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I’d pay a premium for a solid state AC or heat pump. It’s absurd how much they cost to install. And I don’t get why replacing one is an all day job for three p

I’d pay a premium for a solid state AC or heat pump. It’s absurd how much they cost to install. And I don’t get why replacing one is an all day job for three people. There should be standard connections they just plug into. Like a dishwasher.

antisthenes 3y ago
What in the world are you talking about? The hardest part of installing AC is the ductwork. Swapping out the outside + inside heat exchanger unit is a 1-person 3-4-hour job. Sorry if some HVAC company scammed you, but it's definitely not a 3 person job, unless we're talking some commercial building 5+ ton units.
- bilsbie 3y ago
  Just residential. One guy working in the outside part and one on the inside and one helper. Seemed like a lot of wiring and charging things. I didn’t think it should take that long either. Their price was in line with other quotes. I wasn’t paying by the hour or anything.
- ChatGTP 3y ago
  If you're system is hooked up to "floor heating", hydraulic stuff that runs under your floor it's still a one man job but can be a little bit harder to do.
- aurizon 3y ago
  There are a few zero pipe mini-splits. They hang across the window frame and use 1 inch of height with an inside bidirectional radiator and an external one, SCrewed down to the window jamb and connected to 120/240 volts internally. They resemble a window A/C, but the rads are below the window level and are wider and less deep. I am getting a few next year. This is one of many. https://www.greenbuildingadvisor.com/article/startup-promises-window-mounted-heat-pump-by-next-year https://www.greenbuildingadvisor.com/article/startup-promise...
- magicalhippo 3y ago
  We got a Mitsubishi Kaiteki[1], which is a mini-split from what I can gather. We just call them "air to air heat pumps" here in Norway. Anyway, the install itself was about $400, took one guy a few hours like you said. Another $200 for the electrician which had to hook up a dedicated circuit for it as per regulations, though he did it as part of a larger job so would have been $300 as a stand-alone deal. Total it was $2200. This is considered a premium unit over here, we could have gotten something cheaper but alas looks matter. Thing is supposedly guaranteed to provide COP of 2 down to -25C. We've had such low temps here a several times (in fact past week has been around -15 to -17C with a harsh 85% humidity, biting!) and we've never had to turn on the backup floor heating so far. Though you can definitely hear it working harder when it's that cold. [1]: https://mee.no/privat/produktkategori/luft-luft-varmepumper/kaiteki/ https://mee.no/privat/produktkategori/luft-luft-varmepumper/...
  - pjc50 3y ago
    What does the inside/outside setup look like for those? One unit on the inside, one on the outside, short plumbing run between?
    - magicalhippo 3y ago
      Yeah, you can see the two units here[1], also has dimensions for them under specifications. The plumbing is covered by a plastic cover, both for protection and looks. We have a small wooden "shed" for the outside unit[2], to protect it from getting clogged up with snow and also to make it less visible. Both the plastic cover and the "shed" is painted in the same color as our home, so blends in nicely. [1]: https://www.varmepumpeservice.no/mitsubishi-kaiteki-6300-hvit-1 https://www.varmepumpeservice.no/mitsubishi-kaiteki-6300-hvi... [2]: https://mee.no/produkt/varmepumpehus-impregnert/ https://mee.no/produkt/varmepumpehus-impregnert/
- tempestn 3y ago
  At least in our case the inside unit was massive. It was definitely a two person job to get it into its location in our crawlspace.
NavinF 3y ago
There are many YouTube videos of people installing heat pumps by themselves in a few hours. Your quotes are likely inflated by permit requirements and price discrimination. Keep in mind that heating with natgas is way cheaper for most Americans so the HVAC guys know that you have money to spare
- Scoundreller 3y ago
  > Keep in mind that heating with natgas is way cheaper for most Americans so the HVAC guys know that you have money to spare Where natgas can lose its lustre is on delivery/standing charges. And sometimes transmission and distribution charges (those usually scale with use, but can make cheap gas expensive). On smaller/well insulated homes, the fixed gas connection cost can really improve heat pumps economics if you're already on electric grid and can cutoff gas entirely. Or have an aux source like oil/propane/wood. The fun part is that utilities are generally a regulated rate of return business, so as users disconnect, the base costs go up on the remaining subscribers. Pushing more subscribers to disconnect from the gas grid, pushing cost up on the remaining... I wouldn't invest in natgas distribution companies in mild-moderate climates.
  - NavinF 3y ago
