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Thread: Evohome HR92 Installation Issue

  1. #1
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    Default Evohome HR92 Installation Issue

    Hi all,

    I have recently bought an Evohome system for my house, which I installed myself in the end, after receiving a quote for over seven hundred pounds from a plumber, which I didn't think was fair, for what he admitted was less than a day's work. I didn't find it too tricky, on the whole, once I got over the fear factor of tinkering with my boiler's innards.

    It's a pretty bog-standard setup, of 7 HR92s, grouped into 6 zones, and a BDR91 wired into a combi boiler. The only issue I have is that, due to what I presume to be slightly outsized pins on my radiator valves, I had to leave the HR92s a turn or two from being fully tightened. I discovered that when fully tightened, the HR92 was unable to open the valve, as the pin was fully depressed, even when the black wheel was turned fully anti-clockwise. Unscrewing the HR92 a wee bit alleviated the issue, and the system seems to work extremely well, with actual room temperatures closely following my programmed targets.

    I was wondering if having to leave the HR92s was likely to lead to problems, and whether I should perhaps grind a few mm off the valve pins, or even replace the valves?

  2. #2
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    Personally spending so much on a control system, don't scrimp on the valves, replace with honeywell volaves, low cost, quick job and guaranteed to work fine!

  3. #3
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    Have you tried adjusting (reducing) the throw setting on the HR92?

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    Quote Originally Posted by basiluk View Post
    Personally spending so much on a control system, don't scrimp on the valves, replace with honeywell volaves, low cost, quick job and guaranteed to work fine!
    I'd be interested in knowing how this can be a quick job given that you have to pretty much drain the heating system to replace the valves which is not a straightforward task. It would be the best option though to be fair.

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    Quote Originally Posted by grumblemunta View Post
    The only issue I have is that, due to what I presume to be slightly outsized pins on my radiator valves, I had to leave the HR92s a turn or two from being fully tightened. I discovered that when fully tightened, the HR92 was unable to open the valve, as the pin was fully depressed, even when the black wheel was turned fully anti-clockwise. Unscrewing the HR92 a wee bit alleviated the issue, and the system seems to work extremely well, with actual room temperatures closely following my programmed targets.

    I was wondering if having to leave the HR92s was likely to lead to problems, and whether I should perhaps grind a few mm off the valve pins, or even replace the valves?
    Sounds like your valves are not compatible - the HR92 has about 4mm of travel for the pin, so if the black wheel is fully unscrewed and the pin is still fully depressed it must protrude at least 4mm more than "standard" which is a LOT. I assume the problem is the same on all the valves ?

    Do you happen to know what make and model of valves you have, and could you post a side profile picture of the valve body with the HR92 and it's adaptor removed so we can see what it looks like and what the proportions are ?

    I'm not too keen on the idea of filing the pin down - once you do that you can't turn back... I actually did this on one of my valves, I have some cheap Peggler Bulldog valves and they are "compatible" dimension wise but they are not very good - one in particular in the living room is a bit sticky and with the HR92 in normal (stroke 0) mode it won't fully open the valve as the valve won't completely open until the pin is 100% extended, so I have to use "stroke 1" in settings to get it to fully open in cold weather otherwise it can't get up to temperature.

    I filed about half a millimetre off the pin so that the valve should fully open before the black wheel reaches its unscrewed limit but I still find I have to use the stroke 1 setting, which is not ideal because it shortens battery life, and in my experience also tends to cause temperature overshoots as the valve turns a lot further for the same temperature error, so tends to overcompensate and thus overshoot the target.

    I'll be changing all my valves to Honeywell Valencia this summer I think - there's no doubt that a valve that is a bit sticky or doesn't have a fully compatible pin travel range/dimension doesn't perform as well. Since this particular valve got sticky (I think the o-ring in the stem has swollen up) I've noticed a lot more temperature overshoots in a room that used to have perfect temperature regulation, and I'll bet anything that once good valves are fitted the problem will go away again.

