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Thread: Evohome upgrade from CM927, worth the investment?

  1. #21
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    Well, the small amount of HR92 noise you do get used to - just tell her that is the sound of saving money or buy a remote stat and put sound deadening over it lol!

    Have they had to restrict the valve that much? Some valves do make excessive flow noise when the lockshield is restricted down.

  2. #22
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    Dont worry Richard, that was my response...

    It is quite restricted (bathroom rad). Its always has been the nosiest rad in the house, but with the manual TRVs there was typically another rad being heated at the same time so it was less noticeable. Will see how it pans out in the next few days and perhaps open it a little to lower the noise. I do have the variable speed grundfos pump, but BG always tell me to keep it on the fixed setting (II) i think (it was 2 years ago) that when it was on variable speed the pump wasnt circulating the water fast enough so the boiler was getting hot to quickly and would then shutdown on its own thermostat before the rads were getting hot. Is it worth trying the variable speed option on the pump again? as slowing the water velocity down will obviously reduce the noise.

  3. #23
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    Quote Originally Posted by Leigh View Post
    So everything seems to be working as planned from what i can see on the Honeywell phone app. It does show though that one bedroom, right at the front of our house (north facing) seems to be struggling to get up to temperature, so the finned single convector rad may need changing for something with a bit more oomph.
    We too have a room where the radiator is struggling to reach the target temperatures, and although I had some idea before it was not really noticed until the Evohome started monitoring it and showing it could barely hit the target. Our hallway has a reasonably large panel but it's also only a singled finned convector - and in cold weather where its around 0 outside most of the time it can only just get the room to 20 degrees going flat out... There isn't enough room there to fit a full double panel double convector without fouling an inwards opening inner front door, but I think I'm going to change it for a double panel single convector, which is hardly any thicker but gives about 1.5x the heat output. Should be enough...

    Before you go replacing your radiator though, make sure the valve is opening sufficiently. By default the HR92 only operates the valve over a reduced range (approximately 70% of maximum possible travel) to conserve battery life, however on one of our valves which doesn't really fully open until the last turn of the gear wheel I was finding that the radiator was not fully heating up. Changing it to full stroke mode in the configuration fixed this.

    To get an idea whether this could be an issue for you, turn the HR92 up to a temperature at least 2-3 degrees higher than ambient, such as 25, wait a few minutes until the radiator is hot then unlock the HR92 and lift it off the valve, then while listening to the hiss of the water in the radiator, turn the black knob anti-clockwise, you'll probably find that you can turn it another full turn or two and if this makes the flow increase significantly and makes it get significantly hotter, enabling full stroke mode will probably be of some benefit.

    However if it doesn't help its probably time to upgrade your radiator or check the pipes to it aren't blocked/restricted!

    EDIT: Wife has just called to say the HR92s are noisy and woke her up, oh oh... ive told her she will get used to i. She also said that one of the rads was making quite a noise at one point (im guessing during a valve opening or closing) i did hear a small 'gurgle' this morning so am thinking there is some air somewhere even though we have an auto air vent so will go round and bleed the rads later.
    I only have 3 HR92's so far but I have found there is a wide variation in how noisy they are when the motor is turning, the one in my hallway is relatively noisy while the other two are much quieter and the one that is in the bedroom is very quiet. (Yes I have tried swapping them around, it's not the room acoustics, they do actually differ in noise output)

    I've also read about the noise of an HR92 waking people up but in our bedroom unless the window is shut and the room is completely silent (which includes no cars driving by) then I can't hear it at all over background ambient noise. Even with the room silent it's a very subtle noise and there is no way that it would wake me up. (nor has it ever so far)

    So it might be worth listening to your HR92's to see if you have any that are quieter than the one in your bedroom and swap them around. (After clearing the bindings and rebinding them correctly of course)

    Regarding the radiator noise - very hard to say what that could be. Our system is an old vented system and despite being perfectly bled (and accumulating only the tiniest bit of air in the upstairs bedroom radiator over weeks of operation) does sometimes make gurgling noises and sometimes a noise I would describe a a slight crackle where the water enters the radiator on particular radiators. The system has been flushed but some of the radiators are quite old and have sludge in the bottom (cold in the bottom middle for quite a while as they warm up) so over the summer I will replace some and flush out some outdoors with the garden hose... another possibility is a little bit of kettling from the boiler introducing small steam bubbles into the water flow, which can be quite noisy as they travel about.

