marshian

Agreed - lower the flow temp the lower the DT at the boiler Heat Geek reckon a good guide to expected DT is flow temp x .7 to get your return temp Obviously the temps below are guides for boilers supplying rads but UFH flow temps can be a lot lower and the return much closer to flow and DT much narrower Flow Temp Return Temp Diff 80 56.0 24.0 75 52.5 22.5 70 49.0 21.0 65 45.5 19.5 60 42.0 18.0 55 38.5 16.5 50 35.0 15.0 45 31.5 13.5 40 28.0 12.0

Wiser have a similar system called ECO mode - it learns your heating pattern and then uses the weather based on your location to bring the heating on to reach your target temp at the time you need it - used it for a week and it absolutely chewed thro the gas for no real benefit I don't need the house at temp when I get up - I need it to be warming up - ie not fecking chilly just some heat added from the overnight off I need the bath room up to 19 for a shower at 8am not 6am - I don't go near it till then So in summary I probably needed to complete change the target temps and times to make it work for me and I couldn't be arsed I've not tried it since Other opinions may well be different

Flow temps I vary depending on outside temps low to mid 50's normally (never more than 60 so far this year - that cold snap we had) return temps High 20's to Mid 30's (very dependant on flow temps but I get just under 20 deg delta at the boiler once the circuit is up to temp) The boiler has a 10 kW min and due to internal programming gives a 18kW hit for 8-10 secs on restart which is a pain - I have to have an extended POR and ACT settings to give the circuit time to cool as much as possible or it overshoots way to easily and it still cycles a fair bit this means mean water temps in the rads are low 30's this time of year I know I could go ASHP but it's being replaced for a Viessmann 100 W heat only in the summer Boiler is range rated to between 12 and 16kW (acts as my other manual weather comp assisting flow temp changes because we heat intermittantly so I need a reasonably responsive system and a quick warm up) I could try to heat the house to 20 deg all day but the shape of it means those rooms with 3 external walls are my biggest contributions to my heat loss and we don't use 2 of them My 3.9 to 4.1 kW / HDD I'm OK with when it's Autumn or Spring (or a mild day in winter) I can be anywhere from 5 to 9 kW per HDD - that's where I know WC would help because my manual weather comp is never as accurate as a well managed curve (I tend to have temps I know work for autumn winter and spring so miss out on the finer deg changes that weather comp would provide) Annual usage (last 12 mths) 8,147 kW as at 31st Jan

Just for comparison and I'm not knocking your costs v comfort I'd love to be able to heat my house to that level. Early 80's 4 bed detached with a stupid shape (think T shaped where several rooms have 3 external walls it's 113 m2 total with 2 floors (~55m2 each floor) Gas for CH (rads only no underfloor) al HW and we cook on a gas hob most of the time. Heat loss calcs say 4.5 kW at -2 Heating on 0630 to 0815 and 1545 to 2200 weekdays - 0900 to 2200 weekends - rooms not used are set to 18 rooms used are set to 19 - 21 depending on use (Bathrooms higher than living room). Cavity wall insulation, 25 year old SUDG but we did recently replace both sets of french doors for more thermally efficient ones - 100 mm of loft insulation and a 14 year old Glow Worm Flexicom 24HX that has a min kW of 10kW Gas for Dec was £3.23 per day & Jan was £3.05 per day (includes SC and VAT) I'm around 3.9 to 4.1 kW/HDD (with a base line for HDD at 16.5)

I looked at the pictures and went YIKES!!!! But the installation is really neat and tidy even if it looks horribly complicated and possibly highly zoned? I assume Gas is not an option??? Why is a heat pump only 10 years? We have AC units where I work that are 20 plus years old and still work great!! If they fail the have to be replaced because wrong gas but while they work (and don't leak) they are fine - I don't understand why a heat pump would have a shorter life.......

I think that is the perfect answer Our house faces North - back of the house faces south - even in winter we get a little solar gain in the back rooms never ever seen solar gain on the front rooms but get a fair bit in the summer evenings

Cut off with a disk cutter - That's what I had to do in the void underneath my suspended floor - the clay pipe was cracked (probably from when the house was built - was never going to be found till I went under the floor to insulate the pipes and between the joists) 40 years of a small leak wasn't a nice area to work in although suprisingly not smelly!!!

Any update Dee?

All nicely chewing away on his electrickery supply - nice if you can afford it

Ahhh so I just need to find a 10% reduction not 25% - much relief - thanks

Interesting to state 10% - historical data for my house gas usage is 35% more in winter - water usage pattern and temp its heated to is unchanged All year round. My Summer gas usage is consistently 3.7 kW per day My Winter gas usage is 5.0 kW per day However we have cold water tank in the loft so get some solar gain in the stored water in late spring, summer and autumn And I do think I have a thermosyphon issue that probably hurts more in winter than warmer periods

I like the description of the pipework "honestly like they got a delivery of copper pipes thrown in a cupboard and just decided to connect them up wherever they fell. " Brilliant That waste fitting is all kinds of spezial - good luck because if that's what the previous home owners plumbing skills were like the house is going to be the gift just keep giving!!!

Put a K-type Thermocouple on the pipe??? No idea how to get it out of the boiler menus - if you had a glow worm I could tell you without even looking at the manual

So the two vertical 22mm copper pipes that are together and uninsulated go to your HW tank? If that is the case then as @SimonD said you can convert to separate feed for HW and CH pipework wise relatively easily Control wise I'm not in a position to advise but you are in London right? I'd be asking "Urban Plumber" to quote for the changes

Absolutely I mean at the boiler

Actually that was a stupid question - I was think how much effort would it be to run a flow and return to the tank from the boiler - it was stupid because you've already got a flow and return running to the tank..... The question is really how far away from the boiler is the LLH I assume that shares it's feed with the flow and return for the tank!!! Potentially you can split the system at that point

If you think it's only going to be 1000 kW or £75 then as you say not worth worrying about the payback for changing the system about I think I asked earlier - what is your flow temp and what's the return Return is the one that matters but with UFH you should have a fairly narrow delta An indication of the benefits of condensing and the efficiency as a result are below Return Temp Boiler % Eff 65 88% 60 88% 55 88% 50 91% 45 93% 40 94% 35 95% 30 96% 25 97%

Adsibob How far from your HW tank is your Boiler?

I know my HW outlet from the tank and vent pipe to the loft tank are contributing to the losses but they are a constant (they are well lagged all the way to the cold water tank - approx 5m away) I guess it would probably not be a good idea to put a similar drop and return arrangement in that section?

Ahhh gotcha - Boiler would modulate down based on a much higher return temp than the normal mains temp I guess with a closed circuit you could treat the water - what about expansion of water in the circuit?

Can you not exit thro a gable wall - core drill etc rather than out via the roof tiles - then you can do that with a weather tight roof?

Where does the water go after the cylinder?

I thought they (System boilers which aren't combi boilers) had a valve inside to divert between Flow to Cylinder and Flow to CH circuit. The call for HW or CH determines the valve position and the boiler settings for either HW or CH

Just to make sure I've highlighted the section in red on an old picture before I insulated it all and added the proposed amendment in green (Distance not to scale)

Oh that I do know Anyway as stated earlier I know the battles I can win, I know the ones that are going to end up in a draw This one ain't either and it's not worth fighting for a draw or a loss