Central Heating - How the mid position Y plan 3 port valve works
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- Опубликовано: 28 дек 2015
- Part 4 in the heating wiring series covers how the 3 port mid position valve works internally, allowing 3 separate positions from only 2 mains inputs.
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Forget about the mysteries of the expanding universe, JW finally reveals with laser clarity (as always) how this tricky little valve works. I had only pondered this question for the last 30 years 😆😆👍❤️
Thank you. I’ve been a heating engineer for nearly 30 years & had no idea it was this involved inside.
gasmanrus: Yeah, it's absolutely mind-boggling!!!! It's just a small box but yet it's like a whole universe going on in there. Or, could even be a tardis, Lmao.
It is not everyday an engineer is enlightened by the function of Motorized 3 way valve coming from a video on RUclips. I wonder if I collect garbage I would be a sanitation engineer, curious..
@@Preciouspink only if you were paid to do it. If not, you’d just be an odd ball.
Having watched many RUclips videos and experienced many varied methods of delivery, I can confidently say that John is the very best so far.
Perfect content, good speed of delivery, obvious total and effortless knowledge of the subject, crystal clear camera with no focus hunting or other undesirable traits.
So good in fact, it makes you watch subjects you already know about just because they are so interesting. Brilliant!
Agreed. John’s content is near perfect if not so.
All these years as a plumber, and I never fully understood the the way these function.....fascinating! Thank You :) ....
Very interesting & useful.
My mid port valve recently started playing up - when only calling for HW I noticed the CH was getting hot!
Got a new port valve head and all is well - but following your video I checked the two micro switches and one wasn't switching off! I'll fix it and leave it in the garage for if/when the new one head fails!
This is a superb explanation. I am replacing the actuator on a 3-port valve and wanted to check that the wiring colours were correct so thought I should understand what was going on. Even though an electrical engineer myself this excellent description still gives me a headache. I think I shall just replace like with like and cross fingers that the valve head manufacturer is using the same wiring colour convention as for the valve head I am replacing.
Thank you for a clear explanation for someone (me) who isn’t electrically trained. Brilliant…
I just want to add my thanks to JW for his very helpful videos on central heating. The one on the mid position value has been invaluable. It has given me the basic knowledge and confidence required to: safely replace a faulty valve; replace an ageing programmer and thermostat with a Hive device; and understand why the valve remains on H despite the heating being 'off'. Thanks again and happy New Year (for 2021).
Thank you for taking the time to make this video. You have done an excellent job of explaining the mid positioning of valve. This has helped my understanding of mechanical process and electrical operation greatly. I am not a plumber but I am a electrical engineer, now I am confident in modifying my central heating pipes and valves of a old house to suit my needs. Thanks again.
Thanks so much. I now understand why the valve remains energized after the CH has been used until I power-cycle the whole system. I thought this was a fault in the wiring or valve :-)
The best exploration of wiring c/h systems i have come across
What a lovely stream of consciousness. Faultless delivery. Bravo.
Brilliant ! The mysteries of the Y plan 3port valve explained in easy to understand, concise and precise language, thank you !!
Absolutely brilliant video, thank you John. I had often wondered why my valve is constantly consuming power in the heating position even when my boiler is off, I often used to wonder why it didn't just spring back to the hot water position, but now you've explained it perfectly. It does seem quite wasteful but as you say it's only a few watts. However, if you add up all the valves in the country that could be doing this, it does add up to quite a large number!
It is better if the default is hot water, which is needed all year, whereas the heating is only needed in cold weather. In my case the boiler is solid fuel so in summer the water is electrically heated and the electrics related to the boiler can be fully turned off.
What an excellent explanation. You are a star. This is a great argument for S plan, my preferred setup.
S plan? really?
@@LC-qi5ff Please explain S?
Excellent as always JW. One of the best explanations I've ever seen.
John, thank you for your excellent tutorial videos - I don't believe your explanations could be any clearer - I'm guessing you were once a teacher? You've single-handedly saved me from massive expense that I couldn't have met as I'm unemployed. Thanks mostly to you I've managed to keep the family from the misery of the cold over Christmas through one heating system failure after another: pump then thermostat then PCB then cabling inside the walls, then programmer, followed by mid-position valve; these things only ever happen in winter.
I now have my Suprima running off a local mains point as a single-channel device pending the purchase of a new programmer and my completion of total system rewiring and the introduction of a labelled wiring centre (the installer left a rat's nest of wiring and not even a multi-connector block).
