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Thread: First evening with Evo

  1. #1
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    Default First evening with Evo

    Hi all,

    System installed today, all runnng well.

    Few questions-

    I'm using the opentherm bridge to control the boiler - as I speak the boiler is off but the pump is still running, boiler water temp is 37c. And two of my hr92s have valves open about 40% but room temp has been reached. This looks a little odd to me, or is it doing its "thing".

    One further question as the valves are only half open I'm getting a lot of water noise from the valves, it disappears if the valve is fully open. Pump is on its lowest setting. Normal too?

    Many thanks

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    Quote Originally Posted by Norfolkboy View Post
    Hi all,

    System installed today, all runnng well.

    Few questions-

    I'm using the opentherm bridge to control the boiler - as I speak the boiler is off but the pump is still running, boiler water temp is 37c.
    How is your pump controlled - is it controlled by the boiler or is it using a separate pump overrun timer ? It may just be pump overrun.
    And two of my hr92s have valves open about 40% but room temp has been reached. This looks a little odd to me, or is it doing its "thing".
    That sounds about right - that is 40% of the valve pin travel, that doesn't mean the valve is flowing 40%. Typically after the HR92 has had time to calibrate itself the "opening point" of the valve where water actually starts to flow will be at a reported position of around 40%, any less than 40% and the valve will not be flowing. More than about 80% is fully open with 40% to 80% being varying amounts of flow.

    This does depend on the design of your TRV valve body of course - some valves have more or less operating range between closed and open than others but this is what I see with my valves.
    One further question as the valves are only half open I'm getting a lot of water noise from the valves, it disappears if the valve is fully open. Pump is on its lowest setting. Normal too?
    That's going to depend entirely on your system and isn't really a function of the HR92 - all it does is opens the valve a certain amount. A bit more info about you system would help such as:

    - How many radiators do you have
    - Are they only noisy if one or two radiators are on and the rest are off ?
    - Do you have an automatic bypass valve fitted in the system ?

    If you've set the pump speed to low and you still get a lot of hiss my guess is you don't have an automatic bypass valve so when most radiators shut down there is a high pressure differential and the remaining radiators can hiss quite loudly if they are only partially flowing - just like a partially turned on water tap.

    I think some designs of TRV valve bodies can be noisier than others under partial flow conditions as well.

    I have an automatic bypass valve in my system set to about 0.4 bars and regardless of whether I set my pump to low or medium at most I only hear a subdued gentle hiss from any of my radiators, and I would never call it intrusive.

  3. #3
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    Quote Originally Posted by DBMandrake View Post
    How is your pump controlled - is it controlled by the boiler or is it using a separate pump overrun timer ? It may just be pump overrun.

    That sounds about right - that is 40% of the valve pin travel, that doesn't mean the valve is flowing 40%. Typically after the HR92 has had time to calibrate itself the "opening point" of the valve where water actually starts to flow will be at a reported position of around 40%, any less than 40% and the valve will not be flowing. More than about 80% is fully open with 40% to 80% being varying amounts of flow.

    This does depend on the design of your TRV valve body of course - some valves have more or less operating range between closed and open than others but this is what I see with my valves.

    That's going to depend entirely on your system and isn't really a function of the HR92 - all it does is opens the valve a certain amount. A bit more info about you system would help such as:

    - How many radiators do you have
    - Are they only noisy if one or two radiators are on and the rest are off ?
    - Do you have an automatic bypass valve fitted in the system ?

    If you've set the pump speed to low and you still get a lot of hiss my guess is you don't have an automatic bypass valve so when most radiators shut down there is a high pressure differential and the remaining radiators can hiss quite loudly if they are only partially flowing - just like a partially turned on water tap.

    I think some designs of TRV valve bodies can be noisier than others under partial flow conditions as well.

    I have an automatic bypass valve in my system set to about 0.4 bars and regardless of whether I set my pump to low or medium at most I only hear a subdued gentle hiss from any of my radiators, and I would never call it intrusive.

    Thanks for the reply, I do have an automatic bypass but sounds like it's set too high, as it's been set for most of the 14 rads in the stystem to be on at the same time.

    The pump is run from the boiler, it does switch off occasionally but it just appears to be on every time I look, is opentherm trying to keep the room at the exact temp and therefor it's happy to be pumping 30-35c to the rads, rather than room hits set temp and then pump switched off and waits for the room to drop in temp, like a tradional thermostat.

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    If the pump does switch off occasionally while the rooms are at temperature then it sounds like its working properly.

    Yes it will use OpenTherm to try to maintain the set points in the rooms by modulating the flow temperature down as low as necessary, rather than just turning it right off and waiting for the rooms to drop below the set point then turning it back on again. This keeps the room temperatures steady instead of cycling up and down and is a bit more efficient.

    I think a flow temperature of 30 degrees is about as low as it will go before it switches of completely, although I don't use OpenTherm so maybe someone with OpenTherm can comment on that.

    So it sounds like it is working as it should.

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    Quote Originally Posted by DBMandrake View Post
    If the pump does switch off occasionally while the rooms are at temperature then it sounds like its working properly.

    Yes it will use OpenTherm to try to maintain the set points in the rooms by modulating the flow temperature down as low as necessary, rather than just turning it right off and waiting for the rooms to drop below the set point then turning it back on again. This keeps the room temperatures steady instead of cycling up and down and is a bit more efficient.

    I think a flow temperature of 30 degrees is about as low as it will go before it switches of completely, although I don't use OpenTherm so maybe someone with OpenTherm can comment on that.

    So it sounds like it is working as it should.
    Thank you for you help, sounds like it working, just need to get my head around the boiler will be on more but being more efficient.
    Is it possible to know which zone is calling heat?

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    Quote Originally Posted by Norfolkboy View Post
    Thank you for you help, sounds like it working, just need to get my head around the boiler will be on more but being more efficient.
    It might be running for a longer period of time but it will be running at a lower temperature and using less gas to maintain a low flow temperature, rather than going full blast for a short time then going off for a while. Total gas usage should still be less and its better for the boiler to run with a small flame than to alternate between full burn and off all the time when demand is low.
    Is it possible to know which zone is calling heat?
    Unfortunately no. It's something that a lot of us would like but at the moment there is no way to know for sure, at least from the controller.

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    I've just read on a different topic where you have said manual latching open a Honeywell valve only opens it half way, I have done that so will look to alter that tomorrow.

    Presume the pump isdesigned to run for long periods of time? It's a Grundphos UPs 2 running on the lowest fixed speed

    Thanks for all your help!

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    I also have a Grundfos UPS2 15-50/60 and it is currently running on the lowest fixed speed. (I used to run it on medium)

    They are designed to be able to run non stop 24/7 for years (decades) so no worries there. The only issue might be a slight increase in electricity use by having it running for longer however the UPS2 is a very efficient pump and on low speed mode uses very little power. (about 15w I think)

  9. #9
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    Quote Originally Posted by Norfolkboy View Post
    Hi all,

    System installed today, all runnng well.
    Out of interest, which boiler do you have? I am getting a quote for Atag with Opentherm tomorrow.

  10. #10
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    I have an openvent Viessman 100w, had it for a year now and would recommend it HenGus

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