    So I tend to agree with the advice of "don't skimp on the valves". The Honeywell Valencia valves are the "reference" design that the HR92 is designed to fit - if they fit and work on other M30x1.5 valves that's a bonus but not guaranteed, I think. It may fit and work after a fashion but may not work optimally.

    As a stop gap measure you can probably leave the bases unscrewed a bit as you have, however the torque of the motor when it hits the ends will tend to try to turn the whole thing unless it is screwed down, also if you've only brought it out a couple of turns its very likely that your valves are still not fully opening, as a couple of turns is only 3mm. Filing just the right amount off the valve pin would probably work but is a bit risky in the sense that you can't undo the change if you're not happy with it, nor can you refit the original mechanical TRV's at that point if you had to. Getting carried away with a file could lead to a sooner than expected replacement of the valves being required!

    Personally I would get those valves swapped in the summer - as you say its a drain down job and a good few hours of work for DIY'ers like us, but I think it's worth it.


    Quote Originally Posted by g6ejd View Post
    Have you tried adjusting (reducing) the throw setting on the HR92?
    That's not going to help - it defaults to reduced throw (stroke 0) anyway, it's stroke 1 that increases the throw in both closing and opening directions, however if the error in pin length is so great that the valve is still closed even when the black wheel is fully unscrewed, no amount of tweaking HR92 settings is going to help!
    Last edited by DBMandrake; 16th January 2017 at 10:07 AM.

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    Quote Originally Posted by DBMandrake View Post
    Sounds like your valves are not compatible - the HR92 has about 4mm of travel for the pin, so if the black wheel is fully unscrewed and the pin is still fully depressed it must protrude at least 4mm more than "standard" which is a LOT. I assume the problem is the same on all the valves ?

    Do you happen to know what make and model of valves you have, and could you post a side profile picture of the valve body with the HR92 and it's adaptor removed so we can see what it looks like and what the proportions are ?
    All the valves look like this.

    IMG_20170118_185925.jpg

    No idea what type of valve they are, or who manufactures them, I'm afraid.

    I am coming around to the idea of replacing the valves. It would always seem like a job half done, otherwise, wouldn't it. I do reckon that it would be quite an undertaking for someone of my limited plumbing experience, though.

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    Those arrows look nice and confusing

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    Quote Originally Posted by Fireblade69 View Post
    Those arrows look nice and confusing
    Not really - it just means it's a bidirectional valve, as most are these days. My valves have the same arrows.

  9. #9
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    Quote Originally Posted by grumblemunta View Post
    All the valves look like this.

    IMG_20170118_185925.jpg

    No idea what type of valve they are, or who manufactures them, I'm afraid.
    Here's a picture of one of mine: (a faulty one I replaced)



    The dimension that matters is the one shown in red from the tip of the pin to the flat area just above the M30 thread. On mine this is 14mm - yours looks to be a lot longer than that due to the pin being longer. When you consider the HR92 can only move the valve at most 4mm, it doesn't have to be too far from the correct length for it not to work.
    I am coming around to the idea of replacing the valves. It would always seem like a job half done, otherwise, wouldn't it. I do reckon that it would be quite an undertaking for someone of my limited plumbing experience, though.
    If you haven't done that kind of plumbing before then yes it would be a bit daunting. I'm reasonably comfortable with most plumbing work now having started with small easy jobs and gradually worked my way up to much more ambitious ones, (like doing my own S-Plan conversion) but I'm not looking forward to replacing all the valves on mine either.

    The main reason being that every time you replace a valve body like that you have the potential for leaks, especially if the old pipe is in a poor state, multiply that by 10 radiators and the chance of one leaking on first try is quite high.

    When I do it I will be doing a "test fill" of plain water first and running the pump with the boiler turned off so that I can go around the house and carefully scrutinise every new valve for any leaks and resolve any problems before draining and doing a real fill with inhibitor - otherwise if you get a single leak that requires draining back down again to fix you're throwing away your inhibitor...

    If you're not confident in doing the job it might be an idea to get someone else to do it for you - shouldn't take someone that does it for a living long to do.
    Last edited by DBMandrake; 19th January 2017 at 11:11 AM. Reason: 14mm not 15mm

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