I've stripped the diverter motor unit and reassembled it in a way that takes the sideways slop out of its levers, and now all I need is to work out why the motor stops and cycles each time it clicks SW1, so SW2 never sees any action. Given a couple of weeks I'll hopefully work it out with repeat viewings of this superb vid of yours! Many thanks again.
Very informative and slightly more complicated than I imagined. Many thanks.
Great video again John, such a clear explanation, thanks. Amazing design to have got so much function from so few components!
This gentleman has provided a superb explanation of the electrical circuit of the valve. Even as an electrician i(retired) I would have struggled to understand the operation just looking at the circuit. It so happens I have a problem with this type of valve at the moment so this is post is most helpful. Thanks to the instructor and to RUclips. What a resource.
Super clear explanation of the wiring scheme. It works now for the first time since I bought the house.
To get around the problem John brings up at around the 16 minute mark -- the valve motor staying powered after a heating-only cycle, I've added a mains voltage relay to my system. It is switched by the white (heating on) wire and the contacts interrupt the grey (HW Off) connection to the valve so that the grey wire can only be active when heating is requested.
That sounds like a neat solution.
I fitted a WiFi set up as a short period timer and twice a day it powers down the system.
Of course, it could easily be fitted in the valve control wires as well.
The valve that used to get more than warm just sitting there, now runs cold.
@@phils6926 Very good. Before I came up with the relay solution, I had fitted a 'push-to-break' (normally closed) switch in line wiith the grey (HW Off) wire. However I got fed up having to remember to operate the switch after every heating cycle 🙂
That's a great idea. the Valve heads will probably last longer as well.
May I ask what relay you used?
This man is God like when it comes to technical content. Thank you John. This is just what I was looking for.
Thank you, my central heating is working again. Very clear explanation of how the valve works.
This has been a brilliant presentation and explanation of how the valve works. I now understand it better and why they seem prone to failure. Thank you.
John, what an excellent video. For many years I have wondered how the 3-port controller works in detail, especially as I had issues about 6 years ago with the assembly and decided to replaced both the head and valve. Now got issues again, but think I have resolved them.
Brilliant explanation as usual. I always wondered what the second resistor was for.
Excellent explanation. Clearest and best I've seen on RUclips.
Excellent video, that explains why the room stat neon sometimes glows when the heating is off
absolutely spot on ... thank you soo much for this ... explained perfectly ... helped me a lot when installing my new programmer
Excellent video, answered all my questions, thank you
Kudus to you, best explanation out there for Mid-Position Valves
Very very useful, thank you brilliant video. Have also looked at the others you have posted and they also look like good useful content. All the best.
John you are a legend hopefully you do more of this thanks
Lots more, almost 400 videos so far: ruclips.net/user/jjwardvideos
Excellent explanation, though worth mentioning that failure of the Synchron motor is usually due to partial seizure of the valve spindle, which if not remedied, causes premature failure of the replacement motor or valve head...... or overheating due to customers encasing the valve in laundry...
Very nicely presented and very helpful.
I will still have to watch this a few times more to fully understand this rather complicated switching arrangement.
The motorised valve Y-Plan system is of course very clever in the way it works, but is fundamentally flawed in that you have to stall the synchronous motor which it isn't going to like.
You could say it’s designed to fail.
Every time I've had a valve fail, it's always been down to motor burnout to the point where the plastic insulation on the leads deteriorates and falls apart.
Rarely, one of the switches fail or the rack and pinion gear train comes off the rails.
Apart from that, in 2023 we don't want even 6-watts of power being wasted.
What I did in the end was to introduce a WiFi switch that controls the Y-Plan power.
Twice a day, the switch removes power from the system, the valve goes back to the HW position by spring and a minute afterwards, power is returned.
The valve is now in the default position and now runs cold.
It avoids situations where the valve could be in the stalled condition for months at a time depending on how hot water and heating is set up.
The WiFi switch is easy to set up as a timer and gives me control over the system from anywhere with WiFi.
Having worked in industry with a lot of valves with actuators, I've always been tempted to design a better Y-Plan which does away with the complexities of the motorised valve.
Personally, I would use a stepper motor which could open up all sorts of possibilities of position control could go to any position and the natural magnetic detent of the motor and gears would hold it in position without power.
Of course, the stepper motor does need complex control, but that is easily implemented by a cheap micro-controller.
As we go into an era of high energy costs, heating and ventilation of buildings is going to have to go the way that microprocessors have revolutionised the efficiency of vehicles.
Thanks for all the time and effort you have put into the series of videos.
