This is one of the reasons I like air to water heat pumps with a very large buffer, say 3000L. Optimally run to heat up the tank, independent from heating the house. The large buffer can store even several days worth of energy on milder days, meaning the heat pump can run optimally to charge the buffer, and then won't have to run for a day or more at a time.
a 3000L buffer is stupid. it does nothing apart from increasing your bill. trying to heat such an amount takes more energy than just making it when you need it and what you need and no more. trying to do the chinse wok style of heating instead of dutch oven style always consumes more energy and increases your installation cost and energy bills. never ever store heat. the only thing tat barely makes sense is battery storage.
@@SupremeRuleroftheWorld You don't have to heat it all - the point is that you can run the heat pump optimally with a buffer as required depending on the heating requirement. You don't have to worry about flow calculations or anything to make sure the heat pump runs optimally. A well insulated tank like that holds the heat just fine, and anything that escapes just adds to the heating of the building so it's not lost. I have a 3000L tank, which is coupled to both a wood gasification burner as well as a heat pump. I also have 60kWh of battery storage since I'm off-grid. I can use the energy from my solar system optimally that way, which includes running the heat pump during the day when I have sun, and heating when the temperature drops. Similarly, when you're connected to the grid, you can use cheaper rates to heat the tank, and then use it when it would be more expensive to run the heat pump.
@@upnorthandpersonal running a heatpunp harder, hotter and thus with lower COP to store heat in some supidly sized tank is always a net loss compared to just running it when you need it from the battery or generator. the gains in efficeincy just from lowering the supply temperature and running it low and slow easely outdoes any gains you might think you have with running it short and hard. just lowering the supply temp 10 degrees can save you 20% in power consumption. do find it hillarious that you burn wood and have a heat pump. got a real jungian duality of man going there.
@@SupremeRuleroftheWorld But that's the point: you can run it at optimal CoP all the time. You don't need to run it harder/hotter at any time. As for burning wood: I'm at 63 degrees north, and off grid. I'm converting an old tree farm to a natural, diverse forest at the time time - which means trees need to be cut.
At 38° north latitude we need variable speed heat pumps to be oversized in cooling because you’re going to need that extra capacity during heat mode. I need 20 btu/sqft for cooling and 35 for heating. Otherwise, if you size it for cooling, go ahead and install another heat pump just for heating right beside it, because you’re gonna need it. Typically you need about twice as much capacity for heating in the winter time. We don’t have hydronic systems in our residential homes very much in the US and most of us do not want them. I am going to build a small air-water hp for my 80 gal electric to save some energy this time of year. I am totally off grid and it’s all I can do to make it through these dark cold weeks of January and early February. That’s with 32kWp! I have to use a wood burner when it gets below 20F at night.
Hi @rv10flyer84 Thank you very much for watching and sharing your thoughts. I’m curious to learn why you don’t want hydronic systems for residential homes. Thank you! 🙏
Most of us have forced air, air-air hp’s. Some have gas or oil fired boilers and some have geothermal hp’s. I guess the air-water hp’s haven’t caught on much yet and will have to start with new construction. Hey, we are just now getting air-air mini splits here in larger numbers. Mainly because they can be diy. I don’t push them on people, because they are difficult to perform preventative maintenance on them, they don’t last quite as long as our central heat pump systems, we don’t carry parts on our trucks for them, and you can’t add high efficiency air filtration to them very easily. I have a Fujitsu 9000 BTU 33 seer heat pump air to air. I like it a lot, but it’s only two years old so time will tell.
You are welcome, @henrycalson7514. Thank you for watching and sharing your thoughts. 🙏 Exactly, there is no one size fits all. Rather bell curve distributions. Thank you, Katha
Thanks for the video, all very good points. My heat pump is definitely oversized. As you state, this increased the cost of the system, and the extra money spent isn't really helping me. A big downside of the larger compressor is that it's LOUDER. That alone should encourage everyone to not oversize their system.
Thank you very much for sharing, @satoshimanabe2493! 🙏 Most air-source heat pump systems installed today run very quietly. What is the heat pump model and when was it installed? By the way, ground-source heat pump systems are of course completely silent. Thank you! Katha
@@NetZeroTech My system was installed about 10 years ago, a Bryant 286BNA024 (24000 BTU). Compressor is single-speed, dual-stage. Home is 32x16 ft, 3-story with one of the long walls being shared with a neighbor (so effectively no loss through that wall). There have been vast improvements in the past 10 years, and I'm hoping there's better air-to-air equipment out there when I have to replace this in another 5-10 years. (Ground water isn't an option for me.)
