windsor-tg Posted January 8 Share Posted January 8 I recently had a new 2023 Vaillant ecoTec plus 630 (30kW) system boiler installed along with a Low Loss Header (LLH) in my house. I have 21 rads in the house and a room with UFH. The LLH was introduced as I was finding (before the LLH was fitted) that my old boiler (Vaillant heat-only boiler) was anti-cycling as the demand from the UFH was too low for the boiler to remain firing. This issue has gone away since the introduction of a new boiler & LLH. I have noticed in the last couple of days that with the boiler target temp set to 65 degrees, the boiler flow temp (d.40) takes an age to get to 60+ from cold. Even when the boiler was running continuously (with just CH on) for 2 hours this morning, the boiler flow temp reached 61C (d.40), boiler return temp - 52C (d.41) d.00 on the boiler is set to "Automatic". The boiler displays 5 modulation levels and it is currently displaying level 2. Is there any reason on why the boiler is not reaching its target temp and/or why the boiler is not modulating at a higher level to get the boiler flow temp close to the boiler target temp ? Even now with both, CH and UFH, demanding heat from the boiler, the modulation level is at 2. Any suggestions on why the modulation level is not going above 2 will be much appreciated. Link to comment Share on other sites More sharing options...
Temp Posted January 9 Share Posted January 9 Weather compensation faulty? Link to comment Share on other sites More sharing options...
windsor-tg Posted January 9 Author Share Posted January 9 @Temp - I do not have weather compensation. I am using Heatmiser to control my heating and HW Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted January 9 Share Posted January 9 How is the heatmiser connected? OpenTherm or just standard On/Off? I found that my boiler (ATAG) had a setting for the Tmax of CH, based upon differing gradients on a chart, and maybe more importantly for your issue, the Gradient Speed for CH, which tells the boiler how many degrees it can rise in a given time. Clearly a different boiler to mine, but one would assume they have similar settings, and this was done off of the boiler front panel itself. Link to comment Share on other sites More sharing options...
windsor-tg Posted January 9 Author Share Posted January 9 2 minutes ago, MikeGrahamT21 said: How is the heatmiser connected? OpenTherm or just standard On/Off? I found that my boiler (ATAG) had a setting for the Tmax of CH, based upon differing gradients on a chart, and maybe more importantly for your issue, the Gradient Speed for CH, which tells the boiler how many degrees it can rise in a given time. Clearly a different boiler to mine, but one would assume they have similar settings, and this was done off of the boiler front panel itself. thanks @MikeGrahamT21. As far as I'm aware, the Heatmiser is connected through standard on/off. TBH, I'm not sure if there is such a setting on the Vaillant ecotec plus 630 boiler 😟 Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted January 9 Share Posted January 9 Yeah can't see anything in manual for yours. Mine probably has it as its a boiler which can take LPG as well as Nat Gas, and the changes are relevant to fuel type, but there is a range you can set for each, initially mine was set incorrectly and made it take longer to reach the target CH flow temp. Link to comment Share on other sites More sharing options...
marshian Posted January 9 Share Posted January 9 18 hours ago, windsor-tg said: I recently had a new 2023 Vaillant ecoTec plus 630 (30kW) system boiler installed along with a Low Loss Header (LLH) in my house. I have 21 rads in the house and a room with UFH. The LLH was introduced as I was finding (before the LLH was fitted) that my old boiler (Vaillant heat-only boiler) was anti-cycling as the demand from the UFH was too low for the boiler to remain firing. This issue has gone away since the introduction of a new boiler & LLH. I have noticed in the last couple of days that with the boiler target temp set to 65 degrees, the boiler flow temp (d.40) takes an age to get to 60+ from cold. Even when the boiler was running continuously (with just CH on) for 2 hours this morning, the boiler flow temp reached 61C (d.40), boiler return temp - 52C (d.41) d.00 on the boiler is set to "Automatic". The boiler displays 5 modulation levels and it is currently displaying level 2. Is there any reason on why the boiler is not reaching its target temp and/or why the boiler is not modulating at a higher level to get the boiler flow temp close to the boiler target temp ? Even now with both, CH and UFH, demanding heat from the boiler, the modulation level is at 2. Any suggestions on why the modulation level is not going above 2 will be much appreciated. Lots of things that confuse me there Modulation Take it off "Automatic" modulation and set the kW ouput to something closer