What a brilliant video
Nice clear language, well delivered and great diagrams. I’ve always wondered about the inner working
and controls of these valves. Thanks very much.
The Bob Rush of the controls world!
Excellent video thanks.
Brilliant video, so well explained, thanks John, very helpful!
One of lifes great mysteries explained at last!
Great video and well explained 👍
Excellent explanation! Thanks for putting this video together
Saves me explaining it to my lackies, now I just need to get them to watch it👍🏻
Excellent video.
Also regarding the permanently on issue at 15:30 ish ....
It seems to me an extra relay that is energised by the white CH wire could be the solution. When it is energised , it also makes a set of contacts to let WH-satisfied grey signal through to the 3 port. Since that is the only time the 3 port valve needs the signal, to drive the motor into the CH only position. I will have a go at testing this on a 3 port valve that isn't in a system.
These days I guess a solid state relay could be used for extra reliability.
Great explanation. Very clear. Thank you.
I wish I had found this sooner as I was trying to diagnose a fault on one of these. I have only ever used it as a normal diverter valve as the mid position would probably not be effective in my system (solid fuel, gravity hot water with pumped central heating). The pump was running but the valve was staying in the hot water position. I suspect SW1 has failed as the 2 resistors and the diode tested out OK. My solution was to wire the motor direct to the live from the thermostat. I have also now utilised the orange wire to run the pump. This has the advantage that it now only starts pumping when the motor has completed the movement to central heating.
Thankyou so much for this video!Very useful!😃👍
Excellent explanation.
Great video well explained.
Great video and we'll explained 👍
Great video really helped me to understand what I thought was a fault regarding heating only.
It seems to me that the heating only issue, whereby switching heating off at programmer continues to provide power to motor until powering down the system is more problematic than ever. The cheapo after market motors that are available to buy seem to be of much less quality than those employed by Honeywell.
I seem to replace the motor once a year during the winter period. The original lasted 15 years.
Yes, the cheap motors and even the cheap valves do turn out to be a waste of money.
Another pain is that at least one company H*******n decided to put a slightly different thread on their valve turning a simple replacement into a major plumbing job.
Amazing content
Hi JW, Excellent video with simple explanations for amateurs like myself, so thanks for that.
I wonder if you could please recommend a ‘simple’ wiring change which would delete the mid-position function which you describe as “an unwanted effect” in your video. I only ever use either the H/W Cylinder or Heating separately, never both together, so as to never subject the Motor to that mid-position situation. To avoid the “unwanted effect” when I turn off the Heating at the Programmer, I then turn on the H/W Cylinder for approx., 15 seconds, which releases the Motor from the DC Current, and so the Valve is returned back to it’d Default, and totally un-powered, position.
To avoid having to do the above, could I perhaps disconnect both Resistors and the Diode from the PCB, so that little circuit will be prevented from producing the 110 VDC current which facilitates the mid-position? However, would doing that interfere with the power on the Orange wire which initiates the Boiler? Is so, would connecting the White wire, on the Common of SW2, also to the lower of the 2 connections of SW2, where the Orange wire is connected, resolve the problem, or would that not be necessary?
I’m asking this because my current Valve is a Honeywell V4073A unit, but Honeywell also produce the V4044 range, which look identical to the V4073A, except that the V4044’s are listed as 2 position “Diverter” Valves only, (no mid position), which is exactly what I want to achieve (but without spending £ 100 +++ money or my fitting time !!!).
Please accept my thanks in advance of your help, and I look forward to receiving your reply.
Cheers, Fred.
Excellent. Many thanks.
HI John great video explaining operation of 3 port valve I see in certain cases the orange wire which only switches boiler in heating only mode it can have up to 150V on it via the internal resistor I am having a problem where this 150V is causing a boiler to actually try to switch on have you seen this I am considering fitting an external resistor to try to drop it but will have to experiment with value
thanks
Yes, having these odd voltages on the system isn't good.
With boilers having more electronic control rather than hefty mechanical stuff, 150-volts could cause a lot of problems for something expecting either 240-V AC or 0-V AC.
Be careful with resistors though as you might run into over-heating problems if the resistor has to dissipate voltage as heat.
A more complex solution might be to add some other circuitry that converts these in-between states into definite on's or off's
Y-Plan might have been OK decades ago, but boilers in particular have moved on.
