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.

Its a system condensing boiler and heats the whole house which are radiators. Plumbed so all have their own thermostats and timers. Mostly we live in the garden room so usually house heating is off or turned down. Bathroom radiators come on whenever boiler is on. So 70 deg is for water heating. All showers use hot water tank water so no electric showers. House is quite large and built late 80's hence 32kW. There is a third option. UFH has its own boiler? Thanks for the comments.

Hi - I have a 12mx5m garden room with water based underfloor heating. It works well but I am always wondering if there is a better way to control this. At a guess I think there is about 400m of pipe as 4 loops in this area. My installation has a wall thermostat (no floor sensor) and I the normal mixer valve/manifold/pump arrangement and when stat calls for heat it opens a valve (water from boiler to underfloor manifold/mixer valve/pump) which in turn activates UFH pump and turns on boiler. Obviously when stat reaches temperature everything turns off. Now I'm wondering about 2 things: 1. Better control of boiler as a 32kW boiler running at 70 deg C will soon meet mixer valve requirement but the stat is still calling for heat until the room reaches temperature. So I wonder if I use a thermocouple/programmable thermostat to measure return water temperature on the UFH manifold and set this to 45 deg c (?) and if above this turn off the boiler. 2. To install a buffer tank, use thermocouples/programmers to turn on boiler if buffer tank temperature is below 45 deg C and turn off boiler when temperture is above 60 Deg C. Might have to play around with max temperature to achieve a workable value. There will be some plumbing to do between boiler/buffer tank/manifold and extra valves possibly and likely some wiring changes to suit. There might be a better way than what I am thinking so any comments or advice is appreciated.

No advice......maybe another question. How do you fix brackets to the plastic frame so that the brackets can be secured to the steel lintel supporting the inside blockwork that does not have a cavity tray as I expect fixing it this way would be fine. Is this the recommended practice thus avoiding fixing through steel lintel supporting outside brickwork and of course the cavity tray immediately on top of the steel lintel and brickwork on top of that. Hoping for a advice.

You would have thought so but the door and window company did just that a practice they tell me they have been doing for 20 years. It is an expensive well known make of door and can only be bought via and installed by authorised installers. I am waiting for their decision on how to rectify.

New door fitted. Fixings vertically through frame, through steel lintel above door, through cavity tray above that and fixed into masonary sitting on cavity tray. Now water running down fixings into frame above door and into inside of house. Whilst I now read this is normal fixing practice, to drill through lintel and cavity tray, how does this fit with building regulations regarding cavity tray. What is the solution? Any advice appreciated.

Never had a heat loss calc done. House has no draught's but also no cavity wall insulation as house is built of stone and advised not to have cavity wall insulation in case of cavity bridging with stone. Not much loft insulation either as its boarded out mostly. Though extension has insulation. as per current building regs. So thanks for the advice - it looks like a buffer tank will do what I'm looking for. Kind Regards

Thanks for that HughF. The house is a big house before building the garden room and my old 24kW boiler struggled to heat the house in mid winter....its all 15mm insulated copper and oversize radiators...hence upgrade to 32kW. What I did not realise is that we would tend to only use garden room as it is always nice and warm with underfloor heating though there are times when we use the rest of the house with visitors and family and the 32kW cooks the house well. Will look into DHW priority but we only have this on each morning for 1.5 hours before we get up and it gives us stored hot water for the day. I'm assuming you are suggesting DHW priority idea for the bathroom radiator circuit? I've also wondered if a second small boiler just for underfloor heating circuit would be a better idea? Thanks again.

Thanks Temp for the reply and explaining the draw of heat mixing with the return to maintain 35 deg c. Stupidly I overlooked this obvious (now) effect of colder return water.....I was thinking water was easily raised to 35 deg and valve closed until pipework dissipated the heat when the floor is up to temperature ...thinking heat is not easily dissipated into already heated floor....but your explanation is making me think again. Its a new Baxi Megaflow and I do not know if its short cycling or regulating. I assume regulating as its heating the bathroom circuits not only the UFH. I'm just wondering if there is a way to use less gas....it may not even be possible....what I have might be as good as it gets and only a buffer tank would help?

Hi – I’m after some advice. I have a large garden room 60m2 with water underfloor heating, 7 circuits, all on or off as system demands. Due to increased energy costs I’m wondering if there is a better way of controlling boiler running. The boiler is a System boiler, 32kW, running at 60 deg C. It heats a hot water tank, house central heating and garden room underfloor heating each with separate timer control and stat. We have the bathroom radiators piped so they come on whenever the boiler runs. Mostly we only use the garden room and so only the underfloor heating is used and rarely do we have the house heating on these days. This time of year the ufh is on all the time though the stat drops back to 17 deg C at night then back up to 20 deg C during the day, usually we adjust this daytime temperature depending how cold it is. So I’m thinking the boiler (about 5m from the underfloor heating manifold) will not be on long before the underfloor heating manifold mixer valve (set at 35 deg C) turns off which in turn will eventually cause the boiler to shut down once bathroom radiator pipes reach 60 deg C or so causing the boiler to shut down on its own temperature stat. Though it may fire up again later due to its own stat even if the manifold mixer valve remains closed, though garden room stat is still calling for heat as the room is not yet up to temperature even though the ufh pipes are at 35 deg C. I have thought of a buffer tank but I’m wondering if there is something that can measure the underfloor heating manifold temperature so when it reaches 35 deg C it can be used to turn off the boiler as the room stat is still not up to temperature so asking for boiler heat. I’m thinking when the manifold temperature drops below 35 deg C, then the boiler is enabled again and controlled by the room thermostat. Ideally, I wondered if there was a manifold mixing valve that had a means of allowing a control system to know when it was open to accept hot water and also when it was closed and not accepting hot water. At the moment I’m thinking of fitting an electronic temperature sensor to the manifold and setting it to the same temperature as the mixer valve, though I realise the mixer valve is not exact so there will be some trial and error. Hence ideally an intelligent mixer valve would be best I think. The other idea is to use a PLC (maybe a raspberry pi) as the controller to monitor manifold temperature and when it records a maximum temperature, i.e. not increasing anymore, I assume the mixer valve is closed and shut off the boiler. Once the temperature, say, drops 3 deg below this maximum the plc enables the boiler to be controlled by the room stat once again. Anyhow, been googling but so far cannot find such a solution. Any help or comments appreciated.

So - buffer tank - what size? But just to be sure before I buy.... Are my thoughts unreasonable? Buffer tank or Mixing valve with volt free contact to call for boiler when heat required......is there such a thing? or add stat to manifold to call boiler if temp less than mixer valve setting or Dedicated small boiler for UFH only to negate need for buffer tank.......and will it be more efficient? Any thoughts or advice appreciated. Many Thanks.