是的，在明尼苏达州的热泵工作。。。也是阿拉斯加，佛蒙特州和安大略省。今天我会告诉你明尼苏达州明尼阿波利斯的一个特定房子，这是在过去的四个冬天的热泵中加热。这是Gary Nelson，创始人的家The Energy Conservatory，这使得明尼阿波利斯鼓风机门和用于测试房屋和管道系统中的空气泄漏的管道间谍。
First, fix the building enclosure
The result of improving the enclosure so much is that the heating load is very low. He didn’t do a formalload calculation，但他确实知道在装修之前他使用了多少热量。然后，他的加热系统由北极星热水器（化石燃气烧制）和空气处理器组成，以分配热量。他发现，当室外温度为-10°F时，系统几乎连续运行99% design temperature, and the amount of heat he got from the water heater was 17,000 BTU/hr. Then he calculated that the load reduction from his enclosure improvements would be offset for the additional load from an addition that was part of the renovation, so he figured he needed a heat pump with a capacity of 18,000 BTU/hr.
因此，他放入富士通管道的热泵，其容量为18,000 btu / hr。而且因为他了解热转印和明尼阿波利斯天气，他将这种热泵置于没有辅助热量。真的！
Winter 2017-18: This was the first winter after the renovation, and the low in Minneapolis was -15°F. The system performed very well. Even though the outdoor temperature went 5°F below their design temperature, the 18k heat pump held the house at the 72°F setpoint.
2018-19冬天: The outdoor temperature got down to -27°F. The house temperature got down to 62°F but they were away in Australia at the time. Nelson told me that if they had been home, they probably could have gotten the house up close to the setpoint with their body heat and by baking some cookies.
当然，尼尔森措施和记录一切，所以他也知道热泵泵送的热量以及有多高效。在-27°F冷鲷期间，他计算出热泵容量为8597 BTU / HR（2.52千瓦），功耗为1834瓦（W）。性能系数为2.52¼1.834 = 1.37。相比之下，电阻热量具有1的性能系数。
When the temperature rose to -17°F, the heat pump output rose to 13,000 BTU/hr and the power consumed to 1959 W. The resulting coefficient of performance was nearly 2, or double what electric resistance would have provided. (And to think that some HVAC techs tell people toswitch to emergency heatwhen the outdoor temperature drops into the 30s°F!)
2019-20冬季: He had nothing remarkable to report. They didn’t have any weather cold enough to call for any kind of auxiliary heat.
纳尔逊的热泵是f大小几乎完美or heating. In a place like Minneapolis, that means it’s oversized for cooling. Minneapolis does get humid, too, and the result is a house that can stay at the setpoint temperature easily but doesn’t get dehumidified enough. After two summers of dealing with muggy indoor air, he installed an Ultra-Aire dehumidifier in the summer of 2020. As a result, he “enjoyed much better humidity control” during the cooling season.
Yes, heat pumps can carry the load in Minnesota
使用热泵是一个很好的主意，特别是如果你更换气体加热系统。与化石瓦斯不同，电力越来越清洁all the time.
Allison Bailes佐治亚州亚特兰大，是一位发言者，作家，建筑科学顾问和能源先锋的创始人。beplay体育官方下载他也是作者的能源先锋博客并且是writing a book。You can follow him on Twitter at@energyvanguard.。
Good article, looking forward to the new book so I can place it next to the Sigenthaler books and the Manual J. Curious to know what is used for the DHW. The new air to water heat pumps can cool, heat and produce DHW. Water for heat only needs to be 83 to 103f, so DHW at 120F would require more BTU.
Bill, Gary has a GE GeoSpring heat pump water heater, which you can see behind him in the photo above. GE has since stopped producing it.
> he also knows how much heat the heat pump was pumping
How does he know? It's not like measuring the heat output accurately is easy.
> -17°F, ...The resulting coefficient of performance was nearly 2
There are various models, but looks to me like Fujitsu measured a COP of 2.0 at +5F (NEEP). So COP = 2 at -17F sounds wildly optimistic.
My particular mini split was 1.3 at those temps. Now, that's a senville unit, so not as good as Fujitsu. However, when the temps dropped below zero, the system went from around 600cfm to around 400. I made the mistake assuming airflow was the same at below zero temps, and after correcting the mistake, cop went from 2 to 1.3.
