Heat Pumps Explained – How Heat Pumps Work HVAC


hey there guys Paul here from the engineering mindset calm in this video we’re going to be discussing heat pumps the different types and how they work coming up how he pumps work air to air heat pumps air to water heat pumps ground-source heat pumps water source heat pumps as well as animations and system schematics for each of these I just want to take a moment to thank our partner dan Foss for sponsoring this video a critical aspect of heat pumps is how energy-efficient they are and dan Foss has everything you need to make sure your heat pump is running at what they called 360 degree energy efficiency they even built a heat pump website that has business cases case stories ile essence and even have a fun diagram similar to the ones you see on this channel so you can see how it all comes together just click the link in the video description below to see what 360 degree energy efficiency is all about ok the first thing we’re going to look at is the air to air heat pump these are the most common heat pump types they often look very similar to a standard air conditioning split unit with the unit located outside and another unit located inside these can either work as a heating only device alternatively the more popular choice is to have a device which can provide both heating or cooling by making use of a reversing valve we’ve covered reversing valves in our previous videos link so that can be found in the video description below there are a few different ways to configure a reversing valve heat pump I’ll show you a simple typical example the main components we’ll have in this type of system are the compressor the reversing valve the indoor heat exchanger an expansion valve with a non-return valve bypass a bi-directional filter dryer a sight glass another expansion valve with a non-return valve and bypass then we have the outdoor heat exchanger we also have a controller and a number of temperature and pressure sensors around the system in heating mode the refrigerant leaves a compressor as a high-pressure high-temperature vapor and passes to the reversing valve the reversing valve is positioned in heating mode so the refrigerant passes through this and heads to the indoor unit cool air is in blown over the indoor units heat exchanger to remove some of the thermal energy and provide heating to the room as he he’s removed the refrigerant will condense into a liquid having given up some of his energy the refrigerant leaves as a high pressure slightly cooler liquid the refrigerant then comes to the expansion valve and bypass in this mode the expansion valve is closed so the liquid refrigerant passes through the non-return valve he then passes through the filter dryer in sight glass and then passes to the second expansion valve it will then pass through this expansion valve because the non-return valve on this side is preventing flow in that direction as the refrigerant passes through the expansion valve the refrigerant expands in volume and turns into a part liquid part vapor mixture this expansion in volume reduces the temperature and pressure we’ve covered how thermal expansion valves and electronic expansion valves work in great detail in the previous videos do check those out links are in the video description below the refrigerant then heads their outdoor heat exchanger here a fan is blowing outside ambient air over the coil and adding heat to the cold refrigerant the refrigerant boils at a very low temperature and as it boils it will carry away the thermal energy as an example we know that water will carry thermal energy away as steam when it boils and we know that it boils at a hundred degrees Celsius or 212 degrees Fahrenheit well if we then look at some common heat pump refrigerants r134a for example has a boiling point of minus twenty six point three degrees Celsius or minus fifteen point three four degrees Fahrenheit refrigerant r410a has a boiling point of minus forty eight point five degree celsius or minus fifty five point three degrees Fahrenheit so it’s very easy to extract thermal energy even at very low outdoor temperatures we’ve covered how refrigerants work also in a previous video again links that can be found in the video description below so the refrigerant picks up the thermal energy from the outside air and leaves the outdoor heat exchanger as a low pressure low temperature slightly superheated vapor and then heads back to the reversing valve the reversing valve then diverts this to the compressor to repeat the cycle if the system is then switched into cooling mode the system then acts like a normal split air conditioner the compressor forces the high-pressure high-temperature vapor refrigerant into the reversing valve the reversing valve dough verses to the outdoor you the fan of the outdoor unit flows ambient air across the heat exchanger this air will be a cooler temperature so it carries the thermal energy of the refrigerant away the refrigerant condenses as it loses its thermal energy having given up some of its energy the refrigerant leaves as a high pressure slightly cooler liquid he then heads to the expansion valve but this is closed so the refrigerant passes through the non-return valve then passes through the sight glass and the bi-directional filter dryer the next non-return valve is then closed so the refrigerant passes through the expansion valve as it passes through the expansion valve the refrigerant changes to a part liquid part vapor mixture which causes it to drop in pressure and temperature here then flows into the indoor heat exchanger and in here a fan blows the warm indoor air over the coil this causes the heat to transfer from the air into the refrigerant and so the refrigerant boils takes his heat away the refrigerant leaves the indoor unit is a low pressure low temperature slightly superheated state and flows into the reversing valve the valve diverts this back to the compressor to repeat the cycle air to water heat pumps these units work in a very similar manner to air to air heat pumps but without the reversing valve the high-pressure high-temperature vapor refrigerant leaves the compressor but this time it heads into a plate heat exchanger on the other side of the plate heat exchanger water has been cycled through a hot water storage tank cooled water enters the heat exchanger from the tank and as it passes through the heat exchanger it absorbs heat from the hot refrigerant the water will then leave at a much hotter temperature and float back to the hot water storage tank to repeat the cycle as the refrigerant gives up its heat to the water it will condense and they will then leave the heat exchanger as a high pressure lower temperature liquid we’ve covered how heat exchangers work in our previous videos links of these can be found in the video description below the refrigerant then passes through the filter dryer and the sight glass and then into the expansion valve the expansion valve causes the refrigerant to become part liquid part vapour state and will be at a low temperature and pressure it then passes through the outdoor heat exchanger where the outdoor ambient air causes the refrigerant to boil the refrigerant then leaves at a low pressure low temperature slightly superheated vapor and sucked back into the compressor to repeat the entire cycle again the hot water tank then provides hot water to the radiators sinks and showers within the building ground source heat pump there are two main types of ground source heat pumps at being the horizontal and the vertical type both essentially work the same it’s just how they access the heat in the ground that varies we’ll look at when to use the different types as well as the pros and cons of these in our next video this video we’re just going to focus on how they work ground source can be used for heating air or water in the air type system the heat pump can also have a reversing valve and then supply either heating or cooling in both cases the outdoor heat exchanger can be a plate heat exchanger with the refrigerant passing on one side and a mixture of water and antifreeze cycling on the other side the water and antifreeze mixture is forced by a pump around the pipes within the ground this will allow it to pick up the thermal energy in a heating mode and bring this to the heat exchanger the refrigerant on the other side of the heat exchanger absorbs the heat because it has a very low boiling point so as it boils it carries the heat away which can then be used within the building in the air type system there can be a reversing valve this will allow the refrigeration system to pull unwanted heat out of the building and transfer this into the water antifreeze mixture this water will then be pumped around the pipes in the ground and it will transfer the heat into the ground thus returning cooler ready to pick up more heat water source heat pumps water source heat pumps come in two main variations closed and open loop the closed loop sends a mixture of water and antifreeze to collect thermal energy from a pond or river and transfers it through the heat exchanger the same water is then sent round again to repeat the cycle open loop pulls in fresh water from an aquifer or from a river and pumps this into the heat exchanger to collect the heat once it passes through is in release back into the same water source in a closed loop type a water and antifreeze mixture cycles around the pipes to collect the thermal energy and bring this to the heat exchanger where the refrigeration system will then absorb the energy and use it for heating alternatively it will dump the building’s unwanted heat into the water antifreeze mixture to provide cooling for the building the unit then works the same a ground source heat pump in an open-loop type the water is pulled in via a pump and sent directly to the heat exchanger the heat exchanger then pulls a thermal energy out of the water or it dumps the unwanted heat into the water the water then passes through the heat exchanger and returns to the source some distance apart before I wrap things up I just want to thank Dan for one last time for sponsoring this video don’t forget to check out their heat pump solutions by clicking on the link in the video description below ok guys that’s it for this video thank you very much for watching I hope you enjoyed this and it has helped you if so don’t forget to Like subscribe and share leave your questions in the comment section below and follow us on Facebook Instagram Twitter and of course the engineering mindset comm once again thanks for watching