Thank you so much for sharing! Very interesting! Yes, heat pump technology has improved over the past 10 years across the board. I hope you are enjoying your heat pump system regardless. Greetings from Colorado, Katha
This problem really only applies to single stage heat pumps or if you live in a very hot area like Phoenix. For most people the correct way to size a heat pump is to match the heat load. Then be smart and only consider variable speed or inverter models of heat pumps. These are quiet and will do a good job managing humidity levels. Efficiency levels range from 16 to 32 Seer with 19-25 being the economical sweet zone.
Hi Katha, thanks for the video. I've noticed also a lot of commentary about oversizing being detrimental to efficiency but not much quantitative data. Of course it will depend on the application so hard to make a broad statement. Anyway, I noticed in the beginning of the video that you said oversizing is detrimental to efficiency because a variable speed heat pump will be running at its minimum output much of the time, but then later in the video said that this is good for efficiency because the heat exchange area is much greater relative to output. So in that case, wouldn't an oversized variable speed heat pump run a higher efficiency than one sized to be running closer to full capacity more of the time? Not many manufacturers have detailed enough data to answer this question but curious what you've found in your research. I've seen at least some curves showing an efficiency maximum somewhere between min and max output of variable speed heat pumps, so I would think that the ideal strategy would be to size the unit to match that sweet spot to the load for as much time as possible.
Hi @RicknessJ82, Thank you for the comment. Really good points! I tried to get more data into the video. I had a hard time finding data. I asked multiple heat pump experts and scraped the internet. The challenge that I am running into is for these kinds of videos is time for in-depth research. I would have to ask a lot more manufacturers and heat pump designers. But, frankly, and I hate to say it, but if I spend the time doing that, I lose momentum to build the channel. My goal is to grow the channel to a size where I can afford a researcher or other team members, so I can spend more time on research. That's the hard truth at the moment. I am looking into sponsorships. I hope you have the patience to stick with me on the way. Warm regards, Katharina
@@NetZeroTech Thanks for the quick reply, I get that for sure! I like to geek out on those details but for many it may be TMI anyway, thanks for the great content!
Oversizing seems to be an issue in the UK too where there is a push to replace traditional gas boilers with HPs - many plumbers (not heating engineers) aren’t trained in heating design and use the same rules of thumb as they have been for gas rather than doing actual heat loss calculations - many boilers are already massively oversized because “bigger = better” 🙄 and many homes have combi boilers which require huge outputs for instant hot water resulting in homeowners thinking something with a perceived “small” output is not going to be powerful enough - there are plenty of negative stories of poor performance or expensive running costs that hit the headlines in some news outlets with a particular agenda 🙄
Thank for sharing this! Much appreciated. In the a video about the importance of the installer, I mentioned the challenges with installers that are untrained in heat pumps. I think it is a challenge in all places where heat pump demand is growing rapidly, because installers, who used to install furnaces are switching to where the business is going, i.e. to heat pumps and haven't had time to catch up in training. I think this is I pretty much what's happening globally, although a lot of countries in Europe seem to be a bit ahead. And we are still at the onset of the S-shaped growth curve. So, more exponential growth to come.
@@NetZeroTech indeed, it's only going to get worse unfortunately as there are currently subsidies of £7500 for A2W HP installs so the unscrupulous installers will be aiming for the unsuspecting as is always the case when "free" money is there for the taking, albeit with a bit of bureaucracy to tick some boxes - same thing happened with PV a few years back. It's also muddied by the general public not having a clue and the fact that any old gas fitter can refer to themselves as a "heating engineer" as it's not a protected title as it is elsewhere - that and the fact that it's all too easy to install an oversized gas system without calculations which is inefficient because no-one is able to measure it, but the homeowner is happy because it gets warm quickly and gas is still relatively cheap...
Great video! Some models can turn down to just 15% or less of their max output and have impressive COP over 7 at that minimum output, versus 3-4 at high or max output. Do you think that's enough to minimize low load cycling? I think it also depends on the location. Min vs max output needed is much different in an area with a design temp of 32F/0C vs an area with 0F/-18C
Thank you so much! 🙏 Agreed. It absolutely depends on the location. However, systems would work more efficiently if the were sized for their nominal values, meaning they run at their most efficient capacity most of the time. Cold-climate heat pumps have an auxiliary backup resistor that covers the outlier days. Too frequent low cycling happens when the heat pump is too large regardless of COP I think. Hope this helps. Thank you and greetings from Colorado, Katha 😀
Hi @raghuramkalyanam! That’s great! Congratulations to the decision. Air-to-air heat pumps are more popular. 😀 I am a big fan of air-to-water, as the long-term savings are significantly higher. I think you’ll enjoy your investment! 😊 Katha
@@NetZeroTech In Germany most builders are increasingly opting for Air to water HP. Even older buildings are going for geothermal ones, though bit costly.