    AFAIK the fixed cost of keeping a gas line active is ~$4/mo in most places and many homes still need gas for stoves and dryers so I expect ~0% of Americans to cancel gas in the next decade Of course the maintenance costs and the amortized cost of infra is a much larger proportion of the gas bill, but the utility can't pass that on to customers as a fixed monthly fee. Gov't tariffs usually make that illegal
    - Scoundreller 3y ago
      CAD$24 or ~US$18 in most of Ontario Canada. But that's every month, so could be 10% or 100% of your bill. But oddly gas stoves and especially gas dryers aren't that common here, despite gas being cheaper than electric (historically, dunno about today).
hijinks 3y ago
I was quoted 10k a head unit to install mini-splits in a home in the colorado mountains. I needed 8 head units. It was nothing but "only rich people are buying these right now so lets cash in" pricing
- wil421 3y ago
  Would a heat pump work? 8 mini-splits sounds like way too. Mini-splits are also the cheaper option, surprised they cost $10k. A heat pump in my area wouldn't be too much more than $10k (excluding duct work).
- alchemist1e9 3y ago
  For 8 units? That sounds like good price.
  - Loughla 3y ago
    That would be $80,000 total?
  - bill38 3y ago
    10k per unit
  - happytiger 3y ago
    8 zone systems from Mitsubishi are 8-10k https://www.acdirect.com/ductless-mini-splits/8-zone-mini-split-ac-systems.html https://www.acdirect.com/ductless-mini-splits/8-zone-mini-sp... 80k is hilarious. That’s a 70k install for pulling lines, charging them and maybe an electrical run and pad. Even if you have to buy two or three systems the price is laughable.
- amluto 3y ago
  Find another contractor. I got three heads in the Bay Area for around $8500 total. The only caveat was that this didn’t include patching the walls.
- quesera 3y ago
  For that size of a system, ducted is less expensive and more reliable than mini-splits (but it is not always practical to install). A large multi-zone installation (~20 rooms) with all-new duct work and natural gas backup in a major cold-weather US metro can be about $40K.
deedubaya 3y ago
I was just last month quoted 15-23k for an install in the mountains of Idaho. I got a competitive quote and the price was similar. If it cut my electricity bill in half it would take 10-20 years to break even.
- tempestn 3y ago
  For a mini-split system, or central heat pump? Do you have existing ducts? What's the square footage? We recently upgraded our central heat pump as the old one died after 15 years or so. IIRC the total was $13k CAD, so around 9-10k USD, which included indoor and outdoor units for a roughly 3000sqft house, with installation. But all the ducting was there already, so it was just a matter of swapping out old unit for new. (Got some nice government grants too, so it was only a few k out of pocket.)
  - deedubaya 3y ago
    Central, augmenting existing electric forced air with existing ducts. Similar sized home.
    - tempestn 3y ago
      Wow, surprisingly expensive then. It might be worth getting more quotes if you're still interested. I found the ones we got here varied pretty widely, so you may have just gotten a couple of high ones.
- VBprogrammer 3y ago
  > If it cut my electricity bill in half it would take 10-20 years to break even. Presumably there is a useful life on your existing heating system. At some point it would need replacing?
  - speed_spread 3y ago
    Assuming electricity is already used for heating, baseboards heaters are just big resistors and have basically unlimited life.
c_o_n_v_e_x 3y ago
>And I don’t get why replacing one is an all day job for three people. Let's go through the whole process. You need a system changeout for a ducted central HVAC system. Someone comes over and gives a bid. You accept. Your HVAC person needs to go to a supply house and purchase all of the parts and bring them to your residence in a vehicle than can hold everything. Assuming you have an existing system, the refrigerant has to be recovered with a special recovery pump. You can't just dump refrigerant to the atmosphere. This can take an hour or so. You've got to find the right breaker(s) and then turn them off. Disconnect the power wiring. Then you've gotta disassemble the old equipment and remove it. Next you move in the new equipment. Rewire the power. Rewire the controls wiring. Assemble the new equipment, assemble plenums, cut holes in plenums, install collars, run duct work from plenums to boxes, attach and seal all ductwork with tape, mastic, etc. You need to strap up the ducts to properly. You still need to solder the line set at this point. If your new equipment runs on a different type of refrigerant, in all likelihood, you need a new line set (the copper tubes that transport the refrigerant to the evaporator from the condenser and back). Why? Different refrigerants have different working pressures, may require higher flow, etc. Once you're lineset is soldered back to a condenser AND the evaporator, then you must pull a vacuum on the system