marshian

If you think it's only going to be 1000 kW or £75 then as you say not worth worrying about the payback for changing the system about I think I asked earlier - what is your flow temp and what's the return Return is the one that matters but with UFH you should have a fairly narrow delta An indication of the benefits of condensing and the efficiency as a result are below Return Temp Boiler % Eff 65 88% 60 88% 55 88% 50 91% 45 93% 40 94% 35 95% 30 96% 25 97%

Adsibob How far from your HW tank is your Boiler?

I know my HW outlet from the tank and vent pipe to the loft tank are contributing to the losses but they are a constant (they are well lagged all the way to the cold water tank - approx 5m away) I guess it would probably not be a good idea to put a similar drop and return arrangement in that section?

Ahhh gotcha - Boiler would modulate down based on a much higher return temp than the normal mains temp I guess with a closed circuit you could treat the water - what about expansion of water in the circuit?

Can you not exit thro a gable wall - core drill etc rather than out via the roof tiles - then you can do that with a weather tight roof?

Where does the water go after the cylinder?

I thought they (System boilers which aren't combi boilers) had a valve inside to divert between Flow to Cylinder and Flow to CH circuit. The call for HW or CH determines the valve position and the boiler settings for either HW or CH

Just to make sure I've highlighted the section in red on an old picture before I insulated it all and added the proposed amendment in green (Distance not to scale)

Oh that I do know Anyway as stated earlier I know the battles I can win, I know the ones that are going to end up in a draw This one ain't either and it's not worth fighting for a draw or a loss

LLH means 2 pumps two lots of electrickery being consumed - that's a cost to you..... Unless your system is really heavily zoned then I don't see why the boiler couldn't supply the low temp water required for your UFH and the high temp for HW generation when set up with DHWP What flow temp and return temps are you running at the boiler and what flow and return temps are you needing for your UFH

Absolutely - the low loss header should not be needed if you have separate flow temp for UFH and having to run at a fixed temp is impacting efficiency PDHW at a sensible temp for HW tank reheat and a really low flow temp for UFH is what you need

Very interesting - thanks for that observation

A comprehensive destruction of the loft advantage

Good question - really good question....... I'd need a 5m extension to the gas supply and that would have to be run externally (not so keen on that) or internally in a boxed section thro kitchen and bedroom above - boiler is currently right above the gas meter box so the supply is just 15mm and less than 1m. I guess if you increase the length of the supply pipe you'd need to increase the pipe size but I've no idea what any of that would cost? I'd have to brick up the existing flue inside and out but that's not a deal breaker as I already had to brick up the bloody great hole the original non condescending boiler flue left when I last changed the boiler in 2009 I'd need to have the flow and return pipes changed to suit the new boiler location but if I've got to run a gas pipe up inside the house in a boxed section I can run the flow and return back down the same or re-route and go straight to the airing cupboard where the tank is. The question is do I want a boiler in the loft in order to gain a single cupboard space in the kitchen - I'm also pretty sure I'd need to move the cold water store and header tank as I don't really want a system boiler - Do I want a gas engineer to have to go into the loft every year when it needs a service and safety check as opposed to just having to grant access to the kitchen. I think a few houses around mine have done it so it's an option for sure Airing cupboard unfortunately is quite restrictive size wise and having boiler above the tank might be a pain for servicing - SWMBO definitely wouldn't be happy losing her towel warming area (despite the fact I've never had a warm towel from the cupboard ever!!! She'd also whinge at the loss of her summer/autumn/winter duvet storage (in vacuum bags to get them into the space) I could suggest we store them in the additional kitchen cupboard - that would be a fun conversation The loft is certainly something to consider.......

How smart do you want the HW controls to be?? You want HW when you want it? Ideally I want the boiler range rated to the cylinders capacity to transfer the heat and the flow temperature of boiler to be whats required for the end temp of the water in the tank to be what I want. Pointless for me to bugger about trying to achieve condensing temps in my boiler when heating water. The coil in the tank is sized for a 3kW input - the boiler is throwing 10 kW min at it (12kW on start up because that's what I have range rated the boiler to be maximum) Even if the tank is down to 16 deg (ie completely cold) in 36 mins (time not boiler run time cos it'll cycle a few times in that) at a set point of 82 deg the tank stat set at 48 deg setpoint will turn the HW off and it'll gain another few degrees during the pump over-run period If there is any HW left in the tank say 40 deg at top and 16 at the bottom it'll heat it to target in 20 mins If it's -2 outside the house doesn't lose temp in rooms in 20 or 30 mins - there is still heat left in the rads when the water is called for. That's why I will be going DHWP with the next boiler because now I'm doing it manually and in this day an age I want stuff to work for me not require manual intervention and I can leave the boiler to sort out it's flow temps based on weather comp for when hot water isn't needed.

