dpmiller

are they like-for-like, both with top vents?

^ wot he says. But help us help you here- are there any pole transformers or cabling in the vicinity already? Distance? Photos?

We've got the PVC frames and they're very good. Obviously they're near-enough maintenance-free, and are clean and bright. You'd need to go digging to confirm, but they're probably a bit better thermally?

can you post the diagram and a photo or two of the board,for us to chew on?

Fake wood venetians from Blinds2Go here. They're a bit heavier than aluminium but are plenty rugged and the customer service was great.

no chiselling required 🙂

not so unusual really- bottom of stair, top of stair, far end of landing...

No idea sorry, I use them only for gross leaks of anaerobic gas mix as only the small percentage of hydrogen in the mix is easily detected.

a "normal" cheap heated catalysed pellet sensor will do fuel gases

you're overthinking. Having spent more than ten years measuring flows in fume cupboards, Biological safey cabinets, and various laminar flow units, I can confirm that airflow is just-about impossible to read repeatably... Flow in any tube/ duct is irregular and as @S2D2says the longer the straight length before the probe the better. You can use egg-crate to try and straighten/ laminarise the flow, but it's all over kill. Probe in the centre of the duct, fix it there, take readings. Done...

searching the number on the PCB hints at it being a "world pac" unit. I'd be looking closely at the innards to confirm it's actually an inverter unit- should be another smallish pcb with a big heatsink and some big capacitors on, and there should be a 3-wire connection to the compressor, with no additional starting capacitor

auto bypass valve across the rads?

that's GB, not UK, generally...

yep, can't fault them. Connect wires, screw to wall, done. The're pretty slim on the wall. Haven't had any failures yet/ The USB ones seem to charge stuff ok. on the lightswitches, the actual switch can be removed from the faceplete by undoing a couple of tiny screws. This makes it handy if you need to have (say) an intermediate or an illuminated 20A switch in a double or 4-gang faceplate, or want one dimmer in the mix. Like a gridswitch kinda. 3-gangs are different as to cram the three into a single, the switches are in one housing...

adjusting the lockshields *must* alter the DT. After all, if they're closed enough there is *no* flow...

yep, I'd be reducing the pump speed a bit. Easy on the iVT-9

yep, it becomes obvious when you have a couple of panels to-hand where issues will occur. Look at my top row in the photo, there's a raised overlap between each panel and the side flashing sits over that again, that's a height of about 10-15mm that you need to squeeze in underneath whatever...

MK is common in government work. I'd tend to agree with @ProDave that they're a bit dear, and not the best ever quality. I went Hager for ours because they look clean and unfussy, and the lightswitches have a handy neutral terminal

better chance of it arriving in one piece if you collect from the local depot than expecting some courier to take care of it...

that's the valve at the "other" end of the radiator. It's used for isolating during repair, as well as setting the maximum flow- balancing- the system.

It's the DC component that's the issue, not the actual currrent and that could well be RCD brand specific. The original incoming 100mA type-S I installed in our meter box was sensitive to our CE-iVT9, as soon as the inverter was energised (but before actually driving the compressor to any degree) it would trip out.

if it's so easy why haven't you done it yourself?

those fixings have a degree of up-down adjustment and just clamp onto the round tubes, almost anything will fit...

we staggered ours. It meant taking a small slice off the side overlap joint and flashing of the "lower" panel, but the upper one covers it sufficiently and then the flashing roll was slid uo the back of it after tiling

what pump modulation are you seeing and what deltaT are you set to?