to A) remove non condensable gases and B) dehydrate the system so that your refrigerants are clean and the system is efficient. Properly pulling a vacuum is very time consuming. Most guys start by pulling an initial vacuum and then shutting in the system to do a leak test. You may find a leak, this takes more time. You need to repair the leak, then pull another vacuum. Once you past leak test, you pull a final vacuum. You don't want installers skimping on this step as this affects the overall lifespan of the system and system efficiency. At this point, you can start the system (I've had new units dead from the factory... groan), then you can start charging the system with refrigerant. You need to let the system run for a bit to monitor pressures, monitor return air and supply air temps, etc. Once the job is done, all of the old equipment and refrigerant has to be taken to specific places for proper disposal. Everything above is a generally straight forward non-permitted replacement. Other installs may require new circuits run to the equipment, natural gas lines, etc. Some jobs require permits so now the HVAC person has to go to the city, apply for permits, submit plans, have the work inspected, etc. There's quite a bit of work that has to be done which requires transportation, disposal, specialized knowledge, expensive tools, employees, and most important of all, insurance! Also, keep in mind that a lot of this work is done at temperatures FAR beyond ambient AND in low clearance areas, usually filled with itchy fiberglass. This work is also done with risk of bodily harm (electrocution, poisoning (hello phosgene gas), suffocation (asphyxiation from refrigerants), heat stroke, falls from height, exposure to industrial pollutants like asbestos, burns).
pjc50 3y ago
Replacing like for like should be a fairly easy job. But replacing between different systems does seem to be a nightmare. It's interesting that Americans are retrofitting them into HVAC systems, while in the UK we're trying to retrofit into natgas/water based systems, and seemingly the Scandinavians have gone for .. I'm not sure but it seems cheaper? I upgraded to a "hybrid" system because it was the least cost / minimal change, so I continue to have natgas hot water which can optionally heat the radiators if the control unit deems it economic (no, it doesn't have dynamic pricing). And that was still £15,000 even though it could reuse all the existing radiators. Apparently having 8mm "microbore" copper plumbing is a problem for "low temperature" heat pump systems, because they rely on higher throughput. At the end of winter I'll write-up my bills and evaluate the experience.
- kwhitefoot 3y ago
  In Scandinavia we use air to air heat pumps. We generally don't have central heating of any kind so we aren't so tempted to try to shoehorn the heat pump into a system based on hot water. Air to air is much cheaper and is more efficient because it doesn't need to raise the temperature of the working fluid so much and doesn't require a big fluid to water heat exchanger. I'm having a Toshiba Polar 35 heat pump installed soon. Nominal output 3.5 kW, maximum output 7 kW. The total cost is 28 kNOK, about 2.6 kUSD, 2 kGBP. Should be enough for the whole ground floor of about 80 square metres.
  - khimaros 3y ago
    which refrigerant is used in this?
    - kwhitefoot 3y ago
      R-32 [1] "Difluoromethane, also called difluoromethylene, HFC-32 Methylene Fluoride or R-32, " [2] [1] https://www.toshibavarmepumper.no/globalassets/inriver/resources/r106513-datablad-energietikett-toshiba-polar-25.pdf https://www.toshibavarmepumper.no/globalassets/inriver/resou... [2] https://en.wikipedia.org/wiki/Difluoromethane https://en.wikipedia.org/wiki/Difluoromethane
wojciii 3y ago
(sorry about being a bit off-topic, but I got triggered by standard). Funny that you mention standards. It should be possible to swap out the multimedia device in your car with a new one. It should use a standard connector and form factor. So I guess we should start working on standards that would improve our world and make reuse possible instead of buying even more new shit all the time.
amluto 3y ago
A dishwasher is a single object. A heat pump has an indoor part, and outdoor part, and (at least) two tubes between them. Those tubes can carry one of several refrigerants (with attendant oil contamination), water, or glycol solutions. Or occasionally air. There are quite a few standards for connecting all of these, although the standards for air appear to literally be duct tape [0] or sticky goop called mastic. And refrigerant, which is the most common choice, is under high pressure and needs special handling. [0] I mean real duct tape: the UL181 stuff. The world is full of kinds of tape, and many of them are excellent. I’ve never seen anything I would call excellent duct tape. It doesn’t conform well to irregularities, and it doesn’t seem to have anywhere near the stretchiness required to actually seal the inherently curved gap between round ducts.

