marshian

Similar here (I won't repeat myself here) except I've not transitioned to ASHP yet. I've still got the "smart" TRV's but they are serving me well whilst I get the Danfoss RAS-B2 rad valves aligned to the room temps (the app gave me a starting point for all my T22's and single K33 but it's not great for vertical rads - once that's done conventional TRV heads are going on (Just as temp limiters for solar gain in the shoulder seasons) and WC can take care of the house temps 24/7

Yeah it's perfect for the two of us in a 4 bed detached - no need to worry about Legionaires when we pretty much deplete all the water every day Thank you - It's a bit busy in there but I've tried to keep it neat - the insulation is decent Tubolit Polyethylene Pipe Insulation (not skimpy DIY store stuff) with almost identical OD for 15mm or 22mm so I have a tube mitre block set up for 30, 45 and 90 deg cuts I pre-make 90 deg bends and glue them with off cuts (from the last time I did any insulation below the floor) and then I only have to fit bends and then measure the length between them and cut the lengths accordingly

No idea - certainly it seems like it's got a pretty wide hysteresis judging from the overshoot It's been in there since 2012 when the tank was replaced - previous tank was un-insulated copper tank with a puffer jacket that developed leaks after fitting a water softner. Tank replacement is on the list of things to do when I can justify the expense.

Single element electric immersion - Gas boiler Off because system drained down Hmmm it's not very long - 3KW draw - Tank capacity is about 114 Litres (guess based on our daily water usage - up to 4 showers at 30 L each one blended from 50 deg C HW temp to comfortable shower temp) I can heat enough water with it for Mrs BC's bath night but I need to set it to 60 deg temp to ensure she doesn't run out of water mid pour Won't be till next Spring when I do the adjustments to the heating circuit under my suspended ground floor - was on the list for this year but I've missed my window I think that would be the case for a side mounted immersion depending on where the temp is picked up from We only have the immersion for "emergencies" (boiler failure or replacement and when the system is drained) it's always been on a three pin plug (for 34 years!!!! - it's on the list to put it on a wall switch but I only ever thing about doing it when it gets used which isn't often - this is the second time in 12 mths)

Is that considering the utterly dreadful efficiency of 50-60% of a CCGT - I get your point about transmission issues (and losses) for gas supply but I'm running a gas boiler at 97.5% efficiency on CH and 89% on HW What about the electricity transmission losses?

OK I had the system drained down to do so other work (it was planned for summer but well life gets in the way) Work 1. London loop on the HW outlet of the tank (early days but it already seems to have reduced standing tank losses) 2. Re-pipe the bypass so it's after the CH zone valve (it was before so when I restricted the flow thro the HW tank coil it opened the damn bypass and defeated my efforts to slow down the flow thro the coil!!!) 3. Combined 22mm Feed and vent for CH (removing the old 15mm feed) - Thank You @John Carroll it's solved all the issues with air ingress and got rid of another pipe in the cold loft 4. Generally remove a load of joints (from previous versions being adjusted) and clean up the lagging 5. Convert all the main rads to TBOE with Danfoss RAS-B2 flow control TRV bodies Anyway what I needed to say was Immersion stat is set to 55 Deg C (well mid way between 50 and 60) After heating it overshot by a large margin - Tank temp at the top was 60 deg C when it cut out 1 shower later and tank temp at the top was down to 50 and the immersion cut in again Turned it up to 60 because bath night and top of the tank was nearly 70 when the immersion cut out She hadn't finished pouring the bath before the immersion fired up again top of the tank was reading 60 So I'm guessing the temp sensor is lower down the element. Can't do any more tests because the system is now refilled and I'm back on gas and I've finished lagging what I call the plant room (Others might call it an Airing cupboard) Just to be clear - the water damage on the floor is legacy from previous occupants When I replace the tank I'm probably going to replace the floor as well because it's quite crusty

I can't get a kitchen pass two nights running so this week I'm out (Cos NMR club evening is Wed)

Excellent.

Having had fun with all the permutations of pump settings on a DAB pump my only advice is to check again after a day and again after a week PP and CP on my pump initially look fine but flow rate drops over a few days - I have no clue why but the only solution for me was to go to a CC setting as there the flow rate stays constant.

