NSS

I once drove from Southampton to Plymouth on the Bank holiday weekend at the end of May (1988). It took 26 hours and 57 minutes. Granted I went via London, Norwich, Leeds, Newcastle, Glasgow, Aberdeen, Carlisle, Manchester, Birmingham and Bristol. Total mileage was 1,570 at an average of just over 58mph No chance of repeating that these days. Edit: To clarify, three of us shared the driving.

Okay, spoken to the installer and they say that a blending valve is not only unnecessary, but that heat pump manufacturers generally advise against using them. I'll get my tin helmet

Are you buying?

Okay, thanks for that. Anyone else care to endorse this approach? As for the last point, we don't have both on together. If we want to boost the towel rail temperature we simply put the UFH stat for that room into frost protection mode whilst the electric element is on and then switch it back to normal afterwards. With no circulation the towel rail warms with minimal 'leakage' into the feed and return pipework.

Not sure I need to understand what it all does, or doesn't, do, just what would be the simplest way of putting it right (preferably without it costing too much more!). The UFH seems to work well enough, with flow rates on the manifold valves balanced as per (or close to) the design values, and floor surface temperatures when zones are on peaking evenly around 25C ish. My main concern is getting good flow at an appropriate temperature to the air rad. The installer has suggested to Panasonic that we move the feed from the current tee position to between the circulating pump and the manifold, but presumably we'd need to have a valve (perhaps the currently unused 2-port one) downstream of that tee so as not to be circulating water through the air rad unless there is demand. Anyone got a view on this?

Manufacturer describes it as being suitable for most heat pump applications. https://www.seconsolar.com/low-loss-header-3265-p.asp

The only tee between the diverter valve and the LLH is the one that feeds the air rad.

Okay, as most of you will have guessed, a lot of this is going straight over my head. Here's a close up of the 'plates' on the LLH.

Not sure how it effects what you're saying, but it does have a buffer.

Would that not 'choke' the flow to the manifold too?

Both the company who did the original design (since gone bust) and the company that took over were/are specialist heat pump installers.The latter certainly doesn't have a background of traditional boiler/radiator CH systems, and they also undertook our Solar PV install and integrated it (via Power Diverter) to our DHW tank immersion.

Sufficient to take the chill off of a towel, and we can boost them with the electric heating element when the UFH is not running.

Actually there are steel radiators (dual fuel towel rails) in the two ground floor bathrooms. Each is fitted in line to the respective UFH circuits.

Yep, that has me confused too, particularly as the 2-port is not actually wired into anything. They are both Honeywells, V4044C1569 and V4043H1106

2 pics

Though I've never had UFH before so have nothing to compare to, the ground floor seems to be working fine. At present, the hall circuit tends to stay on for a bit longer than it would if it wasn't in effect trying to heat the upstairs too. Looks now as though bypassing the temp probe on the air rad is not a complete solution as it's made very little difference overnight. It calls for heat but there appears to be very little flow rate to the rad. The feed tees off before both the LLH (at least I now know what that lump is) and the circulating pump/manifold so i suspect they are drawing most of the flow. I'll add a pic showing a more general view of the set up.

@Nickfromwales , the original design was done by a company who subsequently went bust (after installing the UFH pipes in the floor and the manifold), but before the rest of the kit could be fitted (leaving me about ₤1800 out of pocket in the process). The company who took over just installed as per the original spec so no blame on them (in fact they've been very good considering they'd never installed Panasonic kit before).

Sorry chaps, the pub was calling. Will read all your replies properly in the morning but to answer one query, yes @Nickfromwales it does also supply DHW.

This is ours manifold

The only thing that sits across the flow and return sides to/from the manifold is this thing.

Nope, we have nothing like that on the manifold.

Okay, thanks guys. Seems I need to have a chat with the UFH installer.

Pass ???

It is.

Panasonic had suggested this was a possible fix, but could not officially sanction it and intimated that doing so would void the warranty (whereas their manual states that it's possible to run it with the probe disconnected so no impact on warranty).