped Y plan .......I THINK it will only need re-wiring (and of course a new 3 way valve) and I would fit a programmer at the same time ..
the only thing I can think of is that the valve is sticking or is not sealing due to debris but the original water was clean and I drained and refilled it adding Fernox anyway..
..
....any better suggestions ?

On HW only, actuator unpowered, you should feel a fairly stiff resistance immediately on pulling on the manual lever, if you do and IF the actuator is attached to the valve spindle then the valve must be positioned correctly to port B (HW), so either the valve is passing or there is some form of reverse circulation, you could just remove the actuator and ensure the valve manually to port B only.
You say "the CH pipe is definitely getting hot.", I would expect the CH pipe to get hot due to conduction (if copper) for a maybe a foot or so but wouldn't expect even the rad tops to become hot.
You might try and see where the cyliner coil returns to the boiler and its position in relation to the rad returns.

 

[davidwf]

Thanks but no, the pipe is getting HOT....... bloody hot....its more than simple conduction along the pipe

 

[davidwf]

IF I do decide to change it to Y plan are there any recommendations or avoids regarding makes.....would like to avoid the cost of the Honeywell one if possible but clearly don't want to be replacing it again next year because I bought a cheap one.

 

[ShaunCorbs]

S plan it eph

 

[davidwf]

Too much re-work....its only a small 2 bed house and the y plan would be so much simpler to install

 

[John.g]

Look up MOMO mid position valve, these apparently are only powered while changing position or modify a normal MPV, it will then allways return to the unpowerd state, only requires a extra relay.

 

[davidwf]

thanks.... that looks interesting rather than having the motor in a stalkled position 99% of the time.....they seem to be quite rare though
Can anybody recommend / avoid a "normal" spring return one ...

 

[John.g]

thanks.... that looks interesting rather than having the motor in a stalkled position 99% of the time.....they seem to be quite rare though
Can anybody recommend / avoid a "normal" spring return one ...

You can see if you read through the attached Link that the MOMO actuator contains far more circuitry than the conventional MPV, I definitely know that the modified MPV above, (I actually got that nice schematic from the attached Link), certainly seems to extend the MPV lifespan as a very old electrical friend of mine did this very mod years ago, he has since passed on but the MPV is still there and must be ~ 15 years old now. You have a electrical background? so should have no problem in implementing it. Some, mistakenly think that just programming on the HW last thing at night for a few minutes is enough to power down the MPV and it will, but only if the cylinder stat is also, very unlikely, calling, there should be at least a 6/7 hour powerd off state alone each night with the mod since CH is normally the last port of call at night.

Motorised Valves - DIYWiki

wiki.diyfaq.org.uk

 

[davidwf]

thanks but......for simplicity I think I would prefer to go with a conventional 3 port spring return motorised one
Which to avoid though ????

 

[John.g]

thanks but......for simplicity I think I would prefer to go with a conventional 3 port spring return motorised one
Which to avoid though ????

Honeywell, I believe, were the go to product at one time but maybe not so much now, I hear good reports of EPH though.

 

[exedon2]

We use eph stuff all the time very reliable but I still wouldn't fit a 3 port valve.
Your draining down and saving £30 against two 2 ports ain't worth doing .
Y plan = shorter lifespan and more difficult to trouble shoot.

 

[davidwf]

OK, I get the idea (and potential benefit) of S plan and I would be quite capable of plumbing it myself....but....the boiler has an overrun that pumps for around 4 mins.....I already have a manual bypass valve (which is closed as there are NO TRV's in the system) but the bypas loop is literally a 15mm bypass around the pump so surely there will be insufficient "loss" in the simple pipework to dissipate the heat?
As it is, the overrun will pump around the HW circuit
and.... 2 x zone valves are considerably dearer than an EPH mid/3 position one which I can get for £65

 

[davidwf]

any thoughts regarding the bypass loop ?