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Starting to plan a switch from Y to S plan with two heat zones

Discussion in 'Plumbing and Central Heating' started by PASUK, 27 Oct 2020.

  1. PASUK

    PASUK

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    Hello

    I'm in the process of having to run a new heating circuit for my downstairs rads as the existing pipes are buried under concrete floors and their developing leaks.

    I could T-off from the upstairs circuit but the way the pipes are run its actually not too much hassle just doing a separate circuit back to the pump cylinder etc. So I'm going to run the new circuit and take the opportunity to zone off up / down stairs circuits - plan is to get a professional in to do the final connections in the airing cupboard.
    I want to do my homework and take the time to understand the job properly so I managed to trace a lot of the pipes and I think I figured a lot of it out. I am sure much more clever people on this forum will correct me....

    I think I have what is called a Y plan, vented indirect system which uses a heat only boiler.

    I'm trying to figure out some of the pipes that lead away from the cylinder following the numbers on my diagram do I have this correct?
    1. Hot water to the kitchen and bathroom taps around the house
    2. Unsure, but I am guessing that this will connect up with the return from radiators and go to the boiler and loop back round on pipe 5?
    3. The red highlighted pipe I couldn't physically reach around the cylinder to trace but my best guess is that this connects to the bottom of the cylinder at the back feeding in cold water as hot water is drawn from the top.
    4. Hot water going out to the radiators.
    5. Heated water from boiler? which before that came from radiators (which came from #4) and came from hot water cylinder (which came from #2)?
      Does that mean the pressure relief valve only allows water to pass downwards when pressure gets too high, a bypass?
    6. Similar to #1 but just the cold un-pressurised feed to taps around the house
    7. Same as #1
    8. Same as #6
    9. Mains cold water feed
    Thanks, once I figure this out i can start drawing out how it should change to become the S plan with the extra zone.

    PipesAC01.jpg
     
    Last edited: 27 Oct 2020
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  3. Madrab

    Madrab

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    Your scheme probably isn't that far away
    1 - Yes
    2 - It won't be a pressure relief valve, probably an autobypass that connect to the return to the boiler, not that important given it's Y plan but certainly required when it's an S Plan
    3 - Yes you will have a gravity cold feed from the cold water storage cistern (CWSC) that enters the bottom of the cylinder
    4 - Yes
    5 - Yes - flow from the boiler
    6 - Yes - gravity cold water feed
    7 - Yes
    8 - Yes - gravity cold water feed - probably to the same outlets as 1/7
    9 - Yes - same as 8
     
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  4. PASUK

    PASUK

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    Many thanks @Madrab ! This closes out my first step of figuring out what is the current situation. Thanks again.
    Clarification:
    Is this what I thought was PRV but its a bypass?

    IMG_1259.jpg

    Next step for me is:
    1. Need to figure out if my cylinder is old and should be replaced or if I can run it longer. Any tips would be great (thinking of posting a photo/label here)
    2. Draw up the new S plan design. Which I think I'll enjoy wrapping my head around.
    3. Find a pro willing to do the work, It's been a struggle engaging anyone for the work.
     
  5. Madrab

    Madrab

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    Yes, that's an autobypass. It's designed to allow the minimum flow through the boiler on overrun when the valves on the system shuts down. Essential for an S Plan.

    The defining factor for your cylinder is recovery time and capacity. How long it takes a given volume of water to heat back up. The older the cylinder then generally the slower it would be to recover, it's usually age dependent .
    Your S-Plan would basically replace the Mid Pos valve with a separate valve for each circuit and then that can go to an S Plan plus which allows the addition of extra individual heating zones.
     
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  6. PASUK

    PASUK

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    Thank you!

    In which case all good, reasonably happy with the current volume and re-heat time.

    Ok thanks I have updated my diagram highlighting in green the specific pipes that need changing and I presume an auto air valve is needed in each zone as shown?

    PipesSplanProposed01.jpg

    To complete the diagram I am going to look at any isolating valves around this system and see if any are missing, if the system is going to be drained i might as well ask for any additional stop valves to be inserted to aid future maintenance.
     