    What kind of boiler do you have, and does it have an automatic bypass valve installed, or a bypass radiator that is never turned off ? Does your system have pump overrun ? I had to add a pump overrun timer to our old (20yr) boiler because the TPI modulation of the BRD91 switches the boiler on and off frequently, if the pump stops at the same time the boiler goes off then you can get micro-boiling of the water in the boiler heat exchanger which after a while leads to steam bubbles building up and circulating noisily around the system. If only one or two radiators are open and the automatic bypass valve is flowing this steam bubble generation can get out of control as they tend to circulate right back into the heat exchanger instead of passing through radiators to cool and condense back into water.

    Adding a pump overrun timer largely solved this problem for us, although I do still hear the occasional gurgles and crackles in particular radiators...


    One thing i did notice last night is that our system was balanced when we had our new boiler installed a few years back and it appears that our 'preferred flow' radiator is situated in the coldest room meaning that it was quite noisy (whoosing), due to the lockshield being closed down when it was the only rad calling for heat last night. Is there anything i can do about this?
    Do you have an automatic bypass valve installed ? (It might be built into the boiler, but often isn't) If not you should get one fitted. They're mandatory for all new builds and a good idea as retrofit for old installs like ours. (I inherited an old boiler and system when we moved in a year ago but I had an automatic bypass valve installed)

    If you do have one its possible that its set too high - usually you can adjust the differential pressure between 0.1 and 0.6 bars. Another possible issue is that you may have the pump speed set too high. Finding the ideal pump speed and ABV setting for a system can take a little bit of trial and error - in theory you can calculate both from charts provided by pump and boiler manufacturer but there can be additional variables in the system that make those rule of thumb calculations less than ideal.
    Last edited by DBMandrake; 21st January 2016 at 11:56 AM.

  4. #24
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    On the subject of a room not heating up. I'd check the sizes of the radiators. When I moved in to my current house, before even putting EvoHome in, it was obvious that the hallway was never really getting warm. I did some calculations on the sizes of the radiators and the sizes of the room itself and it was not physically possible for the 2 single fin radiators in the hallway to heat the room to 20degrees. I replaced both with double fin radiators and now it can heat up and with EvoHome on them it controls them very nicely now.

  5. #25
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    Quote Originally Posted by DBMandrake View Post
    Before you go replacing your radiator though, make sure the valve is opening sufficiently. By default the HR92 only operates the valve over a reduced range (approximately 70% of maximum possible travel) to conserve battery life, however on one of our valves which doesn't really fully open until the last turn of the gear wheel I was finding that the radiator was not fully heating up. Changing it to full stroke mode in the configuration fixed this.
    Thanks for this, i had just this minuted finished reading your post about this in the other thread with some interest. I dont think this is the problem (rad is getting just as hot as the others) but i will certainyl bear it in mind after letting things settle for a few days

    I will also take a listen to the HR92s to see if any are quieter than the others, i didnt really pay attention to that last night

    Quote Originally Posted by DBMandrake View Post
    What kind of boiler do you have, and does it have an automatic bypass valve installed, or a bypass radiator that is never turned off ? Does your system have pump overrun ? I had to add a pump overrun timer to our old (20yr) boiler because the TPI modulation of the BRD91 switches the boiler on and off frequently, if the pump stops at the same time the boiler goes off then you can get micro-boiling of the water in the boiler heat exchanger which after a while leads to steam bubbles building up and circulating noisily around the system. If only one or two radiators are open and the automatic bypass valve is flowing this steam bubble generation can get out of control as they tend to circulate right back into the heat exchanger instead of passing through radiators to cool and condense back into water.
    The boiler is a greenstar Worcester Bosch condensing boiler (not combi, cant remember the exact model number) installed about 2 years ago. A bypass valve was installed at the same time. I didnt pay much attention to it as our plumber set it up and he told me not to fiddle (i have a tendancy to tinker)

