Munchincocopops

Yes forgot....I have 2 ensuite bathrooms without Trv's and a main bathroom with cast iron radiator and trv.....all permanently on...i.e no motorized valve in circuit.

flow to manifold and return has me confused....ok my15 deg return is a guess...its warm but not as hot as flow at 60 deg....its a lot cooler. So I'm still wrong about "heat exchanger" manifold...still learning....I agree boiler pumping to dead end does not seem right....but at a loss where the heat is going...the boiler runs for quite a few minutes. I'm thinking with buffer tank boiler runs for longer than I see now (in my quick investigation) and stays off for a long time as it takes for the UFH to cool the buffer tank (ok plus heat losses). Anyhow.....will give boiler some radiators to heat as well as UFH and see if its better. Thanks for the replies.

I think I got it.......basically hot water from boiler is going to a dead end and only mixer valve consumes the water and only excess return water from UFH to manifold that is not recycled is returned to the boiler? Up to now I thought manifold was like a heat exchanger with a mixer valve to take hot water as required.....my mistake. Blimy - ran like this for past 2 years! Think I will pull CH relay and manually open CH motorized valve. Buffer tank looks like a good idea. OK 4 min or so run but boiler will cycle much less I expect.

I understood the mixer would not take much hot water so I was expecting the return to the boiler to be the unused hot water mixed with a little UFH return.....so to heat up as hot water is delivered to the manifold and "most" returned to boiler? I can reduce boiler temperature and see if its any better.....as I watch it for a while.....later in the week. And (?) for the moment pull CH relay and manually open CH motorized valve so CH comes on when UFH demands heat.....is that worth doing?

Early days and not spent much time on this yet but just been in garage for about 20 mins and boiler cycled 3x. UFH only is on and I turned up stat to ensure it asks boiler for heat when I'm in garage. What I find confusing is that the boiler heats (thought it was set at 70 but its set at 60 deg c) up to reading of 60-64 deg C and stays there for a while but return temp is about 15 deg c (read with chatty ir gun....it also reads output as 45 dec C but it feels hotter....but 15 deg c feels about right). As this is only feeding UFH manifold (CH & HW turned off) and pipe to UFH manifold is about 15ft or so I was expecting hotter return? Anyhow....return feels 15 deg or so when boiler is running then when boiler shuts down it does not take long for the boiler out temp (was reading 60 deg or so on boiler temp guage) to drop to about 38 deg at which point boiler fires up again. Return still feels like 15 deg or not much less (skin meter). I'm waiting for a new multimeter with temperature measurement so will pull insulation box around manifold kit once I get it as I have to move a lot of stuff and shelving to get to it so not a 5 min job. Will spend an hour counting cycles and timing on off maybe later in the week though would be nice to do when I get my temperature meter so I can record temperatures too. Just thought...I did have CH on but turned it off and I know its was off as relay was off in garage. But I guess CH mororized valve could be leaking and allowing pass through so return water to boiler is being mixed with return water from UFH? Will look at this again ensuring CH is off. Thats my update so far.

Thanks for the guide on what to do it is really helpful. I realise these systems are complicated to understand and get the best out of them and I'm no expert in this area but the comments and advice will help me understand better. I will follow your advice, it will take me some time too. Really interesting that you reduced gas consumption by over 50%, that is impressive and of course you know what you are doing. I'm not hoping or expecting anything like that but just wanting to make the best of what I have if at all possible and if (as it appears) I have 2 conflicting requirements of a boiler, then if savings would be reasonable I'm open to spending a bit now to save long run...not too long run as I'm an OAP...LOL. Thanks for all the comments and help everyone. Looks like I have some work to do....I wonder if I can fit a radiator next to the boiler to keep me warm when looking at this...LOL.

Which cheap system boiler to run UFH? Just something to think about.... Thanks for the help and advice.

Thanks again. Lots to think about and nothing perfect for my system to improve cycling or reduce running cost. Guess I need a logger to count cycles over a period of time and measure how much gas used. Easy thing to do is pull relays controlled by CH and HW that ask for boiler heat. Manually open CH & HW motorized valves and allow UFH only to ask for heat and boiler heats CH and HW too. Measure cycling and gas usage. Pick similar days in terms of outside temperature. Logger bit is not easy as I do not have one (yet) but I can measure gas usage. So will have a play over a few days or maybe a week or 2. Finally - looks like a problem anyhow no matter what I do as I need big boiler to heat whole house (I think unless I leave it on all the time? - though 24kW Viessmann never made house cosy) but UFH does not need much heat input. Option 3 might be the solution - a separate boiler for UFH.

Laptop battery is running out so last post of the night for me. Radiators - not sure what else I can add over above. TRV's on all bar living room that is on full as radio thermostat is in that room. Thanks for the comments and advice. Will be back tomorrow night.

Thanks - house used to be drafty when built but I soon sorted that. No cavity insulation bar garden room extension. No fitted any any as advised as house is buit of sandstone....bar garden room. House is cosy warm and quickly heats up in the coldest weather so really happy with 32kW. It used to be 24kW Viessmann which never seemed to turn off when really cold nor house really cosy. 32Kw turned out to slightly cheaper to run CH but I'm thinking its overkill now as we mainly live in garden room with UFH. But must admit in no time house is cosy when full CH is turned on. So will weather comp help to save cycling - does that control flow temp. I will have to google weather comp. Looks like this boiler does not support Opentherm from what I read.....but I'm no expert.

Thanks - will look into this over the week end....dont fancy standing for a hour in the garage but its something to look into.

Baxi Megaflo 32 System ErP Condensing Boiler.

Blimy.....must go and stand next to my boiler as it runs UFH to count how many times it cycles in say 10 minutes. Hope the opentherm is an option now.

Thanks for that. Option 2 I was thinking it would reduce boiler cycling and constant run to heat water from 45 deg to 60 deg or so then turn off. UFH uses buffer tank water temperature to run UFH on stat demand eventually cooling buffer tank water to below 45 deg which in turn demands boiler to reheat to 60 deg. That was my thoughts anyway hence seemed a good idea. Will look into opentherm as it looks good with Hot water and lower temperature for UFH and house heating. Last winter UFH was on constantlyfor 6 months. Sounds like I should simplify and skip CH timer and CH on with hot water demand or UFH demand and use CH stat to control CH need (i.e motorized valve)? Option 3...is it a typo or are you suggesting its a good idea even if complex/costly. Thanks again.

Thanks for the replies. Will look at boiler model tomorrow but I know its a Baxi, 4 years old and I'm not aware of built in DHWP or at least no controls visible to me to alter or select. anything other than on/off and temperature setting I recall. Will turn it down to 62 deg or so as i thought it had to be above 60 for bacteria reasons. Maybe I did not explain properly UFH has own /timer stat and demand on boiler. Radiator CH has its own timer and a room stat and demand on boiler. HW tank has its own timer and stat and demand on boiler. Separate boiler demands achieved via 3 relays (UFH, CH, HW) using volt free contacts wired in parallel connected to boiler demand. ( some additional wiring as demand to boiler comes from motorized valve for each heating circuit) Living room has 5kW radiator, some 14 other radiators in the house with their own valve TRV's except for living room which uses room stat and no valve TRV's. Garden room added recently (attached to house open plan kitchen) hence large boiler before that for CH but now we find we tend to live more in garden room with UFH that is normally on all the time over winter so less need for radiator CH other than keeping the chill off the house. Hope that explains why I ask questions on UFH. So back to my original questions. Option 1 or 2? Option 3 I added later I think will not help.