to what you need?? Have you got an installation manual for it - that will tell you how to adjust the kW If the boiler modulation level is 2 - it's got a 10kW min and 30 kW max I reckon these are probably your kW v modulation settings kW Mod Set 10 0 14 1 18 2 22 3 26 4 30 5 With 21 Rads as well as underfloor your circuit vol must be huge I've got 13 rads (no underfloor) and a circuit volume of about 135 L At a cold start that circuit is at around 15 deg C (rough temp of the rooms) without accounting for boiler efficiencies I would take 7kW to raise the water temp in the circuit to 60 deg C Bearing in mind that I have a heat loss of 4.5 kW and I'm using that circuit to heat rads in rooms I want to temp I have the boiler range rated to 15kW because I want the circuit heated to temp quickly but not so quickly that the difference between flow and return exceeds 20 deg which Glow Worm / Valiant Boilers don't like much So I'd be looking at setting it at 3 or setting the kW to 22 to decrease the warm up time Flow and return temps You said "the boiler flow temp reached 61C (d.40), boiler return temp - 52C (d.41)" That's pretty poor in a circuit that size at a flow temp of 65 Deg Set point - as a rule of thumb return temp should be 70% of the flow temp so 45 Deg would be what I would be targetting At 52 Deg Return it's "only just" still condensing - It should be in the mid to high 40's and condensing all the time I hasten to add I know nothing of LLH and the impact on the circuit Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted January 9 Share Posted January 9 I know this is a bit off topic, but it’s something I’ve been wondering about for a while, is there a point whereby the flow temperature being lowered causes less efficiency, rather than more? Basically is there a sweet spot for gas boilers or is lower flow temp always better? I’m down at 45C flow this year which is heating the bungalow without issue, but is it the best for efficient use of the gas? Link to comment Share on other sites More sharing options...
marshian Posted January 9 Share Posted January 9 5 hours ago, MikeGrahamT21 said: I know this is a bit off topic, but it’s something I’ve been wondering about for a while, is there a point whereby the flow temperature being lowered causes less efficiency, rather than more? Basically is there a sweet spot for gas boilers or is lower flow temp always better? I’m down at 45C flow this year which is heating the bungalow without issue, but is it the best for efficient use of the gas? I think that once the boiler starts cycling more than 6 times an hour you've probably wasting more gas on each cycle start up than you are saving with the condensing benefit of a lower flow temperature I can't run lower than 48 deg on my boiler (when the house is close to target temp) because even when range rated down to min (10kW) it still fires for a few secs at 75% of max (18kW) and at anything below 48 it over shoots the set point without really putting a lot of heat into the CH circuit (the min temp I can set the boiler to is 39 deg (38 deg is OFF) As a result I tend to use 55 Flow for house warm up and 48 to 50 flow for when the house/rooms are closer to target temp It's a compromise that I'll resolve in the summer when I replace the boiler for one which can cope with lower flow temps and has a better modulation ratio Link to comment Share on other sites More sharing options...
Lofty718 Posted January 10 Share Posted January 10 You are wasting the modulating tech of your boiler by not using the ebus system from vaillant to control the boiler, this is why your system it not running properly and probably wasting loads of gas. Get yourself sensocomfort vrc720f controller and scrap the heatmiser. Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted January 10 Share Posted January 10 9 hours ago, marshian said: I think that once the boiler starts cycling more than 6 times an hour you've probably wasting more gas on each cycle start up than you are saving with the condensing benefit of a lower flow temperature I can't run lower than 48 deg on my boiler (when the house is close to target temp) because even when range rated down to min (10kW) it still fires for a few secs at 75% of max (18kW) and at anything below 48 it over shoots the set point without really putting a lot of heat into the CH circuit (the min temp I can set the boiler to is 39 deg (38 deg is OFF) As a result I tend to use 55 Flow for house warm up and 48 to 50 flow for when the house/rooms are closer to target temp It's a compromise that I'll resolve in the summer when I replace the boiler for one which can cope with lower flow temps and has a better modulation ratio Thanks for the info. I don't have the ability to get any cycling data from this boiler, have sent a query to the manufacturer to see if they know the perfect setting. Link to comment Share on other sites More sharing options...