antisthenes 3y ago

What in the world are you talking about? The hardest part of installing AC is the ductwork. Swapping out the outside + inside heat exchanger unit is a 1-person 3-4-hour job. Sorry if some HVAC company scammed you, but it's definitely not a 3 person job, unless we're talking some commercial building 5+ ton units.

bilsbie 3y ago
Just residential. One guy working in the outside part and one on the inside and one helper. Seemed like a lot of wiring and charging things. I didn’t think it should take that long either. Their price was in line with other quotes. I wasn’t paying by the hour or anything.
ChatGTP 3y ago
If you're system is hooked up to "floor heating", hydraulic stuff that runs under your floor it's still a one man job but can be a little bit harder to do.
aurizon 3y ago
There are a few zero pipe mini-splits. They hang across the window frame and use 1 inch of height with an inside bidirectional radiator and an external one, SCrewed down to the window jamb and connected to 120/240 volts internally. They resemble a window A/C, but the rads are below the window level and are wider and less deep. I am getting a few next year. This is one of many. https://www.greenbuildingadvisor.com/article/startup-promises-window-mounted-heat-pump-by-next-year https://www.greenbuildingadvisor.com/article/startup-promise...
magicalhippo 3y ago
We got a Mitsubishi Kaiteki[1], which is a mini-split from what I can gather. We just call them "air to air heat pumps" here in Norway. Anyway, the install itself was about $400, took one guy a few hours like you said. Another $200 for the electrician which had to hook up a dedicated circuit for it as per regulations, though he did it as part of a larger job so would have been $300 as a stand-alone deal. Total it was $2200. This is considered a premium unit over here, we could have gotten something cheaper but alas looks matter. Thing is supposedly guaranteed to provide COP of 2 down to -25C. We've had such low temps here a several times (in fact past week has been around -15 to -17C with a harsh 85% humidity, biting!) and we've never had to turn on the backup floor heating so far. Though you can definitely hear it working harder when it's that cold. [1]: https://mee.no/privat/produktkategori/luft-luft-varmepumper/kaiteki/ https://mee.no/privat/produktkategori/luft-luft-varmepumper/...
- pjc50 3y ago
  What does the inside/outside setup look like for those? One unit on the inside, one on the outside, short plumbing run between?
  - magicalhippo 3y ago
    Yeah, you can see the two units here[1], also has dimensions for them under specifications. The plumbing is covered by a plastic cover, both for protection and looks. We have a small wooden "shed" for the outside unit[2], to protect it from getting clogged up with snow and also to make it less visible. Both the plastic cover and the "shed" is painted in the same color as our home, so blends in nicely. [1]: https://www.varmepumpeservice.no/mitsubishi-kaiteki-6300-hvit-1 https://www.varmepumpeservice.no/mitsubishi-kaiteki-6300-hvi... [2]: https://mee.no/produkt/varmepumpehus-impregnert/ https://mee.no/produkt/varmepumpehus-impregnert/
tempestn 3y ago
At least in our case the inside unit was massive. It was definitely a two person job to get it into its location in our crawlspace.

NavinF 3y ago

There are many YouTube videos of people installing heat pumps by themselves in a few hours. Your quotes are likely inflated by permit requirements and price discrimination. Keep in mind that heating with natgas is way cheaper for most Americans so the HVAC guys know that you have money to spare

Scoundreller 3y ago
> Keep in mind that heating with natgas is way cheaper for most Americans so the HVAC guys know that you have money to spare Where natgas can lose its lustre is on delivery/standing charges. And sometimes transmission and distribution charges (those usually scale with use, but can make cheap gas expensive). On smaller/well insulated homes, the fixed gas connection cost can really improve heat pumps economics if you're already on electric grid and can cutoff gas entirely. Or have an aux source like oil/propane/wood. The fun part is that utilities are generally a regulated rate of return business, so as users disconnect, the base costs go up on the remaining subscribers. Pushing more subscribers to disconnect from the gas grid, pushing cost up on the remaining... I wouldn't invest in natgas distribution companies in mild-moderate climates.
- NavinF 3y ago
  AFAIK the fixed cost of keeping a gas line active is ~$4/mo in most places and many homes still need gas for stoves and dryers so I expect ~0% of Americans to cancel gas in the next decade Of course the maintenance costs and the amortized cost of infra is a much larger proportion of the gas bill, but the utility can't pass that on to customers as a fixed monthly fee. Gov't tariffs usually make that illegal
  - Scoundreller 3y ago
    CAD$24 or ~US$18 in most of Ontario Canada. But that's every month, so could be 10% or 100% of your bill. But oddly gas stoves and especially gas dryers aren't that common here, despite gas being cheaper than electric (historically, dunno about today).

