marshian

Found it https://www.heatgeek.com/do-we-really-need-dt20/ Basically as you lower the flow temps the delta between flow and return will drop I'm currently running ~30 deg Boiler flow with a 7 Deg drop at the return of the boiler Flow Temp Return Temp Diff 80 56.0 24.0 75 52.5 22.5 70 49.0 21.0 65 45.5 19.5 60 42.0 18.0 55 38.5 16.5 50 35.0 15.0 45 31.5 13.5 40 28.0 12.0 35 24.5 10.5 30 21.0 9.0

Sorry I must have missed it but why would you specifically want opentherm over std weather compensation using an external temp sensor?

Alternatively increase your rad sizes (in alignment with room heating requirements) and then lower the flow temp at the boiler. The lower the boiler flow temp the less expansion in the pipes and as a result the clicking reduces. In our house used to be terribly noisy every time the boiler fired up on 70 deg flow temps. Over the years (with improvements to rad sizes and house insulation) I've managed to reduce flow temp to 45 to 55 deg C (manual weather compensation and scheduled heating periods) With a boiler change as well as a move to WC flow temps and heating 24/7 it's now at ~30 deg I only get click clacks from the pipe work just after I have finished a HW cycle (because the boiler heats the HW tank at 80 deg Flow Temp and a small slug of 80 deg HW gets dumped into the CH circuit when the boiler reverts to CH at ~30 Deg C and this does create a little pipe work noise for a couple of mins

Ahh google informs me that is the std for graded timber used in the trusses. I'm pretty sure the Trusses would have been fabricated by local roofing company but they've been amalgamated into another company.

Took pictures so I don’t forget BS 4978 - is what they are marked up as

1. yes lower the return temp (below 54 deg C) the better the condensing and efficiency improvements @JohnMo has experience with atag - I don’t 2. Circuit size and volume of water in the rads normally drives the need for a volumiser @JohnMo is your man for discussion around that 3. No you will always have a difference between flow and return unless your room and rad temps are equal 4. You really want to make A, B or C work don’t you???? I’ve no further comments on any of those schemes

On the plus side @Ann D Mann credit is due for the choice of user name - did make me chuckle a liitle

much better reply than mine - said it all so well bravo @SteamyTea

so as “waste not want not” people surely you can see that adding 1. A boat load of extra cost 2. A shed load of complexity and probably 3. A bucket of safety risk (kettling a HE behind a stove leading to steam which considerably ramps up the pressure in a circuit and that would be “sub oprimal” Would not be a “waste not want not” solution Treat the stove as a stove and let another heat source do what it should be good at all in my opinion of course you will do what you want at the end of the day but remember one thing - you came on here asking for advice If you came on here asking for your options to be validated you should have said so at the start - no-one would have responded

@Nickfromwales any chance you can fix the replies within quotes by @Ann D Mann - makes it hard to read….. @Ann D Mann reply outside/below the quoted box please or your replies get buried in the quotes and they need to be expanded to read

from my perspective 1. Zone valves do wear out (or rather the heads fail eventually) 2. zone valves (if not exercised) can stick so in the late spring, summer and early Autumn where in a conventional S plan zone valve arrangement the CH zone valve would see no activity at all because the HW zone valve would be the only one opening and closing once a day. with NO and NC valves they both get “worked” every-time HW is requested (so you could say in that period I am doubling my zone valve electricity consumption but as it’s only for a short period I’m comfortable with the cost benefit analysis. I will also switch the boiler from weather compensated operation to dumb boiler mode as the viessmann HWD box - throws everything at the HW circuit in order to minimise HW re-heat time (20-30 mins) and this does have a cost. I can revert to a 55 deg flow temp for HW - give the boiler an easy life and get condensing efficiency gain for the 60 mins the HW will take (as opposed to the first 3 mins of the PDHW set up) it’s about 1kWh of energy saving a day

yes and no On my system the two zone valves are wired together NO (Normally Open) zone valve for CH - no activation required and has no influence on CH circuit - call for CH or no call for CH it remains open * NC (Normally Closed) zone valve for HW - it’s at rest closed - call for HW come and it opens - and the feedback signal energises the NO CH valve to close that valve. HW complete the NC valve for HW closes back to it’s unpowered rest position - the signal/voltage to the NO valve for CH is lost and it reverts to rest position (ie open) Result is (in my house) 23.5 hours out of 24 hours the zone valve consume no power at all