>“... Cop = 2在-17F听起来很乐观。”
Agreed, but "...nearly 2... " is what it being alleged, not "... COP=3..." .
The "...nearly..." part is subjective- a COP of 1.5 would qualify in some peoples' minds, 1.8 (still a credible number for best in class air source heat pumps) in others'.
Output = 13,000 BTU/hr x (1 kW / 3,412 BTU/hr) = 3.81 kW
输入= 1,959 W = 1.959 kW
COP = 3.81 / 1.959 = 1.94
So, nearly 2 means very close to 2.
Now, whether that's correct or not is another matter. Gary did tell me, "This seems pretty impressive. I believe Manufacturer’s data only go down to -5 and my data agree pretty well with theirs at -5 and above."
Would be nice to see much more of the collected COP data. Including the exact model #, so we can find the manufacturer’s data.
Can the few COP points that manufacturers list be accurately linearly extrapolated for lower temps? The data here suggests a suspiciously different COP degradation slope from 5F down to -17F vs -17F down to -27F.
My 99% design temperature is a comparatively balmy 0°F. We've never had an issue over six winters with our Fujitsu heat pumps keeping up with cold weather. I'm surprised that the COP is as high as reported at very low temperatures, but it sounds like he's pretty organized about data collection. And even if some supplemental heat is needed once in a while, it's no big deal.
Obviously, the key is a robust, efficient envelope because it allows you to cruise through the occasional cold snap without interior temperatures dropping much.
> he should have installed aux heat
Always do a proper Manual J/S.
I say this many times in the questions, that people kind of expect the minisplits to just 'work' but they are just manufactured items, they do not understand the conditions around them. Using them for AC I tend to leave the setpoint and manage comfort with the fan speed. Sure it would be nice if the auto setting was perfect, but until they get 50:1 turndown ratio and wifi integration with the National Weather Service, we may have to deal with occasionally hitting the button on the remote.
同意，流行且错误的看法是过大的AC提供较差的湿度控制（与右侧和尺寸的热泵相比）。但它几乎完全是关于CFM / TON的。得到正确的，甚至2x过尺寸的逆变器热泵工作正常。
Jon R - 只是想补充一点，我经常在与AC设备和除湿相关的线程上看到您的评论，我很感谢您对此事的看法。您与（佛罗里达州的一些装备）相关的实地研究是有用的，但超越了我的肯，你做了很好的简化它。
That's because that rule applies to fixed capacity systems, not variable capacity.
你能指出关于右上尺寸CFM / TON的更多信息吗？
I'm struggling with this exact question right now trying to size a ducted heat pump for the house we're building in Zone 6. Installer wants to go bigger so the heating is right sized, I'm inclined to go small so the AC is right sized and use the wood stove as needed. But if the larger unit will work just fine for cooling then that would be great.
A dehumidifier is different in that it doesn't cool the space. It's not just about fan speed. If the load is 100% latent, then A/C alone probably can't manage the humidity. My heat pump is matched to both peak heating and cooling loads. I still can't keep the humidity below 60% a lot of the time, no matter what settings I use on the heat pump.
Can't recall if Mitsubishi units can measure humidity. Only one carrier midea unit I know of can.
Realize the more your unit focuses on humidity removal, the more energy it will take and efficiencies nosedive. Also, you'll have more moisture inside and more chances for mold buildup. That's why they try to not do that. To remove humidity, the unit has to generate low refrigerant temps by high compressor speeds and run near 0 superheat.
我目前在北部修建两个小房子n BC that are using Arctic heat pumps out of Winnipeg. They say that at -20c they have a COP of 1.7. In addition as a backup system for below -25, I'm using a storage tank with an electric boiler build in, again supplied by Arctic. The hydronic hot water is heating the house, preheating the domestic hot water and heating incoming kitchen exhaust make up air all from the storage tank.
I'm in Northern Minnesota, -30C/-22F design temp. We have a house that's been up an running on a Mitsubishi central ducted system (one of the PVA Multi-position air handler heat pumps, 24,000 BTU) with an integrated electric plenum heater for the past two winters. During this past winter's polar vortex, where temps didn't get above -18C/0F for nearly 10 days, the homeowner said temps never dropped more than 2 degrees below the setpoint in the home. They said there was a slight lag between the ASHP cutout temp and the electric plenum heater, but no major comfort issues.