    Quote Originally Posted by DBMandrake View Post
    Another possible issue is that you may have the pump speed set too high. Finding the ideal pump speed and ABV setting for a system can take a little bit of trial and error - in theory you can calculate both from charts provided by pump and boiler manufacturer but there can be additional variables in the system that make those rule of thumb calculations less than ideal.
    The grundfos pump is variable speed and i know from before that running it this way certainly reduces the noise but every BG service engineer that has visited has said to leave it on fixed speed (setting II) but could explain what the issue with leaving it on variable speed was (save my comment about about the water not circulating quick enough to get out of the boiler)

    Roy, thanks for the comments on rad sizing, we had our hall and master bedroom rads replaced with the boiler as the rooms struggled to heat up and i concluded they were undersized. Our second bedroom is rarely used so i hadnt though to much about the rad size in there until this morning when i was monitoring the room temps on the app. Will try and work it out to see if it is undersized.

    Thanks for the help

  6. #26
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    Just stumbled across this forum/post which seems to suggest BG are wrong and that as TRVs are installed i should not run the pump in fixed speed mode. Will be changing that this evening when i get home.....

    http://www.diynot.com/diy/threads/gr...needed.251943/

  7. #27
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    I'm no expert on these matters so I am happy to be corrected, but I don't think you would normally run the pump in variable speed mode on a system with an external automatic bypass valve.

    I have a Grundfos UPS2 15-50/60 which I fitted new a few months ago to replace the very old (original 20 years ??) Grundfos pump that had got very noisy and started to fail... unlike the old pump that had I, II and III it can also be switched between three fixed speeds and 3 variable speeds, probably like yours. (in fact it's possible we have the exact same pump, it seems to be a pretty common model)

    I too experimented briefly with the variable speed modes but they were a complete no go for my system with the pump running far far too slow on any of them. I think you'll find that you can only use a variable speed mode with a boiler that is specifically designed for a variable speed pump.

    Variable speed mode slows the pump down as the flow becomes more restricted (eg as radiators close) and speeds it up as the flow becomes less restricted. If you look at the load lines for the pump you'll see that they actually trend in the opposite direction to fixed speed mode. Eg in fixed speed mode as radiators close and start restricting flow the pressure will increase, (to a dangerous point if you didn't have some kind of bypass) but in variable speed mode pressure will actually decrease as flow reduces due to electronically limiting the torque of the motor...

    This inverse relationship does not react well with an automatic bypass valve that is mounted after the pump as ABV's usually are, and will prevent the ABV from regulating the pressure properly. But as I say I don't think you're supposed to use a variable speed pump with an ABV anyway, it is an alternative to an ABV, but it obviously can't be used with any boiler that has a minimum flow rate requirement and does not have any internal bypass of its own or other design feature to allow it to work with a variable speed pump.

    So if your ABV is mounted after the flow output of the pump and/or your boiler isn't designed for a variable speed pump you can't use variable speed mode.
    Last edited by DBMandrake; 21st January 2016 at 01:30 PM.

  8. #28
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    I have my pump set at CP1... I have an 18 year old condensing boiler + 9 radiators (all with HR92's) + ABV all controlled by evohome. My boiler does have a high minimum flow rate and the CP1 setting seems to work well.

  9. #29
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    Interesting... what size pipe work is your system ? Many of my radiators are microbore and thus would increase flow resistance somewhat.

    All three variable speed settings on my pump are far slower than even the lowest fixed speed mode and are definitely not sufficient to keep the boiler from short cycling on my system. The strange thing is when you look at the load line graphs that come with the pump, the maximum flow rate in variable speed mode is way lower than the fixed speed modes, even in a case of low restriction, like all radiators being open...

    You can see this in the graphs on the last page: https://uk.grundfos.com/content/dam/...eet%201214.pdf
    Last edited by DBMandrake; 21st January 2016 at 03:13 PM.

  10. #30
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    My system is all 10mm microbore. When BG fitted my pump they just set it to the highest fixed speed and tried to assure me that was the correct setting. Having read all the Grundfos literature at the time it seemed to me that the Constant Pressure settings were more correct (all rads fitted with TRV's, ABV fitted and boiler that does have a minimum flow rate). I therefore set the pump to CP1 with the option to increase to CP2 if any issues. I have not had any problems, all rads heat up correctly when heat is called for etc and therefore have not increased to CP2.

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