windsor-tg Posted January 10 Author Share Posted January 10 so I changed d.00 to 28kw. The speed of the boiler immediately increased and the modulation level went up to 4. I am now finding that the boiler flow temp is reaching the boiler target temp of 65C and the rads are heating up nicely. However, reading my IHD linked to my smart meter, I have found that I am using approx £15 per day of gas in the last few days of this cold weather spell. Would reducing the boiler target temp make a big difference to gas consumption? Also, I am not sure whether increasing D.00 to 30kw (the boiler's maximum capacity) is a good or bad thing to do? @Lofty718 - I have been thinking about the Vaillant controls but I first wanted to change the boiler to make sure it was running without any problems. The Vaillant controls are pretty expensive especially the ones I was initially looking at, i.e. sensocomfort vrc720 (wired version), sensohome vr92 (for controlling the UFH), vr 940f internet gateway. The wiring centre VR71 is really expensive so I then started to think about the sensoHOME setup. Still not sure and how bigger difference this will really make. Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted January 10 Share Posted January 10 3 minutes ago, windsor-tg said: so I changed d.00 to 28kw. The speed of the boiler immediately increased and the modulation level went up to 4. I am now finding that the boiler flow temp is reaching the boiler target temp of 65C and the rads are heating up nicely. However, reading my IHD linked to my smart meter, I have found that I am using approx £15 per day of gas in the last few days of this cold weather spell. Would reducing the boiler target temp make a big difference to gas consumption? Also, I am not sure whether increasing D.00 to 30kw (the boiler's maximum capacity) is a good or bad thing to do? @Lofty718 - I have been thinking about the Vaillant controls but I first wanted to change the boiler to make sure it was running without any problems. The Vaillant controls are pretty expensive especially the ones I was initially looking at, i.e. sensocomfort vrc720 (wired version), sensohome vr92 (for controlling the UFH), vr 940f internet gateway. The wiring centre VR71 is really expensive so I then started to think about the sensoHOME setup. Still not sure and how bigger difference this will really make. Try a flow temp of 55C and see if that improves things? 65C is pretty high, but all depends what the return temp is, for condensing to occur. Link to comment Share on other sites More sharing options...
marshian Posted January 10 Share Posted January 10 6 hours ago, windsor-tg said: so I changed d.00 to 28kw. The speed of the boiler immediately increased and the modulation level went up to 4. I am now finding that the boiler flow temp is reaching the boiler target temp of 65C and the rads are heating up nicely. However, reading my IHD linked to my smart meter, I have found that I am using approx £15 per day of gas in the last few days of this cold weather spell. Would reducing the boiler target temp make a big difference to gas consumption? Also, I am not sure whether increasing D.00 to 30kw (the boiler's maximum capacity) is a good or bad thing to do? Target temp of 65 is pretty high if you have decently sized rads - I'm unsure of how you LLH would react but try turning the flow temp down gradually say 5 deg at a time and see if the house stays at the desired temp - if it starts to lose temp in rooms and more and more rooms aare calling for heat and not being satisfied you can notch it back up again a deg or two at a time The efficiency gains in a condensing boiler come from the lower return temps Return Temp Boiler % Eff 65.0 88% 60.0 88% 55.0 88% 50.0 91% 45.0 93% 40.0 94% Regarding the cost - depends on size of your house and heat loss Mine is 113 m2 floor area (across 2 floors so 56 m2 per floor) std 2.4 m Ceilings so 290m3 of heated space My heat loss calculations say it's 4.5kW per hour at -2 Last 5 days have been an average of £3.74 per day at 7p per kW in gas (Not including daily standing charge or the 5% vat) Link to comment Share on other sites More sharing options...
marshian Posted January 10 Share Posted January 10 7 hours ago, MikeGrahamT21 said: Thanks for the info. I don't have the ability to get any cycling data from this boiler, have sent a query to the manufacturer to see if they know the perfect setting. Oh good luck with that 🙂 Cycling data is easy to get if you have an hour free Phone stopwatch function Time a burn Lap 1 when it ends Lap 2 when next burn cycle starts Repeat for the hour Number of burns in 1 hour is cycles per hour Easy if your boiler is in the kitchen - make tea while doing the analysis If the boiler is somewhere like garage or loft - still easy to do just colder 1 Link to comment Share on other sites More sharing options...
marshian Posted January 11 Share Posted January 11 20 hours ago, Lofty718 said: You are wasting the modulating tech of your boiler by not using the ebus system from vaillant to control the boiler, this is why your system it not running properly and probably wasting loads of gas. Get yourself sensocomfort vrc720f controller and scrap the heatmiser. 100% agree Watch from 10:10 Syzmon is pretty clear in his statement - Installing a Valliant/viessmann use their controls - using 3rd party controls - fit any other boiler Link to comment Share on other sites More sharing options...
