marshian

Not sure I'd want to start again - I'd add a radiator sized to cover the shortfall in watts running at the same flow temps as the floor?

Does flammable count as recycling?

I'm leaving this house in a box..................

^ WHS beat me to it Valiant are catching up with their recent boiler so also worth consideration - their controls are also highly regarded Intergas are also in with a shout Whatever you go for find an installer that does specialises in the brand - boxt and other "box" movers are unlikely to get the best out of the install

I've discussed EPC's elsewhere on here I've never had an EPC done on my house - been in it 35 years so never needed one House near me - same size, shape and occupancy My total max energy usage for CH and HW per year is 10,000 Pretty sure if I had an EPC done it would be a similar result........ They are garbage

If your heating on demand (or to a schedule based on occupation times) then you need a powerful boiler to get it up to temp fast sounds like that's what you are doing Viessmann boilers even relatively old ones have excellent modulation (or turn down) I have a basic 16 kW Viessmann that will happily modulate down to 4 kW - I run the heating 24/7 at low flow temps with weather compensation The boiler typically fires 20 - 25 times a day When it's cold outside it runs for 50 mins in the hour at no more than mid 30's flow temp When it's warmer like today 20 mins in the hour at very low 30's flow temps My energy usage is directly related to the outside temps (because I'm only ever replacing the heat lost and the heat loss is driven by the outside temps) Problem is when you end up with a big boiler with a poor modulation ratio and you are trying to heat a small space it's unlikely to be happy with the situation Weather comp controls flow temp however it's better suited to whole house heating and 24/7 I have used it for scheduled heating and it was OK but it's not really the point. Open therm is weather comp via internet sourced local weather (or rather outside temperatures)

Well reading the manual it does appear that it's capable of running lower flow temps (Although it's not a low temp boiler) 10.6 kW min output is quite poor but if you have a big drafty house with very little improvements to insulation it would be fine on a whole house heating system..... Maybe not so much heating a small area It looks like weather comp is available (as an in flue sensor) - that's something I've seen mentioned before with Baxi boilers but previously only with combi boilers. Don't know if it can be range rated at all - couldn't see anything in the boiler manual - probably not as it's made in a range of sizes and it should have been sized to the property needs...

10 mins won't give you much of a clue most boilers have 3 min anticycle timer Seriously if a boiler is running more cycles than 3 per hour it's likely to be losing efficiency I did once count my old boiler doing 10 cycle in 1 hour it's one of the reasons it's now recycled into bean cans................... If a boiler is running on a 70 deg flow temp it very unlikely to be gaining much at all in condensing efficiency 88 or 89% at best Get the flow temp down to below 55 Deg for CH and it's going to be condensing all the time and in the 90's from an efficiency point

Really need to know "boiler model" to be able to find out if it can be configured in DHWP and Open therm or Weather compensated - gut feel having read a few Baxi install manuals over the recent years is it will be unlikely. UK Boiler manufacturers are mainly still in the dark ages unfortunately - only thing that will bring them kicking and screaming into the 21st century is people buying better configured boilers from Europe where they've been facilitating low temperature weather compensated flow to maximise condensing efficiency and DHWP

If you are removing the downlighters why would you not use a decent thickness of PIR between the joists? Would be a big improvement compared to just 50mm PIR backed plasterboard

I did the sane thing many years ago - had a glow worm boiler that had given sterling service so chose another glow worm the same KW rating - it was a big mistake!!!! I didn’t take into account insulation improvements to the house, SUDG, CWI improved Loft insulation etc boiler was massively oversized - couldn’t do DHWP, had a terrible modulation level 24 KW max 10 kW min and as a result cycled like a twat in shoulder seasons and wasn’t that great in the winter either find a better boiler as @JohnMo says - preferably with same pipework configuration and flue position and get some real benefits and savings with a better modulation

What make and model boiler - does it have the functionality to do DHWP (Domestic Hot Water Priority) if it does then you wouldn’t have to run the boiler at 70 deg all the time just to satisfy the HW tank recharge temp required you coud probably drop the boiler temp to 60 - 65 and still get a decent volume of HW at a slightly lower temp storage

If we are talking about basic plumbing (not derogatory term - just simple basic plumbing) then 30 years ago I was in the same boat....... I had two poor jobs done by local plumbers which disappointed me - a lot - despite paying what I thought at the time was a high cost for a half days work. I decided like many DIY aspects that if I couldn't get a decent job done by a professional I would buy the tools I needed to do the job myself as I needed them. With a little research from books originally and later from the internet with a little practice I trained myself to gas solder copper, later to bend pipes to reduce the number of joints (aka risk of failures) and most recently bought a pressfit tool which is a bloody game changer for my next job on the list. Unless of course you are time constrained in which case you have my sympathy for the lack of interest.

Sorry about that - I’ll see if I can delete my post

Mine is set up with normally open on the CH side normally closed on HW side call for HW opens the normally closed on the HW and signal from the now open HW valve tells the CH valve to close but I guess it can be done in other ways I liked the simplicity of valves being exercised all year (ie in summer when the CH valve would do nothing for months) and both valves only consuming any power during the short HW recharge period

Indeed............