Hi John
Thanks for the video (and the others), explains the Y-plan really well. I'm currently having an issue with my Y-plan set up and I wondered if you had any ideas. We have an oil fired boiler which runs all the time by gravity feed. The temperature control is mechanical on the boiler so the room stat is not used (effectively always set to closed). The programmer is set to run the HW from 3am to 5am, then turn off. The CH runs from 5am to 7am, there are other times but I don't run both together. It's this HW to CH switch that sometimes fails. The valve starts to move from HW to CH but never gets there. The pump is stopped during this time. If I manually push the lever to move the valve the second microswitch can be heard to change over and the pump then starts.
I've checked the valve out without the accuator fitted and thats smooth and clonks into one or other position firmly if the pump is running. The motor seems to run OK when removed, trying to mechanically stop it takes quite some force so it should be easily overcomming the spring.
I did replace one of the microswitches as I thought it was maybe sounding different and less definitive compared to the other, but that's not fixed it. When I did that I had not seen your video so was not sure if it was SW1 or SW2, I think SW2 as there were orange wires.
Do you have any suggestions? Based on your video I can't quite see why the pump stops on the change over (this is a problem as it starts cooking the water by convection). I guess it could be the controller, perhaps a sticky relay, but I do here clicks when selecting other settings on the CH and HW (off, 24hrs, auto, etc.).
Cheers
that was a no..
Great video!!!. I though there was something wrong with my mortised valve, as i noticed that the valve would only close if i completely cut power to the control panel, just turning off heating would still keep the motor operating and so valve open. Thanks to your video i now know this is actually not a fault at all and just a poor design
Great video
hello john I am wondering could you do a video about diagnosing a faulty immersion heater with a multi meter.thanks
brilliant. thank you.
Hi
Is the force required from the motor non directional ? Is the mechanism designed in such a way as either polarity will achieve the required result.
Excellent explanation. I now understand why I’ve had to replace the valve motor 3 times in 20 years. Unless the system is de-powered at the end of the day for a few seconds the motor keeps the valve in the CH position all night. I’ll see if the time switch/controller allows a quick switch to ‘HW only’ at the end of the day to fix this automatically. Thanks.
Interesting point. I leave my hot water permanently on at the programmer and rely on the tank stat. I think that would answer your point, although today I’m replacing a six year old Danfoss mid position valve, the previous of same brand had lasted 12 years using same programming philosophy. They clearly don’t make ‘em like they used to. Also ensure you run inhibitors like Fernox F1 to keep the paddles lubed.
@@MikeSmith-tx2lp , yes I do always use Fernox F1 after replacing any part of the system but I suspect the original installer when the house was new did not. I’ve now found that even when setting the hot water to switch off 30 minutes after the last heating cycle at the end of the day it still does not de-energise the 3 way valve. I have to remember to manually de-power the timer at the main switch to open-circuit the latched contacts. In the summer months when the heating does not come on I don’t have to do this. I suspect that as stated in the video that this is a design flaw with this Y plan valve system.
I did see someone discussing this elsewhere.
I have been trying to do this by turning on the water before going to bed, but as the tank of water is already hot, and will stay hot all night, the hot water only option does not cut in until the following morning when someone starts to use hot water.
If it does cut in earlier than that, I suspect that the energy used by the gas and the pump heating the water at night would far exceed any saving on 6W on the synchrynous motor running.
Someone suggested installing a cut-out switch to de-power the unit at the end of the central heating cycle.
This sounds like the best solution, but quite difficult to design and install and would possibly intefere (and damage) something else in the system.
It is a pity that the designers of the valve head actuator do not build in a timer switch to cut the power after five minutes of inactivity. (Or perhaps some do??)
@@worcesterexchange554 , yes, a switch, relay or circuit that automatically de powered the system at the last timed switch off at the end of the day would be the solution, but for now at the end of the day I just manually de power the system with a quick turn off and back on, and this is enough to de latch the 3 way valve into the unpowered position.
@@Thruxtonite Are you trying to extend the life of the actuator motor or save on 6W of electricity ?
Interesting video, thanks for posting John. My siemens 3 port is the same but minus the resistor between diode cathode and the orange wire. It looked like sw1 was faulty but I replaced to no effect. I also replaced the valve last year from an ebay purchase but assumed it was faulty also as it did not fix the problem. The system gets stuck in the mid position when the HW is last to be called for. It's odd as, if I understand correctly, that's when there is no power on grey or white if wired correctly. The problem goes back sometime and I am now suspecting it's wiring issue from when the boiler was moved. The plummer said he fixed the fact ther was no overrun of the pump for the boiler. I did not give it much thought at the time but I am now thinking this may be significant. Any thoughts on what may be happening?
if wired correctly for the valve to get to the mid position there must be power on the white wire. if it gets stuck there check if power stays on white wire when heating turned off or if grey wire has power when hot water turned off. the latter should have power when hot water turned off and heating turned on. if it does not then this may also be the fault. there may be the correct powers still or where both are turned off but the valve is broken or stuck.
what voltage would you expect on the grey wire during mid position? what would it mean if there was 80V?