@@raghuramkalyanam Agreed. I think in my video "Solar for Heat Pumps" I mention that air-to-water systems are already the most popular system for new buildings in Germany and are becoming increasingly popular in the US (ua-cam.com/video/QmunFWEvh60/v-deo.html). Thank you very much for watching and commenting! 🙏Greetings from Colorado, Katha
Hi @donalddouglas5988. Thank you for watching and sharing your thoughts. A correctly sized heat pump maximizes the efficiency and the lifetime of the system, so that little to no energy is lost do to improper sizing. For the coldest days cold-climate heat pumps have auxiliary backup electric heaters. Apologies if this didn't come through in the video. I hope this helps. Thank you, Katha
To keep me from over-sizing my heat pump, I would need to see some data that accurately predicts the local climate for the next 15 to 20 years. The data must include things like climate change and the effects of natural disasters or even a nuclear war.😐
Great point. That would be needed to size any heating or cooling system. My assumption is that temperatures will keep rising. In regions where cold is the limiting factor, this means, you’d even need a smaller heat pump in the future. Overall I would assume the effect of a changing climate on heat pump size is minimal. Thank you for sharing! Greetings from Colorado, Katha
This is one of the reasons I like air to water heat pumps with a very large buffer, say 3000L. Optimally run to heat up the tank, independent from heating the house. The large buffer can store even several days worth of energy on milder days, meaning the heat pump can run optimally to charge the buffer, and then won't have to run for a day or more at a time.
@upnorthandpersonal, 100 % agreed! Thank you for sharing. Hope you are doing well, Katha
a 3000L buffer is stupid. it does nothing apart from increasing your bill. trying to heat such an amount takes more energy than just making it when you need it and what you need and no more. trying to do the chinse wok style of heating instead of dutch oven style always consumes more energy and increases your installation cost and energy bills. never ever store heat. the only thing tat barely makes sense is battery storage.
@@SupremeRuleroftheWorld You don't have to heat it all - the point is that you can run the heat pump optimally with a buffer as required depending on the heating requirement. You don't have to worry about flow calculations or anything to make sure the heat pump runs optimally. A well insulated tank like that holds the heat just fine, and anything that escapes just adds to the heating of the building so it's not lost.
I have a 3000L tank, which is coupled to both a wood gasification burner as well as a heat pump. I also have 60kWh of battery storage since I'm off-grid. I can use the energy from my solar system optimally that way, which includes running the heat pump during the day when I have sun, and heating when the temperature drops. Similarly, when you're connected to the grid, you can use cheaper rates to heat the tank, and then use it when it would be more expensive to run the heat pump.
@@upnorthandpersonal running a heatpunp harder, hotter and thus with lower COP to store heat in some supidly sized tank is always a net loss compared to just running it when you need it from the battery or generator. the gains in efficeincy just from lowering the supply temperature and running it low and slow easely outdoes any gains you might think you have with running it short and hard. just lowering the supply temp 10 degrees can save you 20% in power consumption. do find it hillarious that you burn wood and have a heat pump. got a real jungian duality of man going there.
@@SupremeRuleroftheWorld But that's the point: you can run it at optimal CoP all the time. You don't need to run it harder/hotter at any time.
As for burning wood: I'm at 63 degrees north, and off grid. I'm converting an old tree farm to a natural, diverse forest at the time time - which means trees need to be cut.
At 38° north latitude we need variable speed heat pumps to be oversized in cooling because you’re going to need that extra capacity during heat mode. I need 20 btu/sqft for cooling and 35 for heating.
Otherwise, if you size it for cooling, go ahead and install another heat pump just for heating right beside it, because you’re gonna need it. Typically you need about twice as much capacity for heating in the winter time.
We don’t have hydronic systems in our residential homes very much in the US and most of us do not want them. I am going to build a small air-water hp for my 80 gal electric to save some energy this time of year. I am totally off grid and it’s all I can do to make it through these dark cold weeks of January and early February. That’s with 32kWp! I have to use a wood burner when it gets below 20F at night.
