Posted by: @jancold

↑

@bimbleuk That is interesting. Can you tell me where you found that setting on the MMI please?

Enable installer mode - 5678

Enter the Space Heating/Cooling menu

• Enter Pump Operation Mode - Select Continuous or Sample (default)
• Enter Pump Limit - Select 60%/70%/80%/90% Pump Limit During Sample

Be careful to only change the pump sample speed from that menu. Expert advice should be sought first before making changes to avoid incorrect pump operation of course.

When still in Weather Dependent mode + Thermostat you don't see the pump sample mode as a selection. I think it was demand or continuous.

@radwhisperer Thanks I don't think I need to change mine but I will have a look out of interest. Since going to LWT I had noticed the water flow at times though it's not noisy. The one that is noisy is drawing off hot water can make a roaring sound but it does not always happen so it is difficult to track down.

Posted by: @jancold

↑

@radwhisperer Thanks I don't think I need to change mine but I will have a look out of interest. Since going to LWT I had noticed the water flow at times though it's not noisy. The one that is noisy is drawing off hot water can make a roaring sound but it does not always happen so it is difficult to track down.

Have you considered the Thermostatic Mixing (Blending) Valve (aka Anti-Scald or Tempering Valve) that mixes the hot water with mains to control the temperature and maintain pressure. Usually mounted on the side of the hot water cylinder.

Maybe that needs a tweak by a plumber. I get quite a lot of pressure from the hot tap initially but run the cold as well and it immediately drops to "normal".

@radwhisperer It does seem to occur most loudly the morning after the legionnaires cycle, so that could be it.

I don't seem to have a mixer valve. Just pressure regulator.

@jancold 

Not a plumber but I believe that is the blending valve and pressure regulator. No experience on how to adjust it.

Another thought now I've been using LWT for a week. When my HP switches to a setback timeslot I sometimes hear a surging noise. Could be the fan or pump going to 100% duty but it's distinct. My gaming PCs do similar things with programmed fan curves for example.

@radwhisperer Thanks but that is definitely not a mixer valve as my water temp is low and there is no feed to hot water just the base of the DHW cylinder and a pressure dump valve. But I do suspect this is where the noise comes from, however no noise recently.

@jancold - that thing is a pressure reducing valve, used to reduce mains pressure to something more domestic, typically 3 bar. I have the same thing in my system.

It is adjustable. Following a major repair to the water main outside my house, my pipework started to make a humming/whining noise when a tap was turned on. I guessed the water main had somehow altered the mains pressure a bit, and so set about adjusting the valve to get rid of the noise. You have to remove the small black plug/cap in the centre of the grey cover to get at the adjusting screw (a hex socket screw) and turn it to adjust the outlet pressure, arrows show which way is which. The black plug/cap is not easy to remove, I had to stick a very sticky gorilla tape to it to pull it out. I made a very slight increase in pressure adjustment and the noise stopped. For peace of mind, I also got a water pressure gauge and put that on a tap to check I hadn't set up a water bomb waiting to explode, and got a reading of 3.1 to 3.2 bar. I figured that was within limits and have left things as they are.   

@cathoderay Thanks for confirming. When I looked closely I thought I had seen one before somewhere in my shed, rescued after the clubhouse renovation! ( I am a notorious skip diver 🤣 ).And there it is!

Thing is it is one of those intermittent things. Yes I could fix the gauge somehow to the hot tap in the bathroom about level with the tank I could find what pressure it is set to?

Posted by: @radwhisperer

↑

@toodles Useful reply and because Heat Geek mentioned it in the Daikin MMI vid I didn't do any further checking. Using Grok again to sift through all the online data there may be a mix up of a 25C minimum LWT for efficient hot water heating. There is an anti-freeze mode for temps below 15C so does look like it can go lower but as say there is some guidance to minimum settings relating to the desired room temps. So yeah some more playing required.

Also a red herring was my LWT was 26C when I was playing the first morning and the HP just happened to stop when I adjusted the slope and it dropped to 24C!

JT

So after a week of playing with the LWT mode I'm now back to setting my WDC LWT minimum flow temp to 25C. Below this the HP does not resume reliably to the zero setback schedule periods even if the outside temp is also below the WDC minimum.

Also found I can hear the pump in sample mode switch between on and off states so I set it to 60% duty cycle. Then after a 3-4 hour setback period the HP came back on at full tilt resulting in 25 l/m flow rate which is quite loud in my master bedroom. I can't limit the global pump speed in heating if the sample speed is limited. Current solution is to run the HP in quiet mode and change the Delta T to 10C. Now the max flow rate is down to 20 l/m which is fine in heating mode.

There's no hard off setting in the schedule so next best thing appears to be -10C setback. Should work down to all but lowest outside temperatures. House is 19C to 21C currently with 4C being the lowest outside temp experienced. Current WDC set points are 40C @ -3C & 25C @ 12C.

Posted by: @radwhisperer

↑

Also found I can hear the pump in sample mode switch between on and off states so I set it to 60% duty cycle. Then after a 3-4 hour setback period the HP came back on at full tilt resulting in 25 l/m flow rate which is quite loud in my master bedroom.

Is it possible there is air still trapped in the system.  Mine took a month to clear and despite the presence of an auto bleed valve one radiator needed daily bleeding.  Alternatively have you got an almost shut valve somewhere through which the water is being forced causing noise.  Are all, or at least most, of your TRVs set to max so constantly open. 

Flow through pipes should be close enough to silent not to matter so the noise is more likely to be a valve or bend or air or such like.