marshian

I agree ^ don't need 4 pipe unless you want to get a Viessmann that goes down to 1.2 kWh (which is nice but I needed a boiler that fitted inside a kitchen cupboard Heat only Viessmann with HWDB (HW Demand Box) and external Weather compensation sensor CH set up with a NO zone valve - clean and simple it just runs HW set up to close NO CH valve and open NC HW zone valve Get a decent tank with a 3m coil and you'll have really fast HW recovery This set up with DHWP and what is really a small tank knocks a combi out of the bloody park!!!

It's like a bloody good whodunnit

Not disagreeing with you because you are absolutely correct but the same result can be achieved with a pump set to too high a flow for the circuit - the main issue with this thread is no one knows if the situation was the same before the pump was replaced

It’s not the only option because it’s clear the HE isn’t totally blocked as OP still gets HW and CH (albeit CH with some pump over into F&E tank) OP hasn’t fitted magna clean yet but in preparation he could put a decent quantity of system cleaner in the circuit and see if that puts any restriction due to magnatite or sludge back into suspension Personally I’m still leaning towards a pump that is over powering the circuit And as @John Carroll has said they aren’t a popular choice amongst gas engineers/plumbers (not sure how the benchmark brand for circulation pumps gets itself into that situation but it seems they have) If @Peaklander gets it resolved I’m hoping I can have the old selectric pump (if it has working speed selector) and I’ll cover the postage

If the house is 70’s or 80’s my money says It’ll be expansion and contraction on a HW pipe cut into a joist and pinned with a nail folded round it.

I'd avoid a combi for a lot of reasons They are over spec'd for space heating but frequently not powerful enough for multiple showers or a show and a bath Because they have a huge demand for gas the gas line frequently needs upgrading to a larger size If your water pressure is low on a combi you get what you get same with UVC Without a tank options for solar HW or even HW via PV and immersion are out 2 bar mains is going to be about 15 litres per min - need @SteamyTea

Often very ancient pipes and hot water My house a lot of the underfloor pipes are 42 years old - System was filthy when we bought the house - probably 9 year old inhibitor - bleed a rad and the water came out black indicating a lot of corrosion in the system. It's clean now but I was surprised at the level of muck in the bottom of the last original rad that I cut open when I replaced it

Oh that's a good call - I guess they did isolate when the pump was changed or maybe a partial draindown was carried out so no need to close the isolation valves??

Where is your parents place - rough location? It's really not a massive job to replace that H section - I don't like compression fittings but it could be done with those - I much prefer solder fittings but if you can find a plumber that has press fit in 15mm and 22mm that section would be easy to replace with minimal drain down and I'd very much suggest that you do the combination vent and fill that @John Carroll recommends I going to do that on my system fairly soon to solve a different pump issue I have with the new pump being a bit too meaty for the application compared to the old selectric I had.

Oh lovely - replacing it all is pain free process apart from the financial impact and he's on the receiving end of that 5K and some uplift in the process due to a stupidly large combi being a big draw gas wise. On top of that you are going to end up with a presurised system - weren't you worried about pipes buried in the concrete floor? My advice find a better gas enginer/plumber or go with your plan B Maybe consider @John Carroll suggestion to combine Feed and Vent

How open is the lockshield valve on that rad? I don't think drop legs from a flow and return circuit above will make any difference but heat will always prefer to rise Ages ago I got into a discussion with a chap who had a type of reverse return circuit for flow and return in the loft of his bungalow - all the pipes dropped down from ceiling to the rads The last radiator fed with the flow was the first on the return leg really high primary balance and all the lock shields were pretty much fully open

Thanks for that explanation - it's an expression I've never heard of and it didn't translate well without the background My rough calcs of radbots market penetration wasn't far off I wonder how many smart TRV's (accross all the manufacturers) have been sold - They are quite an expensive purchase Ahh the "energy saving" combi boiler where water heating demand means hang the biggest kW white box on the wall that has a piss poor modulation rate so totally unsuitable for space heating without cycling but saving on water right?? Crazy situation promoted by industry with a lack of education in installers and homeowners. In my view we've learnt something from the combi process but unfortunately I don't believe the UK is fully prepared for ASHP introduction - I don't believe the grant process is helping either - it's just inflating the cost of the change from gas to electric

29.9 million homes in the UK majority using water based heating systems - for shits and giggles lets say average number of rads per home 6 500,000 radbots (Never heard of them but google educated me) so a market penetration of less than 1% I'm not sure why you would be eating your own dog food - strikes me as petulant comment adding nothing to the discussion which was going rather well I though as a pro's and con's of TRV's I'm 100% OK with your views on TRV's but I'd hope you can understand that there are ways in which they can drive up energy usage.

I freaking love the internet for stuff like that - well found sir It certainly clarifies the position

I missed this edit because I quoted before you'd added it but can I just say I 100% agree with this - I think my long reply says pretty much same thing TRV's can save energy but badly used they can drive up energy usage and smart ones can do far more damage whilst apparently being sold as the next best thing.

