Zoning with new combi

Discussion in 'Plumbers' Talk' started by Rmprop, Oct 29, 2018.

  1. Rmprop

    Rmprop Member

    Our combi boiler died unexpectantly earlier in the year, so we had a new Baxi one fitted. I don't think we have either an S or Y plan system, as the heating is just a main branch up throught the house and each floor loops off that.

    Before I go trying to find a plumber, please can somone tell me whether it would even be possible to make each floor its own zone, and what would be required to make it work?

    Thanks
     
  2. nigel willson

    nigel willson Screwfix Select

    It is possible, BUT, it depends on pipework layout as to where it’s possible fit zone valves.get a heating engineer to ave a look
     
  3. Mike83

    Mike83 Screwfix Select

    2 zones could be easy. But if it’s 3 then a bit more difficult.
    Would probably just need 2/3 zone valves and 2/3 programmable stats.
    Some pipe work modifications and wiring added.
     
  4. Allsorts

    Allsorts Super Member

    Hi Rm.

    You can have as many zones as you want - one in each single room if you take it to the extreme :)

    All you need are 2-port 'zone' valves, one for each zone. This is fitted in the 'flow' pipe to that zone, so obviously everything beyond that valve will then be affected by it. The 'return' pipes should remain common to all the rads as they are currently.

    Then, for each 2-port zone valve, you'll need a method of controlling it - a Room 'Stat or (ideally) a Prog Room Stat, and then each of these 'valve+stats' combinations will need a cable (either 3-core +E or possibly a 4-core+E) to go to it.

    It's actually very straight-forward in principle; all these zone cables will go back to the single wiring centre near the boiler (which you'll have to fit if you don't have one - it's basically a wiring box with terminals inside). Each cable will do two things; one is to provide power to each room stat & valve combination, and the other is to return an 'on' signal back to the boiler when needed.

    Then, whenever a zone's room stat 'calls for heat', it'll operate its associated zone valve which will open it and this will then send a switching signal to the boiler to come on. If 2 (or 3 or 4 or...) room stats are all calling for heat, then all their valves will be open and all will be sending that same signal to the boiler to come on, so the boiler will explode.

    No it won't - it'll just be 'on'. It's like having 10 light switches switching on a single light; the light will just be 'on'. Any switch will turn on that light. Two won't make it any brighter.


    So, think about the useful zones you could have - having bedrooms on a separate zone makes huge sense since they are usually unoccupied during the day and eve - and then check your plumbing layout to see if fitting a zone valve in the flow to them will have any other side effects such as affecting the office/study which is on the same flow pipe run. See how good access is to that flow pipe and fit the valve there. Don't mistake that for a return pipe...


    The worst part of the job is to get access to the pipe. Oh, and run the cable back to the boiler. And running a cable to the room stat.
     
  5. Rmprop

    Rmprop Member

    Allsorts, thanks for your informative reply, thats pretty much what I was hoping to hear. My house is currently in a possition where I can run cables and access pipework. I redid all the plumbing not long after moving in as there were a couple of leaking solder joints, and vaguely planned zoning into the layout ready for when we had a new boiler. Typically the old boiler packed up at the worst possible time, so adding the valves was put on hold.

    There is a junction box next to the boiler, although I've not looked at it in detail, I do recal seeing lots of different wires in it as the plumber was doing the instal, so can I assume this is where the current wireless stat reciever is wired in?

    Thanks
     
  6. Mike83

    Mike83 Screwfix Select

    Honeywell sundial rf2 pack 5 could be something that would help.
     
  7. Allsorts

    Allsorts Super Member

    That junction box will be your 'wiring centre'. For a combi boiler, this will currently be very straight forward.

    If you have good access to the pipework and an easy route for cables, you are good to go.

    Plan out where you'd want the zones to be. Remember that as soon as you fit a zone valve, everything beyond that will be affected by it. So if you have your F&R (flow and return) pipes running along a floor supplying 3 bedrooms and a study, if you fit a zone valve there it'll affect your study as well as you bedrooms. If your study needs to be separate, it'll need a new flow pipe from before that 'bedroom' valve. Make sense?

    Anyhoo, plan out where the valves should be fitted and where the room stats (programmable...) for each should be mounted, and go from there. I'm not sure how plumbers would wire this - whether to run separate cables for each stat and the valve back to the wiring centre and sort it all out there (a 'mare) or whether to run just a single 4C+E cable to each zone and have a wee junction box fitted there to supply the valve & stat (I think that's what I would do).
     
  8. Mike83

    Mike83 Screwfix Select

    The Honeywell rf2 pack 5 has one twin channel programmer and two wireless thermostats.
    If there was only 2 zones then this may simplify things.
    You would only need to add in the 2 zone valves with 5 core cables from the wiring centre.
    No cables required for the room stats.
     