Very interesting and well explained and also Part 1 2 3
BRILLIANT !!
So here's a curious thing. In the Summer I turn off both heating and hot water (and use immersion powered by solar pv), but from time to time I operate the 3 port valve manually just to prevent it from sticking. When I did this and rather than just a quick wiggle, I must have moved the valve to the mid point, the valve continued to the CH position ... which is to be expected, BUT the boiler also fired up! How can that be?
hi - thanks for explanation, On my Y plan system , when you switch the HW off on the timer, the heating only wont come on ,so therefore we leave the HW on all the time. I was wondering if this could be rectified?
230 v to both the grey and white wires should provide voltage to the orange control wire down to turn on boiler and pump for heating only should nt it?
Hi Kim, I have the same problem you experienced 10 months back, (no power to the orange wire once the HW switches off) did you manage to fix it? It seems you didn't get a reply to your query unless it's hidden. I'm about to investigate this problem this coming week and think it may be one of the microswitches in the Drayton three-port valve actuating box that could be faulty. I'd appreciate to hear your findings as you're the only one to post this issue.
Excellent video and explanation. In my system I am unable to get CH only. The boiler won't turn on unless HW is also on, I assume the valve is in the central position. What could be preventing the valve moving over fully to the CH position and staying there?
Many thanks
If the valve never moves to the CH only position, the grey HW OFF wire isn't connected.
@@jwflame Thanks for the response. I'll look into it some more.
AAAAAAAGH, just found out why i can have hot water or heat and not both...cheers John.
Having just replaced an actuator motor, I was intrigued to see how these worked. The whole thing looks like a horrible kludge to be honest. A bit like the standard of wiring I found. In my experience plumbers don't do wiring properly...
nb. excellent explanation by the way.
Total rubbish is a better description.
My next door neighbour was a plumber, but he hated Y and S-plan systems.
Not the pipework side of it, but the wiring.
I have some experience of industrial control systems so I used to help him out on jobs.
Yes, some of the wiring done by professionals could make you weep.
If plumbers are short of a wire, say four cores needed when there was only three cores available, they thought nothing of using the protective earth instead.
Run a new cable? No chance.
Hi John, A question, I have a honeywell 3 way valve that sticks and clicks in the mid position. This happens when HW is called for when the CH has been on. It's the same regardless in HW & CH on together or HW only, after being in CH only. It also occurs when coming from HW to CH and HW together at the same time. Do you think this is caused by resistor break down or micro switches? I checked power when on HW only after coming from CH only and 240v White 240v Orange and a small pulse reading on Grey. ( The 3 way it stuck in the mid position though) If I cut all power letting the spring move the valve back to the HW position and then put it on HW onlt, it runs fine and readings are 0v white 0v Grey and 240v Orange. I'm looking at changing the head only as it's only 3 years old. I have looked at the EPH D1P, which fits directly on via a plate provided.
I was a Corgi engineer and always wondered how that works
Well, - thankyou very much for this lucid explanation, John. Very helpful. But all I kept thinking was how did the industry come to accept such a complicated design!? Certainly not using the KISS principle!
I have radiator heating but hot water heating is not working. I have had the motor head and pipework of the 3 port valve relaced to no avail. I replaced the control unit (easy) and checked out the tank thermostat, all to no avail. When I fully understand where and what the control voltages should be I might be able to sort it. I think my plumber gave up a bit too easily and at the moment it still looks like a plumbing problem to me and not electrical.
Anyway, Cheers!
Hot water is just switching he boiler on, and nothing to do with the valve at all - it stays at the default position so doesn't need any power.
thank you! My 3 way motor is making a lot of noise tonight and seems to be stuck- heating went off. I manually moved the lever a bit which brought heating back but still very noisy, even when timer had switched heating/water off...why would it still be running when timer is off John?? I have read you can park the lever in manual, but it isnt locking and still more noise when I try that position!!
The grey wire is powered when both CH and HW are off, and it is possible for the motor to be in a position where it receives power from that grey wire even with everything off. Switching HW on only for a few seconds will fix that problem.
However if it's making a lot of noise and not working properly, it will need to be replaced.
