marshian

I can understand the concerns but studies have shown that the risk of catching Covid from physical items is very low - the risk is mainly airborne and close contact with someone who has the virus is probably the biggest risk Transport for London have long since abandoned the hand sanitiser stations https://tfl.gov.uk/transport-accessibility/cleaning-and-air-quality You do you but if you haven't had Covid 19 already I'm amazed and you've done very well to avoid it. I seriously doubt that wiping everything you come into contact with with sanitiser is going to make the slightest bit of difference to your chances of catching it. I had Covid in November 2019 - an unintended consequence of a holiday in North Vietnam on the border with China or migrating thro two large airport hubs I was never sure where I caught it It (the original strain) was proper nasty and I wouldn't recommend it to anyone but a virus that kills it's host doesn't tend to last long - it's evolved into a much less aggressive strain over time Not had it since either - the human species is quite amazing in it's ability to deal with pathogens that it's had to meet.

With HW demand box it's not possible to cap the boiler output on HW mode (Viessmann Technical told me this when I asked how to stop the boiler throwing 19kW at a 3kW HW coil) I know on CH it is possible and I know 10.6% is my boiler min (3.2 kW in low temp operation) because I've measure consumption at that rate in long stable burns. I did a little study a while back on HW to see what the boiler was really kicking out 100% is 19 kW (on a 16kW rated boiler - go figure) 50% is 10 kW 33% is 7.4 kW So I've set it to 20% and see if that stops the issue but still gives me some head room on restarts

How bloody right you are - today was 11.5 Deg C - flow temp target on the WC curve was 26 deg Cycling wasn't great - rooms maintained temps but at the expense of frequent short burns over 30 burns so far today I think the driver is the flow temp rises too fast for the boiler to modulate down rather than the circuit being too small I increased the room temp target to 25 which skews the WC curve to be 34 at 10 deg C and got a couple of decent length burns at the expense of room temps bouncing of the TRV temp ceiling I'm going to range rate the boiler to 5kW (or whatever % that works out to be) and see if that fixes the issue

Here's my math for my rad sizing In a nutshell what I had was a calculated heat loss at -2 and a rad kW output at T50 - what I wanted to see was where as I stepped down flow temps was I likely to have a problem with rooms not meeting the target temp (ie the rad was borderline) In truth I think my heat loss parameters for ACH and loft losses were a little pessimistic and so my heat losses for some rooms are a little higher than reality. But it does show clearly that I am likely to have an issue with three or four rooms

It's actually I think hard to match rads to exactly the room heat loss requirements and not get them oversized (OK I did in one room) For 95% of the year they are oversized by virtue of the outside Air Temp being above the worst case outside temp. Pretty much agree with that

My other half and her mate bet on every single horse in the Grand National once......... 2009 was a lucky year for that process 100/1 winner

If rads are also oversized then you can reduce the flow thro that rad at any given temp and basically make it behave like a smaller rad Quite hard to go the other way mine except winding up the flow and sacrificing the return temps I can definately save some gas by turning the heating off when I'm not in the house but the re-heat process means I have to start quite early before I get home and I'd rather have the house heated a little lower all the time than burst of high energy heating I think there is a lack of clarity in the discussion but you only get clarity by discussion so lets keep it going in the good natured way it is World is too damn polarised now Exactly what I mean by polarised viewpoints - there is no right and wrong only different approaches (with the UK's housing stock - there is an awful lot of grey and I'm not talking about the fashion trend for windows and cladding)

If I hadn't done the math @SteamyTea would have but he'd have used Joules or some other unit of measure 😉

Quick bit of maths 300 L tank heated to 85 Deg C You only use 250 Litres so 50 litres remain at 80 deg after 14 Hrs (Assumption is minimal losses) That 250 Litres has been replaced by 250 litres at 10 Deg temp (It's winter average delivery temp) So you've got 250 litres at 10 deg and 50 Litres at 80 deg If you mixed them you get 300 Litres at 21.6 deg C The mixing occurs when you turn an immersion on that's in the side or the bottom of the tank

Yes they do work differently - it's called stratification The hot water stays at the top of the tank and loses a small amount of temp due to tank convection losses - it's replaced by incoming water at anywhere between 5 deg and 20 deg depending on the season - there is minimal mixing between the two You heat a well insulated UVC to 85 deg C you are probably going to get 80 deg water out of it after 14 hrs until you hit the boundary layer then you are going to get 5-20 Deg water - like a switch!!!

