Heat Pumps – The Well-Tempered Future of A/Cs • Hacker News Board

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

#391

Post by simonblack » Thu, Jul 06, 2023, 8:50 PM UTC

sokoloff wrote: post #361

simonblack wrote: post #304

Earlier quoted context omitted.

I don’t want a 2.5-3 hour dry cycle ??? That's excessively long. Our heat-pump dryer takes about 20-30 minutes to do one of our loads.* The dryer invariably ends up waiting for the washer to finish. * Our loads aren't excessively tight in the machine. You have to allow room for the clothes to tumble loosely thus allowing lots of surface area for evaporation.

I quickly googled for “how long does a heat pump dryer cycle take” and got several answers in the 2.5-3 hour range, which is long enough to provoke complaints. Obviously, if every heat pump dryer took 20-30 minutes, you would not hear complaints about that (that’s much faster than my gas dryer).

Power-input. US dryers would typically work on 110 volts mains. Those similar dryers in the EU or Australia are working on 220 volts mains. Took me a while to click on why the great differences in working-times. 15 amps wiring in the US means 1650 watts, the same wiring in EU is 3300 watts.

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

#392

Post by samtho » Thu, Jul 06, 2023, 8:51 PM UTC

nerdbert wrote: post #258

thrashh wrote: post #240

Earlier quoted context omitted.

Well the word “efficient” always needs context. You have to define the goal first before you can define efficiency. OP said electrical efficient so the goal is conversion of electricity to heat and it’s 100% efficient. Even an electric heater compared to a propane heater is more electrically and energy efficient, but it’s not as storage-efficient (because fossil fuel gases have much higher energy density per volume A…

> OP said electrical efficient so the goal is conversion of electricity to heat and it’s 100% efficient. I am not an engineer and I am only nitpicking to have fun, so don't engage me if it's not fun, but doesn't some of the energy go into degradation of the materials used to build the device?

Yes, but energy is not consumed by that process, it is only converted into heat. The degradation usually is a result of the heat produced. If we’re talking about mater to energy transitions, we need to start talking about special relativity.

I said 100% electrical efficiency because from the prongs of the plug, through the conductors in the appliance cord, the rheostat, all electrical connection and contact points, and of course the hearing element itself all will product heat as a consequence of electricity flowing through, and being resisted by, it’s various components.

It was pointed out that this does not mean “energy bill efficient” which is totally correct: this whole thing is a somewhat silly thought experiment to consider what it really means for something to be efficient.

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

#393

Post by brewdad » Thu, Jul 06, 2023, 9:04 PM UTC

nerdbert wrote: post #228

phpisthebest wrote: post #59

Earlier quoted context omitted.

>>Same with cold weather, I 100% disagree with this... Heat is made by everything, waste heat is a byproduct of all modern things, and there are TONS of easy low cost ways to make heat even it is just as simple as burning something. Also the body makes head naturally so adding layers to trap this heat does not require continual inputs from an outside resource Cooling on the other hand is MUCH harder, and electricity…

> Cooling on the other hand is MUCH harder, and electricity is really the only avenue to make cooling. Gas-powered fridges and coolers have existed for about two hundred years and are still a normal technology today - often used for camping and off-grid life. Here's a whole bunch of propane fridges for your viewing pleasure: https://bensdiscountsupply.com/collections/propane-refrigera...

And yet the propane stove, designed to heat, is about 1,000 times more common.*

* citation needed.

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

#394

Post by sokoloff » Thu, Jul 06, 2023, 9:22 PM UTC

simonblack wrote: post #391

sokoloff wrote: post #361

Earlier quoted context omitted.

I quickly googled for “how long does a heat pump dryer cycle take” and got several answers in the 2.5-3 hour range, which is long enough to provoke complaints. Obviously, if every heat pump dryer took 20-30 minutes, you would not hear complaints about that (that’s much faster than my gas dryer).

Power-input. US dryers would typically work on 110 volts mains. Those similar dryers in the EU or Australia are working on 220 volts mains. Took me a while to click on why the great differences in working-times. 15 amps wiring in the US means 1650 watts, the same wiring in EU is 3300 watts.

That's not it. Electric dryers in the US are overwhelmingly 240V and on a 30A breaker. At 80% of rated, that's 5.7kW available. (Gas dryers here are typically on a 120V, 15A circuit.)

Every heat pump dryer I looked at on the home center's website is 240V. (Edit: I found one Miele on another home center that was a 15A@120V.)

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

#395

Post by autoexec » Thu, Jul 06, 2023, 9:24 PM UTC

MivLives wrote: post #274

ashayh wrote: post #232

The article mentions the most important point towards the end: “The better you insulate, the less heat you need in the first place,” No heat pump will help if your house is leaky or under insulated.