^ WHS - your heat loss determines your cost to heat the house - how you put that heat into the house doesn't matter Std scheduling of central heating in the UK are normally 10% lower than 24/7 heating but if your boiler can modulate to a low level and you run lower flow temps the consistant temp profile can reduce that 10% I could go back to scheduled heating and get a 10% reduction in my energy use but it would save me just £15 in gas over a year - that's not even a decent evening in the pub If you improve the heat losses of the building (Improved insulation or insulation under the floor then you can expect to reduce the cost of heating the house because you've reduced the "heat loss"

Just as we did before TRV’s were even a thing 😉

As @JohnMo said heat moves to cold - Insulation can slow down the movement I would not consider an overlay UFH system on a ventilated sub floor unless there was insulation under the sub floor and that's a very disruptive process if you are living in the house @Sparrowhawk and myself have both done it and the improvement is great in terms of energy saving but it requires careful thought and preparation - sub floors are vented for a reason You really need to do a room by room heat loss - if you have this information you can size radiators to the room requirements and flow temps to maximise boiler efficiency - this video from Urban Plumbers will help to simplify the process of room by room heat loss I'm running flow temps in low 30's - Return temps are mid to high 20's - Boiler efficiency is 97.5% when doing CH To get to this position I know exactly what my heat loss is in every room at -2.4 Dec OAT I have no UFH it's all radiators in all 13 rooms. The radiators are all sized to match the heat loss at low flow temps (Boiler is weather compensated and DHWP) Every rad has the correct flow rate supplied by Danfoss RAS-B2 "pressure independent" TRV valves - I have all TRV's set to max (ie no intervention to manage room temps) If you don't know your room by room heat loss you can't size your rads correctly for each room If you've oversized rads you'll get overheating and need TRV's to manage room temps - this will shrink your CH circuit and result in more cycles so more energy used If you've undersized some rads you need to up the flow temp to get those rooms to temperature - this will result in rooms where rads are correctly sized overheating so you'll use TRV's to control the overheat and it's the same result as over sizing rads It's all just maths at the end of the day and it's not even difficult maths

You could just shut the valve down to restrict the flow and manage the room temps Hot swapping rad valves without draining down can be done - but you need plenty of towels and everything near to hand

Still working out which is best. Until the Wiser I've been running on manual boost as required, now exploring other options. One of my rooms has pretty much all its two external walls as not thermally broken aluminium double glazed floor to ceiling sliding doors and is hugely lossy. I don't really use the room so until now I've not be actively controlling the temperature there (just leaving some radiators relatively low and the room gets whatever heat comes from them when the heating is on for the other rooms). This arrangement has its downsides and I'm hoping that the efficiency gain of being able to run the boiler at a lower temp offsets the additional gas that I expect to need to regulate that rooms temperature (early signs not inspiring confidence). Edit: I opened your big boiler journey thread earlier, not (re-)read it all yet but plan to. Thanks! Sounds like you have a similar issue to one of my rooms Good luck reading the Viessman thread it's taken me a while to get to grips with it!!! It's still got some niggles!!! Yep I think they can be good but they also a layer of WTF which can be confusing Came across that one in the wiser forums. Opinions are mixed as to whether it's a benefit on a good modulating boiler. (Mine goes from 30kw to 6kw) Edited 7 minutes ago by -rick- It's not really anything to do with the boiler ability - more an algorithm in the Wiser control program - it's especially bad with multiple "smart" TRV's and 24/7 heating but it can just as easily do the same with a single room stat Main Room with thermostat (or multiple rooms with "Smart" TRV's) get close to target temp and Wiser switches off the boiler - it's one of the reasons my Wiser hub doesn't have a connection to the boiler now - I'm running 24/7 with WC and TRV's are set to temp limiters (just above target temp - so it was interpreting that as potential house over heat and shutting down the boiler Switching it to "oil" reduced the frequency of that intervention - it's just something to bear in mind when setting target temps or placement of the thermostat. I'm still a fan of the Wiser system - I've just dialed out the clever - I don't need or want ECO I'm running flow temps below 35 deg - I don't need Comfort because I'm not scheduled heating slots and WC is doing all the hard work. The App interface is brilliantly simple just don't try and make it complicated

Was not aware of that - thanks for the heads up

Sorry I was directing the question to @gaz_moose My wiser unit isn't connected to the boiler at all - I'm heating 24/7 😉 Boiler is set up with DHWP and WC already Wiser schedule for HW switches the boiler to recharge the cyl via a HW Demand box so there is actually no need to connect Wiser to the boiler. I will eventually connect it again just to use the away function but right now I just use the Viessmann app to do that...

Having had Wiser for a few years now and gone down the route of smart TRV's and micro control of rooms my advice is keep it really simple if you are running a scheduled heating process (if 24/7 ignore me) 1. Set up base programme for Heating and Hot Water like you would an older digital programmer 2. Device lock the Room Thermostat (so it can't be boosted accidentally - this is a fun game for all the family) and control in the app 3. Make sure the away facility does not apply to HW 4. Steer clear of ECO and Comfort Modes until you are very comfortable with the system 5. If you notice the boiler being turned off mid cycle - change the boiler type to Oil.

Is your old controller base unit mounted on a universal backplate - sometimes called industry std backplate? If it is a wiser hub should be easy to install no "gas safe" engineer required I replaced my original controller below (library image as the original item got trashed by a toaster - don't ask some people are just stupid) With a Danfoss 24/7 digital programmer that had a universal back plate - so I had the headache of working out what the wires did what on the original. No smoke escaped from the wires so once done further swaps of the controller have been isolate power - remove old - replace with new and power up.