  7. oldbuffer

    oldbuffer

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    1. Make sure that the LAST connection on the return pipe before the boiler is from the hot water cylinder. Otherwise you can get reverse circulation and hot radiators with just the hot water on.
    2. I wouldn't fit any isolation valves in the circuit. They are generally:
    2a. Not rated for continuous central heating temperatures.
    2b. Unless very good quality, will eventually leak.
    2c. Unless full bore, are extremely restrictive of flow.
    3. You might consider having the system power flushed while the work is going on. Far from essential, but in my opinion a good idea unless the system is perfectly clean.
    4. If you haven't already got one, fit a filter (Magnaclean or similar) to keep the system clean.
    5. Don't forget the inhibitor.
     
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  8. ericmark

    ericmark

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    The main advantage of the Y Plan was water can cool with thermosyphon to the DHW store, some boiler need this ability to cool so I was told, so depends on fuel type.

    As to zones there are cases where it makes sense, my flat and main house are on zone valves as flat is seldom heated, however the house has 7 rooms, not counting bathrooms and utility rooms, and the 4 rooms upstairs were clearly designed to be bedrooms and down stairs kitchen, living room and dinning room. However we use the dinning room as a bedroom, and two of the upstairs bedrooms are craft room and office, so zone up/down would not work, and it does not work for most families, be it kids in bedroom doing home work, or mother down stairs as she can't climb the starts, we over the life of the house change what rooms are used for.

    So programmable TRV heads are far better than zones as easy to change to program to suit use, and with the eQ-3 starting at £10 also likely cheaper.

    May need a by-pass valve adding, but with a modulating boiler it is analogue, and in the main you want analogue controls, not off/on if it is to work efficiently.
     
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  10. PASUK

    PASUK

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    @oldbuffer
    Hi sorry, it's me not knowing the correct names for components, but basically looking to know where to position components like a ?Lever valve? that would help me isolate a section of the system for any future maintenance. I know just above and below my pump I have the ability to close off the supply for replacing the motor if ever needed, I have no idea what that is called! It's not a lever valve.

    Good point, its been about three years since the system was flushed and inhibitor put in. Magnaclean sonuds like a good idea.

    @ericmark
    I am using a Worcester 30 ri compact boiler which I think doesn't need thermosyphon to the DHW store, I do know the pump is supplied its electric supply from the boiler so it can run for a period after heat to continue circulating water I think to avoid damage to the boiler. I really don't know if that's related to this.

    We are using Hive system in our house and their digital TRVs are so expensive. I haven't considered mixing this up with another brand like eQ-3 but with 14 radiators in the house and the way the pipes run its actually not too bad to go to zones.

    Wow, no idea what this means!
     
  11. ericmark

    ericmark

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    My idea was to use eQ-3 upstairs and Energenie down stairs as using Nest, but Nest withdrew their support for Energenie and I have found simply using same schedule with both wall thermostat and TRV works reasonably well, so I realise had I used 9 eQ-3 instead of 5 eQ-3 and 4 Energenie it would have worked just as well.
     
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  12. Madrab

    Madrab

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    oh my ... it's all gone from what was relatively straightforward to all of a sudden very complicated :whistle:
     
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  13. PASUK

    PASUK

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    :D Tell me about it! But learning loads. I have to say I am struggling to find a plumber to agree to do the job, three have turned me down due to too much other work. I may have to do this myself.
    @Madrab I don't suppose you can help answer a prior question of mine, where to put lever valves (or other valves) and sensible places to be able to isolate the system e.g. before and after the pump.
     
  14. Madrab

    Madrab

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    There would normally be gate valves before and after the pump, to allow the pump to be removed.

    What on the system would you want to isolate? Once the system is up and running then you want to minimise any valves on the primary (HW) and CH circuits as suggested. They not normally used as part of a domestic system design.

    If you do want to use them then they need to be full bore and designed to be used on CH systems with it's higher latent heat and be resistant to the system chemicals.
     
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  15. PASUK

    PASUK

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    OK good point and yes @oldbuffer did also suggest against - I lost track.
    Many thanks all!
     
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