300 L to 85 Deg C from say 20 Deg C only uses 15kW of electric? If the tank is being fully consumed daily and it sounds like it will be with that level of occupancy then to get 300 Litre of water from 20 Deg C to 85 Deg C is going to need a heat input of 22 kW So by my rough math your calcs are understating you usage by 45% With a 3kW immersion it's going to take 7 and a bit hours which is quite a chunk of time to recover

I'll take that as a compliment 😉 Background - for my last 40 years in work I've been a data analyst - it's really bloody hard when you are good at working with data to ignore it in a home environment. Basically if I can't validate something with data then it's a guess or a hunch and I don't do either of those

I'm reminded of the ultimate race horse designed by a committee Yes I know camel racing is a thing but that's not the point I'm making

I'm clearly not most people Below is my daily gas usage and below that my HDD data both by day for December Pretty clear to me my heating consumption of gas is driven by the outside temp and there is a close relationship

Just for comparison When I have my heating on I have 1 circulation pump running at 15W Boiler and Control system consuming 55W (when running) No Zone valves powered up at all (NO zone valve for CH) Only when I do HW do I have a zone valve energised for 21 mins a day.

My octopus app says I used 8% more gas this last week 33.9 m3 than the previous week 31.4 m3 The local weather station HDD says last week was 74.9 HDD The previous week was 64.9 so 15% colder I'm going to chalk that up as a win

I think you may miss a slight but subtle difference in the conversation In my case I'm not trying to nail room temps to a 0.1 deg difference - I'm quite happy to accept a slight over or under over 24 hrs I'm not controlling room temps with TRV intervention - I'm only controlling the boiler flow temp to maintain the room temps in the target area. As a result circuit size doesn't change - the TRV's remain fully open and I'm using all the 150 litres of water in the CH circuit acting as a nice buffer for heat distribution to the rads If I was running the same process using an elevated flow temp and was reliant on TRV's to manage the room temps the circuit size could be anything from 2 rads to 13 rads. This is what I believe would be a wasteful approach in terms of energy because the boiler would cycle like a bitch in shoulder months as my heat loss is 4.7 kW at -2 and the min the boiler can get down to is 3.2 kW so at 10 deg C outside my heat loss is probably 2.2 kW If my CH heat circuit was down to 2 rads the boiler would be cycling like crazy pissing energy out of the flue as the kW input would be massively over sized for the circuit volume.

If they don't have threaded inserts in the base - pretty much any damn self tapper will resolve that!!!

https://surewayheating.co.uk/products/new-003051-stat-cl6po134-genuine-spare I wouldn't mind betting the only difference is the length of the capilary tube and if the one above is 134 mm and your original part is 117 mm

I don't think a little thread jacking hurts - it was an old post resurrected anyway PS I'm finding the discussion really interesting

Exactly - we are not talking about wasteful overheating of rooms (ie more than the heat loss of the room) but carefully matching the loss - now that may mean constant operation but at much lower flow temps I'm far more comfortable in a room constantly heated to 19 deg C than I am in a room which is heated to 21 deg when occupied and loses 5 deg overnight The energy required to get the room back to temp is only slightly less than the energy required to keep it at a constant but lower target temp Agreed - as stated elsewhere - condensing boilers were mandated but not the adoption of lower temp emitters which were essential to get the boiler efficiency improvements from the condensing mode they were designed to run in. Effectively condensing boilers were installed and then run at the same flow temps as the old non condensing boilers - it doesn't get more stupid than that!!!

I’m fairly happy with it now - there are no low flow alarms - circuit is running constantly at 0.5 m3 per hour Boiler on restart peaks at 50% modulation but rapidly drops to 10.6 % modulation and happily sits there for 30 mins before flow and return temp rise to the point the boiler turns off and waits for it’s restart point Mean Rad temps are around 27 deg C and if flow temp is 30 deg return to the boiler is 24 deg C Roughly 4.0 to 4.9 kWh per HDD so I am using a smidge more gas than scheduled heating (3.5 to 3.9 kWh per HDD) but the room comfort makes up for that - it wasn’t about saving energy it was about making a stable house temp

I'm pretty sure that when I was in the middle stage I was getting a lot of cycling Right now the number of cycles per day is between 14 and 21 (So less than 1 cycle per hour) Watching the boiler yesterday it would burn for ~30 mins and be off for 45 mins - this was consistently the pattern throughout the day. (Fired 5 times overnight according to the ViCare app)

