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Thread: What Valencia valve parts to buy?

  1. #11
    Automated Home Legend
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    Quote Originally Posted by Dan_Robinson View Post
    Would suggest pump set too high with valve bodies on the return.
    Thanks. I will chat to my installer. The something was happening with my old boiler and separate pump. The clunks, as far as I can tell, are the the HR92 bodies hitting the adapter as there is a certain amount of twist/play.

  2. #12
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    Quote Originally Posted by DBMandrake View Post
    Looks good on paper however I'm not sure how much difference that would make in real life in an Evohome system and whether it is applicable.

    The reason being, it's not just differential pressure that will vary when the demand of other zones change, the boiler flow temperature will change dramatically as well due to the way every individual Evohome can call for heat from the boiler - and that's a much larger factor controlling how much a given zone is influenced by what other zones are doing...(like a previously stable zone at equilibrium overshooting because other zones just came on full blast)

    If anything, some variation to differential pressure of a conventional valve will "help" reduce interference between zones - when other zones close down the heat demand will drop and the flow temperature will drop but the pressure will increase through the remaining radiator possibly partially counteracting the natural tendency for its temperature to drop.

    Conversely when other zones come on and demand a lot of heat the flow temperature will increase due to the higher boiler duty cycle but the differential pressure will drop and reduce the flow through this radiator a little. Regulating the flow through each valve irrespective of differential pressure would only make that worse.

    So I don't see a point to it with an Evohome (assuming you have an ABV to iron out the biggest changes in differential pressure) and counterintuitively it may actually cause more interaction between zones instead of less.
    I'm not an expert at all but asked a CH engineer to help me on this one:

    The problem I was facing was that if only a few smaller zones were asking for a lot of heat, the boiler produced 75 deg water, but the rads only managed to cool it down by 5ish degrees (because of the high flow speed). Causing the boiler return to still be very hot, and allowing it nowhere near condensing operation, and thus being pretty inefficient. I've now limited flow in the rads to achieve a deltaT (output - input) of around 20 deg when facing 70deg input water temp. My previous thermostat used to be more conservative, firing up the boiler at lower temps, so I think for my situation, with evohome there are higher benefits from the reduced flow speed through the rads than before. In morning operations, I regularly see deltaT over 30 degrees, whereas before the new valves, it was closer to 15.

    The pressure overflow helps reduce the pressure and thus flow in the system, but returning the hot water to the boiler immediately does not allow the boiler to run in condensing mode.

    The house does take a bit longer to warm up though, but feels less toasty around the rads in the morning.

    I'm not sure what ABV stands for, sorry. Googling gives me alcohol related responses only. I do appreciate a drink every once in a while if that was your question

  3. #13
    Automated Home Ninja Dan_Robinson's Avatar
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    Automatic bypass
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

  4. #14
    Automated Home Legend paulockenden's Avatar
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    Quote Originally Posted by Dan_Robinson View Post
    Automatic bypass
    valve. ;-)

  5. #15
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    Quote Originally Posted by Dan_Robinson View Post
    Automatic bypass
    Quote Originally Posted by paulockenden View Post
    valve. ;-)
    Ah thanks, nowhere near the dutch "overloop" that I liberally translated as overflow ...so please think ABV when you read overflow above.

  6. #16
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    Just to confirm - The VHL-120 products are manual Valencia valve bodies (with or without lock stoppers) which will directly take a HR91/92 or can be used with a manual knob?

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