Nickfromwales

Panasonic uses the wall mounted controller for internal info. How the feck will yours know what's going on indoors if you don't have one? Other than the difference between flow and return, which would be cruder than a semi-sober welsh plumber.

WC will still prevail. Currently the rads are strangled. One step ahead, my man.........

Have we proven that L is getting there?

I'm not, the OP didn't say there was an issue there

Try again, lol.

You'd be shot if you didn't, ma' man.... How long has this worked for, to date, without issue?

No you don't. The (then higher) fixed flow temp will arrive at the TMV, and the UFH will see zero change in circumstance or performance. The FF rads will receive x degrees higher flow temp and actually do something. The rads go on TRV's to manage the difference in the size of the spaces that they are now able to satisfy. You balance and attenuate the lift in flow temp degrees at a time, until the happy medium is achieved.

You don’t have to keep saying sorry lol. Water hammer noises are difficult to locate / fault find, but as said the diverter (ahem) valve does a smooth transition, so would not be the usual suspect.

:reaches for drinks cabinet: 🙃🤣.

Yup. When we feather dry sand and cement screeds from 10mm to 30mm, there needs to be a very particular primer used, one iirc that stays tacky unlike PVA or SBR, to stop the layer from separating from the slab. From 10mm to 0mm you then use SLC.

From what I gather, and as per Dave above, there was a working light here before.

Yup. Defo the culprit if it’s not a diverter!!

Yup. If the old one worked, this one can be made to work. Light needs to come off and we need to see some pics, whilst I’ve still got hair! 🙃

Ah! I think you have the wrong valve. Google says this is a mid-position valve, and you should have a diverter valve. Can you confirm you have a mid vs diverter plz?

Pumps usually last a minimum of 10 years in a typical household, often much longer. Good to hear it’s sorted, but how old was the pump they replaced? Did they leave the old one there, and did they offer an explanation as to why they thought the old one had failed?