Hi @rv10flyer84 Thank you very much for watching and sharing your thoughts. I’m curious to learn why you don’t want hydronic systems for residential homes. Thank you! 🙏
Most of us have forced air, air-air hp’s. Some have gas or oil fired boilers and some have geothermal hp’s. I guess the air-water hp’s haven’t caught on much yet and will have to start with new construction. Hey, we are just now getting air-air mini splits here in larger numbers. Mainly because they can be diy. I don’t push them on people, because they are difficult to perform preventative maintenance on them, they don’t last quite as long as our central heat pump systems, we don’t carry parts on our trucks for them, and you can’t add high efficiency air filtration to them very easily. I have a Fujitsu 9000 BTU 33 seer heat pump air to air. I like it a lot, but it’s only two years old so time will tell.
Interesting. Thank you very much for sharing! 🙏 I appreciate it. Katha
Interesting , thank you . A fine example of the consiterations and concerns involved in having the best and most effective system that works for YOU
You are welcome, @henrycalson7514. Thank you for watching and sharing your thoughts. 🙏 Exactly, there is no one size fits all. Rather bell curve distributions. Thank you, Katha
Thanks for the video, all very good points. My heat pump is definitely oversized. As you state, this increased the cost of the system, and the extra money spent isn't really helping me. A big downside of the larger compressor is that it's LOUDER. That alone should encourage everyone to not oversize their system.
Thank you very much for sharing, @satoshimanabe2493! 🙏 Most air-source heat pump systems installed today run very quietly. What is the heat pump model and when was it installed? By the way, ground-source heat pump systems are of course completely silent. Thank you! Katha
@@NetZeroTech My system was installed about 10 years ago, a Bryant 286BNA024 (24000 BTU). Compressor is single-speed, dual-stage. Home is 32x16 ft, 3-story with one of the long walls being shared with a neighbor (so effectively no loss through that wall).
There have been vast improvements in the past 10 years, and I'm hoping there's better air-to-air equipment out there when I have to replace this in another 5-10 years. (Ground water isn't an option for me.)
Thank you so much for sharing! Very interesting! Yes, heat pump technology has improved over the past 10 years across the board. I hope you are enjoying your heat pump system regardless. Greetings from Colorado, Katha
This problem really only applies to single stage heat pumps or if you live in a very hot area like Phoenix. For most people the correct way to size a heat pump is to match the heat load. Then be smart and only consider variable speed or inverter models of heat pumps. These are quiet and will do a good job managing humidity levels. Efficiency levels range from 16 to 32 Seer with 19-25 being the economical sweet zone.
Thank you very much for sharing, @alberthartl8885. Much appreciated! Katha
Thank you again for your well researched video. I always enjoy your content.
Thank you so much! 🙏 I appreciate it. Glad you enjoyed it. 😀 Katha
Hi Katha, thanks for the video. I've noticed also a lot of commentary about oversizing being detrimental to efficiency but not much quantitative data. Of course it will depend on the application so hard to make a broad statement. Anyway, I noticed in the beginning of the video that you said oversizing is detrimental to efficiency because a variable speed heat pump will be running at its minimum output much of the time, but then later in the video said that this is good for efficiency because the heat exchange area is much greater relative to output. So in that case, wouldn't an oversized variable speed heat pump run a higher efficiency than one sized to be running closer to full capacity more of the time? Not many manufacturers have detailed enough data to answer this question but curious what you've found in your research. I've seen at least some curves showing an efficiency maximum somewhere between min and max output of variable speed heat pumps, so I would think that the ideal strategy would be to size the unit to match that sweet spot to the load for as much time as possible.
Hi @RicknessJ82, Thank you for the comment. Really good points! I tried to get more data into the video. I had a hard time finding data. I asked multiple heat pump experts and scraped the internet. The challenge that I am running into is for these kinds of videos is time for in-depth research. I would have to ask a lot more manufacturers and heat pump designers. But, frankly, and I hate to say it, but if I spend the time doing that, I lose momentum to build the channel. My goal is to grow the channel to a size where I can afford a researcher or other team members, so I can spend more time on research. That's the hard truth at the moment. I am looking into sponsorships. I hope you have the patience to stick with me on the way. Warm regards, Katharina
@@NetZeroTech Thanks for the quick reply, I get that for sure! I like to geek out on those details but for many it may be TMI anyway, thanks for the great content!
