new to evoHome - existing Honeywell wireless room thermostat

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  • DBMandrake
    Automated Home Legend
    • Sep 2014
    • 2361

    #46
    Originally posted by bruce_miranda View Post
    Or you use a single bdr91 but with HW priority that just closes the CH valve anytime there is HW demand. But on other times it is open.
    Yeah you could do that very easily. But in my case a full cylinder reheat from completely cold is about 25 minutes so I'd have no heating for that time, so I don't really want full hot water priority. I have a balancing valve for the indirect loop that means both radiators and hot water cylinder each get a pretty fair share of the flow when both are demanding heat, but if I was to add a simple overrun timer to the heating zone valve then when it was trying to modulate the heating at say 20% but there was also hot water demand not only would the flow temperature be boosted for hot water reheat, the heating zone valve would remain open when it thought it was controlling it to 20% so there would be a major overshoot in radiator temperatures.

    I figured that if I dropped back to TPI control of the heating zone valve when hot water demand was present (by disabling the overrun when hot water is on) this would avoid this. But I don't think I'll do any of this as I quite like the better temperature control I'm seeing from just letting the heating zone valve do its thing.
    Apparently the normal motorised zone valve were never designed to stay open for long durations and hence many don't recommend that they are used for UFH purposes. There are other valves that are designed for that. Problem is most plumbers and electricians swear by the Honeywell valves so will only ever use that. The compromise I guess is to make sure the valves open and close regularly so that they don't seize.
    I've actually wondered the reverse - I would have though the two port zone valves were designed decades ago with non-TPI systems in mind - where your heating zone valve would cycle maybe once per hour or so at most. On a TPI system your heating zone valve is cycling on and off every 10 minutes - that seems like a lot of cycling and I do have to wonder whether they are up to all that extra opening and closing over a period of years or whether it will wear them out prematurely...has TPI been in wide use for long enough for this to be determined yet ? What is the average life expectancy of a heating zone valve with and without TPI control ??
    Last edited by DBMandrake; 4 November 2016, 11:08 AM.

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    • paulockenden
      Automated Home Legend
      • Apr 2015
      • 1719

      #47
      Originally posted by DBMandrake View Post
      has TPI been in wide use for long enough for this to be determined yet ?
      First references I can find to TPI are 2008, but knowing Honeywell it was around before that, just called something else!

      P.

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      • DBMandrake
        Automated Home Legend
        • Sep 2014
        • 2361

        #48
        Originally posted by paulockenden View Post
        First references I can find to TPI are 2008, but knowing Honeywell it was around before that, just called something else!
        Right, so we don't really have enough historical data yet to see how two port zone valves hold up under constant TPI operation and what that might do to their lifespan.

        I decided to spend a little bit extra and go for the Honeywell valves since everyone seems to say they're the most reliable... the irony is if you shop carefully on ebay and/or amazon you can actually find new unopened V4043's for not much more than a lot of the cheaper brands...

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        • bruce_miranda
          Automated Home Legend
          • Jul 2014
          • 2307

          #49
          Infact a plumber recently almost forced me to change a Vaillant supplied valve to a Honeywell one, because he said it was a ticking time bomb. Since I supplied the valve, he didn't even charge me anything to replace it, that is how strongly he felt about it. And yes, I agree, if you shop around there are some good prices to be had on them.

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          • DBMandrake
            Automated Home Legend
            • Sep 2014
            • 2361

            #50
            Originally posted by bruce_miranda View Post
            Infact a plumber recently almost forced me to change a Vaillant supplied valve to a Honeywell one, because he said it was a ticking time bomb. Since I supplied the valve, he didn't even charge me anything to replace it, that is how strongly he felt about it. And yes, I agree, if you shop around there are some good prices to be had on them.
            For something so critical to the operation of your heating that you can't easily replace without draining the system down, (well you can replace the motor head without a drain down, or you could install gate valves on either side but I don't have the room to do that) I figure that you don't cut corners. Anything that needs a full drain down to replace I don't cut corners on.

            I found one on Ebay for £35 new and unopened including shipping, ordered that to do a C Plan conversion (just adding it to the gravity loop) and then changed my mind a few days later and wanted to go the whole hog and do an S-Plan conversion, so I needed a second one - went back to the same seller and they were now sold out! Found another one from someone else on ebay for £45 including shipping also new and still boxed and still a lot cheaper than list price. Both are absolutely new and genuine Honeywell units.

            Check the listings carefully on Ebay - there are a lot of similar looking valves that say they are V4043 compatible, but they are not actually Honeywell valves when you read closely...
            Last edited by DBMandrake; 4 November 2016, 03:47 PM.

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