BobBiggar

thanks @sharpener I'll look into this as another tool to try and control the circulation pump. I don't have the sensocomfort and cannot see this functionality on my VRC700 but it may be hiding there somewhere. so far I am looking at 3 functions that might help reduce so much circulation pump activity when no space heating is required - maximum outside temperature - this is a bit of a blunt instrument but can be useful as an upper threshold. 16 or 17 deg seems like a decent starting point - @ectoplasmosis suggestion to use the sensocomfort thermostat reading in "expanded" mode. This seems like a good mechanism. I haven't been able to try it properly yet as I still have the VRC700 in the plant room with an unrepresentative temperature reading, but it works, functionally - the possibility to highjack the DHW scheduler to control MA2 as a heating circulation pump. Again, seems like a blunt instrument, but might be useful

yes, that's the plan. This should address a big chunk of the problem I still think Vallient controls should do more to minimise wasteful circulating pump operation. Pumps are a well known energy waster

yep, I feared that. we have the winter coming up so this only starts to be really annoying when the warmer weather arrives. By then I hope to have the sensocomfort fitted. thanks for the pointer in the right direction

the options given under "Room Temp Mod" are - None (current setting) - Temp. mod - Thermost. not sure which would correspond to expanded Also, the VRC700 is in our warm utility room. If the functionality relies on a temp sensor within the VRC700 it might be challenging. Nevertheless i'll certainly give it a try and hopefully can find some setting which work.

thanks @ectoplasmosis, this may become an option if I upgrade our current older VRC700 to the Sensocomfort.

@sharpener do you mean connecting an additional heating circulation pump to MA2 as opposed to the Valliant recommended MA1 ? Connected as Valliant recommend in the attached (to MA1), the additional (post buffer) circulation pump follows the same behaviour as the HP-internal circulation pump. So basically 2 circulation pumps now running continuously. It's even a little worse than that since the additional pump is not speed controlled down when the compressor is off. MA2 is nominally for the DHW secondary return pump as per the attached so are you suggesting somehow highjacking the controls for DHW secondary return if that is not required and using them to somehow control the additional heating circulation pump? Then there's the integral calculation. This surely requires circulation during the compressor OFF time so the measured flow and return temperatures are meaningfull and the HP knows when to turn on again. This seems to be counter to any attempts to externally alter the system flow since this will distort the temps and calculation. The only way I have found so far to get the HP-internal circulation pump and any MA1-connected circulation pump to switch off is to set the Max Outside temperature to below the current measured temperature. This can therefore work ok for the warmer days, set to something like 16-17, but all the rest of the time, and overnight even in the summer, the pumps run all the time. It's entirely possible I have misunderstood something and hope someone can enlighten me. I don't have the fancy monitoring capabilities of some here and cannot observe the VSW-AI all day to see what is happening when. I would have thought some sort of sniffing functionality, where (when the compressor is OFF) circulation is also OFF and then intermittently turned ON for a short while to enable valid flow and return temps to be measured, might be possible. The integral calculation would become more complicated but surely possible.

thanks for that, very interesting discussion in that thread. It can be challanging properly understanding control systems without detailed specifications, a bit like backwards engineering, but the essence of it seems clear enough. or at least it is regarding the compressor. I'm still unclear about the circulation pump and even @Dreadnaught in his little summary says "There are more subtleties than I have mentioned above … such as overrun of the sum and the control of the separate building-circulation pump … but that's the essence of it."

thanks again, this gives me a focus to look for what is keeping the pump on. I think you might be right about the DHW schedule as the source of this. Assuming this resolves the constantly running pump I still don't know how the HP will know when to start heating again in open loop configuration (no external demand signal). If it works, I suppose I don't have to and can just let Valliant do it's WC fully open loop thing.

thanks @sharpener, this is very helpful. As mentioned in my previous comment, I don't see the internal circulation pump turning off when the compressor shuts down. However, this is perhaps because the wiring configuration is not as you outline. I don't have a VR71 so using the EVU terminals in the VWZ AI looks like an option to try for me.

thanks @JohnMo First of all, apologies if some of my terminology/jargon isn't quite right. I'm only just getting to understand our system after 6 months living with it and am trying to learn how to optimise it's operation. My observations are all a bit subjective but I haven't yet worked out how to pull data off the system and analyse this objectively. My system has GF UFH and 1st Fl rads, but all designed at 35 deg WC flow temp and configured as a single zone. There is a buffer between HP and emitters which I'm not sure is necessary. It's a modern highly insulated building including a MVHR system. Essentially everything on all the time trying to maintain 21 deg (playing around a little with 20deg or 19deg setback). It doesn't seem to cycle too often. The installer fitted a 12kW Arotherm which I think is overkill. I haven't noticed it running at more than 30-40%. Heating curve is 0.55 and temperature throughout the house is consistent and doesn't decrease too quickly. Sensing temperature every 30 mins or even 60 probably wouldn't see much difference. We have just been through our first summer and the internal circulation pump ran continuously (at 1100 lph according to VWZ AI) when the HP was only active a couple of hours each night for DHW. 6 months of circulating with no heat demand seems like a real waste of energy. I know it's possible to alter this pump behaviour but I have only seen either fixing it to between 50%-100% or "Auto". Its set to Auto but I don't know what that means since it only seems to switch between 1100 lph (compressor off) and 2000 lph (compressor on).

It would be great to get an update on this and how you have been getting along with the system. Specifically, did you ever get a satisfactory answer to the question about the Arotherm ASHP internal pump. More specifically, does it keep running 24/7/52 at the minimum 9l/min even when the compressor is not operating? or is it doing something a little more energy efficient and turning off, then occasionally on to sense return temperature? yours is the only online post I have seen asking about this behaviour and it seems relatively important when operating systems completely open loop as is becoming more common.