If I can avoid them I will and I'll use solvent weld as much as possible but if I have no choice then that's what I try to do when I do use one. Downside of an 80's house where several people have had their fingers on the plumbing over the years

Thank you @Nickfromwales - That's certainly what I would do to add a bit of easy maintenance access when using solvent weld I also only tend to use compression/gasket waste fittings on vertical drops less chance of a leak on a vertical pipe (obviously you can't do much about P traps and bottle traps as they are all gasket type)

Just a comment....... I like solvent weld pipe far more than I like gasket fittings but when using solvent weld I always consider how I'm going to be able to either remove the section or rod / hose out the pipework in the case of blockages - washing machine powder can build up in pipe work if "someone" over doses the machine on a regular basis (I think this is amplified by cooler temperature washes). In fact the think about future access / maintenance applies to a lot of plumbing in homes.

In a DHWP set up the flow to rads or UFH stop - the heat source re-charges the HW cyl and then the system reverts to heating House doesn't or shouldn't lose much temperature in the time it takes to do HW unless it's a massive tank

It seems that way initially but like most things but you do get you head around it eventually Unheated rooms will steal heat from wherever they can - let me help with an example My house (stupid T shape) has front bedroom above front hallway both having 3 external walls and with the added bonus of north facing - being a "lets not be wasteful with energy sort of chap" (Mrs Alien says "tight b'stard") I didn't heat the front hall for most of the time just bringing it up to temp for the few hours we might use it (arriving and leaving). The Rad in the bedroom above had to have much higher flow rates as well as a higher set point than the other bedrooms (one because of the 3 external walls and two because some of the heat was being stolen by the hall below) Now you might say but heat rises and yes it does but a better statement is that heat always moves to cold and it doesn't care if down is a direction it can move in. So now I heat the front hall to 17 deg - it's cooler than the rest of the house but it does have an internal door to separate it - as a result the bedroom above needs a lower flow rate to the rad because the difference between the two rooms is much narrower So by all means run rooms at lower temps but consider the impact on rooms above or below is all I would say - if you size rads or UFH for low flow temps to provide the heat needed based on a heat loss calculation you could find that the room won't reach target temp if it's having it's heat stolen by a room above or below or even beside it.

Blimey 34.5 litres a min is 2070 litres per hour.... that feels like a heck of a lot of flow.

Modern pumps are a real head fug - they are a bit to damn clever sometimes My limited understanding is the faster the pump speed the smaller the delta between flow and return so you give the emitter more time to get rid of the heat (That's the impact in my house) but in your case where you are trying to get the emitter to give off more heat it may well prove effective - guess testing and monitoring are required Having said that constant curve is what I settled on (mainly because the flow on proportional settings changed from when I first set the pump up to maybe a week or so later - some learning logic I think)

Just to add to @JohnMo's comments - Covered very well below with a bit of the maths Hell yes - Been there done that - "Smart TRV's" that can call for heat from the boiler even if only one room needs it will result in massive energy wastage as the boiler fires up and then potentially short cycles until demand increases

You might not need to split the circuits - Heat Geek did a video on pump distortion not that long ago

Every house I appreciate is different and responds accordingly but I was running 2 deg setback in most of the rooms for 4 hours at night and 5 hours in the day and in a week of relatively stable OAT's I used more energy on the setback days than I did on the 24/7 (if anything the setback days were slightly warmer although I was only looking at the average temp between coldest and warmest temp across 24 hrs (it could have been colder for longer on the warmer days) It's one of those experiments that you do for fun

I know that on my house set up (all rads) setback temps (2 deg setback) just don’t save me any energy - the reheat from setback uses more energy than maintaining a stable temp 24/7 perhaps if I used either a smaller setback or a larger setback it might be different but if I used larger setback I might as well just go back to a schedule and a smaller one seems pointless

I'm running pure WC mode but I still have a hallway thermostat - it's acting as a master off switch if the house ever gets to a temp that heating is not required because the hallway has the only rad that is undersized for the area and heat loss (Includes full height stairwell and unheated upstairs landing)

Oh yes sizing for 35 v 45 results in a significant increase in rad size as I found out I specified DHWP and WC on my boiler install and got S plan............ To give the installer credit he recitified the error and we got there eventually but fundamentally it was what he knew and he thought it would be fine.......... He also couldn't read a WC curve properly until I explained it... Trouble is installers talk a different language to customers - when you talk their language they don't always think you actually know what you want.

