j_s Posted January 5 Share Posted January 5 Does anyone know why my Vaillant would be reporting the efficiency as 107% ? This is for central heating and perhaps less so for the Newark heatgeeks cylinder but hot water shows as around 103 or 104 most of the time. This is surely impossible as I'd be lucky hitting the max efficiency of above 90% although would like to think it's up there. Heat curve is 0.6. Ultimately it's not an issue just interested how it could come up with that. All controls are Vaillant and installed in late September with the latest wireless Sensocomfort that I believe is a very recent release. Thanks. Link to comment Share on other sites More sharing options...
John Carroll Posted January 5 Share Posted January 5 Maybe something a bit like Ideal Vogues "Super Efficiency" ??, this was their reply to someone who was seeing very "poor" efficiencies of less than 65%, at least Ideal arn't claiming 100% +. A bit off topic but is your boiler their latest offering of the 630 where you can run in one of several hydraulic modes, one of which is temperature spread? Link to comment Share on other sites More sharing options...
JohnMo Posted January 5 Share Posted January 5 If you are into condensation mode, so low return temps, then the steam from combustion is being condensed and you are gain latent heat, aiding to the heat transfer process, so yes not made up. Graph below. Read up on boiler condensation mode. All boilers are capable of this and have been for a couple of decades, just installer try their hardest to mess this up, because of the lack of proper training. Link to comment Share on other sites More sharing options...
John Carroll Posted January 5 Share Posted January 5 That's Net Efficiency based on the lower heating value of the fuel, natural gas wet gas loss is around 10% to 11% and to attain a true 100% efficiency would require the flue gas temperature to be as low as the combustion air temperature IMO. Link to comment Share on other sites More sharing options...
j_s Posted January 6 Author Share Posted January 6 JohnMo, yes aware of condensing mode thanks. I had read that this is what makes boilers run in the 90 to 95% efficiency range and also why so many households are not getting the most out of their boilers as not setup correctly. I run mine between high 20s and high 30s flow temps using weather compensation but will take internal temperature into consideration and switch off. It is range rated but modulates down to minimum it will go most of the time anyway. John Carroll, yes it is the latest Vaillant Ecotec 630, not looked into the hydraulic modes but will see what I can find. So the efficiency is Vaillant's interpretation and a certain point of view rather than the true efficiency. Link to comment Share on other sites More sharing options...
John Carroll Posted January 6 Share Posted January 6 (edited) Where are you seeing this efficiency figure?, I didn’t come across it in the MIs. What you can do is something like these tests, ensure boiler/system up to temperature. Test Results. (calculations, in brackets) Target Modulation 78% (boiler output (0.78*30,23.4kw) D.029 Heating flowrate 1575LPH. Flow/return temps D.040/D.041, 62C/47C. (Boiler Output 1575*(62-47)/860), 27.47kw. This consistently shows ~ 10 to 18% higher output than that from target modulation, which I presume is the actual % boiler output. Gas meter readings were taken exactly 3 minutes apart and the consumptionX11x20 to give the energy input in kw, cant find the figure now but it gave a efficiency of 91% based on the target modulation but 106% based on the flow & dT, so maybe that’s where Vaillant are getting their efficiencies from. When/if you do these tests, compare them with the Vaillant figure, might be interesting. I would appreciate if you would carry out the tests sometime as requested and post them in the more appropriate Topic , “Vaillant Ecotec Plus 630 dT” Thanks. John Edited January 6 by John Carroll Link to comment Share on other sites More sharing options...
JohnMo Posted January 6 Share Posted January 6 38 minutes ago, John Carroll said: Vaillant are getting their efficiencies from There are are several ways to calculate the efficiency and that is where the higher number comes from, it's the same calculation used for all boilers sold in Europe and comes from a DIN standard I believe. Link to comment Share on other sites More sharing options...
burgessl Posted January 6 Share Posted January 6 @j_s where do you find the efficiency values? I've got an ecotec plus 625 installed October '24 but I can't see anything reporting efficiency in the boiler data or on the sensocomfort controls. Link to comment Share on other sites More sharing options...
marshian Posted January 6 Share Posted January 6 28 minutes ago, JohnMo said: There are are several ways to calculate the efficiency and that is where the higher number comes from, it's the same calculation used for all boilers sold in Europe and comes from a DIN standard I believe. Pretty sure the UK used an above 100% rating when early condensing boilers came in - heat geek did a video on it a while back explaining how it was worked out - it'll be buried in a video somewhere and I'll have a go at finding it Link to comment Share on other sites More sharing options...
JohnMo Posted January 6 Share Posted January 6 This what my boiler data sheet says When I had my heat meter in the gas boiler circuit, I was recording efficiency in the 105 to 110% range on regular basis, that was based on a simple energy used to energy delivered calculation Link to comment Share on other sites More sharing options...
John Carroll Posted January 6 Share Posted January 6 (edited) 1 hour ago, marshian said: Pretty sure the UK used an above 100% rating when early condensing boilers came in - heat geek did a video on it a while back explaining how it was worked out - it'll be buried in a video somewhere and I'll have a go at finding it I seem to remember that the gas analysers reported the efficiency based on the LHV when condensing boilers appeared, of course what must be remembered is that they are still ~ 7/8% more efficient (in a nonn condensing state) than a non condensing one because they knock more sensible heat out of the flue gas by reducing it by 120/150C more. Edited January 6 by John Carroll Link to comment Share on other sites More sharing options...
