Running heating without hot water currently not possible

Discussion in 'Plumbers' Talk' started by EdSlocombe, Dec 3, 2017.

  1. kiaora

    kiaora Well-Known Member

    The plumbing may be gravity hot water, but the wiring may not!
  2. EdSlocombe

    EdSlocombe New Member

    Thanks for all the replies so far :D really appreciate it!

    Just Googling, and could well be that I have a Y-plan, not gravity as I originally suspected. Anyone got a link to a good article that explains all that plans and how to identify? I'm trying to find one and I can't find an article that compares a Y-plan to gravity...

    Regardless, sounds like I don't just have wiring that suggests it's possible, but also plumbing, since I do have the 3 way valve. And the valve will move to all three positions at times, just not always the times I've asked it to.

    @Devil's Advocate to answer your questions;

    - The upwards facing port goes into the attic. I have two tanks up there, one small, one large. Couldn't tell you which one that pipe connects to. Worth finding out? Let me know if it'll help and I'll have a look.
    - The whole valve was replaced, it's not sticking.
    - I have a British Gas programmer (pic here) but can't find a wiring diagram for it so couldn't tell you if it has a HW off connection easily - perhaps at the weekend

    Just done another test. It was in the same position as last night - 3 way valve/actuator on heating only but both hot water and heating were on, assuming cylinder is satisfied because again, it had been on a while.

    I left the head attached, turned off everything, then did the following:

    - Turned on hot water only = actuator stays in hot water position (I say stays because when everything is turned off that's where is goes)
    - Turned on heating only = actuator goes to mid position
    - Turned on both = actuator goes to heating position > it normally goes to mid but it's all been on for a while
  3. nigel willson

    nigel willson Well-Known Member

    Ur welcome
  4. nigel willson

    nigel willson Well-Known Member

    Deffo wiring problem! Get a sparks round whose familiar with heating wiring. Some of them don’t have a clue!
  5. "The upwards facing port goes into the attic." Hey, man - that port's pipe (where the air vent is) bends round and heads downwards - that ain't goin' to the loft, man. So where? To the cylinder or to the rads?

    Almost certainly there is no 'gravity' in your system at all - it's all 'pumped' with a 3-port valve which means 'Y' plan (Bi-flow).

    Does that BG programmer remove from the wall leaving a wiring backplate behind? If so, usually only one wee screw will secure it, and the wiring behind should be pretty standard. This would show if there's a DHW 'OFF' connection (as well as DHW & CH 'ON' connections), which I 'understand' is required for the correct operation of a Y plan system.

    Anyhoo, from your last test - turning on each prog setting at a time - it seems pretty clear it's a wiring issue as Nigel says.

    In that airing cupboard you should have a 'wiring centre' - a rectangular box where ALL the wires go to. It'll look a 'mare in there when first opened (with the power off...) but modern ones are actually well labelled and not that hard to follow.

    The first step is to ID each cable - where does each cable come from/go to. Then you tackle each component - prog, room stat, cyl stat, motorised valve, etc - at a time, checking the colour of each wire at the component end, and that it goes to the correct terminal in the wiring centre too.

    Most of this testing doesn't even need a meter, provided the correct cables were used with different coloured wires. It's like "Hmmm, the yellow at the prog is for thingy, so that should go to term X on the wiring centre - does it?"
  6. EdSlocombe

    EdSlocombe New Member

    Ha, agreed, the pipe going down is not going to the attic :D. Sorry, I thought we were talking about the pipe off the pump, not sure why now re-reading. Anyway, the one we are talking about goes into the hot water cylinder, entering around mid-height.

    Thanks for all your help. Will take a look to see whether the programmer has a CHW 'OFF' connection and have a look at the junction box in the airing cupboard.
    Deleted member 33931 likes this.
  7. Cool - I was just checking that the 3-porter was connected the right way around... :)
  8. leesparkykent

    leesparkykent Well-Known Member

    I bet it's the cylinder thermostat.
  9. Ed, do you have a test screwdriver or multimeter? Can you use them without killing yourself?

