@gary Hi gary, I'm quite interested in your DT of 8 and and ecodan comment 

I've got an 11.2kw ecodan, flow rate 28 l/min.  When its cold outside, below 3 and all my zones call for heat (zone discussion for later!), I often see DT or 7 or 8, which means its actually putting out something like 13+ Kw, give or take some losses here of there.  This quickly ices up the unit and kicks it into frequent defrosts that actually spiral the temp and cause house to drop in temp. The only way I can get out of this is to shut off some of the bigger zones.

Would it make sense to reduce the flow a little on my ecodan to try to prevent the compressor trying to reach such high Kw?? The problem is, i actually need most of the 11.2 Kw consistently in cold weather. 

Or am i think about this wrong?

Dave 

@grumpidoc I see that Gary is answering your Ecodan specific questions and as our system is a Daikin, I won’t encroach however, I think balancing the radiators using the Lock Shield Valves is still very relevant. Also if you have a number of radiators that are overheating the rooms, this suggests they need taming via the LSV’s. You may well find that if you have numerous radiators shut off completely, your system may need a reduction in heat output to match, the noise might well be in part, due to the water pressure and when you adjust your Wilo pump speed, things will quieten down somewhat. Adam Chapman of Heat Geeks has produced a presentation on You Tube about shutting off the heating in rooms which you might care to find and view too. Regards, Toodles.

@gary

We have a single zone, all radiators, though a fairly long run from one end of the bungalow to the other. the cylinder and pumps are pretty much in the middle of the building.

Below are pics of our set up. As far as we can see there are 2 identical pumps, both Wilo (with the small green dials on the front), one near the big white box marked 'Ecodan', which is the pump for the heating and the one from where the noise was originally coming. Interestingly when we turned it down last night it was still very intrusive, tonight less so, no idea why! The hot water pump is the same model, up near the ceiling, and since turning the other down we are more aware of the noise from this one. Could it be some sort of resonance with the different frequencies they are producing???

Can't see any other pump which might be the primary pump........

@toodles thanks - I'll search out that presentation

@grumpidoc so as it’s one zone you should only have that one pump for the heating.  As I posted above you should be able to turn that all the way down to 15-16L/min and everything should still work on the coldest days 

@grumpidoc You may be interested in what I have done to reduce my system noise.

My system is Ecodan 11.2kw > Primary Pump (Grundfos UPS2 25-80) > 25L buffer > Secondary Pump (Wilo Yonas Pico 25/1-8M) > 16 Radiators.

The Grundfos primary pump was on speed setting 2 which gave a flow of 24Lpm (using the Ecodan service menu > Running Information > 540). Mitsubishi recommend a range of 14.4 to 32.1. I reduced the Grundfos speed setting to 1 which gave a flow of 19Lpm and much quieter. No noticable effect on the DHW or heating.

Now, my understanding is that when there is a buffer, and presumably the same applies to a Low Loss header, the secondary pump flow to the radiators should be either equal to but probably less than the flow speed from the primary pump. So, in my case, the flow from the Wilo secondary pump should be 19Lpm or less.

I tried the Wilo at 1.1 Cmh (19Lpm) but it was still quite noisy with the whine you mention.

I gradually reduced the speed of the Wilo using the "Radiators" guide on the side of the Wilo until the whine disappeared. The guide for my Wilo 25/1-8M is "Medium House" = 20 radiators and "Small House" = 15 radiators. With my 16 radiators, I felt that as long as I didn't get down to the "Small House" point, I was reasonably safe. I ended up with a Wilo reading of 0.7Cmh which is 11.67Lpm. Again there is no noticable effect on the DHW or heating.

I realise that there is a difference between the Primary Pump flow of 19Lpm and the Secondary Pump flow of 11.67Lpm and there is probably a far more technical way of determining the correct flows but I have just gone with what I have available until my installer is able to visit.

Everything seems to be working fine and far far less noise! 

@richard24738 There is the added bonus of much reduced power consumption from the pump. Our Wilo Pico currently runs on ~6-8 watts (and very quietly!). Regards, Toodles.

@richard24738 and @gary Thank you so much for your input - I am learning loads and I think my brain is going to explode! I think I'd better take a step back to (even more!) basics, and beg for your patience:

This is our installation 

The Wilo pump top right is connected to the pipes going up and via the loft to the heat pump. This Wilo runs when the system is doing either space heating or water heating. This was set at installation to level III = about 23 l/m of the 'constant' setting (from the Wilo manual: Constant speed Recommended for systems with fixed system resistance requiring a constant volume flow. Constant speed (I, II, III):The pump runs uncontrolled in three prescribed fixed speed stages) This is the pump where the whine is now originating (it may have been there all along masked by the noise from the other pump?). It was described to us as ' the one that does water heating', 

I very briefly turned this pump down from III to II which dropped the pitch to a lower and therefore less irritating whine. However I wasn't sure whether this was ok for the system so turned it back up pending further information.

The wilo on the extreme left of the photo was described as 'the one that heats the house'. It runs, we believe, only for space heating, was set by installers at about 35 l/m. It was producing the original whine, the engineer changed it from the 'radiator' setting (for 2 pipe systems) to the 'underfloor heating' setting (for one pipe systems) which didn't help but we reduced the speed to about 26 l/m and that has got rid of the whine from this pump. 