hijinks 3y ago

I was quoted 10k a head unit to install mini-splits in a home in the colorado mountains. I needed 8 head units. It was nothing but "only rich people are buying these right now so lets cash in" pricing

wil421 3y ago
Would a heat pump work? 8 mini-splits sounds like way too. Mini-splits are also the cheaper option, surprised they cost $10k. A heat pump in my area wouldn't be too much more than $10k (excluding duct work).
alchemist1e9 3y ago
For 8 units? That sounds like good price.
- Loughla 3y ago
  That would be $80,000 total?
- bill38 3y ago
  10k per unit
- happytiger 3y ago
  8 zone systems from Mitsubishi are 8-10k https://www.acdirect.com/ductless-mini-splits/8-zone-mini-split-ac-systems.html https://www.acdirect.com/ductless-mini-splits/8-zone-mini-sp... 80k is hilarious. That’s a 70k install for pulling lines, charging them and maybe an electrical run and pad. Even if you have to buy two or three systems the price is laughable.
amluto 3y ago
Find another contractor. I got three heads in the Bay Area for around $8500 total. The only caveat was that this didn’t include patching the walls.
quesera 3y ago
For that size of a system, ducted is less expensive and more reliable than mini-splits (but it is not always practical to install). A large multi-zone installation (~20 rooms) with all-new duct work and natural gas backup in a major cold-weather US metro can be about $40K.

deedubaya 3y ago

I was just last month quoted 15-23k for an install in the mountains of Idaho. I got a competitive quote and the price was similar. If it cut my electricity bill in half it would take 10-20 years to break even.

tempestn 3y ago
For a mini-split system, or central heat pump? Do you have existing ducts? What's the square footage? We recently upgraded our central heat pump as the old one died after 15 years or so. IIRC the total was $13k CAD, so around 9-10k USD, which included indoor and outdoor units for a roughly 3000sqft house, with installation. But all the ducting was there already, so it was just a matter of swapping out old unit for new. (Got some nice government grants too, so it was only a few k out of pocket.)
- deedubaya 3y ago
  Central, augmenting existing electric forced air with existing ducts. Similar sized home.
  - tempestn 3y ago
    Wow, surprisingly expensive then. It might be worth getting more quotes if you're still interested. I found the ones we got here varied pretty widely, so you may have just gotten a couple of high ones.
VBprogrammer 3y ago
> If it cut my electricity bill in half it would take 10-20 years to break even. Presumably there is a useful life on your existing heating system. At some point it would need replacing?
- speed_spread 3y ago
  Assuming electricity is already used for heating, baseboards heaters are just big resistors and have basically unlimited life.

