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Heat Pumps – The Well-Tempered Future of A/Cs

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Re: Heat Pumps – The Well-Tempered Future of A/Cs

#111

Post by kevin_thibedeau »

Maxburn wrote: post #81
kevin_thibedeau wrote: post #38

Earlier quoted context omitted.

It's not just buzz. It's more efficient than resistive heating and modern units have better performance in cold temps. Hence the push to promote them. The downside is that you have added complexity driving up installation costs and reliability down.

Walk around in the American Heating and Refrigeration conference for a while to get a feel of these trends, this was specifically called out by many manufacturers as driven by the green movement.

It's being driven by government pressure to reduce energy consumption and dependence on fuel imports. That isn't a bad thing. It's the sort of thing a responsible government should be planning for.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#112

Post by rimunroe »

ramesh31 wrote: post #34

Swamp coolers are massively underutilized as well. The vast majority of residential cooling in all but the most humid climates can be done with nothing but a fan and some cold water; no compressed gases necessary.

> The vast majority of residential cooling in all but the most humid climates can be done with nothing but a fan and some cold water

Aren't swamp coolers only really useful when the humidity is under something like 50%? I guess I'm assuming you're talking about the US, but I don't think "vast majority" of people live in such areas. A quick search for average humidity of US states in July and August shows many of them have an average daily humidity of over 50%.

It certainly rules out every place I've lived on the east coast (Richmond, Virginia, Long Island, and the Boston area), as the humidity in those places is usually at least 60% at the height of summer when most people actually use their AC.

As a side note, I suspect most people overuse their air conditioning and don't let their bodies adapt to the warmer summer weather. It's weird how many people keep their houses under 75 °F when the heat index is only in the mid 80s.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#113

Post by addisonl »

chickenpotpie wrote: post #110
addisonl wrote: post #109

Earlier quoted context omitted.

Like the other commenter who already corrected you, it makes perfect sense if you actually understand how wet bulb works, here’s a calculator for you: https://www.omnicalculator.com/physics/wet-bulb Hint: Phoenix is at 17% humidity today, even their all time high of 122 doesn’t push the wet bulb temp out of the safe range.

I understand how wet bulb temperature works just fine. You didn't need to write a snarky response to engage in this discussion. Now include climate change raising the temperature and changing the length and severity of monsoon season, continued development raising the heat island effect. It doesn't matter what the average wet bulb temperature over the entire coty over a long period of time. It matters what the peak w…

The entire south is at a much higher risk from wet bulb: https://www.iflscience.com/southern-us-reaches-dangerous-wet... so my point still stands, wet bulb isn’t an issue in Phoenix.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#114

Post by ramesh31 »

rimunroe wrote: post #112
ramesh31 wrote: post #34

Swamp coolers are massively underutilized as well. The vast majority of residential cooling in all but the most humid climates can be done with nothing but a fan and some cold water; no compressed gases necessary.

> The vast majority of residential cooling in all but the most humid climates can be done with nothing but a fan and some cold water Aren't swamp coolers only really useful when the humidity is under something like 50%? I guess I'm assuming you're talking about the US, but I don't think "vast majority" of people live in such areas. A quick search for average humidity of US states in July and August shows many of them…

>Aren't swamp coolers only really useful when the humidity is under something like 50%?

They are less effective, but still work. As long as the dew point is ~72 degrees, or lower, they can still cool enough to do the job (although of course not to the extent of an AC). But yes, ultimately it comes down to people being ok with not setting the AC to 68 degrees when it's 80 degrees out, and using the minimal amount of cooling necessary to be comfortable.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#115

Post by __MatrixMan__ »

jillesvangurp wrote: post #97
__MatrixMan__ wrote: post #15

I live in a colder climate where heat pumps are not popular. After talking with a number of HVAC people about this I was surprised to learn that despite being very similar to an AC system in principle, in practice converting an AC system into a heat pump system doesn't make economic sense--you end up just ripping one out and installing the other. I don't fully understand why this is the case, but I hope that there's…

This persistent myth just needs to go away. People use heat pumps all over Scandinavia, including in the arctic circle. They are extremely popular there. They were early adopters of this technology there decades ago. There are two popular varieties: - Ground source heat pumps. Those work pretty much anywhere; just dig below the perma frost and you are good to go on the northern tip of Canada, Alaska, Norway, or where…

I've been on zoom calls with two separate co-workers who are all bundled up because their heat pump can't handle the weather. It doesn't mean that the technology is inadequate in principle--probably their systems have some problem that competent HVAC installers know how to avoid.

But its an unfortunate fact that there are places in the US where installers that recommend heat pumps can't be found for 100 miles. It doesn't really matter if I'm technically correct about the merits of the tech in principle--if I can't find somebody to fix my system and my pipes start exploding, I've still made the wrong decision.

Also, heavy snows cause power outages in places where tree limbs fall on overhead lines. If gas outages happen... well I've never experienced one. Sure, if I lived in Norway I'd have a government that cares about updated infrastructure and I wouldn't have these problems, but since I don't, I do.

