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Plumbing (Boiler/Valves) Help

Discussion in 'off topic' started by wiresandmore, Jan 14, 2022.

  1. wiresandmore

    wiresandmore pfm Member

    I wonder if any PFM’ers can advise me here.

    We have had ongoing plumbing challenges for quite some time in our home. It’s a large semi-d; 3 storey and 6 bed/4 bath. We have a De Dietrich boiler using mains gas, it was expensive and is apparently suitably sized for the house (I think it’s 38kW), it’s coming up on 10 years old but still seems to work well. We also have a Hive system which splits the flows into three zones + HW.

    Our challenge has always been that the zone valves seem to be at best partly effective. If the hot water is on, the ground floor heating comes on too (maybe not fully, but it significantly heats the ground floor). And, it’s hard to get the top floor to come on at all as it seems the ground floor valve never closes fully and therefore much of the heat escapes into that circuit.

    The answer would seem to be to change the valves. But even when the valves have been replaced (which they have been more than once), the problems persisted, they’ve not gone away. I’ve asked the plumber to find some more resilient, stronger valves with better shutdown mechanisms so that the zones really work properly but he says they are all very similar and some of our problems are just due to the pressure in the system and some valve leakage is common. Frankly, I doubt that - but I am struggling with my searching on the net to find what would be demonstrably better than what we have (which are Myson valves, costing around 70-80EUR here in Ireland).

    Anyone got any advice on this and what the best valves might be? Alternatively, can you get boilers with zones built-in (we’d need 3 + HW) and can a hive system be configured to support that. Which brands should I look at?
  2. NigelP

    NigelP pfm Member

    Are the valves accessible as you maybe able to see if they full turn to certain positions ? Or just add a manual valve ?

    not really helping I know.
  3. Copperjacket

    Copperjacket pfm Member

    Have you had your system pressure cleaned and treated to get rid of the old gunk?
  4. twotone

    twotone pfm Member

    Probably your best bet would be to install wireless remote TRVs which are affectively single zone valves so if you have one on each rad then you have as many zones as rads.

    Not cheap but about what you quoted above plus a controller.

    Honeywell Evo home is good, think the kit for about 8 rads plus controller is about £1000, you can fit the valves yourself (no need to drain the system) and have the whole thing pre-bound for about another £50.

    Loads of manufacturers do similar these days, Dreyton, Wiser, Worcester Bosch do their own stuff for their own boilers and there's loads more.
  5. dweezil

    dweezil pfm Member

    Could the top floor problem be low pump output?

    I turn the heating circuit pump down a notch in the summer.

    You might have Bluetooth or manual control.

    My system doesn't turn off fully in winter so there's always a residual flow for background or frost protection. Manual override then turns it off fully for March to November.

    There must be some facility to turn off completely in summer.
  6. Darth Vader

    Darth Vader From the Dark Side

    As above we use the ambiSENSE smart TRVs on 16 radiators

    They can be set manually or as we have done have the whole installation centrally controlled via an app on your smart phone or tablet.

    With this system you can tailor the heating in each room and if necessary issue an over-ride for a set period. My wife does this as we have her office at 18 degrees but when she is working at the computer bumps this up to 20 degrees or so whilst in there.

    We also have a modern weather compensated boiler and the two together works great and our heating bills are starting to come in lower. We'll know for certain in August when we get our annual summary.


    wiresandmore and twotone like this.
  7. wiresandmore

    wiresandmore pfm Member

    Thanks for all the input. To be clear, the valves are actuator valves I believe, and they seem to work in that you hear the whooshing noise as the spring changes position when the Hive controller sends a signal to them.

    I did think about the radiator control option but we have 29 of them in the house so it’s a huge cost. I’ll have a look and spec out, so thanks for the recommendations there. It may be the most practical way forward.

    I was rather hoping I could source some premium actuator valves for each zone which would be stronger and more definitive in being on/off. Are they really all equally poor? My PFM audiophile brain is set on sourcing some (probably German or Japanese) actuator valve exotica to solve the problem!
  8. John Phillips

    John Phillips pfm Member

    The idea that you can get impactful flow through any reasonable closed zone valve seems odd to me (with some, but rather limited, CH system experience).

    The two things that immediately occur to me are:
    • the (probably silly) idea that the mechanical override on some zone valve may have been left in the commissioning position - not too likely I would think but I would check them all for operation just in case (as @NigelP writes and I think you have already done); and
    • the control system is keeping the pump running for a while after all demand for heat has been satisfied and the zone valves have all closed (known as "pump overrun"), combined with the pressure-sensitive bypass valve needed for that circumstance not opening properly. So is there pump overrun? If so, is there an automatic bypass valve to check? This all depends on a lot of details I don't know about how the Hive control system works, so it's not easy to guess intelligently.
    I do know the basics and have maintained/updated my own CH system (to the extent legally permitted) over a number of years. But modern CH systems are getting much more complex to get them to be increasingly efficient so my knowledge of CH systems may run out quickly.
    wiresandmore likes this.
  9. twotone

    twotone pfm Member

    Personally I fit Honeywell zone valves OP imo they’re the best but I don’t think that their quality control is what it was however if you don’t want to go down the individual motorised wireless trv road I’d recommend replacing the existing valves with Honeywell valves and I’d also replace the pump and take it from there however reading your OP it would appear to me that the plumbing hasn’t been done properly initially so you might not see any improvements the only thing that will definitely work is the wireless trvs.
    wiresandmore likes this.
  10. wiresandmore

    wiresandmore pfm Member

    Thanks again. I’ll put those to the plumber and see what they say.
    twotone likes this.
  11. Richard Lines

    Richard Lines pfm Member

    You need too get to the bottom of why the zone isolation valves aren't doing what they should, I don't think TRV's are the solution to your challenges at all. You also need to look at the overall system pressure and adjust to the minimum required to get flow on the 3rd Floor.


    wiresandmore likes this.
  12. twotone

    twotone pfm Member

    The motorised wireless TRV aren't just ordinary TRVs they're effectively zone valves fitted to each rad so they'll definitely work.