c_o_n_v_e_x 3y ago

>And I don’t get why replacing one is an all day job for three people. Let's go through the whole process. You need a system changeout for a ducted central HVAC system. Someone comes over and gives a bid. You accept. Your HVAC person needs to go to a supply house and purchase all of the parts and bring them to your residence in a vehicle than can hold everything. Assuming you have an existing system, the refrigerant has to be recovered with a special recovery pump. You can't just dump refrigerant to the atmosphere. This can take an hour or so. You've got to find the right breaker(s) and then turn them off. Disconnect the power wiring. Then you've gotta disassemble the old equipment and remove it. Next you move in the new equipment. Rewire the power. Rewire the controls wiring. Assemble the new equipment, assemble plenums, cut holes in plenums, install collars, run duct work from plenums to boxes, attach and seal all ductwork with tape, mastic, etc. You need to strap up the ducts to properly. You still need to solder the line set at this point. If your new equipment runs on a different type of refrigerant, in all likelihood, you need a new line set (the copper tubes that transport the refrigerant to the evaporator from the condenser and back). Why? Different refrigerants have different working pressures, may require higher flow, etc. Once you're lineset is soldered back to a condenser AND the evaporator, then you must pull a vacuum on the system to A) remove non condensable gases and B) dehydrate the system so that your refrigerants are clean and the system is efficient. Properly pulling a vacuum is very time consuming. Most guys start by pulling an initial vacuum and then shutting in the system to do a leak test. You may find a leak, this takes more time. You need to repair the leak, then pull another vacuum. Once you past leak test, you pull a final vacuum. You don't want installers skimping on this step as this affects the overall lifespan of the system and system efficiency. At this point, you can start the system (I've had new units dead from the factory... groan), then you can start charging the system with refrigerant. You need to let the system run for a bit to monitor pressures, monitor return air and supply air temps, etc. Once the job is done, all of the old equipment and refrigerant has to be taken to specific places for proper disposal. Everything above is a generally straight forward non-permitted replacement. Other installs may require new circuits run to the equipment, natural gas lines, etc. Some jobs require permits so now the HVAC person has to go to the city, apply for permits, submit plans, have the work inspected, etc. There's quite a bit of work that has to be done which requires transportation, disposal, specialized knowledge, expensive tools, employees, and most important of all, insurance! Also, keep in mind that a lot of this work is done at temperatures FAR beyond ambient AND in low clearance areas, usually filled with itchy fiberglass. This work is also done with risk of bodily harm (electrocution, poisoning (hello phosgene gas), suffocation (asphyxiation from refrigerants), heat stroke, falls from height, exposure to industrial pollutants like asbestos, burns).

pjc50 3y ago

Replacing like for like should be a fairly easy job. But replacing between different systems does seem to be a nightmare. It's interesting that Americans are retrofitting them into HVAC systems, while in the UK we're trying to retrofit into natgas/water based systems, and seemingly the Scandinavians have gone for .. I'm not sure but it seems cheaper? I upgraded to a "hybrid" system because it was the least cost / minimal change, so I continue to have natgas hot water which can optionally heat the radiators if the control unit deems it economic (no, it doesn't have dynamic pricing). And that was still £15,000 even though it could reuse all the existing radiators. Apparently having 8mm "microbore" copper plumbing is a problem for "low temperature" heat pump systems, because they rely on higher throughput. At the end of winter I'll write-up my bills and evaluate the experience.

kwhitefoot 3y ago
In Scandinavia we use air to air heat pumps. We generally don't have central heating of any kind so we aren't so tempted to try to shoehorn the heat pump into a system based on hot water. Air to air is much cheaper and is more efficient because it doesn't need to raise the temperature of the working fluid so much and doesn't require a big fluid to water heat exchanger. I'm having a Toshiba Polar 35 heat pump installed soon. Nominal output 3.5 kW, maximum output 7 kW. The total cost is 28 kNOK, about 2.6 kUSD, 2 kGBP. Should be enough for the whole ground floor of about 80 square metres.
- khimaros 3y ago
  which refrigerant is used in this?
  - kwhitefoot 3y ago
    R-32 [1] "Difluoromethane, also called difluoromethylene, HFC-32 Methylene Fluoride or R-32, " [2] [1] https://www.toshibavarmepumper.no/globalassets/inriver/resources/r106513-datablad-energietikett-toshiba-polar-25.pdf https://www.toshibavarmepumper.no/globalassets/inriver/resou... [2] https://en.wikipedia.org/wiki/Difluoromethane https://en.wikipedia.org/wiki/Difluoromethane

wojciii 3y ago

(sorry about being a bit off-topic, but I got triggered by standard). Funny that you mention standards. It should be possible to swap out the multimedia device in your car with a new one. It should use a standard connector and form factor. So I guess we should start working on standards that would improve our world and make reuse possible instead of buying even more new shit all the time.

amluto 3y ago

A dishwasher is a single object. A heat pump has an indoor part, and outdoor part, and (at least) two tubes between them. Those tubes can carry one of several refrigerants (with attendant oil contamination), water, or glycol solutions. Or occasionally air. There are quite a few standards for connecting all of these, although the standards for air appear to literally be duct tape [0] or sticky goop called mastic. And refrigerant, which is the most common choice, is under high pressure and needs special handling. [0] I mean real duct tape: the UL181 stuff. The world is full of kinds of tape, and many of them are excellent. I’ve never seen anything I would call excellent duct tape. It doesn’t conform well to irregularities, and it doesn’t seem to have anywhere near the stretchiness required to actually seal the inherently curved gap between round ducts.