The house you are referencing is highly insulated and very airtight. Just as is Gary Nelson's house (from retrofit) in Minneapolis. To get good results from cold climate heat pumps in MN the building envelope will have to be high performance.
谢谢，伟大的信息和提醒“电力正在变得更加清洁”。是否有机会知道SQ FT和CU FT以及它是单一级别还是多级房屋（以了解外表面积的想法到SQ FT / CU FT，脚印等）和附加车库？（我懒得从500立方英尺每分钟在50麦克斯人中退出Cu ft，但也许我会把它放在一边，像1 ach有500 cu ft / min = 60 min / hr x 500 cuFt / min = 30,000 Cu ft为1个空气变化一小时，因此30,000 Cu Ft内部体积，假设10英尺的天花板产生3,000平方英尺的房屋？）18,000 Btu / h在明尼苏达州3,000平方英尺3,000平方英尺？
> 50个Pascals 500立方英尺
AFAIK,刮风的一天(20英里/小时)可以背包e 50 pascals across roughly 1/2 of the house. So say 250 CFM and that it's a mild 0F outside. That's 19,440 btu/hr for the infiltration load alone. Then switch on a kitchen exhaust fan and double that...
I'd want to see a lot more data from Nelson's house before forming any conclusions.
Hmm, so have the blower door test on a calm day ;-) Or, have multiple blower door tests under multiple wind conditions to see impact of wind on things like sliders, maybe an argument for the aerodynamic passive house, on a spindle to always point into the wind.
有趣的是，这种情况和评论中讨论的案件所有使用的管道系统。我将预期的导管是这里的首选（和更好的表现）系统。有什么想法吗？我正在考虑哈德森谷（东海岸 - 4/5区），并正在努力假设导管是实现Subxero Temp性能的唯一途径。
Everything I've seen indicates that ducted mini-splits and ductless mini-splits are similar in performance. Just a little more energy to move air around.
I'm definitely not an expert here, which is why I phrased it as a question. But besides the inherent losses you'll find in even the best ducted systems, the HSPF and SEER ratings of mini-splits are much higher than central (ducted) heat pumps. It's pretty hard to find central heat pumps with HSPF of 10, which is required to be a certified Cold Climate Heat Pump. The HVAC contractors I talked with all said this as well (don't always trust what they say though). Anyway, I would love to hear if anyone has researched information on this.
It's an interesting question. Luckily just an academic one for me as our climate here is so temperate.
If you go to the NEEP database:
您可以找到充足的数千个千分之一 - 具有Hspf> 10的中央管道模型，有些> 12。
与Q＆A相同的答案：对您来说，拥有它们的唯一原因是，如果您的热泵机械故障 - 在压缩机中或制冷剂泄漏 - 热带可以以高电平的成本，保持在等待服务时，房子温暖。但他们也可以错误地踢出自动踢，如果有控制失败，可以使用大量的能量。我要么安装它们并留下断路器，需要在您的部件上进行手动操作以在紧急情况下激活它们，或省略它们。
>"For you, the only reason to have them is that if you have a mechanical failure of your heat pump--in the compressor or perhaps a refrigerant leak--the heat strips could, at high electric cost, keep the house warm while you wait for service."
The other reason for strip heat is for comfort during defrost cycles. It's a common feature in ducted heat pumps to engage strip heat during defrost to avoid blowing tepid/cold air out the registers.
但是4.5千瓦（约15,000 btu / hr）的条带热量足以覆盖大多数代码的实际设计热负荷或比洛杉矶的代码房屋更好。在热泵条带控制和热带本身之间安装开关，以便在热泵失败时能够启用它，而不是巨大的成本加法器。
Have the heating and cooling loads of this house in New Orleans been carefully calculated with a Manual-J? Most AC and heat pumps that get installed are way oversized for the actual loads, and installing a right-sized modulating heat pump could be the best of all worlds, even without strip heat during defrost.
达纳：我没有想过在除霜周期中使用电热条！近在咫尺，近一点，那些只是冷天气A / C循环与压缩机扇子，如果条带截止，它会在内部吹风空气，并且我将当前的空气保持关闭。我想我会在除霜循环期间避免冷空气楔子。如果我们切换到电池备份，我总能锁定它们......如果我醒了。
Manual J will be done once I've settled on a contractor. They ballpark a tonnage for the free estimates, but the two finalists both say they will do the full calculations. They know I know.
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