Snotgobblers I call them One thing I did like about Covid was it showed the world how good a childs developing immune system was and how it could take on a novel pathogen (CV-19) and just bloody laugh at it like all the other colds and coughs They didn't need vaccinating and there never should have been any attempt to do that all the data screamed that!!!

Ahhh OK but it's not a flow it's just a rise and fall of the level - water level increased due to expansion and drops due to cooling However if the system is pumping over constantly into the F&E tank then potentially it could be creating a circuit where the F&E tank is acting like a very poor radiator...........

I think for me there is an educational step missing in the industry, the manufacturers, Installers and the end users Go back to before TRV's were a thing - your control over the rad was a valve that could be opened or closed at one end You didn't use it to trim room temps unless you had to because the result the next day could be the opposite so as a result most of the time there was an element of "overheating" Then TRV's come along with their fancy numbered scale and all of a sudden room temp could be set or trimmed with some degree of repeatability - as a result energy saving - trouble is if one TRV in one room works well then fitting them to all rooms must be 100 times better Then system becomes over zoned and cycling screws up the boiler efficiency but as you are already saving energy a little loss here doesn't hurt right?? Then comes along "smart" TRV's - they aren't really smart as such they just have a better level of control than the old waxstat variety and they can really screw with boiler efficiency because these TRV's can call for the boiler to fire............ Yes one room drops below the setback temp and the boiler fires up running a circuit size of maybe as little as 30 litres so burns are super short but the room temp is recovered Now fit a house with a bunch of those and you can have all the rooms individually calling for heat at different times - I've been there with Wiser - 8 hrs overnight 53 boiler fires - fifty bloody three times in 8 sodding hours!!!! TRV's have a place but it needs to be a place of "balance and control" and people need to seriously consider a strategy for their implementation, operation and level of control they are allowed. Manufacturers want to promote what they sell TRV's Good - More TRV's better - Smart TRV's must be better than "dumb" TRV's therefore more smart TRV's must be even better when in real life too much of anything can be bad. Installers need to explain the risks of over zoning and giving smart things control of dumb things............. 99.9 % of the "General Public" are not going to have the understanding needed to make even a remotely educated call JM2pW PS I know 2/10 bloody poor rant and lack of variety in expletives

Because the level doesn't change in the F&E tank?

Bloody ingenious - I wish I'd have thought of that before I fitted a replacement pump - still got the info anyway now but it would have been nice to compare the old grundfos 3 speed pump - pretty sure the new one uses less electrickery but pumps harder. Actually I still have the old pump but the speed control is broken - if I can get a second hand pump with a working speed controller I could swap it over and refit it - perhaps I should sling a wanted post up.

They should be able to sort it I was with Scottish Power - took me a lot of effort to get tariff changed to std rate for all hours with my old E7 meter but got there in the end - however when I moved to Octopus they took a similar amount of effort to get them to agree to a single rate tarrif with an E7 meter. When I had the "direct communication meters" fitted (I refuse to call them "smart" as there is nothing smart about them) I hoped to go to a single daily consumption but no when I look in the app I still see day and night rate readings recorded even though the meter only has one reading - bloody weird but at least it means I can still make the calculation if E7 type tarrif would work for me. (It did until electricity costs sky rocketed and the suppliers loaded the day rate far higher than the night rate saved (£200 a year was my saving in ditching the E7 rates)

Regression tool is on this site - dead easy to use if you have data in xls or similar table format https://www.degreedays.net Only caveat is do your best to exclude HW energy usage or you'll get a funny answer (ie a lot more than your true baseline temp) Eskimos had the right idea then

16.5 is my base - slightly higher than the normal 15.5 but the HDD site has a regression tool that I used to establish it after the last round of improvements and I’m pretty happy with the base line You have to bear in mind it’s a stupid shape house with a lot of rooms having 3 external walls which means it’s not a std box with two levels

Nice work Here's my favorite From top to bottom Elec kWh for 2019 to 2024 Gas kWh for 2019 to 2024 HDD data for 2019 to 2024 Bloody labels disappeared for some reason!! Yes 2024 is an increase on both elec and gas but electric was driven by my hobby (welding takes a fair chunk of electrickery) and Gas is a result of going 24/7 this heating season. Data For a 113 m2 (290 m3) 4 bed 2 storey detached house with 2 occupants (one of which makes a lot of noise if it's cold) Oh and just to say when we moved into the house in 1991 we were using 25,000 kWh of gas a year - but the house had single glazing throughout the house, 25mm of loft insulation, no jacket on the uninsulated copper HWC and a non condensing glow worm boiler from 1982 that needed to run at 80 deg on the flow temp all winter to allow the 10 undersized T11 rads to be able to get the house warm.......... Now I'm running 30 deg flow temps at Zero outside!!!!!

I was under the impression that once air had been removed from the system the heating was working again but I could be wrong?