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Honeywell three port motorised valve - replace the whole thing? And other questions...

Discussion in 'Plumbing and Central Heating' started by DIYNotIan, 21 Aug 2021.

  1. DIYNotIan

    DIYNotIan

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    Hi again

    I'm on a roll with the plumbing questions today! So here's query #2...

    We've not used our hot water for quite some time, and it now doesn't work. From what I can gather based on what I've learnt in the last hour or two, I think the problem is with the 3 port motorised valve. When just hot water is selected at the controls, we don't get hot water, but we do get hot radiators. Just to be clear, that's with hot water selected to continuous, heating off, and the heating thermostat turned right down. Up in the airing cupboard, I can feel - at the valve - that the pipe going from point B to the cylinder stays cold, while the pipe from point A warms up. The little lever bit doesn't move and stays in auto position. So presumably the valve for one reason or another is stuck and no matter what the controls tell it to do, only port A is open. Does that sound about right?

    If so, I wondered if anyone could help with the following please?

    1. We've got some major plumbing work coming up soon, which will require a full drain down. As such, would it be worth changing the whole unit? I've seen some try just changing the motor, others just the power head. But whilst drained down is it worth spending the extra and just replacing the whole thing?

    2. My unit is a Honeywell V4073A1088. The one you tend to see most is the V4073A1039. I looked into it and all I could find is the former is 28mm and the latter 22mm. I presumed that related to the pipes feeding it, but does it? The reason I ask is because I have 22mm pipes and yet mine is supposedly the 28mm version. Which has me scratching my head!

    3. One forum thread I was reading stated: "“It explains why you can't use a mid position for your HW and RADS and then add a two port for extra rads or UFH.” Is that correct? Is it a blanket statement? Later in the year we are looking to have UFH installed elsewhere in the house, so I'd be interested to know if it would need changing again at some point. For reference, the quote comes from here:

    https://community.screwfix.com/threads/motorised-valves-that-little-lever.173511/

    4. Is it the heating controls or the room thermostat which control the valve?

    Sorry for all the questions, and help with any of them would be much appreciated.

    Massive thanks!


    Some photos in case they help:

    IMG_20210821_103942342.jpg

    IMG_20210821_153409440.jpg

    IMG_20210821_153459179.jpg
     
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  3. flameport

    flameport

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    HW is open by default - as in that's open when there is no power to the valve, so if it's stuck on CH only it's either jammed internally or there is permanent power holding it on CH - which is likely to have burnt out the motor long ago.
    Replacement of the whole thing would be sensible.

    In terms of controls for Y plan, its a combination of the programmer/timer and the thermostats which determine the valve position, and the boiler is switched either directly from the cylinder thermostat & programmer in the case of HW, or via a switch in the valve for CH.

    However Y plan only works with HW and a single heating zone, so if you want more than one zone or UFH, you would be far better disposing of the existing valve and converting to S plan with 2x 2 port valves. Additional zones can then be added later as required.
    Y plan is essentially obsolete, and would not be used for any modern installation.
     
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  4. ericmark

    ericmark

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    This shows how to remove the head, as @flameport says possibly stuck, I would first try to latch that lever shown on the video, often you can feel if valve opening and closing, there could be either of two faults, either the valve has stuck or the micro switch has stuck, as the guy in video says best is to swap whole valve, but you can take the head off without loosing water so may be worth a go.
     
  5. Elkato531

    Elkato531

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    The valve you have is a 28mm valve with reducers fitted to bring the size down to match the 22mm pipes. If you change the whole valve and want a straight swap, you will need get the more expensive 28mm version. You could use the 22mm version but need to adapt the pipes to suit.
     
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  6. spareshunter

    spareshunter

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    Just change the head plus cover with the ball and hand clean the ports. A 22 mm complete valve will do as the internal bodies are the same.
     
  7. DIYNotIan

    DIYNotIan

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    Many thanks for the great replies and explanations. I've got to admit, I love learning about this kind of stuff. Not that I always fully understand it though!

    If I could bother you with some more questions please...

    - Is there no way UFH could be added - as a separate zone - to my current system with 3-port valve? 100% not? Appreciate this is a naive question, but can it be on a completely separate feed from the boiler itself, or does the boiler just have a single flow and single return?

    - The reason I ask is because we're not sure if we're going to have any UFH heating yet or not. If we do go for UFH, it would seem a shame to put in a new 3-port unit now only to have to change it all again soon. But if don't end up with UFH, it would be an unnecessary waste and expenditure changing to two-port units.

    - Which leads me onto seeing if my existing unit is fixable, in which case we can continue using that until we've decided on UFH or not and then have a new unit(s) installed accordingly. So tomorrow I'll re-read the above, do a little more googling, and watch a couple more vids to see about diagnosing the fault with the unit.

    - This is more for my curiosity... I don't mean to be thick, but where exactly does the change from 22mm-28mm take place? I'm pretty sure that when I measured the visible pieces of pipe where they go into the unit they were 22mm. I can take a photo tomorrow. So is the reducer/adapter out of site or am I just not getting something (something which is no doubt extremely obvious to everyone else)?

    Right, that's enough excitement for tonight!

    Cheers
     
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  9. Johnmdc

    Johnmdc

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    It is probably just the motor in the valve which needs changing (it's most likely jammed in the heating only position) these are about £20 from screwfix.
    You can see in your picture the adaptors that change the pipe size from 22mm to 28mm soldered to the ends of the pipes. It is more obvious on the bottom pipe.
    If you are getting UFH then yes it will need changing to an S plan plus system, (3 x 2 port valves) because with a Y plan one of the ports is always open. So if you only wanted the UFH on then either the hot water or the radiators would also heat up.
     
  10. Harry Bloomfield

    Harry Bloomfield

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    Before spending any money, it would first be worth removing the actuator head part of the valve (as in the video above) and seeing how tight the valve spindle is to turn by hand. It should almost turn with just finger pressure, but may need a pair of pliers.

    Worth also testing the actuator head separately, off the valve. Turn room stat to max., set room heating to on and actuator should move slowly to heating. Turn water heating on and the actuator will move to the water heating position.
     
  11. DP

    DP

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    That will work for non Honeywell valves. When Honeywell actuator is powered off the valve body the drive will disengage from the the motor cog and keep jumping to home position.

    Try it

    Agree with rest what is written
     
  12. jeff the gasman

    jeff the gasman

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    If you want underfloor Heating you need to go S plan.
    3 port valve is always open.
     
  13. flameport

    flameport

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    100% not possible.

    If there is any possibility of UFH being required, the 3 port valve needs to go away.
     
  14. DIYNotIan

    DIYNotIan

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    Thanks for the continued great help. I really do appreciate it. Didn't get the chance to check the unit today but will...

    On the subject of UFH, I was just wondering if all boilers are suitable for it? A bit off topic I know, but seeing as I brought up UFH it got me to thinking. I have a Worcester Danesmoor 20/25 (oil). Can anyone confirm if there's any reason UFH wouldn't be compatible with that boiler?

    Cheers
     
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