4 ms·

A world map and efficiency/consumption would be nice, so we can see where in the world heat pumps are most effective.

akira2501 2y ago
> so we can see where in the world heat pumps are most effective. They're not efficient when the temperature drops below a certain point. This is predictable and based on system design criteria. It doesn't mean it's not effective, it's just that it wouldn't be a reliable source of heating year round. It may still make a worthwhile addition to another system, or combined with several other upgrades, may become an acceptable single solution.
- brnt 2y ago
  Reliable and efficient are different things. A solution that is inefficient two week a year but efficient the rest can still be cheaper than some hybrid setup. If it is expected it simply won't work a few weeks a year, sure, that's clearly not effective.
  - akira2501 2y ago
    You've summed my points exactly while missing the major one. You don't need monitoring to determine any of this. You can just look at the construction of the building and the weather charts and you're done with the "will a heat pump be effective?" question.
    - sokoloff 2y ago
      Sort of. My house is 100 years old and was built without insulation (some rooms were insulated through remodels over the years). It uses water circulation and cast iron radiators and stays comfortable with my ancient cast iron boiler and 180°F water. To know whether a heat pump (air-to-water) can replace that boiler effectively and maintain comfort, I had to find out whether the house would be comfortable with water temps of 135°F or so. Is there an amount of “that’s just looking at the building construction” to make that analysis? I think maybe technically yes, but practically no. As it was, to get an answer, I abused my old boiler by turning the water temps down (causing condensation and slow damage [planning to replace it anyway]) and seeing what happened on cold days.
      - wenebego 2y ago
        You didnt need to do that, though. It peobably wouldve been easier to use manual j (or some software) to estimate the heat loads in the house, with given set points, using weather station data.
        sokoloff 2y ago
        I can find/closely estimate the heat loss easily. What is much harder to find is the heat gain/transfer into the room from 1920s cast iron radiators at 135°F flow and the balance of the system flow temperatures at those 45°F lower flow temps than originally designed. Then, because the answer is almost always going to be "yeah, it's going to be really close...", I felt well-advised to prove it via experimentation rather than commit to changing the heating plant to a system that could not provide 150°F flow temperature.
        rainbowzootsuit 2y ago
        If you are ok with IP units the formula is 500 * GPM * delta-T for water as the fluid.
        sokoloff 2y ago
        The question is not about the general hydronic heating formula [nor manual J heat loss estimations], but rather "what will the delta T of the rad in this particular room, in this piping network [it's a converted gravity feed system, now being a pumped], using 69°F room temp and 135°F leaving water temp from the heat source?"
        brnt 2y ago
        For the, for lack of a better word, standard radiators there is a formula with a dT^4. But I totally agree, this isnt all that straighforward, given that for the dozons of installers, experts and home owners I have spoken, Ive heard dozens+1 methods for estimating. Estimating heat loss from a given building and estimating power output of a given installation of radiators, very few people seem to be able to calculate that. If your heater can go low (mine bottoms out at 50 unfortunately), by far the easiest is to just test.
    - brnt 2y ago
      Yeah no. It's become a bit of a hobby of mine, heatpumps. If I ask 5 experts/installers to take a look at a building I'll get 6 estimates, varying wildly. Plus, installers are still consistently over dimensioning and thus killing your sCOP, because they don't want customers to complain 'its slow to heat' and so on. Calculating the heat loss of a house is really not trivial. Often you'll have no idea of the materials used or the quality of installation, and not really a way of finding out unless your up for some destructive investigation.
- KeplerBoy 2y ago
  Heat pumps are reliable even in unfavorable conditions. You will have to invest a lot more electrical energy and you might not be pumping heat as much as just converting electrical energy to heat, but let's not spread the myth that a heat pump will leave you freezing once outside temperatures drops below a certain threshold.
  - akira2501 2y ago
    A heat pump without a resistive heating /option/ will absolutely cease working below a certain temperature. They do, for whatever reason, sell systems that way in some regions.
    - KeplerBoy 2y ago
      That's true. Strictly speaking a heat pump doesn't need a resistive heating element, but I've never heard of units not containing that feature. After all it's dirt cheap and enables the reliability, we're discussing here.
    - jwr 2y ago
      Perhaps, instead of spreading FUD, it would be worthwhile to mention these "certain temperatures", so that people can make an educated decision of whether it applies to them at all. I'm looking at the datasheet for my Fujitsu system and it is specified to work down to -25°C. Does it lose efficiency when it's cold outside? Sure. But guess what, it's still more effective than resistive heating! I am starting from a SCOP of 4.89.
      - bluGill 2y ago
        The UNIT is specified to work down to -25. The SYSTEM includes the building it is installed in: the local climate, the size and heat loss of the building, how the install was done, and likely some other factors I'm not aware of. If you get less heat from the unit than you lose via other means the system isn't working even though it is delivering heat.
      - akira2501 2y ago
- HPsquared 2y ago
  Ground source heat pumps don't have the icing problem. More expensive to install, though.
  - ClumsyPilot 2y ago
    I think this could be Resolved by scale, but that’s precisely what the west is really bad at If we standardised ground source heat pumps as a must have all multi dwelling developments like apartment blocks and rows of terraced houses who could share one well et cetera, It would not be a noticeable cost at all
    - bluGill 2y ago
      Maybe, where are live there isn't much ground water and so no well can deliver enough water to be useful for a large building HVAC needs. There are a lot of ground source heat pumps around me, but they are all the coil in the ground style which doesn't scale the same way and so will be a lot more expensive to install.
deleted 2y ago
[deleted]