Given my local constraints, a dual-fuel system sounds pretty great.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#116

Post by MrRadar »

davidmurdoch wrote: post #56

Being a Florida native, seeing an article titled "Heat Pumps [are] the Future of A/Cs" feels like it should have a ` [1973]` tacked on to the end of it. A heat pump is pretty much the only thing we use here, we just use them in reverse. Literally. Most residential units have a "reversing valve" that must be held open by a constant 24V in order to cool the air - the default mode is heating -- which is so smart to have…

A large part of it is that heat pumps only within the past decade became efficient enough to install in northern US climates, where temperatures are below freezing 4+ months of the year. It's relatively easy to design an air-source heat pump that will work efficiently down to freezing, it's much harder to design one that will work efficiently well below freezing, and frankly the A/C manufacturers who traditionally sold to the US market haven't really tried all that hard (they probably don't/didn't expect a large enough market to offset the development costs). It's newer market entrants from Asia that are really pushing the envelope of heat pump efficiency and making it feasible.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#117

Post by elcano »

triceratops wrote: post #85
afavour wrote: post #72

Earlier quoted context omitted.

Heating is considerably more energy efficient than having to run ACs all over the place. And if you need to go outside when it's cold you can: you add layers of clothing. In Arizona, in the middle of summer, you could be buck naked and you'd still overheat (and get burnt, to boot).

> Heating is considerably more energy efficient than having to run ACs all over the place. That's actually incorrect. Heating takes considerably more energy. When you're cooling you're looking at a temperature delta of at most 20 degrees C/45 degrees F between outside and inside. When you're heating, it can be easily be twice that. Or even more, in parts of Canada or the Great Lakes states. Air conditioning is a heat…

Heating under usual winter conditions would consume more energy than cooling under practical conditions. Yes.

But that's very different than claiming than cooling is more efficient than heating. In A/Cs the ratio of energy (in the form of heat) removed to energy consumed is very low, around 10-15%.

In furnaces the ratio of energy added to energy consumed is around 90%, which was pretty good until the emergence of heat pumps. There almost all the energy consumed is added to the output in addition to all the energy removed from the other side. That's why the efficiency in heat pumps is beyond 200%.

In summary, no. Cooling is not more efficient than heating. But given the temperature differential when cooling the energy consumption is usually higher.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#118

Post by mathgeek »

afavour wrote: post #61
mathgeek wrote: post #57

Earlier quoted context omitted.

As a thought experiment, the same logic can be applied to any region where lack of shelter or heating would make human life unsustainable.

If you completely ignore the concept of energy efficiency, sure.

That’s why I mentioned it as a thought experiment. We have been burning energy for centuries to keep folks alive in both extremes of climate.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#119

Post by jillesvangurp »

__MatrixMan__ wrote: post #115
jillesvangurp wrote: post #97

Earlier quoted context omitted.

This persistent myth just needs to go away. People use heat pumps all over Scandinavia, including in the arctic circle. They are extremely popular there. They were early adopters of this technology there decades ago. There are two popular varieties: - Ground source heat pumps. Those work pretty much anywhere; just dig below the perma frost and you are good to go on the northern tip of Canada, Alaska, Norway, or where…

I've been on zoom calls with two separate co-workers who are all bundled up because their heat pump can't handle the weather. It doesn't mean that the technology is inadequate in principle--probably their systems have some problem that competent HVAC installers know how to avoid. But its an unfortunate fact that there are places in the US where installers that recommend heat pumps can't be found for 100 miles. It doe…

Gas outages happened at a large scale in Texas when they were struggling with a bit of cold weather. When they needed it the most, it failed them. Coal plants also struggled. Both had challenges with supply of fuel and cooling water being disrupted. That kind of systemic infrastructure failures is on the rise in the US. There are all sorts of reasons why governance just isn't great in the US. But the reality indeed is that things are unlikely to improve on that front.

Which are all good reasons why the market for domestic solar, batteries, and heat pumps is so hot right now. The US is no exception to this.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#120

Post by triceratops »

elcano wrote: post #117
triceratops wrote: post #85

Earlier quoted context omitted.

> Heating is considerably more energy efficient than having to run ACs all over the place. That's actually incorrect. Heating takes considerably more energy. When you're cooling you're looking at a temperature delta of at most 20 degrees C/45 degrees F between outside and inside. When you're heating, it can be easily be twice that. Or even more, in parts of Canada or the Great Lakes states. Air conditioning is a heat…

Heating under usual winter conditions would consume more energy than cooling under practical conditions. Yes. But that's very different than claiming than cooling is more efficient than heating. In A/Cs the ratio of energy (in the form of heat) removed to energy consumed is very low, around 10-15%. In furnaces the ratio of energy added to energy consumed is around 90%, which was pretty good until the emergence of hea…

> In A/Cs the ratio of energy (in the form of heat) removed to energy consumed is very low, around 10-15%.

Why is that?

Obviously I'm referring to efficiency in practice. In theory, heating and cooling should be equally efficient for a perfect heat pump, right?

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