Fortunately he doesn't but I get the "inference" Problem he has is I'm just a lay person - I know nothing about boilers and I'm not a trained gas engineer or boiler installer - his Gas engineer is trained and therefore he knows what is best and much more than a lay person. I've made a suggestion on how he can reduce his gas bills (60% more than mine in the same size house) and if he ignores it I can't help that.....

I've sniped out a lot of your post just to focus on a few comments Point 1 - they aren't that complicated but you really need to match the controls to your needs Point 2 - Yeah I get that when you get used to a "smart" system you ar reluctant to change to something else and have to relearn every thing to do with set up and programing- trouble is a lot of so called "smart" systems are really just "Smart On and Off" and you can cause yourself issues by micro zoning Point 3 - Not wanting to cause offence but - How much of the design was down to you already having an opinion already on what you thought you wanted or needed? I'm just a guilty of Point 3 when I had my current boiler installed and very guilty of it when I installed a wiser system thinking that out of the box it would resolve my issues at the time - it's taken a long time to actually get the system and boiler settings to work well with Wiser - biggest thing is to stop unnecessary zoning

Superb Post Nails the problem with both customer expectations (don't want to pay for the extra effort required to set up the system to work at it's most efficient) and poor knowledge of boiler installers (who throw the biggest boiler at the wall and set it to a much higher temp than needed on the grounds that they won't ever get a call back for a house not heating up). My neighbour won't change his flow temp from the boiler ECO setting becuse the gas engineer he uses says that's the best setting for the boiler all year round - I've measured the actual flow temp - it's 68 deg C - his return is 54 deg - it's only condensing in the warm up phase once the house is up to temp and the delta between flow and return narrows it's never going to condense.

I think I've answered my own question Last two nights tank has been heated to 51 Deg (this is the lowest the tank stat will accomodate) Note - I normally only heat to 45 deg (To minimise losses) and do it based on a timed cycle with a set boiler flow temp (30 mins and 68 deg Flow normally sees it settle at 44-46 which is spot on) Attached is the Tank Temps by Hour and Losses By hour over the two nights and a graph showing the difference It's pretty clear to me with the 3 port valve open to the boiler (AK at rest) I lose temp from the tank far faster than with the 3 port valve closed to HW and open to CH

No - that was bath night for SWMBO That was after the bath had been poured The tank I have stratifies quite well - there was about 40 L left in the tank at 57.7 Deg - there will be a slight zone where the temp gratuates but then everything below that was at 18.6 Deg (cold water tank temp) I've just had to manually do my DHWP as our water usage today was higher than normal (SWMBO left the bath tap on a very slow trickle after the morning cleaning session - ooops) it took the tank down to 22 deg top and bottom 36 mins with the boiler shoving between 10 to 12kW in thro the 3 kW coil and the top is at 51 and the bottom 50. Best delta I get heating water is 16 Deg due to the coil being a std 3kW one

You could use something like a Sonoff Temp Sensor 3/4 of the way up the tank - set the temp set point to just below your target tank temp and then use the switch facility as an output signal to fire HW as you would be about to run out of HW at that point?

Forgot to add a Picture

I did similar but only top and bottom

The pipework I can cope with - However it's depth exceeds a std 300mm wall cupboard which means it's going to need to be on show - imagine if you can a line of lets say black wall units broken by a bright white boiler.......... I can live with that - SWMBO can't - life is full of compromises I know when I can win this isn't one of those times

SWMBO has issued statement that if we change the boiler this year she's not going to be happy if a few years later we swap out for an ASHP so on that basis I'm very sure it's the right decision to go with a gas boiler again When we replaced the kitchen 28/29 years ago we had the original non condescending Glow Worm heat only boiler (fuelsaver 15/30 I think) previous owners of the house had painted it green to match the units or wall (can't remember which) so we built the new kitchen units around it (whilst still maintaining service access) to hide the ugly damn thing (also helped with noise as it was a pretty noisy thing) When replaced the boiler in 2009 one of the selection criteria was she didn't lose any cupboard space so the new Glow Worm was selected to fit in the hole left by the previous boiler - the cupboard doors still close and hide it away despite it being slightly deeper. Now apparently if you've had a gloss white kitchen for 28 years you can't have another gloss white kitchen - I don't understand the female logic - so it's very likely the new kichen will be absolutely anything other than white. If any boiler is on show it's very likely to be white and a white appliance in a coloured kitchen apparently won't do either so it has to fit in the same damn hole and be hidden from view. My flow and return monitoring also shown with today's flow and return levels