marshian

Just to repeat - I asked for X plan - I got S plan (2 NC zone valves) with weather compensation (turned off because I like HW not CW) and set it up with a 55 deg flow temp no HWD box no wifi interface (was on back order) Installer came back with one new NO zone valve, HWD box (after I told him the part numbers for both) and said will you order it or shall I?) and the long awaited for wifi module he’s had two opportunities to get it working right on x plan DHWP and hasn’t really got it right - I still have issues with control on CH side so I revert to what I often have to do “If I want a job doing properly I need to do it myself’ DIY means starting from scratch working out what all the wires do and drawing up a schematic that makes sense to me - Electrics are not my strong point but so far no fuses have been sacrificed to my electrickery knowledge quest

you’re a very clever chap but either I am really rubbish at explaining stuff (and I can accept that criticism if I am) or your reading and comprehension skills are a bit poor and I’m going to assume it’s the former rather than the later for now As I said in earlier post CH side is not fnished in the drawing - I’ve just managed to get the HW side working as it should along with the transfer from CH to HW and back to CH having completed HW - not finished would account for some missing wires OK

You do realise "my drawing" is of all the wiring centre (well when I finish it) and what you have posted is a diagram of how the HW demand box integrates with the boiler 😞 I must admit I've borrowed the base drawing from an S plan which is what the gas engineer set the system up to work as despite being asked to set it up as X plan!!! 51011_01-mBox-L32-S-Plan-connection-drawing-FRAMELESS.pdf

I must have watched that video a bunch of times and I've not spotted that element Annoyingly the only video that Syzmon has done that featured a Viessmann 100-W B1GA turned into a little whinge fest about how he wasn't impressed about the fact the HW demand box and wifi module were add on units and the boiler front cover didn't have a sound insulation panel in it like the system or combi boilers did. He was making a valid points The HW demand box is a bit of an add on The Wifi module is hard to fit in the space and route nicely - if the ribbon cable was 2 cm longer it could be routed away from everything and look much neater than crossing the PCB at 45 deg When heating HW at 100% modulation the 16kW rated boiler I have is throwing 19kW and 80 deg flow temp at the HW circuit and it's nowhere near as quiet as it is when it's doing CH at 3.2 kW and 37 deg C I didn't want to convert to a 4 pipe system for all the disruption that caused and I wanted a boiler I could hide in a 300mm dept cupboard because SWIMBO wants to change the kitchen from white to black/dark gray and a white boiler on show would look crap Sometimes we have to compromise to someone else's needs/wants

But tying the two browns together does that too doesn't it?? Not being confrontational here - if I'm not doing the right thing then I'm happy to learn why I need to do it a different way but to my mind both ways achieve the same result I used the orange to power the HW demand box so I could have that in it's own section on the wiring centre because it's Viessmann thing to have an additional HW demand box.

I need a feed to go to the HW Demand box Putting Brown to Brown works and keeps the HW demand part simple CH in normal operation the NO valve is consuming no power and idle When HW is demanded - NC HW Valve and NO CH Valve share the Brown so both effectively energise CH Closes from Open HW Opens from closed Why wouldn't that be OK?

It is a good video But "Ideal Vogue" use 2 switched lives

I can't work out how to split up a long list of questions into individual responses so see below Yes (EB4 TRV bodies) and flow rates are suitable for lower flow temps When all rads in circuit - flow rate is about 1.1 m3/hr When TRV's start to cut in it drops down to around 0.5 m3/hr I'm not looking for 20 deg drop across any of my rads at a flow temp of 37 deg C - it would be impossible - the return temp would be less than the room target (or actual temp) Using heat geek table is a better guide to expected drop across the rads (or diff between flow and return) Flow Temp Return Temp Diff 55 38.5 16.5 50 35.0 15.0 45 31.5 13.5 40 28.0 12.0 35 24.5 10.5 Rads are sized to the rooms and all but one room they are oversized for the flow temps currently being used I'm not blaming anything on the boiler - I'm seriously impressed with the Viessmann 100-W "Heat only" - But I do have some control issues which I am working thro Done IR wall floor and ceiling checks - this thread is not about heat loss or improving it - I know what I need to do there and it comes after boiler control issues are sorted

Indeed it is - thank you sir One issue I see is that it uses a relay arrangement which I'm trying to avoid as I think it's not needed with a NO CH valve and a NC HW valve That diagram uses 2 NC Valves for CH and HW (hence the linking of the two oranges to energise boiler and pump) But It gives me a start that is slightly easier for me to get my head round than the Viessmann diagram (which I find really complicated) Not sure the world is ready for how far I've got (not complete) drawing up the X plan with crayons (to the same format as the std Wago (L16 wiring centre) but I'll share it so you can laugh