Lofty718 Posted January 11 Share Posted January 11 (edited) I watched that video and bought the same setup On 10/01/2024 at 09:54, windsor-tg said: so I changed d.00 to 28kw. The speed of the boiler immediately increased and the modulation level went up to 4. I am now finding that the boiler flow temp is reaching the boiler target temp of 65C and the rads are heating up nicely. However, reading my IHD linked to my smart meter, I have found that I am using approx £15 per day of gas in the last few days of this cold weather spell. Would reducing the boiler target temp make a big difference to gas consumption? Also, I am not sure whether increasing D.00 to 30kw (the boiler's maximum capacity) is a good or bad thing to do? @Lofty718 - I have been thinking about the Vaillant controls but I first wanted to change the boiler to make sure it was running without any problems. The Vaillant controls are pretty expensive especially the ones I was initially looking at, i.e. sensocomfort vrc720 (wired version), sensohome vr92 (for controlling the UFH), vr 940f internet gateway. The wiring centre VR71 is really expensive so I then started to think about the sensoHOME setup. Still not sure and how bigger difference this will really make. 15 a day is a lot but it doesn't surprise me on a poorly controlled setup. Is your boiler the new ecotec with the digital controller on the front? if so you are hugely missing a trick by not using the proper controls. sensohome won't work for your setup and you could use a vr70 rather than vr71. I picked up a vr71 on ebay for 150 pounds, also you would need an electronic mixing valve to control the ufh which is wired into the vr70/71. the kit is quite expensive but it's an investment, my boiler runs at 45c on these cold days and is heating 24/7. how big is your house? @marshian I've watched that video a few times, it's one of the reasons I bought the same setup Edited January 11 by Lofty718 1 Link to comment Share on other sites More sharing options...
marshian Posted January 11 Share Posted January 11 2 minutes ago, Lofty718 said: I @marshian I've watched that video a few times, it's one of the reasons I bought the same setup Have you seen Syzmon's latest video where he hacked an older glow worm boiler to use Valliant controls - bloody impressive - but it was his own house and I guess we all like to experiment on our own properties Link to comment Share on other sites More sharing options...
windsor-tg Posted January 11 Author Share Posted January 11 @Lofty718, yes, my boiler is the new ecotec with the digital controller on the front. I’ve read mixed opinions about the Vaillant controls, some have said it’s the best thing since sliced bread but others have said that it will take many years to recoup the investment of these controls and their house does not feel as warm as before. I’m more than happy to find a solution that will reduce by daily gas consumption and happy to pursue going down the path of the Vaillant controls if it will work with my setup. Why do you say the sensohome will not work? When I got in touch with Vaillant technical team, they said I needed the vr71 to work with sensohome but you mention that I could use the vr70. Since my existing Heatmiser controls are all hard wired, I would like to continue using the hard wired concept with the Vaillant controls. For the UFH, why would I need an electronic mixing valve? I would find it a challenge to run any cables from my UFH manifold to the wiring centre vr70/vr71. I do have a wire though running from the UFH manifold to my existing wiring centre. I don’t know off hand the dimensions of my house but it’s an extended 4-bed detached house. Upstairs, I have 4 bedrooms, 3 bathrooms/en-suites and landing. On the ground floor, I have the kitchen, hallway, and 3 reception rooms. All the upstairs and these rooms are heated through the use of radiators. About 18 months ago, I had an orangery built which has UFH. I will view the Syzmon video soon as well as looking in reducing the boiler target temp which is currently set at 65C. Link to comment Share on other sites More sharing options...
Lofty718 Posted January 12 Share Posted January 12 (edited) An electronic mixing valve does not need to be wired from manifold, it goes only from the mixing valve to the wiring centre, my mixing valve is next to the boiler. I've not heard anyone say their house is cold from using Vaillant controls,on the contrary mine is very comfortable with the low and slow form of heating. The reason I say you don't want sensohome is that it does not come with weather compensation out of the box and it also has quite a few other limitations. Weather comp will make the boiler more efficient and house nice and comfortable. The heating will be controlled by the weather on a curve which you set that suits your property, this is why you need an electronic mixing valve as heatmiser and standard UFH mixing valve will not work. Your setup could still be wired into the Vaillant wiring centre relay but it would only work as an on/off type of control which is pointless Also the setup allows hot water priority, so you can run your boiler at 3 different flow temperatures like urban plumbers video, currently mine is running at boiler 42c flow temp, ufh 38c and radiators 36c and keeping the house nice and warm 24/7, when cylinder calls for heat heating shuts off and boiler ramps up to 70c to heat the cylinder. Another cost you would need to consider is an extra pump needed for the radiator circuit. I have two external pumps one for ufh and one for radiators costs were esbe actuator -£90 esbe mixing valve - £110 vr71 - £150 vrc720f - £235 vr92f - £120 extra pump - £100 Edited January 12 by Lofty718 Link to comment Share on other sites More sharing options...
windsor-tg Posted January 12 Author Share Posted January 12 (edited) @Lofty718 - am I right to assume that the attched photo is not an electronic mixing valve that you're referring to? Edited January 12 by windsor-tg Link to comment Share on other sites More sharing options...
JohnMo Posted January 12 Share Posted January 12 That's just a normal mechanical one Link to comment Share on other sites More sharing options...
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