    Allsorts likes this.
  9. Allsorts

    Allsorts Super Member

    Too complex for me, pal... :oops:
     
  10. Mike83

    Mike83 Screwfix Select

    No it’s not DA.
    You know your stuff and it’s actually more simple than your idea.
    Less cables to run and more flexibility with stat position.

    Anyway the programmer is hard wired but the 2 stats communicate with the programmer,as the receiver is built into the programmer.
     
    Allsorts likes this.
  11. Mike83

    Mike83 Screwfix Select

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    The Teach likes this.
  12. Allsorts

    Allsorts Super Member

    I like wires... I hate wireless...

    :D
     
  13. Allsorts

    Allsorts Super Member

  14. Mike83

    Mike83 Screwfix Select

    Told ya.
     
    Allsorts likes this.
  15. Rmprop

    Rmprop Member

    Thanks for the help chaps.

    I actally need 3 zones, so whats the best stat etc to use for that setup?
     
  16. Allsorts

    Allsorts Super Member

    Over to Mike... :p
     
    Rmprop likes this.
  17. Mike83

    Mike83 Screwfix Select

    You could change your current room stat to a programmable stat for that floor.
    Then use the other setup mentioned for the other 2 floors.

    There is other setups to choose from but what will determine things is if it’s possible to run wires to the stat locations
     
  18. MGW

    MGW Screwfix Select

    I also would prefer wired, however not found wired motorised heads for thermostatic radiator valves, so I have used wireless, theory is great, each radiator has a head on the valve which is programmable so every room becomes it's own zone, so in theory very easy to install and very controllable.

    Practice however not so good, OK hind sight and hind sight is easy should have bought more expensive versions and fitted Evohome, however even that would not cure all the problems.

    We in the main today use analogue boilers, well in my case digital zero to 6 kW and analogue then to maximum output of 28 kW, so timed zone valves OK, on/off wall thermostats controlling zone valves is not OK. Whole idea is the boiler is cool before we switch it off, then less heat is lost through flue, and we switch it on/off as little as possible and manufacturers go to great lengths to write anti cycle software to reduce how many times the boiler switches on/off.

    There is a problem in that without some thing external to stop it, the boiler would continue cycling on/off all summer to test if heat required, so the wall thermostat is one way to stop that happening, I suppose one could put a wall thermostat in every room set to same temperatures as the TRV head all in parallel so if any room needs heat boiler will switch on, however in real terms it is unlikely we need to go to those lengths, maybe two or three thermostats in coldest rooms, but not one in every room.

    However faced with the option of multi wall mounted thermostats, or an EvoHome thermostat which is in essence multi thermostats one in each room plus EvoHome can connect to with some boilers to the bus with OpenTherm, I think being lazy I would pay extra and get EvoHome if I was doing it all again.

    However I have MiHome Energenie which will work with Nest, so analogue heads should work well with an analogue boiler however if the thermostats turn off the boiler clearly the analogue heads will not work correctly, in deep winter when boiler is between the two limits they work well, Autumn and Spring no so good, just fitted two more so now 4 rooms with these heads, I found on fitting, radiators stayed just warm, did not seem to switch them off completely, but as time as gone on, they seem to improve, I will guess the old TRV heads were not exercising the valve, and now valve is being exercised they are improving, however it is the valve at fault not the heads.

    Point is once electronic heads are fitted to the radiator valves, then the zone valves become redundant, so is it really worth fitting them?
     
  19. Rmprop

    Rmprop Member


    I can get wires where ever needed at the moment, and would prefer wired over wireless where possible.

    I currently have a wireless programable one which does the entire house - from the living room. Which means when the fires lit and downstairs gets warm, the stat turns the heating off and upstairs (2 floors) gets cold. We live in an old house and I've fitted cast rads which don't have TRV's, hence wanting to zone instead.

    So, if I used the current stat for the ground floor, when it signals to turn the heating off, the other 2 floors will signal to stay on, correct?
    So I'll have to add a valve onto the ground floor loop too and some how make the existing room stat opperate that one?

    Or should I just but 3 wired programable room stats and 3 valves and do it that way?

    Thanks for your patients Mike!
     
  20. Mike83

    Mike83 Screwfix Select

    You need to think about how you want to control the heating on each floor.
    What I mean is, if you have 3 programmable stats and wanted to boost the heating on all 3 levels then that would mean visiting all 3 stats.
    Or you could fit a programmer/s on one level meaning any level can be boosted from the one spot. You would then have a stat in each zone controlling the temp.

    Wired controls are far superior and easier to do basic fault finding on.

    There are 3 channel programmers on the market. This would then switch to the zone valves via its roomstat
     

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