36 thoughts on “Heat Pumps Explained – How Heat Pumps Work HVAC

  1. Here in New Zealand if the outside temperature goes below -5 Celsius the heatpump stops to defrost too often and is virtually useless.

  2. ⚠️ Found this video super useful? Buy Paul a coffee to say thanks: ☕

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  3. I’m 36 and have been an HVACR tech for 17 years now. Heat pumps have come a long way. I don’t care who says what they are very practical and efficient. Check out the Mitsubishi Hi-2 versions. They give you 100% heat capacity at 5 degrees Fahrenheit and 95% heat capacity at -15 degrees Fahrenheit!!! That’s insane.

  4. Great 'happy hour' text at the top. A bit confused but it seems to do with different modes of the heat/compression relationship.

  5. So basically your compressor in the video would be the heat pump since it can heat and cool? Compressors only cool right??

  6. Sure looks like a lot of components that could fail…and who has the skills to properly diagnose and then there's the cost of replacement parts $$$

  7. Excellent video on heat pumps as I kept hearing this being used in other countries. Now that I have seen how it works, it appears that the limit of the system for heat output is the power consumption of its compressor. It seems that a heat pump is less efficient than an electric heater as some heat is lost from the outdoor unit.

  8. Hi Paul. Just watched your Heat Pump election and comparison, and have a question re your 1KW to 4KW for ASHP. Could solar panels provide this and if so, at what cost….assuming batteries might also be needed? Ideally looking to only use electricity for cooling and light

  9. I've been looking for a simple explanation like this. The only way this could be better is if you showed an example of the physical devices for the indoor and outdoor units or parts. And thanks for the great video!

  10. Here in the UK they're really expensive vs gas boilers. Most people who've fitted have ended up decommissioning them, as the hype hasn't materialized.

  11. Thank you for this. The video that "Carrier" put out with two idiot goons explaining "it pumps heat from outdoors" was worthless. This is actually how i always thought these systems worked. When I get the explanation that "it pulls heat from the outside", it makes no logical sense whatsoever. Heat being a relative term, i know that at 0°F outdoors, there's now way in hell there's going to be enough "heat" to make me warm in my home.
    Compressed refrigerant is hot. Expanded refrigerant is cold. Control which direction it goes, and you have either hot or cool air coming out of each end of the unit. Simple.

  12. I'm still curious to find out how many watt hours is consumed by the compressor per celsius degree increase of room temperature. If I know the need of energy for a room (kWh/m2), SCOP of the heat pump and both the outdoor + indoor temperature – it should be possible to know how many Wh it takes for it to heat up the room 1 degree, right?

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