    I'm guessing that the OP has 'normal' TRVs fitted on some rads, probably the bedrooms at least.

    Just found these OP, they might do what you want.
    wiresandmore likes this.
  13. cctaylor

    cctaylor pfm Member

    We had a problem with the valve for our hot water. The valve was sticking slightly open resulting in the hot water temperature being too high and circulating pump running 24/7.

    The actuator was removed and after a spray of lube it was wiggled back and forth with a spanner. This freed it off and normal service was resumed.

    Another issue became apparent. When the new boiler was fitted the flow to hot water cylinder was reversed. These valves are often opened by the motor and closed by a spring against the flow. In my case the valve was shutting with the flow helping the spring resulting in an annoying and potentially damaging water hammer when it closed. The valve has since been turned so that the spring closes against the flow.
  14. misterdog

    misterdog Not the canine kind

    No.. ask a heating engineer.
  15. wiresandmore

    wiresandmore pfm Member

    Fair point. Challenge is where I live (Dublin) when I search for heating engineers, I get list of plumbers. Is there an accreditation I should look for?
  16. twotone

    twotone pfm Member

    There really isn’t such a thing as a heating engineer per se except for the likes commercial heating for example I’m a time served plumber (40+ years) and I do central heating and gas work, that’s pretty typical for domestic heating work, obviously there are time served domestic heating engineers and gas engineers too but most of them will cross over into the other disciplines.
  17. westsea

    westsea Retirement present

    I think you might have to look at the overall system, we have a two zone system, and the zone control valve
    is not particularly special, and is OK over 20 years without replacement. That said, there is some transfer of heat continuously to some parts of the house. In our case the system is described as as continental, that is the boiler heats water in the cylinder, which is pumped around the radiators, hot water is supplied at mains pressure through a coil in the cylinder. We have the usual two room thermostats controlling the zones, and a control timer for the system. In each radiator there is a manual flow control valve ...cone shaped I think, these are set by the plumber/heating engineer to balance out the flows to each room and the zones, a suck it and see process. you may not have these in and old system. Check the pipe runs; if flow and returns for different zones are close together then heat transfers across them As others have said, it is difficult to imagine that on off control valves leak to the extent that you describe.
    The difficulty is that many plumbers do not fully understand all systems. One, who came to give me a quote for a new boiler, just didn't believe how the system worked..... There are heating engineers about, but generally they apply to commercial buildings and plant. Large domestic systems seem to fall 'betweeen two stools' as it were. Not much help I'm afraid , difficult to diagnose without seeing the whole system
  18. John Phillips

    John Phillips pfm Member

    @misterdog is right but also so are you in that it's not easy to find someone with broad CH system design expertise, and experience of your specific components.

    Some more thoughts. Based on suspecting that you have the EMC-M 34/39 MI boiler from what you write. If so it's very capable, according to the installation manual (found online) but necessarily quite complex.

    It sounds to me as if there is more than one problem that needs addressing. At least: (i) the lack of circulation to the highest floor/zone; and (ii) unwanted circulation to zones where the heating demand is satisfied. There may be one fault causing these but maybe more than one. I could suggest some trouble-shooting tests but I'm sure the system is more complex than the ones I am used to, so someone who understands the boiler would be a better bet.

    Has the system ever worked properly? The words in your original post are not clear ("for quite some time"). From a quick perusal of the assumed boiler's manual I would expect it to be happy driving three reasonable-sized zones + HW continuously. But with your 29 radiators total (almost 10 per zone) I suspect it's not over-specified.

    The boiler above does seem to have pump overrun and calls it "pump post circulation" from 1 to 98 minutes or continuous (default is 2). What is that set to?

    If the Hive control system is such that it simply closes a zone's valve when the zone's demand for heat ceases, then there has to be some working arrangement to handle the continued flow during the overrun time when there's no flow to any zone. The manual says you need an external bypass or expansion vessel for this situation. Is there an external bypass or expansion vessel? I expect so. Is it in good operating condition (but I am not immediately sure how to test that)?

    Regarding the lack for upper-floor flow, what is the maximum pump circulation speed set to? The pump has a 6.5 metre head capability and that's more than normal so it should be very capable.
  19. wiresandmore

    wiresandmore pfm Member

    Thanks for the further replies. The system has never worked all that well, we have always had the problem of some degree of overspill and lack of control of the system. I neglected to mention that we have large Victorian style radiators which look great but do stay hot for quite some time after the heat has been switched off to them.

    The point about over-run is interesting, that seems easy to find out and also the circulation speed. I’ll see what I can sort out this week.
  20. matt j

    matt j pfm Member

    My Mum's system used to pass hot water into the rads when they were supposed to be off and she also got through a few motorized valves before she finally had the system flushed and a knackered boiler replaced, it has been fine since.

    She had a magna clean fitted with the new boiler (required for the 10 year warranty) and the first few times I cleaned it it was full of crap even though the system had been flushed. I only do it once a year now and there is only ever a miniscule amount in it.

    I wonder if sludge is fouling up the valves?

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