It didn't change a thing (well all that did happen is the room that needed the highest flow lost temp because it was being shared out to other rooms and it's the last in the circuit) So I reverted it to a dumb boiler and manually set the flow temp - still did the same thing ramping up randomly mid burn cycle - often causing + 5 deg trip. Then I needed to do HW cycle so manually increased the flow temp First thing boiler was only slowly increasing temp (because range rated to 4 kWh - ahh bugger need to undo that setting - Increased range rating to Max because it's one button press in the menu. Then boiler reached my previously set max flow temp cap of 45 deg. So that got changed for 70 Deg and then the boiler froze as I was trying to exit the menu - it was doing HW so I just walked away and left it to heating water (it's happened once before and the solution was to turn the boiler off at the main switch) So when it finished the HW I powered down the boiler (made a cuppa and then switched it back on) house needed a top up heat wise so I range rated it back to Min and waited for it to fire. Guess what happened next? It fired - ramped up to 58% and over the course of 2 mins modulated down to min 10.6% and sat there at min for 17 mins and 30 secs - used 0.103 m3 of gas which by my calcs is 3.98 kWh....... It didn't miss a beat for the rest of the day. This morning however it was back to it's old tricks - starting to really get on my wick now So I switched off the boiler waited 5 mins and then waited for it to fire for the next cycle and it respected the min range rating again. So now every time it starts to play up I have a solution to the issue - it's not pretty and I don't believe it's acceptable but I have some information now to go back to Viessmann with to point out that it still has the same problem it had before (and crucially what resets it back to how it should operate) It doesn't seem to matter what pump speed I use Constant Curve 1 or Constant Curve 2 the only difference that makes is the DeltaT at the boiler is 9 deg C with CC1 and 5 Deg C with CC2 Pump in CC1 5.5 w 1.1 m head 0.4 m3/hr Pump in CC2 16 w 3.1 m head 0.6 m3/hr

Well it hasn't 😞 so I'm going to put my thoughts down and maybe a proposal for consideration from the great minds of Build Hub The "niggle" now only occurs between 6 deg OAT and 12 Deg OAT So lets cover the data I can provide Pump Pump Speed 0.5 to 0.6 m3/hr set on Constant Curve Watts 15 Head 3.1 m Rads I have 13 Rads all with TRV's in the house table below explains what they are room sizes Heat loss at -2.5 Deg C OAT and how they are set up (Because there are issues with getting the flow rate low enough for some rads and solar gain with some rooms) I regard the circuit as well balanced both upstairs and downstairs I have a pressure relief by-pass but it's fully closed as the circuit never shrinks enough to need it. Boiler Viessmann 100-W "Heat Only" 16kW set up with Weather compensation and DHWP (Using an outside temp sensor and HWD box) It's piped up as X Plan It's running a delta between flow and return at the boiler of 6 to 7 deg C at Weather compensated flow temps Weather Compensation Curve When it's not in the OAT temp range where I see the niggle this is how the boiler behaves Good Days On CH the boiler fires up when the flow temp drops "X" deg below WC Target (Gut feel is X = -7 Deg C below target temp) It will do an initial start at 58% modulation and then over 90 secs drop down to the lowest modulation level that enables the boiler to maintain the target flow temp typically 10.8% It will then run happily at that level until the flow temp exceeds the target by "Y" Deg (Pretty sure "Y" is 5 Deg C above the target temp) Bad Days When it's in the "Niggle" window its behaviour is different during the burn Even if the Boiler is range rated to min (19 out of 100 in the menu = 10.8% or ~4.0 kWh) the boiler ignores the range rating Initial start up is identical to above but very quickly into the period after the start it starts to miss-behave - modulation swings between 10.8% and 30% This frequently results in the Target temp + "Y" being reached during the higher modulation and the boiler shutting down before it's fully refreshed the water in all the rads that were open for heat. My thoughts are that the return temp is changing as some rads have quite a large flow and a decent delta between flow and return and some other rads have much smaller deltas and the boiler is trying to maintain the target flow temp so modulating up and down to provide a stable output. If you read all that - thank you. Proposal So I had a thought what would happen if I set all the rads to an elevated flow rate said sod the balancing control - leave the TRV's to manage the room temps and flows and bring back into play the by-pass (just in case all the rooms hit target temp and TRV's shut down the flow). Part of me says I should just try it and see what happens Part of me says the TRV's will end up managing the flows as they close and the flow rate in the system and the return temps will be the same so it won't change a damn thing. Anyone think anything else will happen?

Interesting point - maybe there is something I can improve as our current SUDG windows and doors were fitted in 1997 so are coming up for 28 years old................Question is how much better because there are no drafts from around the closures (the window seals are good) they haven't gone yellow like some cheap windows do. I'm thinking its going to be mainly thermal improvements in the glass and gas between the panes and they aren't big windows (circa 1.7m2 in total apperture area for each one) I'm guessing the payback for that level of capital investment would be a bloody long time