Bosch gas heater, 110% efficiency? - Page 1
Forum section: electronics / general

author: nuclearcat
author_rank: Unknown
timestamp: August 08, 2021, 09:15:28 am
content: We recently laughed at the Solus heater about their "efficiency".But today I stumbled upon a new one, "This feature, when combined with a burnout combustion chamber, helps to achieve seasonal efficiency levels of up to 110%."And this is Bosch!https://www.bosch-thermotechnology.com/gb/en/commercial-industrial/knowledge/about-us/news/2017/gas-fired-commercial-condensing-boiler/Do I understand correctly that Bosch is also carried away by deceitful and misleading marketing, which declares more than 100% efficiency for gas heaters?I understand that somewhere there must be a footnote, that this is a comparison with other conventional heaters/etc , but it seems to me that idiotic marketing scam won there too.As i know only heater that can do over 100%, is one that transfer head efficiently, and consume less energy than it transfer, heat pump, which is not the case for this Bosch heater.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 08, 2021, 09:31:22 am
content: For gas / oil burning the efficiency depends on how you define the energy contend of the fuel. When nurning natural gas this produces quite some water in the exhaust gas. The classical definition for oven efficiency uses the energy content with the exhaust water as gas. Having the exhaust water in liquid form can give some 25% higher energy contend for the fuel.Modern gas oven cool the exhaust so far that a large part of the water condenses and this gives you more heat. A good modern gas oven can this way get more heat out than is possible with the water as gas like in an old style (e.g. before 1990) oven. Using the efficiency definition based on gaseous exhaust this can give >100% efficiency. This is nothing magic or doggy - it is just a slightly odd (but AFIAK still the official standard) definition for the efficiency for ovens.

author: nuclearcat
author_rank: Unknown
timestamp: August 08, 2021, 10:33:31 am
content: Quote from: Kleinstein on August 08, 2021, 09:31:22 amI understand that the word efficiency can be understood as anything, but if the manufacturer is honest, he puts a footnote and explains what his efficiency is and methods measuring it.Otherwise, it is very close to fraud, since it turns out that the electric heater is 100% efficient, and the Bosch is 110%, although in fact the electric heater is really 100%, but the gas _always_ loses heat if the exhaust gas does not come out with the ambient temperature. Well, or if exhaust goes into a heated room, but this is no longer a heater.Technology itself is not dodgy indeed, but marketing of technology is dodgy as hell, similar to Solus. Actually Solus was even more honest and did remarks about "comparing with other heating methods".

author: dl6lr
author_rank: Frequent Contributor
timestamp: August 08, 2021, 10:34:55 am
content: Quote from: nuclearcat on August 08, 2021, 09:15:28 amThis is state of the art since about 30 years. The efficiency of a heater is traditionally defined as the lower heating value LHV (as this was the only way to build a heater in those days). A lot of energy is wasted in the exhaust system with high exhaust temperature and vaporized water in the exhaust. Since about 30 years, the exhaust gases are cooled down and the energy from the exhaust is used to increase efficiency (and the gas heater has a drain pipe for the water). See the difference between LHV and HHV inhttps://en.wikipedia.org/wiki/Heat_of_combustion#Higher_heating_value. Methane has about 55.5MJ/kg HHV vs. 50MJ/kg LHV.

author: nuclearcat
author_rank: Unknown
timestamp: August 08, 2021, 10:54:54 am
content: Quote from: dl6lr on August 08, 2021, 10:34:55 amI understand that. But again, no remark about HHV/LHV.And here it is well explained, why this dodgy manipulation of efficiency is bad:https://www.powermag.com/plant-efficiency-begin-with-the-right-definitions/This is from the category of "unreadable small letters footnote", when customer are to blame, that he didn't study subject well enough. Vendors should not be able to do that, "well, you know efficiency we mean, it is generally accepted in Europe LHV".

author: emece67
author_rank: Frequent Contributor
timestamp: August 08, 2021, 04:02:18 pm
content: .

author: SiliconWizard
author_rank: Super Contributor
timestamp: August 08, 2021, 05:50:32 pm
content: EU customers understanding this? Heating installers certainly. Your basic end-user? I don't think so.

author: emece67
author_rank: Frequent Contributor
timestamp: August 08, 2021, 06:33:01 pm
content: .