The worst is when you rent. I live in an area that doesn't really expect much cold or heat. All the windows are single paned. The sun beating on the roof raises the top floor to the outside temperature plus 5 degrees. I can't fix any of it because I'm only here for a few years.

It's kind of nice in cool climates. I've rented places where I never had to turn on the heat once all winter thanks to all the heat coming up from lower floors. Temps were almost always above 60F and usually above 65 which is perfectly fine for cozy sweaters and blankets.

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

#396

Post by willio58 » Fri, Jul 07, 2023, 1:48 AM UTC

xenadu02 wrote: post #275

nsxwolf wrote: post #193

When I needed a new air conditioner a couple years ago I was quoted $17,000 for a heat pump. I can only guess at that point whatever energy cost savings it would bring would never be realized within the service life of the system. I went with a $6000 standard replacement AC unit.

Unless the installer was ripping you off those were not comparable units. I've seen the manufacturer MSRP sheets and the cost difference between heat pump and non-heat pump for the same unit is small. Nowhere near enough to account for $11k. It sounds like they quoted you a bottom of the range 11 SEER A/C vs a top of the line multi-stage compressor variable speed blower 19 SEER heat pump system. Those are not the sam…

Was just going to say I’ve been looking at heat pumps myself and I can’t imagine what the quoted heat pump was that it would cost that much more.

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

#397

Post by gooseyman » Fri, Jul 07, 2023, 3:20 AM UTC

gizmo686 wrote: post #387

glogla wrote: post #341

Earlier quoted context omitted.

I think the consensus on why heat pumps _should_ be the future is that you can power them with low carbon electricity, as opposed to literally world destroying natural gas.

A quick Google search says that natural gas -> electricity has an efficiency of about 44%, with an additional 5% loss during transmission. Lets call this about 40% efficiency for getting energy from natural gas to your electric heat pump. A heat pump operating at 250% efficiency will use just as much natural gas as a furnace operating at 100% efficiency. Modern heat pumps can often exceed 250% efficiency, making them…

I made a note for myself to go do this math. You beat me to it and answered the question. Thank you :)

I vaguely recall I did some back of envelope math a couple years back and determined that a natural gas powered heat pump was actually more efficient (in terms of emissions) based on my grid power source mix. Solar breaks that equation obviously.

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

#398

Post by cycrutchfield » Fri, Jul 07, 2023, 5:44 AM UTC

Alupis wrote: post #226

cycrutchfield wrote: post #197

Earlier quoted context omitted.

Induction cooktops heat faster and more evenly than gas

There's many good reasons induction cooktops aren't used in commercial kitchens... and those reasons apply for home-cooks as well.

Inertia? Ignorance?

I've seen induction cooktops in commercial kitchens before, maybe they were just being stupid?

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

#399

Post by throw0101a » Fri, Jul 07, 2023, 11:14 AM UTC

Maxion wrote: post #178

throw0101a wrote: post #139

Earlier quoted context omitted.

Perhaps think of "heat pump" as something that can (also) bring heat into a building, whereas A/C generally (only) removes heat from it.

An A/C is a heat pump. Stop trying to change existing terminology

> An A/C is a heat pump. Stop trying to change existing terminology

I am not trying to change existing terminology, I am using existing terminology. Air conditioners (A/C) are devices sold to only cool a house:

* https://www.lennox.com/products/heating-cooling/air-conditio...

* https://www.carrier.com/residential/en/us/products/air-condi...

* https://www.trane.com/residential/en/products/air-conditione...

Heat pumps are devices sold to both cool and heat a house:

* https://www.lennox.com/products/heating-cooling/heat-pumps

* https://www.carrier.com/residential/en/us/products/heat-pump...

* https://www.trane.com/residential/en/products/heat-pumps/

* https://www.ehpa.org/about-heat-pumps/

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

#400

Post by rainbowzootsuit » Fri, Jul 07, 2023, 12:01 PM UTC

nsxwolf wrote: post #193

When I needed a new air conditioner a couple years ago I was quoted $17,000 for a heat pump. I can only guess at that point whatever energy cost savings it would bring would never be realized within the service life of the system. I went with a $6000 standard replacement AC unit.

The difference of heat pump an AC is pretty much just a reversing valve, so as others have noted this is probably not an equivalent unit.

One caveat to that is if you have a furnace, they may have wanted to install a full new air handler and run electric emergency heat vs just swapping the coil and condenser.

You can configure a heat pump coil with a furnace as the emergency heat but it might take some more thinking than an off the shelf AHU condenser pairing that maybe the contractor wasn't comfortable with doing that.