dpmiller

so this is about 11kW, depending on configuration. The brochure is sparse on details of efficiency vs temp, is it possible that being an HT unit it'll perform better at a slightly higher LWT?

no I mean can you prove there's flow at each grille? With your restrictor setup you're working on someone else's guess... Id be dangling a bit of tissue in front of each vent or using a smoke pencil to confirm it, personally. Airflow is a funny animal, I've spent too many years measuring and setting up fumecupboards and the like, all the calcs might say there will be flow but one extra tight bend in a duct and...

if the airflow haven't been checked, you've no idea if there actually *is* flow in all and every room...

what inverter has a 1.5kV input? Surely these strings are going to be separate or series pairs at the most?

It will work but you'll never know why as it addresses both points raised here- lack of flow in the supply loop to the manifold *and* @Nickfromwales's assertion that coils don't transfer heat in this situation. In fact, just increasing the LWT in heating mode a few degrees would likely cure it too, as I think on it...

where is the "blanking plug"? It's normal for there to be a cap in place where the meter goes but it should not affect flow.

He won't even check if it's accidentally half-closed?

RCD was replaced on Page 1 was it not?

I'll drop Chris an email...

while there are stats that can be switched between heat and cool (chinesium wifi ones, for example) and some manual stats with changeover contacts, you might not actually need anything? The ASHP is just looking for the dry contact closure to turn on, so setting the heating stat to max (a programmable one, so you can choose a time period for the cooling) will bring it on and the buffer will already be at setpoint once the mode is changed on the controller. Alternatively give Chris a shout, there are a couple of undocumented inputs on the unit that might help. I've been meaning to ask myself, but it hasn't been pressing. The normal on-off control is on the "AC linkage switch" ID3, but there are also inputs ID2 "linkage" ID4 "cooling linkage" and ID6 "heating linkage"; maybe he can clarify whether these can be used as demand inputs or whether they hard code the unit to a single function on demand?

have you looked at the valve yourself?

No discrete buffer tank here, but all heating flow passes through the 35kW coil in the bottom of the thermal store.

Doesn't the surrounding volume of water act as the additional volume? The ASHP isn't measuring any volumes, it just wants a manageable DeltaT to stop short-cycling...

Monitor the temp of the pipe from the diverter valve to the DHW tank when the buffer is heating. It should drop to ambient. If not, the diverter *isn't*...

another vote for beechwood here, they're just down the road from us.

do it if you really want it. And if that changes in the interim, sell it again...

I hate fancy setups with a vengeance (having been an installer in my teenage years) yet in a previous life was the one called on to debug the MD's £4k car system... I'm pleased therefore to say that just tonight I fitted the rear speaker sockets in our "good room" for the 5.1 system that I'll be happy with til I'm removed feetfirst hopefully...

and that's where I'd start looking. Diverter or mid-positio? Make sure it's going the whole way over and back.

got a schematic for your system? Are DHW and buffer on zone valves?

yes, should work fine. the OSB should be a bit lighter than PB I'd think?

gotcha. can you remove the NRV and preload the spring with a spacer or give it a stretch out?

where is the NRV?

I've the opposite issue with my system- *too much* flow from the manifold to the ASHP. Thankfully the pump set has a bypass and a restrictor, so you can throttle back the return flow even if the thermo valve is wide open; I'm playing with that currently to control the DeltaT at the ASHP.

I wonder if adding a restrictor (disc with hole in) at the joint between return rail and the bottom pump manifold might upset the flows enough to force more return out and back to the buffer?

@vfrdave I picked up an AGS Gardencare hydrostatic machine for good money and - you know how rough our site is yet- it cuts perfectly well at the fully-raised "travelling height" setting. /for info the AGS machines are the same as Starjet and made by Seco in the Czech republic. The same factory produces for a number of the bigger names too...