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 08, 2021, 10:06:49 pm
content: If the fuel is used to run a heat pump, either absorption or a conventional heat pump driven by a generator, it is indeed possible to have more heat delivered than the energy contained in the fuel.For example, you have a generator that's 30% efficient at generating electricity, a thermal recovery system that is able to extract 90% of the heat from the generator, and a heat pump with a COP of 3.The generator takes 1 unit of fuel and gives you 0.3 unit of electricity and 0.7 unit of heat, of which 0.63 unit is recovered by the thermal recovery system. You use the electricity to run the heat pump giving you 0.9 unit of heat, for a total of 1.53 unit of heat.

author: nuclearcat
author_rank: Unknown
timestamp: August 08, 2021, 11:43:04 pm
content: Quote from: NiHaoMike on August 08, 2021, 10:06:49 pmNo doubt, this is why heat pumps are amazing.But thats not the case of that heater, the only thing it have "special" - condenser of exhaust vapour, that provides a bit more heat than "conventional" heaters.

author: dzseki
author_rank: Frequent Contributor
timestamp: August 09, 2021, 05:47:02 am
content: Quote from: nuclearcat on August 08, 2021, 11:43:04 pmTo be fair, since 2015-2016 for new installations only condensing gas boilers are allowed in the EU.

author: james_s
author_rank: Super Contributor
timestamp: August 09, 2021, 06:22:08 am
content: Quote from: nuclearcat on August 08, 2021, 10:33:31 amElectric heaters are 100% efficient at turning electricity into heat, but when you factor in the entire process which in many cases involves burning fuel elsewhere, turning that into mechanical energy, converting the mechanical energy into electricity and then transmitting it to the point of use, the total efficiency is quite a lot lower I think than burning the fuel at the point of use if the goal is to get heat. I don't know off hand how the numbers stack up when dealing with a heat pump, those can deliver roughly 3x the heat for the same amount of electricity than resistance by refrigerating the outdoors. A heat pump can't generate enough heat to run the boiler that generates the electricity to power the heat pump though, that would violate the laws of energy.

author: dl6lr
author_rank: Frequent Contributor
timestamp: August 09, 2021, 08:48:21 am
content: Quote from: SiliconWizard on August 08, 2021, 05:50:32 pmThe end-user only looks at the figures and compares them. He knows: Higher efficiency is better. As the EU regulation uses the LHV to calculate efficiency, you can get figures above 100%. It would be more confusing if there are alternative methods of calculation allowed, so you could get a traditional combustion which resembles a higher calculated efficiency (due to using the LHV) as a modern heater, using the HHV as a calculation base.So this is only confusing to badly informed people that already have some technical knowledge

author: newbrain
author_rank: Super Contributor
timestamp: August 09, 2021, 09:20:10 am
content: Quote from: dl6lr on August 09, 2021, 08:48:21 amQuote from: Alexander Pope

author: Circlotron
author_rank: Super Contributor
timestamp: August 09, 2021, 11:19:52 am
content: Quote from: james_s on August 09, 2021, 06:22:08 am

author: james_s
author_rank: Super Contributor
timestamp: August 09, 2021, 06:53:54 pm
content: Quote from: Circlotron on August 09, 2021, 11:19:52 amMy knowledge is admittedly out of date. I got very interested in refrigeration and installed several heat pumps around 15 years ago, at that time the 14 SEER unit I installed in my house was considered very good. I gather they have improved quite a lot since then by using VFDs to control the compressor and fans but I have not really kept up.