So given all the above, which Wilo would equate to primary and secondary - positioning / connection suggests to us the primary is the one on the right, but the pump speeds were set with the higher on the left. I guess I really want to know what things we can  - and should - safely change without risking damaging something. I should say my other half suggests the high flow rate on installation might be to do with the fact that it is single zone and quite a large area (200m2 or thereabouts) and is loath to make any changes until the installer gets back to us (our contact is 'waiting on their technical team'). So anything you might kindly suggest might not be attempted until we speak to the installer again - I have a long list of questions for them!

Thank you for your generosity in sharing information. Honestly we're not stupid, but this is completely new to us (including my technically minded husband) and we're on a very steep learning curve !

You are correct primary is the top right from the heat pump, secondary pumps round the rads you can’t break anything by turning them down.

Turn primary down to 1 and see what the flow is if it’s above 15L you will be fine.  

Secondary you will have to experiment you may find with slower flow rates the rads at the end of the circuit may not be hot enough but will just be trial and error 

@grumpidoc Please remember I am just a new heat pump user and not a heating engineer but I have picked up a few things on my journey! None of the below is a recomendation as to what you should do; it's simply what I have done to mitigate the noise from my system which is similar to yours; a two circulator pump system.

STEP 1: SETTING THE CORRECT FLOW RATE FOR THE PRIMARY CIRCUIT

The Wilo pump (top right hand corner) going to your heat pump is the primary pump and is in what is known as the Primary Circuit. I understand that your Primary pump is currently on fixed flow setting 3.

The Mitsubishi display unit on your wall will tell you the flow rate of the primary circuit. Ecodan Service Menu > Running Information > Code 540. I changed the Primary pump speed so that the value from code 540 was close to the recomended value for my heat pump.

If your heat pump model is PUZ-WM85 then the flow rate should be between 10.8 > 21.4 with a Mitsubishi recomendation of 15.2 LPM.

In my case, the flow rate from the 540 reading was much higher than the recomended Mitsubishi flow rate. So I reduced the pump fixed flow rate speed from 2 to 1 and then monitored the Code 540 value and if the system threw up any errors. No errors, primary flow speed now close the Mitsubishi recomended and noise level was down!

Result: Considerably less noise and no noticable effect on the system performance

STEP 2: SETTING THE CORRECT FLOW RATE FOR THE SECONDARY CIRCUIT (YOUR RADIATOR HEATING CIRCUIT)

I now needed to adjust the other Wilo pump on the secondary circuit heating the radiators.

My understanding (non technical) is that when there is a buffer, the secondary pump circuit should not have a faster flow rate that the Primary Circuit. I don't know whether the same rule applies to Low Loss Headers but given that my buffer is only 25L, I suspect it performs much like a LLH anyway. 

There must be a technical way of calculating what the correct flow speed for the secondary circuit should be but it's not in my skill set so you will need to take advice from your installer.

However, here is what I did. As a starting point I used the Wilo data sheet (Instalation and Operating instructions Wilo-Yonas Pico page 17) for my pump which, for the Radiator setting showed "Large House", "Medium House", and "Small House". Each of these variable settings relates to a number of radiators.

In my case, I have 16 radiators so the dial is set between the Medium and Small House. It's a good starting point.

Now to ensure that the flow rate on the secondary circuit (heating) is less than the Primary circuit.The misubishi panel does not display the flow rate of the secondary circuit but the good news is that, if your Wilo is the same as mine, it shows two flashing LED values on the pump: Energy usage and Flow Rate. The flow rate is in Cubic metres per hour CMH so you need to convert that to what misubishi use Litres per minute (LPM).

In fact, I gradually reduced the secondary pump speed, to the point where I didn't get the horrible whine. As long as I didn't go below the dial point for my number radiators, I felt I was safe from doing any harm.

My result: much quieter system and no noticable performance effect

I guess I keep repeating this but I am a beginner so I expect my changes to be validated or otherwise by my installer when he visits.

Hope the above helps.

Thank you @richard24738 and @gary  you have been so helpful! I will post back here when we finally get it sorted.

@richard24738 and @grumpidoc Very similar to my own experience I think. My primary pump is contained within the Daikin monobloc so that has been set and left; it provides a Delta T for the system coming into the house and as far as the LLH of 5 pretty much most of the time (as confirmed by the Homely Dashboard graphs.) My secondary pump is the Wilo Pico and is running in it’s ‘sweet spot’ as I think of it where it runs almost silently. The pump is running at ~ 0.6-0.7 cubic metres per hour and consumption is ~ 8 watts or less. The pump does adjust itself I find and I think this relates to the speed changing on the primary pump when it adjusts to hold a stable Delta T of 5 degrees; the Wilo Pico seems to just vary a little in response.

I took advice from this very RH hub some time back; I bought four temperature probes (I checked them against each other to make a note of the reading all four produced when all bunched together so that I could note the different readings to apply compensation to the readings) The four probes were then placed on the 4 pipes connected to the LLH. The aim is to have the input from the heat pump and the output from the LLH as close to the same temperature as possible and the same applies to the return going into the LLH and the LLH output returning to the heat pump. By gentle adjustments of the secondary pump’s speed, you should be able to obtain a speed that provides minimum differences on the flow into the LLH and the output from the LLH. NB. the similarly matched temperatures between the return to the LLH and the return flow to the heat pump will likely show a ~3 to 5 degree drop compared with the flow temperatures as this is the Delta T across your radiators.

So to summarise, flow into the LLH and out to the radiators should be as similar as possible and the return to the LLH and the LLH out back to the boiler should be as similar to eachother as you are able to achieve. As long as the last radiator in the circuit is still receiving enough heat to serve the comfort level you require, the secondary pump is still running fast enough! Please feel free to enquire further if I am not clear enough. Regards, Toodles.