marshian

@Peaklander responded to my request for the pump that he replaced at his parents house - it wasn't working properly and had been replaced but it had a working speed selector - mine got broken by a hamfisted gas engineer and was stuck on speed 3 - so I replaced it with a DAB pump Now I know the DAB pump has lots of functionality - tells you water flow in m3 per hour, watts being consumed and the working head in m - all lovely useful stuff but ever since the DAB pump was installed I can't get a happy system on speed 1 - it's not quite enough flow for the boiler to be happy on low flow temps I've had to put it on speed 2 and as a result boiler is happy - radiators have a good DT for the flow temp I'm running around 6 deg for pretty much all the rads. It's declaring 14w consumption, 3.0 m Head and 0.5 m3/hr But I'm not happy......... I'm not happy because the overall system noise is higher and Mrs Alien is a really light sleeper and doesn't sleep well with even the slightest background hum I'm running the CH 24/7 on weather compensated flow temp which means at 0 deg C OAT the flow temp is 30 Deg C. 10 out of 13 rads are set with TRV's as "high limiters" so an elevated temp set point that the flow temp cannot achieve so I don't have system noise because TRV's are shutting down flow and making the system noisy So why do I want to get my original Grundfos pump working on three speeds again because speed one was bloody perfect for best part of 30 years before I changed to DAB and the system was as near as damn it silent. Only time the speed went to speed 2 was with the original 1980 Glow Worm Fuel Saver boiler (non condensing) and it was really damn cold and max flow temp 80 Deg C wasn't cutting the mustard and when it got a little clogged up and I didn't realise that it wasn't flowing as much as it did with the last Glow Worm Flexicom 24hx. (fit a magnaclean before the pump was the lesson learnt) Now it might be rose tinted specs and I swap the DAB out for a restored Grundfos and find for some reason speed 1 isn't enough but now I've hopefully got the original pump issue sorted I want to try it again with the current Viessmann boiler.

Thermostatic mixer showers can really struggle when the HW side is quite low - Both our showers really lose the plot control wise when the HW temp drops below 40 deg - above it it's fine and it will manage to control the shower temp nicely with no changes to the mix

Back in the late 70’s I watched a little known band called Iron Maiden in various london pubs - they were good even then OT I know

Looks better You can potentially avoid bigger rads by heating longer (ie 24/7 or with very minimal set backs outside of scheduled heating periods) I was heating to a schedule and running 50 deg flow temps (at zero OAT) - to get the room up to temp within the schedule Moved to 24/7 heating and I'm running 32 deg flow temps (at zero OAT) Setbacks with recovery didn't seem to save any energy v a 24/7 heating period Only proviso is the boiler needs to be happy at the lower flow temps

I don't think so @John Carroll I think @Peaklander parents system is dirty - the magnetite has built up in the H above the pump and in the pump itself The original issue was probably caused by the blockages in the pump impeller but replacing the pump for a new one (and probably much more powerful in terms of flow rate) resulted in the pump over that wouldn't have happened with the original pump It's not the first time I've seen a pump restricted like this it happened to my own system - I couldn't work out why a system that had run for 15 years on the lowest pump speed and the boiler was happy and then I needed to use speed two to reduce the boiler short cycling because it was unhappy It took me a long time to work out what was happening - probably too long if I'm honest I'm adding to the post just so anyone searching for similar faults can see that a check on the pump might be a good first port of call

That's actually bloody clever................. We've only been burgled once and they smashed the 2G glass in the french door after trying unsucessfully to jemmy the door and then the hinges on all four doors!!!! Seems the French have a more intelligent class of burglar!!! Edit to add - Having read the article culprits were Albanian and Italian so maybe I gave the French too much credit

Gave up trying to clean it out after removing this much detritus pump has a much thinner impeller than my one despite being the same pump???

Well @peaklander sent me his old pump and tonight I had chance to strip it down and transfer the speed controller (to replace the one on my pump which was broken by a hamfisted gas engineer) Easy job but being of an inquisitive mind I couldn’t resist stripping it down completely and I wasn’t surprised at what I found this post is with permission of Tim @Peaklander this is the impeller from above side view other side I could only find a couple of channels that looked like they would pump water

Anyway the bump was to hopefully help get an answer to your question @MikeGrahamT21 - I don't have a clue on what the impacts would be

That's pretty damn impressive on a 15mm mains Love that ^ One of the reasons I still have a CW tank in the loft and vented system - yes unvented would allow me to ditch the pumps I have on the showers but then I'm totally reliant on the mains pressure and it can be a bit patchy here!!!

good tool - I should have borrowed this one sooner

Just because of continuity (and a bump for a question unanswered) The diverter only actually stops the flow past the first two columns Here's the rad in situ And here's the thermal image

Got to do a borrow of the work FLIR camera - once I got my head round the fact that the heat scale very much relates to the difference between the coldest part of the image and the warmest part of the image........ So in the case of the image below the big wall being red is warmer than the area in yellow so heat being leaked Boiler Plume management kit shows up well in white

I have the Nuaire version (with heater) I bought the heated version as I wasn't sure of the impact of cold air on house temps in the winter and thought I'd be better having it and not needing it than not having it and needing it (the difference in cost was pretty minimal) I thought I had the heater disabled but that little cold snap in November caught me out - we were on holiday and the CH was on very low - pretty clear something was driving the additional consumption and it turned out to be the PIV heater Normal daily electricity usage when the house is un occupied is 5.5 kWh. This jumped to 9.0 kW when we had the cold snap so the heater impact was 4.5kWh per day (or an additional £1.12 per day) The PIV unit has been running all winter on speed 2 (so consumption of 5W) - that does a good job in AC terms and the air under the outlet might be a little cold you can't feel that a few feet away and it's nicely dropping the humidity in the house when running (scheduled times). It (heater) is now turned off / unplugged.............