> so we can see where in the world heat pumps are most effective. They're not efficient when the temperature drops below a certain point. This is predictable and based on system design criteria. It doesn't mean it's not effective, it's just that it wouldn't be a reliable source of heating year round. It may still make a worthwhile addition to another system, or combined with several other upgrades, may become an acceptable single solution.

brnt 2y ago
Reliable and efficient are different things. A solution that is inefficient two week a year but efficient the rest can still be cheaper than some hybrid setup. If it is expected it simply won't work a few weeks a year, sure, that's clearly not effective.
- akira2501 2y ago
  You've summed my points exactly while missing the major one. You don't need monitoring to determine any of this. You can just look at the construction of the building and the weather charts and you're done with the "will a heat pump be effective?" question.
  - sokoloff 2y ago
    Sort of. My house is 100 years old and was built without insulation (some rooms were insulated through remodels over the years). It uses water circulation and cast iron radiators and stays comfortable with my ancient cast iron boiler and 180°F water. To know whether a heat pump (air-to-water) can replace that boiler effectively and maintain comfort, I had to find out whether the house would be comfortable with water temps of 135°F or so. Is there an amount of “that’s just looking at the building construction” to make that analysis? I think maybe technically yes, but practically no. As it was, to get an answer, I abused my old boiler by turning the water temps down (causing condensation and slow damage [planning to replace it anyway]) and seeing what happened on cold days.
    - wenebego 2y ago
      You didnt need to do that, though. It peobably wouldve been easier to use manual j (or some software) to estimate the heat loads in the house, with given set points, using weather station data.
      - sokoloff 2y ago
        I can find/closely estimate the heat loss easily. What is much harder to find is the heat gain/transfer into the room from 1920s cast iron radiators at 135°F flow and the balance of the system flow temperatures at those 45°F lower flow temps than originally designed. Then, because the answer is almost always going to be "yeah, it's going to be really close...", I felt well-advised to prove it via experimentation rather than commit to changing the heating plant to a system that could not provide 150°F flow temperature.
        rainbowzootsuit 2y ago
        If you are ok with IP units the formula is 500 * GPM * delta-T for water as the fluid.
        sokoloff 2y ago
        The question is not about the general hydronic heating formula [nor manual J heat loss estimations], but rather "what will the delta T of the rad in this particular room, in this piping network [it's a converted gravity feed system, now being a pumped], using 69°F room temp and 135°F leaving water temp from the heat source?"
        brnt 2y ago
        For the, for lack of a better word, standard radiators there is a formula with a dT^4. But I totally agree, this isnt all that straighforward, given that for the dozons of installers, experts and home owners I have spoken, Ive heard dozens+1 methods for estimating. Estimating heat loss from a given building and estimating power output of a given installation of radiators, very few people seem to be able to calculate that. If your heater can go low (mine bottoms out at 50 unfortunately), by far the easiest is to just test.
  - brnt 2y ago
    Yeah no. It's become a bit of a hobby of mine, heatpumps. If I ask 5 experts/installers to take a look at a building I'll get 6 estimates, varying wildly. Plus, installers are still consistently over dimensioning and thus killing your sCOP, because they don't want customers to complain 'its slow to heat' and so on. Calculating the heat loss of a house is really not trivial. Often you'll have no idea of the materials used or the quality of installation, and not really a way of finding out unless your up for some destructive investigation.
KeplerBoy 2y ago
Heat pumps are reliable even in unfavorable conditions. You will have to invest a lot more electrical energy and you might not be pumping heat as much as just converting electrical energy to heat, but let's not spread the myth that a heat pump will leave you freezing once outside temperatures drops below a certain threshold.
- akira2501 2y ago
  A heat pump without a resistive heating /option/ will absolutely cease working below a certain temperature. They do, for whatever reason, sell systems that way in some regions.
  - KeplerBoy 2y ago
    That's true. Strictly speaking a heat pump doesn't need a resistive heating element, but I've never heard of units not containing that feature. After all it's dirt cheap and enables the reliability, we're discussing here.
  - jwr 2y ago
    Perhaps, instead of spreading FUD, it would be worthwhile to mention these "certain temperatures", so that people can make an educated decision of whether it applies to them at all. I'm looking at the datasheet for my Fujitsu system and it is specified to work down to -25°C. Does it lose efficiency when it's cold outside? Sure. But guess what, it's still more effective than resistive heating! I am starting from a SCOP of 4.89.
    - bluGill 2y ago
      The UNIT is specified to work down to -25. The SYSTEM includes the building it is installed in: the local climate, the size and heat loss of the building, how the install was done, and likely some other factors I'm not aware of. If you get less heat from the unit than you lose via other means the system isn't working even though it is delivering heat.
    - akira2501 2y ago
HPsquared 2y ago
Ground source heat pumps don't have the icing problem. More expensive to install, though.
- ClumsyPilot 2y ago
  I think this could be Resolved by scale, but that’s precisely what the west is really bad at If we standardised ground source heat pumps as a must have all multi dwelling developments like apartment blocks and rows of terraced houses who could share one well et cetera, It would not be a noticeable cost at all
  - bluGill 2y ago
    Maybe, where are live there isn't much ground water and so no well can deliver enough water to be useful for a large building HVAC needs. There are a lot of ground source heat pumps around me, but they are all the coil in the ground style which doesn't scale the same way and so will be a lot more expensive to install.

deleted 2y ago

[deleted]