John you explain things in plain English thank you my freind
Wish you were my teacher fanatic explanation
Interesting. My heating system seems to have a manual 3port valve.
Hi John, I have recently replaced 'Switchmaster' valve & programmer, also replace room & cylinder stats. heating appears to work Ok but when hot water is selected valve appears to operate - switch on but then cycles between off & on about every 1/2 second (clicking noise inside valve (microswitch operating). do you have any ideas what I may have done wrong
problem solved. it was a break in permanent live
If you had a faulty valve that was stuck in CH only mode (and worked in that mode), does it alter the way those microswitches operate the boiler at all. I notice there is a copper metal lever that appears as if it just mechanically moves to operate those switches? Also, there is a lever on the outside that allows you to operate the valve manually? How does that work? You didn't explain?
If it's stuck in CH only, then the switches inside will also be stuck on, but that won't change anything - the system will just work with heating only, no hot water will be possible even if selected. Depending on how broken it is, the boiler may work when HW is selected, but will just heat the radiators.
The lever on the outside is used when filling or draining the system, and just moves the valve to the mid position.
Thank you
You say that when the system calls for BOTH that the grey wire has not volts on it... but it is fed from the HW Off which is always live as shown on may circuits. Can you explain why yours is a different Yplan// Thanks
For both HW and heating, HW Off is not powered. If it was, you would get heating only.
Hi John, I have a drayton 3-port valve on my system, I'm wondering if you can solve the problem I'm having with it...with the central heating control turned off and just the hot water selected on the programmer, the motor drives the valve right across to the hot water only position, but after a few seconds goes back to the centre position and remains there giving a constant clicking sound. This of course allows hot water to the radiators when it shouldn't. I've removed the head to take a look and the valve is quite easily operated with my fingers, the motor seems to run ok, could it be one of the micro switches causing this problem?
Your help would be much appreciated, Ken.
Ken Meadows did you solve this?
Yes, on closer inspection I could see that the actuator on one of the micro switches was stuck in. I sprayed it with some electrolube and allowed it to soak for a while, I then poked it up with a sharp needle and it released. More lube sprayed and pressed in and out a few times, it was now clicking away nicely ! I continued to operate the switch actuator a while longer until I was confident it was ok. I refitted the head assembly and I'm pleased to say it's working fine...and still is to date. I've bought a new micro switch off e-bay, Burgess XCG3-Z1 Plunger Microswitch, 5 A cost me £2-35 and will replace if needed, fingers crossed!
Regards, Ken.
Help please-I’ve got a Y plan system. When the central heating is called, the SW to the boiler is switched @240v. When the central heating is turned off, the SW retains a voltage of 90v. I’ve changed the clock. But still remained. I’ve changed he valve. But still remained. I’ve got through the wiring many times over & I can’t see a problem. It seems the valve when the CH is switched off, it’s doesnt open either of the micro switches.
The only way to clear the 90v is to put the HT on, then turn it off. This then stop the boiler firing.
I’d appreciate any response. Regards.
This is a 'feature' of the valve design, and is due to other components inside the valve (resistors and a diode). Most boilers do not have a problem with this, but there are some which will activate with the lower voltage.
The solution for those boilers is to fit a suppressor between the switched output and neutral. Some boiler manufacturers sell a specific part such as Worcester part number 87161092750, but a generic item such as uk.farnell.com/roxburgh/xeb1201/rc-network-250v-0-1uf-flying-lead/dp/1187659 will also be fine.
A nice explanation of what is basically a flawed design
Honeywell nearly got it right, but not quite.
Having the valve stuck in the heating position as it will do, does mean the motor getting more than just warm.
When I looked at the first 3-port valve installed 30-years ago, the insulation on the motor leads had simply crumbled away owing to the over-heating. Not very safe.
Other actuators have failed because of the poor, sloppy mechanics (very small motor gearwheel driving a rack like a hacksaw blade).
I don't use the boiler for hot water, so when the heating goes off during the Summer, the valve can sit for 6-months getting very hot indeed.
This is a design flaw.
To get round this, I now have a WiFi switch (Sonoff) sitting between the fused spur and the boiler system power.
The switch is scheduled to switch power off after the morning heating and last thing at night for one minute.
This allows the system to relax back to its default position and no more over-heating.
Going WiFi allows the boiler power to be seen from anywhere and manually turned off if needed.
If I was designing a valve actuator now, I would use a direct or geared stepper motor and do away with all the complex microswitches, springs and over-heating.