Warning long post - Bit of a catch up going on Still working with the boiler to get the house heating where I want it In November I was still heating to a schedule Got the weather comp pretty much dialed in for that type of heating method now. I've tempered the HW demand boxes appetite for throwing everything the boiler has to give at the HW tank (I've opened the the gate valve on the HW Tank return to 33% - lower than this and the boiler occasionally hunts a little as well as opening the bypass a little which you don't want on HW heating) On weather comp a 1,4 Slope is a good compromise for scheduled heating - lower than that and the house takes a little too long to get to temp. (especially the living room which as I've said a few times is slightly compromised - a 600 x 1400 T22 rad at one end of a 6.2m x 3.6m room was on the borderline when I did the heat loss calcs last year but I thought with less cycling and a more constant flow temp from the new boiler planned it would be OK) Higher slope than that and it gets the house up to temp a little quicker but too many rads shut down and then the circulation flow is too low for the boiler to be happy. Flow temps at the boiler around 8 deg C outside temp is 40 deg and return at the boiler is around 30 deg C All the rads are running at around 6 to 7 deg drop between flow and return I'm pretty near my target 4,00 kWh/HDD (slightly over some days when temps are a little warmer - slightly under when cooler) On one day the boiler did one burn from 3 pm to 7.30 pm which I am really happy about but more importantly all the rooms warmed up equally - even the living room but that's nothing to do with getting the weather comp dialed it...... What the difference?? I dipped my hand in my pocket weekend before last and purchased a new rad and I fitted it back end of last week. 700 x 1400 K33 (triple panel, triple convector) Yes I know it's a smidge below the min recommended height above the floor - I'll fix that next summer (consequence of raising the floor level by 20mm when I fitted oak flooring) but it's solved the rooms issue of always being the last to get to target temp. At the weekend Mrs BC (not known for her tolerance of cool temps) actually said can we have the heating off.............. In December I moved to 24/7 heating with set backs (as opposed to off with scheduled heating) As a result I moved to a WC curve of 1.0 with 2 deg setbacks however Initial results were good from a Mrs BC perspective but sheesh it really didn't work well on warmer days - the house overshot temps and my kW/HDD was way over target. WC is supposed to be better than that so I was a little disappointed. The other main issue was the boiler wasn't modulating down to min before shutting down (I think reduced circuit size was having an influence due to some rooms being up to temp and others still needing heat) I have controls on my phone for Boiler and room temps I decided to push it a little and try 24/7 with no set backs and over the course of 5 days I reduced the curve from 1.0 to 0.6 and the slope from 4 to 0 However I know the rooms in my house that lose temp fastest and they are areas not used all the time (Study, Front hall, kitchen - all north facing) so a few areas as still on schedule the rooms used most are now pinned 24/7 on anywhere from 18 to 21 depending on room function Anyway Flow temps at Outside Temps for the three WC curves are below Outside Temp WC 1.4 WC 1.0 WC 0.6 20 20 20 20 10 36 32 27 0 49 42 33 -10 60 51 39 So in a nutshell at 0 deg outside where I was running 49 deg C on scheduled heating slots - I moved to 24/7 with setbacks running 42 Deg C and I'm now running 33 Deg C 24/7 effectively with no set backs The boiler runs for nice long periods at min modulation - initially I was a bit concerned that it was going to be an expensive experiment but kW/HDD is slowly shifting back towards my design target of around 4.0 Last week as we were home for Xmas I had time to experiment and set the majority of the TRV's as high limiter (ie 2 deg above the room target temp) and watched to see if rooms exceeded the target temp - a couple did so I knocked back the flow to those rooms using the EB4 TRV bodies restrictors. This was clearly a little too coarse an adjustment so had to revert back and so instead dropped the WC curve down to 0.5 and now most of the TRV's don't intervene at all - the heating is on 24/7 with no setbacks in the main living areas and bedrooms - I still have a couple of areas where I am using scheduled heating (Front Hall, Study, Utility and Downstairs Loo) because these rooms either lose far more heat being on the north side of the house or have slightly oversize rads which makes them respond quickly to heat input. Now all I need is a cold spell so I can see how the curve works with a much colder outside temp Hope you all had a good Xmas and wishing you all a Happy New Year

"Pump over" into the header tank is normally down to the pump having too much pressure for the circuit demand/size Those Grundfos Alpha pumps have a lot of different pumping modes and they don't have a great reputation compared to the old three speed basic pumps but I can see from the first picture the old pump was running on max speed. The fact that they are both fitted upside down makes my teeth itch a bit (but they are in the correct flow direction according to the arrows on the casing) I tried to work out what I was looking at circuit wise and labelled up this picture Your plumber might be right and there is a blockage somewhere but that's pretty tricky to find Does the boiler behave on HW cycle ie doesn't cut out