Right I'm resigned to sorting out the control side of the boiler myself HW demand is now working fine - ramps up temp and modulation and tops up a tank of water to 55 deg in 15 mins so no issues there The problems I have are I can't find a wiring diagram where a NO valve is used for CH and a NC valve is used for HW Often X plans are on boilers where HW/CH selection is done with 2 switched lives Closest I can find is However whilst it gives some valve wiring options it doesn't cover the X plan set up I don’t have an NTC sensor (Shown as Cylinder limit Thermostat) so ignore that The HW tank supply has the 2 port Normally Closed valve NC Valve has 5 Wires Live (Brown), Neutral (Blue), Earth (Yellow/Green), Grey (Live feed for the internal Switch) and Orange (240V output when valve is fully open) The CH supply feed has a 2 Port Normally Open Valve NO valve has 3 Wires Live Brown), Neutral (Blue) and Earth (Yellow/Green) I've set that side up so when the Cyl Stat calls for heat the brown “Live” powers up the Normally Closed Valve to Open (the grey wire has permanent power but it only goes to an internal switch that makes when the valve is fully open and puts 240v to the Orange – the power from that goes to the Cylinder demand box to tell the boiler it it’s doing HW – it ramps up to 80 deg C and modulates as high as it can based on return temps to heat the HW cylinder (coil) to the target stat temp in the shortest time possible The same signal Live also powers the Brown for the Normally Open Zone valve for heating so it closes stopping elevated temp HW going round the CH circuit As soon as the tank stat is satisfied the live circuit to the zone valve is removed, the HW zone valve closes, the CH zone valve opens – the Live feed to the HW demand box is removed and the boiler reverts to weather compensated flow temps The only other issue on the HW side is if the HW tank stat picks up a significant drop in temp (the hysteresis is quite broad) then without anything being on the HW valve will open and the CH valve will close and the pump will start so I think I have a wiring issue in either wiring centre, Heating controller or very possibly Boiler.

And the best bit tonight I've established that in the current configuration giving the boiler control of the pump means it runs 24/7 regardless of a call for heat!!!

When it was all we had to control the flow thro the rads you had one at each end of the rad

And back to a dumb boiler again Pump wired directly to the boiler (so it has control) still getting 75 fault codes so that was a lot of effort for no gain HWD box reactivated - worked brilliantly - fired up the boiler and ramped up the power - tank of HW generated in 25 mins Switched over to CH in weather compensated mode - and the bloody boiler thinks it's still doing HW so instead of a 37 deg flow temp it goes straight for 80 deg........... On the positive side new pipework for flow and return to the airing cupboard is all done so at least I can put the floor back down

Does the water circulate thro the HW coil in reverse too?? Easy to check if TRV bodies are bi-directional they have a double headed arrow on them

Anyway system now drained down (again........) I'm ready whenever he finishes his current job Might turn off the water and replace an iffy isolation valve (been on the list for a while)

Sounds like that would screw with your head!!!

Viessmann curves below

I've just looked at the curves for the boiler at 0.2 slope Outside temps and boiler flow temps is in the table below Outside / Flow temp 20 - 20 15 - 22 10 - 23 5 - 24 0 - 25 -5 - 26 Mighty impressive - I'd have to rebuild the house to achieve that - I think I'll be doing really well to get down to 1.0

What's your heat loss at -2?

I have thermostatic mixer controls for both showers in the house - they are quite happy down to 40 deg supply temp on hot side. They only get a little fussy when the HW temp is below 38 deg C They are nothing special - both purchased on line (think soak for one and victoria plum for the other)

Update time Friday afternoon the gas engineer is making another visit - hopefully we will have the system running as it should by the end of the day........... FLW!!!

As I had to have the floor up in the room above the kitchen (where boiler is on an external wall) to run a 3 core cable from Circ pump in the airing cupboard (centre of the house) I looked at the flow and return pipes and decided now was the time to break up the twins so to speak (roughly 2 x 4m of 22 mm copper pipework run bang along side each other (with the traditional nails bent over to hold them in place) New pipework is far enough apart to allow 19mm of insulation around them - annoyingly I don't have enough spare 22mm lagging so that'll need to get ordered asap - just waiting on the gas engineer to come and connect up the pump to boiler wire. Still waiting on a resolution for the HWD/Weather comp situation so running it manually as temps start to get colder. I am absolutely amazed at how stable the flow temps are at 30 Deg and the length of the burns at very low boiler output. SWIMBO is less inclined to comment about the "cold rads" if the house is a comfortable temperature Bodes well for for my estimations that 1.4 slope would probably be a bit high but if I adopted a 24/7 approach I could go as low as 0.8 - but I think we will end up with 1.0 to 1.2 bearing in mind we heat intermittently as the house insulation overall isn't good enough yet. Hopefully the process can move forward again soon - I am mildly miffed that I'm still having to manually change boiler temps for HW and CH but I feel it's moving in the right direction

FF = Ferguson Formula - A 4 wheel drive system that was applied to quite a few marques back in the day (Jenson and Opel) I've got more knowledge on the Opel side (as they are what float my boat) that and the fact a Jenson is out of my budget

I use sonoff (TH100 from memory) - mains powered - can do temp and humdity with one type of sensor or just temp with another type power consumption is very low can use an app on my phone to see temps/humidity from anywhere over wifi or 4G Logs data hourly and keeps up to 12 mths data

About 30 mins max for me and I have 13 rads If it's taking you longer then you are either trying to get a specific temp drop across each rad or you are trying to achieve a perfection that will change every time a TRV calls for heat or turns of the flow to a rad and that's a waste of time