Having just replaced the last power head that only lasted 6-years at a cost of £120, knowing that it will fail again, the stepper motor option would be cheaper and more flexible in the long run.
Exam question - explain the workings of Y-Plan. Despite your explanation, I would still struggle!
I agree, a flawed design. I have a 20 year old S-plan system and I've had to replace power heads three times, each time because the motor burned out.
I would much prefer a system with a bi-directional motor and no spring return.
@@davidfaraday3085
Yes.
The Honeywell power head, and everybody else's power head relies on a one way power driven direction and a spring return.
To hold the valve in the mid position and the third port, they deliberately stall the synchronous motor by switching off the AC supply, rectifying it with a diode and a resistor.
This is a gash way of doing it and the motor protests by getting sometimes very hot.
If you don't use the heating during summer, the valve can sit in this stalled position for months.
I fixed this by adding a switch in the system power line.
The switch is a WiFi switch (Sonoff Mini) and is very easy to program.
I switch the power off for 1 minute every day at 10:00 and midnight.
This ensures that the valve always goes back to the spring unpowered position and over-heating is non-existent.
I can also operate the boiler remotely by a phone application.
If I had time, I would knock up a stepper motor design that would power drive the valve in both directions.
Once in position, the motor is turned off and the natural resistance to move of stepper motors holds the valve position.
It is surprising that a company with the resources of Honeywell still turn out rubbish like the three and two port valves.
It keeps plumbers happy but nobody else.
The design must be 50-years old by now and has earned Honeywell a lot of dosh.
Mind you, a lot of their other stuff is rubbish as well.
I've got through three of their programmable room thermostats that either lost or gained a lot of time, or the screens packed up.
I use real time clocks in electronics a lot, and for a few pennies more, they could use a chip like Maxim DS3231 that would be accurate to at least one minute per year instead of 1-hour per year.
I won't buy any more and already have a hot water cylinder thermostat running using WiFi switches and temperature controllers.
They use GPS or Internet time so are accurate to the second. I can also control it from anywhere from the phone.
Not only is it cheaper, but it is a lot easier to program from the comfort of the phone
@@philipslater5015 At least with the S plan system there is no risk of the motor being energised for months as it can with the Y plan, but the motor is still stalled for the whole time the valve is open. So whilst the S plan system isn't as bad as the Y plan, its still pretty crap.
A stepper motor seems a bit OTT to my mind, a simple capacitor split AC motor can run in either direction simply by switching the supply from one side of the capacitor to the other. I have a motorised curtain system that works that way. On the other hand a stepper motor would eliminate the need for limit switches so might work out cheaper.
@@davidfaraday3085 We'll agree it is crap.
A stepper motor is actually quite easy to implement and thanks to the Far Eastern manufacturers, the price is very competitive, certainly less than the price of a genuine Synchron motor.
The downside is you have to do a bit of programming (coding), but even that is easy now, certainly not beyond Honeywell.
The synchronous motor is a variation on the stepper theme and every cheap clock uses a version as well. I'm not sure what Dyson uses in his V11 Digital Motor vacuums.
I get digital control, but a digital motor is a tall claim
Steppers are universally used in applications where precise positioning is needed from 3-D printers to surgery and vehicle manufacture.
I was thinking of using one to open and close the vent on my greenhouse
If you had any sort of lead screw on it, in the unpowered mode, it is virtually unmovable. Also, you remove that gash rack and pinion mechanism, two microswitches, and the spring. The only tricky bit would be the manual lever, but I'm sure that could easily be engineered if it was needed at all.
What I don't like is having a bit of kit tucked away somewhere that gets hot enough to degrade mains voltage wiring
Thank you John! However, I am not clear as to why my mpv is remaining open, on heating only. I cannot get any hot water at the moment and thought it was a thermostat issue. I briefly turned the whole system off (depowered) but the valve remains in the same position. I can confirm that the valve spindle is free as the mpv head is removable. (Clip on). Any ideas please?
The spring in the actuator is broken. You need a new actuator.
Hi John - I checked the springs which appear alright so I have assumed the motor is seized, sent for a replacement! Any other suggestions?
I presume the spring-biased manual lever (with locking indent) on the side of the valve, sets the mid position for draining down.
Correct
Warning ---- push the lever VERY VERY SLOWLY .....
Warning - do not do what I did and try to push this lever quickly.
It stripped the nylon gear wheel and I had to replace the unit.
I see that I can buy a replacement motor for £10, but only found out what the problem was some time after replacing the unit when I got round to opening up the little gear box on the motor.
If you need to push the lever - then push it VERY VERY SLOWLY .....