I originally had just a drain on either the flow or the return - Found that when I needed to modify the pipework under the floor there was still a lot of water in the pipes so fitted drain points to both. Added bonus was I could run an air line to one from my garage and use a low pressure air feed to scavenge the water out of the pipes. The rads all drain fine it's just the circuit I want to clear out. I've got to modify the pipes again this summer to improve the circuit (simplify and get rid of a 15mm piggy back circuit when I added another radiator and get rid of a couple of compression fittings that were used as drain points before I put the external drain points in)

@seanblee Any updates sir?

I debated ASHP but decided to stick with a gas boiler so current boiler is Viessmann 100-W Heat only (16kW with Weather comp and DHWP - range rated to 4.5 kW for Space heating) I was merely posting to support the statement you made that historical energy usage can be a good guide to sizing of ASHP provided you are heating in the same way - ie low and slow rather than scheduled

I used the heat engineer software to calculate my heat loss (at -2.4 Deg C) Heat Engineer software suggested that my heat loss is 4.93 kWh - but I did make a couple of mistakes in the process which when I spotted them I back calculated the difference and got to 4.7 kWh However I have also been measuring my gas usage v HDD (Heating Degree Days) for nearly 3 years however until Dec 2024 I heated to a schedule rather than 24/7 which compared favorably to the heat loss calc because of the periods where heat loss is reduced due to a lower internal house temperature so my kWh/HDD was 3.5 to 3.8 Moving to 24/7 heating with a weather compensated flow temp has increased the kWh/HDD figure to 4.2 to 4.6 If a HDD value of 20 is a good fit for 24 hrs at -2.4 deg C (pretty sure it is) then my heat loss is between 3.5 and 3.75 kWh

Pictures of what I did and where I was working in this thread if it helps any

75mm PIR I had to do it from under the floor due to tiled surfaces and 25mm oak planks

Actually yes comfort was the biggest benefit - to a point where Mrs Alien wasn't happy if the living room was below 21 and I was happy with anything above 18 Now it's 19.5 to 20.5 and she's happy with room comfort (this means she can find something else to whine about which is not so great!)

None - we still heated to the same temp - just got there quicker on scheduled heating slots and didn't drop off a cliff as soon as the heating went off. Looking at data from before insulation at similar OAT (around zero Deg C) All the main ground floor rooms we would lose about 0.7 to 0.5 deg C per hour After insulation around 0.25 to 0.20 deg C per hour So taking one room as an example heating went off at 10pm at 20 Deg C room temp you could pretty much expect it to be around 13 deg at 8am next morning After insulation you could expect it to be around 18 deg C Takes a lot less energy and time to get a room from 18 to 20 than it does from 13 to 20

3 years ago I would have agreed with you and said insulating under the floor was a lot of work for little gain I was very wrong - in my house it made a massive difference and along with a few other improvements halved my energy usage for space heating

Yes - just remember HW needs are occupancy driven I don't think the ATAG goes down to 3kW I agree 30kW is too much 16kW would be plenty You are on a journey - you haven't got to the destination yet. My previous boiler I based the choice on existing boiler was a glow worm - it had been very reliable so get another Old boiler was ~15 kW non condensing (single glazed wooden windows - 30mm of loft insulation - T11 rads and no CWI) - house had been extended so new boiler 24kW with a 10kW min Totally unsuitable for a property that now had SUDG, CWI and 70mm of loft insulation I spent about 6 mths working out what boiler I should get this time......... If your heat loss is 6kW at -2 deg c that situation is maybe 10 days out of 365 - rest of the winter it's going to be 4kWh at 5 deg C so I'd want a min modulation of 4kWh but 6kWh wouldn't be terrible.

No probs but you didn't learn enough 😉 It only matters that the return is as low as possible - as discussed elsewhere if you have a room temp of 20 deg and a flow temp of 35 deg you are never going to see a delta T of 20 deg c We aren't buying boilers 2 x bigger than necessary - some (not all) gas engineers have just been lazy and thrown bigger boilers at the wall rather than do the required calcs because it was easy and required no thought One that can modulate down to as low as possible and is sized to meet the house heating demand plus HW requirements A good rule of thumb is to always try to get boiler manufacturers own controls and avoid 3rd party controls - the manufacturers controls are designed to work with the boiler and maximise the efficiency of the boiler 3rd party controls can be good but most are fancy on/off controls which are dumb (even when labelled as "smart")