Heating- Reversal of 3-way valve.

Discussion in 'Plumbing and Central Heating' started by beano1939, 31 Mar 2010.

  1. beano1939

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    I have a y-plan combined HW/CH open vent conventional system. There are other separate systems for HW e.g.Rayburn and Solar. Consequently the 3-port valve is almost always programmed in the CH position and is permanently energised. Can the valve be plumbed the other way round so the CH port is normally open, thus saving power and strain on the actuator motor. The wiring would have to be altered too of course.
    I suppose I could do without the valve altogether,but I would prefer to keep the HW option as a back-up for the other sources.
     
  2. Andygasman2010

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    I can't really see the advantage of what you're describing.... Are you thinking it'd be less wear on the valve?
     
  3. stem

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    You could, but it would require a rewire of the controls and possibly a new room thermostat with changeover contact to provide a 'central heating off signal' you would also need a 'central heating off signal' from the programmer/timeswitch.

    As an alternative, you could consider converting it to a 'S' plan with 2 x 2-port valves. The wiring connections would need changing slightly, but you shouldn't have to run any new cables.
     
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  4. Andygasman2010

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    As stem said, S-plan is pretty straight forward if you're good with electrics.
     
  5. beano1939

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    Thanks,both of you for helpful replies. As my system is almost always on CH only,I was hoping to have a control system where the valve is normally open and not energised. It saves a bit of power and is likely to be more reliable.
    With a 2-port arrangement,either valve would have to be energised to open,so this does not fully meet my needs. I can easily fit a room stat. with changeover contacts as I don't have one at all now and am planning to fit a wireless one. So if I can figure out how to wire the stats and 3-way valve to the connector box,then I thought reversing the valve in the plumbing would be the cheapest solution.
    Alternatively,how about substituting the mid-position valve for a 3-way diverter[W-plan] again with the valve reversed so the CH flow is in it's unpowered direction?
     
  6. picasso

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  7. PEDANTICVINDICTIVEMAN

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    What you want is an s plan with the CH valve sprung open and powered shut, I think Honeywell do one if you look through there stuff.
     
  8. stem

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    Methinks that would be worse, because it would need to be powered shut whenever the heating wasn't required such as summer and night time, otherwise if the hot water came on so would the heating.

    It's slightly better than with a 'Y' because, for example if the programmer turns off at bedtime, whilst the heating was 'on' the valve remains energised until the hot water is required next time it switches on, probably the following morning. This is the one main drawback of the 3 port valve. The 'S' plan does avoid that.
     
  9. beano1939

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    I have googled the Sunvic momo valves and although the concept seems good,their reputation for reliability seems to be dubious. Honeywell are better regarded, so as they make both normally-open [V4043B ] and normally-closed [V4043H] 2-ports, I have decided to go for one of each and change the plumbing to S-Plan as suggested.
    Thanks Stem, for your last note. As my system is almost always programmed for CH only, then I assume If I use a normally-open valve for CH , it would be permenently sprung open and would power shut only if I select HW alone which I would do very rarely if the other HW systems fail or are being serviced.
    The other 2-Port [H] on the HW circuit would be normally sprung closed.
    So: CH only selected; B sprung open, H sprung shut, both not energised.
    HW only selected[rare], B powered shut, H powered open.
    Both HW & CH selected [even more rare], B sprung open, H powered open.
    How does this sound?
     
  10. D_Hailsham

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    :idea: I think this would work :idea:

    If you join the grey and white wires of a mid-position valve together and feed them from a common supply, the valve becomes a diverter (Port A or Port B open, but not both at the same time).

    Reverse the valve - Port A to cylinder, Port B to heating
    Connect room thermostat call to the boiler Sw Live terminal
    Connect the combined grey and white wires to the HW cylinder call terminal. The orange goes to boiler SW Live.

    The valve then opens to HW only when the cylinder stat calls for heat. It is similar to the W Plan, ie CH or HW
     
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  11. PEDANTICVINDICTIVEMAN

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    So going for my idea then normally open valve :rolleyes:
     
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  12. stem

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    Beano1939, I'm not sure what you are using for your central heating heat source. My understanding of your original post, is that the Rayburn & Solar are for the hot water only. Do you have an oil or gas boiler for your radiators?

    The reason I mention it, is because the normally open valves I've seen don't have a microswitch for boiler control. I guess because they are normally used with solid fuel systems so they fail open. If you do have another boiler that needs a 'run' signal, you would have to find a way of operating it and also maintain isolaton between the HW & CH controls so that they don't operate each other via the boiler. Unless of course someone does produce one with a microswitch.
     
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  13. beano1939

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    Thanks, D Hailsham for the wiring advice. That's an elegant and cost -effective solution, worth trying as there are no significant plumbing changes..
    Thanks also, Pedanticvindictiveman. I thought your suggestion was fine until the latest input from Stem. My radiator boiler is Oil pressure-jet,so it needs a signal from the valve to fire up. Honeywell's website [and their distributors who copy the same thing] does not make it clear that the V4043B is only 3-wire with no microswitch. A tense phone call to Honeywell confirmed this. I had ordered [and now cancelled,fortunately] a valve assuming it would be 5-wire like the 4043H.
    The Sunvic MOMO as suggested by Picasso, would suit because they are only powered when changing, but reliability?
    Does anyone know of a good normally-open 2-port with a switch?
    Thank you everyone for your contributions.
     
  14. Agile

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    I really dont understand your excessive concern about trying to spend about £70 to buy a new valve and thermostat when there is nothing wrong with your system at the moment.

    Dont assume all wireless stats will have change over contacts on the receiver.

    Nearly 4 million homes have valves powered for heating like yours so I dont see why it bothers you so much.

    Tony
     
  15. stem

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    You could always wire a relay across the motorised valve terminals that will give you a potential free contact. The relay coil will use a small amount of current when energised though, and it will need an enclosure to contain it safely.
     

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