    If so, refer to your wiring diag in your post #10 and check that the cyl stat 'COM' is receiving power when the prog is 'on' for DHW (and not for anything else) and then confirm that the two 'outputs' from the cyl stat (calling' and 'satisfied') become live in turn as you rotate the control past the 'click' point.

    'Calling' should become live when you turn the control UP beyond 'click', and 'Sat' when you turn it down.

    Actually, because of the DHW 'OFF' connection, you will also get a live at the 'Sat' (and possibly 'com' if the stat is turned down) when the prog is set to DHW 'off'.

    It's all a bit confusing...

    However, do try it with the programmer ONLY having DHW 'on', and check that the cyl stat seems to work - do you see that it's effectively a two-way 'switch'?
  10. EdSlocombe

    EdSlocombe New Member

    Think I understand what you mean, perfect, thanks again. Will have a look when I get a chance this week. I have a test screwdriver that I've used before - reckon I'll survive, fingers crossed :D.

    I would say I'm slightly confused as to why the cylinder stat might be the cause when it seems to be one of the things that works, i.e. it does turn the hot water off (as in, repositions the head / valve) when satisfied.

    I also took covers off various things last night to get photos so that at some point this week I could try and compare to wiring diagram just using colours to start, before testing when I have more time. I'm gonna post here possibly more for my reference but maybe someone will find this useful one day...

    British Gas programmer:


    British Gas thermostat:


    Junction box in airing cupboard:

  11. leesparkykent

    leesparkykent Well-Known Member

    There appears to be no hot water off connection from the programmer...terminal 1? HW off on programmer would normally terminate with grey of the 3port valve and normally open of the cylinder thermostat.
    Deleted member 33931 likes this.
  12. The first photo of the programmer ain't that clear - can you confirm which wires go where (not the L&N, they are ok)?

    Why does the cylinder stat matter? Because it's a 2-way switch and not just an on/off type. I can't say I understand the implications of it being faulty in that respect, but you should still check.

    Also, as LeeSpark says, there doesn't appear to be a connection in your programmer for when the DHW side is 'off'. I don't know for sure, but I understand this is required for the correct operation of a modern 3-port valve.
  13. EdSlocombe

    EdSlocombe New Member

    Hmm, yes confirmed no DHW off. Took the cover off again today and there's definitely nothing going into the 1 or 2 connectors. Presumably this is certainly not going to help!

    As I briefly mentioned in an earlier reply, I want to get this sorted before I / someone installs a Nest system. Having now looked again at the wiring diagram for the Nest, I can see that practically all of the connections in the junction box will be replaced with the Nest's heatlink box. Given that, I think I'm going to leave this for now, assume the missing DHW off is the cause and hope that when the Nest is installed it all just works, fingers crossed.

    Thanks for all the help again!
  14. leesparkykent

    leesparkykent Well-Known Member

    You need the HW off terminal to connect with the grey of the valve and normally open of the cylinder thermostat. If the nest heatlink is installed where your existing wiring center is then shouldn't be a problem.
  15. leesparkykent

    leesparkykent Well-Known Member

    If you haven't got a spare core for HW off you could always install a relay, connect a perm live out of wiring centre to common, connect grey of valve and normally open of the cylinder thermostat to normally closed of the relay, and use HW on to trigger the coil.

    One of these installed in a 1g surface pattress and blank plate.
    Last edited: Dec 17, 2017
  16. Kryust NO!

    Just run a bludy wire!

    Relay ma botty.
  17. leesparkykent

    leesparkykent Well-Known Member

    Why not? Simple cheap fix...running a cable might not be an easy option due to decoration.
  18. The Teach

    The Teach Well-Known Member

    So the programmer is missing the hot water off wire (1)

    The boiler installer should have corrected that fault but thats history,so it works as best as it can and its not a priority job and can wait for when the wifi controller is fitted.

    Sometimes when removing the existing programmer backplate there will be a spare wire lurking away out of sight also in the wiring centre there could be a spare wire again hidden away.

    The diagram in #10 is for a generic 3 port valve setup your better off using a diagram from the worcester wiring search for the Y plan on page 6.
    Deleted member 33931 likes this.
  19. Och, fair do's - as a last bludy resort :p

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