@@RicknessJ82 Thank you for watching! Keep geeking out! I love it! Katha
in my experience the extreme temperature is not the reason. its simply installers that dont want cold calls so they just oversize to the extreme.
Interesting. Thank you for sharing! 🙏 Much appreciated. 😊 Katha
Oversizing seems to be an issue in the UK too where there is a push to replace traditional gas boilers with HPs - many plumbers (not heating engineers) aren’t trained in heating design and use the same rules of thumb as they have been for gas rather than doing actual heat loss calculations - many boilers are already massively oversized because “bigger = better” 🙄 and many homes have combi boilers which require huge outputs for instant hot water resulting in homeowners thinking something with a perceived “small” output is not going to be powerful enough - there are plenty of negative stories of poor performance or expensive running costs that hit the headlines in some news outlets with a particular agenda 🙄
Thank for sharing this! Much appreciated. In the a video about the importance of the installer, I mentioned the challenges with installers that are untrained in heat pumps. I think it is a challenge in all places where heat pump demand is growing rapidly, because installers, who used to install furnaces are switching to where the business is going, i.e. to heat pumps and haven't had time to catch up in training. I think this is I pretty much what's happening globally, although a lot of countries in Europe seem to be a bit ahead. And we are still at the onset of the S-shaped growth curve. So, more exponential growth to come.
@@NetZeroTech indeed, it's only going to get worse unfortunately as there are currently subsidies of £7500 for A2W HP installs so the unscrupulous installers will be aiming for the unsuspecting as is always the case when "free" money is there for the taking, albeit with a bit of bureaucracy to tick some boxes - same thing happened with PV a few years back. It's also muddied by the general public not having a clue and the fact that any old gas fitter can refer to themselves as a "heating engineer" as it's not a protected title as it is elsewhere - that and the fact that it's all too easy to install an oversized gas system without calculations which is inefficient because no-one is able to measure it, but the homeowner is happy because it gets warm quickly and gas is still relatively cheap...
@@Umski Thank you so much for sharing your thoughts! 🙏 Have a great time! Katha
Great video! Some models can turn down to just 15% or less of their max output and have impressive COP over 7 at that minimum output, versus 3-4 at high or max output. Do you think that's enough to minimize low load cycling? I think it also depends on the location. Min vs max output needed is much different in an area with a design temp of 32F/0C vs an area with 0F/-18C
Thank you so much! 🙏 Agreed. It absolutely depends on the location. However, systems would work more efficiently if the were sized for their nominal values, meaning they run at their most efficient capacity most of the time. Cold-climate heat pumps have an auxiliary backup resistor that covers the outlier days. Too frequent low cycling happens when the heat pump is too large regardless of COP I think. Hope this helps. Thank you and greetings from Colorado, Katha 😀
I am going to get a air water heater pump, hope it is properly dimensioned! I find most of it specific to air to air heatpump right?
Hi @raghuramkalyanam! That’s great! Congratulations to the decision. Air-to-air heat pumps are more popular. 😀 I am a big fan of air-to-water, as the long-term savings are significantly higher. I think you’ll enjoy your investment! 😊 Katha
@@NetZeroTech In Germany most builders are increasingly opting for Air to water HP. Even older buildings are going for geothermal ones, though bit costly.
@@raghuramkalyanam Agreed. I think in my video "Solar for Heat Pumps" I mention that air-to-water systems are already the most popular system for new buildings in Germany and are becoming increasingly popular in the US (ua-cam.com/video/QmunFWEvh60/v-deo.html). Thank you very much for watching and commenting! 🙏Greetings from Colorado, Katha
Maybe she could define oversized and correctly sized . A heat pump needs to be big enough to work on the hottest and coldest day of the year.
Hi @donalddouglas5988. Thank you for watching and sharing your thoughts. A correctly sized heat pump maximizes the efficiency and the lifetime of the system, so that little to no energy is lost do to improper sizing. For the coldest days cold-climate heat pumps have auxiliary backup electric heaters. Apologies if this didn't come through in the video. I hope this helps. Thank you, Katha
To keep me from over-sizing my heat pump, I would need to see some data that accurately predicts the local climate for the next 15 to 20 years. The data must include things like climate change and the effects of natural disasters or even a nuclear war.😐
Great point. That would be needed to size any heating or cooling system. My assumption is that temperatures will keep rising. In regions where cold is the limiting factor, this means, you’d even need a smaller heat pump in the future. Overall I would assume the effect of a changing climate on heat pump size is minimal. Thank you for sharing! Greetings from Colorado, Katha