In my domestic system ,a few years ago the motor failed .I fitted a new motor and to get round the problem of the motor being energised when the boiler was off,I fitted a relay from the white wire to the neutral.The contacts of the relay break the grey wire.This has the effect that when water heating and central heating are both off the motor is not powered up.With the system in my house another way to de-energise the motor is when you switch the central heating off .switch the water heating on for a few seconds .then off again, this has the effect of returning the valve to the de-energised position and it stays there.The system in my house is 26 years old, so more modern systems are probably different.
I am an electrician, not a heating engineer ,when I first investigated how these 3 port valves worked, with the motor energised a lot of the time I thought it was a peculiar way to do things.I would hope that with modern systems they have a more sensible design.
Modern 3 port valves are still the same, so have the same problem. However most new systems use 2 port valves which do not have that problem.
Considering most households will run just the central heating in the evening during winter, resulting in the motor being energised throughout the night until the hot water comes on in the morning. I'd agree; it's not the smartest and I'm not aware that three position actuators have evolved at all to address this issue. ☹️
Neat !
From A Ford
John, I have just watched your video on how the 3 port Spring return valve works. I find it extremely interesting but it does not have to operate in the way that you describe it. I would like to discuss the operation of the valve with you. Can I contact you? Do you have an email address? Or is there another way we can communicate ? I am sure that you will find what I have to say interesting.
Best regards A Ford
Can you imagine what would happen if white and grey were swopped? I am wondering if this is causing a problem a friend is having.
i will try that in my wiring centre.i guess nothing wouldnwork. if grey was then wired to the room thermostat it would mean switching the CH on would shut off the HW and white wired to the cylinder thermo satisfied would mean CH would only come on if HW satisfied.
Think I’ve just come across where the motor is stuck in the mid position for ever. As it’s heating the house when heating the water and vice versa. What’s the solution, change the motor again?
If it's physically stuck then change the whole valve. However if it returns to HW only when all power is removed, it is an electrical problem, either with the actuator or more likely some other wiring problem elsewhere.
John the lever is loose and doesn’t move as it should when the CH is turned off, however both the controls for CH as well as DHW fires the boiler it just the valve is stuck in the mid position.
If I click the lever into the on position, will it mean that this circuit stays on and does not listen to the programmer telling when to turn off?
No. The lever only moves the valve to the mid position so that water can flow. When the valve is powered and the motor moves the valve, the lever will be released. Same applies to 2 port valves.
@@jwflame so clicking it into place won't result in the central heating staying on and not going off then? I thought the whole point of that function was to allow the circuit to be on and uninterrupted by any controls/programmers?
@@da_great_mogulIt's purpose is to open the valve when filling or draining the system. If controls are not working, then they need to be replaced/repaired.
top drawer
Can anyone explain why the default position is for hot water? In our household, the central heating is demanding far more than hot water. Surely, it would have been more sensible for the designers to make the central heating the default position and only to drive to the hot water when required.
Central heating only used for the winter months, hot water is used all year.
@@jwflame OK, I can accept the reasoning behind that logic, but I'm still not convinced. When the temperature drops, the CH tends to be on continuously, for hours at a time. The HW cylinder, by contrast, tends to heat in less than an hour then switch off. Even in summer. I'd still have thought that the default position could be CH position in the summer and the motor driven to HW when needed.
Still, it's rather academic, as the die has been cast and I doubt it would be changed now, even if my theory were accepted. And combi systems probably don't need the valves anyway.
I'm not convinced that the small saving achieved by having just one valve justifies the over complication and subsequent reliability issues.
It doesn't now. Probably made more sense decades ago when valves were expensive items and almost no one needed more than a hot water cylinder and a single heating zone.
Any modern system should be using separate valves.
can see why most people have gone to two port valves instead
You can lock up the valve in manual which holds the valve in mid position untill you get an engineer out happy days
How strange, why would you have the motor even act against a spring?
The valves I have just run the motor right or left depending on which terminal you apply power.
It would be most useful if you could show these weird and wonderful heating components so we can see what they actually look like.
Maybe when there is no power, it stays by default on opened HW. Why need spring? Maybe to don't let presure to move valve.
+just5444 That's possible, but as far as I know these gas fired systems won't work without power anyway?
The ones I have just stay in the last position, or you can disengage the geared motor and set them manually with a rotary knob.
+stefantrethan
Maybe won't work, but preasure doesn't disapear.
+just5444 Without the circulation pump running, there is no (differential) pressure in a central heating system.