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Hi, I've done a fair bit of googling and reading posts in this forum regarding my current setup. Probably stuck with what I have, but would like to be 100% sure. So any extra insights would be very welcome. Thanks in advance. I have a large 5 bed detached house, 16 radiators in all, with a...

@D_Hailsham from what I can see about the pump and bypass (Vaillant ecotec 637) it's a bypass between flow and return as in diagram 1 you gave. So would you say the following is correct: With bypass at default settings, that would allow 1200 litres of water to be pumped around at diff...

@Bunnyman Yes, I think we can agree the boiler is grossly oversized. Nothing I can do except replacing it - it came with the house. Must have been a case of 'bigger is better' from the previous owner. It's on 22mm pipes and from what I've read you can't even shift 37 kW through that without...

@Onetap Yes there are 4 curves, that's part of my puzzle. I think because it is a) a two speed pump. It is fixed at speed 1, as the graph indicates this would be the -.- line i believe. the -- line would be the second speed. b) there is an automatic bypass valve in the system too: "The...

Hi, I've been looking for some info on how to correctly read pump graphs. Information seems to be a bit difficult to find. Anybody with knowhow can give me some details how to read the following chart? (Pump is fixed on stage 1 by setting d19) The residual pump discharge height depending on...

@hossacd yes, weather compensation is something I'm definitely going to look at - as soon as I'm sure the rest of the system is up to snuff. Currently it's wired up on 240v on/off so can't set the heating temperature freely or the hot water might not get hot enough. Thank you for confirming...

@hossacd thanks for the info! Radiators big enough I believe, but rated at higher temps, yes. So increasing flow somehow would benefit output - at 75/65/20 they should be enough but at 70/50 probably not. Which is where I think the problem is: flow through system is insufficient. Results in...

As luck will have it last night was a gentle 10 degrees, nothing like the -4 the nights before... So not sure if there's any difference, as the house didn't cool down much under 19 degrees during the night. Ok, set d0 to 20, let system cool down and monitored it for the better part of an hour...

Yes, sorry, that was a typo, I've corrected it, will set d.0!

Ok, thanks @Bunnyman, I appreciate your time and knowhow and your help is much appreciated! I will set d.00 to 20; leave everything else as is. I will monitor live status when starting up from cold and report back. For my understanding (don't get me wrong, not second guessing, just want to...

@Agile, agree it's for the engineers as it's inside the sealed case. I've had an engineer and he adjusted the ABV to maximum (350 mBar from 250 mBar) and though it reduced how much the ABV let through the return after the ABV/Pump was still about 10 degrees hotter than the return temperature...

@Bunnyman you mean don't bother about the ABV? It looks like the boiler is not pushing enough hot water around the radiators and is mostly idling at minimum even though house still cool. Radiators do get hot after some time, and eventually I get a return around 55 as I mentioned. No cold...

Agree with the impression that the ABV is letting hot water through to the return flow. From what I understand, the system needs an automatic bypass valve in order for the water to be able to flow around and cool down the heat exchanger if a) TRV's are closing down most of the radiators so the...

@MrTherm - for my understanding, how would they counteract? If one is on a higher setting wouldn't it just not open as the other one opens first? Or would one open, closing the other, and then close again, opening the other or something like that? And if there are no isolation valves, would...

It's on big copper pipes, continuing the size that Vaillant has sticking out of the boiler - I'd estimate 25mm but will measure to be exact. Pipes go up through the house and disappear in floorspace, so no knowing but 'assume' they stay this size pipes. I can see them going up in a cupboard...

Thanks for looking into my post, here's some more info: It was in the house so don't know about sizing, but as I said it's a large 5 bed 3 bath detached. Moderately insulated. 14 (several quite large) radiators + 210 l cylinder, 37 kW might be a bit too big (from what I read in the forum) but...

Hi, First post so please forgive me where I go wrong. Wondering if anybody has some detailed knowledge about a suspected bypass valve that is not working as I expect it to. To elaborate: I have a Vaillant Ecotec 637 boiler, with an S-plan layout. Large 5 bed, 3 bath detached, decent...