John Carroll Posted January 6 Share Posted January 6 1 hour ago, JohnMo said: This what my boiler data sheet says When I had my heat meter in the gas boiler circuit, I was recording efficiency in the 105 to 110% range on regular basis, that was based on a simple energy used to energy delivered calculation This is from the Ecotec Plus 630 It does show +100% efficiencies based on "30% Efficiency, G20" whatever that means, but more significantely it gives the nominal heat input and the DHW output in kw, all these give efficiencies < 100% at 96.73%, 96.61% & 96.57%, don't know if nominal is based on the LHV or the HHV but suspect its the LHV, so based on fully condensing but a bit of a nonsense as the flue gas temp would probably be ~ 80C, (with little or no condensing), assuming a combustion air temp of 20C then the sensible heat loss is ~ 4.5%*60/100, 2.7%, gives 97.3%. Link to comment Share on other sites More sharing options...
marshian Posted January 6 Share Posted January 6 30 minutes ago, John Carroll said: This is from the Ecotec Plus 630 It does show +100% efficiencies based on "30% Efficiency, G20" whatever that means, but more significantely it gives the nominal heat input and the DHW output in kw, all these give efficiencies < 100% at 96.73%, 96.61% & 96.57%, don't know if nominal is based on the LHV or the HHV but suspect its the LHV, so based on fully condensing but a bit of a nonsense as the flue gas temp would probably be ~ 80C, (with little or no condensing), assuming a combustion air temp of 20C then the sensible heat loss is ~ 4.5%*60/100, 2.7%, gives 97.3%. Nice to see Vaillant finally getting closer to Viessmann on the lower range of modulation - Well they aren't there yet but the gap is narrowing 4.0 v 3.2 at 40/30 range I hope that's real rather than claimed Link to comment Share on other sites More sharing options...
JohnMo Posted January 6 Share Posted January 6 33 minutes ago, John Carroll said: gives the nominal heat input and the DHW output in kw, all these give efficiencies < 100% at 96.73%, 96.61% & 96.57%, Is that based on a combi or system boiler? Combi has an additional heat exchanger so will take an efficiency hit. Link to comment Share on other sites More sharing options...
burgessl Posted January 6 Share Posted January 6 39 minutes ago, marshian said: Nice to see Vaillant finally getting closer to Viessmann on the lower range of modulation - Well they aren't there yet but the gap is narrowing 4.0 v 3.2 at 40/30 range I hope that's real rather than claimed It's real - my boiler chugs along at just under 4kW. Shame I didn't argue harder for a smaller boiler (eg the 620 or lower) which go down to 2.7kW minimum. Link to comment Share on other sites More sharing options...
John Carroll Posted January 6 Share Posted January 6 51 minutes ago, JohnMo said: Is that based on a combi or system boiler? Combi has an additional heat exchanger so will take an efficiency hit. Its based on the "6" series owhich are system boilers, the 4 is a heat only, the 8 is a combi and the 9 is a stored combi. Link to comment Share on other sites More sharing options...
marshian Posted January 6 Share Posted January 6 1 hour ago, burgessl said: It's real - my boiler chugs along at just under 4kW. Shame I didn't argue harder for a smaller boiler (eg the 620 or lower) which go down to 2.7kW minimum. Excellent - hopefully this level of control will soon move into the heat only boilers - currently they are still a poor 4.7 to 7.2 when used at low flow temps Link to comment Share on other sites More sharing options...
j_s Posted January 6 Author Share Posted January 6 (edited) @burgessl It's in the My Vaillant mobile app under energy info , you select it in the bottom right once the app is opened. Looking at it again I should have clicked on the big obvious info button on the energy efficiency box 🙄 Edited January 6 by j_s Link to comment Share on other sites More sharing options...
burgessl Posted January 6 Share Posted January 6 Ah thanks, I don't have the gateway and app (yet) so no wonder I couldn't find it! Link to comment Share on other sites More sharing options...
John Carroll Posted January 7 Share Posted January 7 This is the sort of efficiency chart that IMO is (more) correct as its based on the HHV of the fuel which, after all, we are charged on. If I had a gas boiler I would measure the condensate flow, that will then give a very accurate number for the boiler efficiency. Link to comment Share on other sites More sharing options...
marshian Posted January 7 Share Posted January 7 16 minutes ago, John Carroll said: If I had a gas boiler I would measure the condensate flow, that will then give a very accurate number for the boiler efficiency. Oh please tell me how the chuff that works maths wise Link to comment Share on other sites More sharing options...
John Carroll Posted January 7 Share Posted January 7 (edited) From my many many years on Steam Driven Plants, or look up Spirax Sarco Steam Tables, or even Google, you will see that it requires 2257kj to evaporate 1kg of water, its good enough to call 1kg of water 1L, so 2257kj/L = 2257/3600, 0.62694kwh/L, = 1/0.62694, 1.595L/kwh, the wet gas loss of nat gas is ~ 10% = 1.595*10%, 0.1595L/kwh of fuel burned, in other words if a boiler is fully condensing then the condensate flow should be 0.1595L for every kwh of fuel burned, a 28.5kw boiler will burn 30kwh/hr of gas at 95% efficiency which should result in a condensate flow of 30*0.1595, 4.785LPH, I have seen numbers of 3.5L/30kwh if fully condensing, this is only 73% of my calculated figures so maybe some mistake in my calcs, Vaillant MIs state condensing flow of 3.1L for a 30kw (output) 630 at flow/return temps of 50/30 which is close to fully condensing so there must be something up with my calcs but not sure where. ( The boiler numbers would be true (compared to mine) if burning oil which has a wet gas loss of ~ 6.5%. Anyway get out your bucket and run the condensate into it for say 30 minutes, taking the gas meter readings at the start and finish. Edited January 7 by John Carroll 1 Link to comment Share on other sites More sharing options...
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