@toodles Yes, it's a Wilo Pico 25/1-8 (ROW).

When I adjusted the speed, the LED display went from 39w / 1.6 to 20w / 1.3.

I have no idea if this is good or bad except to say that is resolved the noise issue. The rads don't appear to be affected and no short cycling.

The other doubt I have concerns flow temps and the Delta T. I am assuming that the difference is measured when the pump is running. Well, my Delta T is at the moment is 2.5c. Does that mean I should slow the Wilo down a bit more to increase the Delta T?

@richard24738 Yes, when the pump is running and the system has been running long enough for the LWT to be stable. That worked for me; the water passes through the radiator more slowly giving it chance to transfer the energy into the radiator before leaving via the return. If the water is passing through the radiator too quickly, it does not dissipate as much of the energy (heat). My Wilo Pico display indicates 7-8 watts consumption these days and the radiators provide all the warmth required to keep the house at 22.5 degrees C. The Homely controller’s Dashboard displays a Delta T on LWT and RWT of approx 5.0 degrees C and the COP is in the region of 5 - 5.5 in the present weather (mild) conditions and the worst I have seen was approx. 3.25 when the OAT was -7 or -8 degrees C. at the end of November - beginning of December last year.

I have searched for the topic on LLH and had no luck as yet, I have to use a much magnified image and I think, lose some of the details. Chances are if you search for ASHP LLH and Delta T, you may find the topic, the postings were fairly active last Autumn. There was some very good advice from Derek M at that time. Regards, Toodles.

For context, we live in a 4 bedroomed 1930’s semi in the South East of England and have 10 radiators and a dual fuel towel rail. When the Daikin service engineer came last Spring, he remarked how low the water circuit resistance was.😊 The DHW is handled separately by a Sunamp Thermino ePV210 heat store powered from our solar PV or from grid via a MyEnergi Eddi. Regards, Toodles.

@toodles my system is slightly bigger than yours with 16 rads and of course with a 25L buffer.

With your Wilo wattage of 7-8 watts versus mine of 20 indicates that your pump is running slower than mine.

On the Wilo I am particularly interested in the second LED reading which, if I turn down the wilo, will reduce the flow. Mine is currently 1.3. Can you read yours?

I realise our systems are not directly comparable but it would give a bit of comfort before the installer returns.

Oh, it's nearly 1pm and time to take advantage of the Free Energy offer from Octopus.

@richard24738 Just taken another look with a magnifier: 7 watts and 06 cubic metres/h. Yes, that hour is nearly up and I have drawn 12.4 kWh so far… Toodles.

That display does not show a zero, just ‘06’.

Regards, Toodles.

The only noise I hear with my Panasonic Aquarea is the 3 port switching between DHW tank and heating.  Other than complete silence in the house.  I do not have a buffer tank.  

It's strange being in the original cylinder cupboard with all the new gear and not hearing a thing!

Which, as I believe there is a point in there that I cannot see, means I have a flow rate of 10 litres/minute. Regards, Toodles.

@thebinman After having had a gas boiler and several pumps running in the airing cupboard in days of yor … it is uncanny! Toodles.

@toodles Thanks. The LED display is not very clear. Appreciate you looking.

I will try lowering the speed on my Wilo secondary pump to see if it widens the Delta T.

@thebinman Thanks for the comment.

I suspect my system was simply set up on the medium settings and the noise problem didn't materialise until the recent switching on of the heating system. Anyway, it's certainly quieter now that the wilo secondary pump has been slowed down.

To be honest, I regard this as temporary fix until the installer visits.

@richard24738 I think that ‘finessing’ the settings for smooth and most efficient running are not high on the priorities list of many installers😳 Toodles.