I don’t understand why anyone is using S or Y plan if they have a boiler capable of running PDHW - it’s just nuts. I’d also just echo the comments of @JohnMo and @Nickfromwales - what you are proposing is a metric ton load of complexity and cost for very little gain - use the stove as a stove and enjoy the ambience and hope you neighbours don’t mind the atmosphere. You are designing the perfect racehorse but you’ll end up with an elephant or a camel both of which aren’t competitive at horse racing events. Yes I know camel racing is a thing but that’s not really the point.

Just for the records

Thanks all that made the effort to get out on this cold winters evening and @Alan Ambrose for the prior "site visit" Sorry (Not sorry) for my structuring exercise 😉 As I said I "planned" the discussion points in the car on the way to the meet. Something to "build" the evening providing some "Dimension" and "Detail" that could help conversation flow and it's often said confession is always good for the soul What's said at a Build Hub EA meet up stays within the group

To use your own words you'll get over it

No - it was most excellent

My approach would be 1. lower pump speed (I hate system noise and if you are running 24/7 with setbacks it’s costing you money via higher wattage drawn by the pump) if boiler overshoots 2. open lockshields a bit more but with 9 or so rads in circuit you really shouldn’t need a high pump speed and the balancing should be fairly easy to achieve Then with a stable system circuit running quietly I’d start to back down the flow temp - as you do this your individual rad deltas between flow and return will drop anyway so don’t be tempted to tighten the circuit to keep the same 10 deg delta heat geek had a really good table of what to expect delta wise at the boiler at various flow temps - it’s a really useful table that stops you from fretting about low delta T at the boiler. As you drive the flow temp down you might need to adjust the boiler hysterisis but you are doing that to be inline (ish) with the circuit flow and return temps (to get to a point where the boiler doesn’t spend ages coasting while the circuit cools) all of the above with an eye on keeping the house comfortable temp without long recovery times after a setback at night

Little bit of info here - easier than explaining it https://www.pistonheads.com/gassing/topic.asp?h=0&f=47&t=1911876&i=0

Me too so you won't be dining alone 😉

The BBC covered the cost of a full set of tyres, a set of brake discs and a new clutch....... Just to clarrify - I purchased it direct from Lotus a year later (following a sealed bid auction process - which I didn't actually initially win) as part of a "fire sale" of all the Lotus "collection" Like I said the car has an interesting history - looked at from completely honest perspective you could probably say that technically it's not even a real one as it was not part of the original run of 950.

Name badge is at the ready - see you at 7 (ish)

That picture was at Shelsley Walsh Hill Climb It's mainly a road car but it gets used for sprints, hill climbs, track days, navigation rallies and of course European road trips - it however the tattiest LC in existence because of that - it's also the last one ever built by lotus but that's a story all on it's own......... The montage below was from a "year in the life of an LC" - I'm not precious about it - it's a car not a museum piece - I hate show and shine but it has done a few over the years - prefer to use it as intended - I've owned it for 24 years (bit of a love hate relationship and I'm never sure who is actually the abusive partner) Also might have been abused by someone else for a TV show

Important thing (stating the bloody obvious) is the boiler has to get the house warm - no point having a boiler thats tweaked to the max to give longest burns possible at lowest flow temps if the house is cold………. I reckon you’ll be able to reduce the flow temps along with a few more tweaks and maybe even drop the pump speed too last question are the lockshields reset to where they were or still a 1/2 turn open more?

That’s better - still probably things can be tweaked but I’ll take that as a win