HVAC Heat Pump Basics

In this video, HVAC technician Jesse covers some heat pump basics for beginners. The basics cover how a heat pump works and the operation of all components of a typical heat pump.

In the cooling cycle, the liquid line leads into the TXV where the refrigerant pressure rapidly drops and some flash gas is produced. From there, there's a short expansion phase into the evaporator, where the refrigerant absorbs heat from the space and boils. The refrigerant travels to the compressor via the suction line as a superheated vapor. The compressor rapidly raises the temperature and pressure of the vapor and sends the refrigerant to the condensing coil through the discharge line. The condenser rejects heat from the refrigerant and turns it back into a liquid. From there, the cycle repeats itself.

In a heat pump, you have all of the same basic components. However, the evaporator coil in cooling mode becomes the condenser in heating mode, and the condenser in cooling mode becomes the evaporator in heating mode. In the air handler, you will also have heat strips, which provide electrical backup heat. When the system goes into defrost, the heat strips also turn on to prevent the space from cooling too much. Heat pumps also have two metering devices: one for cooling mode and one for heating mode. TXV systems have check valves that allow the refrigerant to bypass the metering device that is not in use.

At the outdoor equipment, a heat pump has a defrost board, reversing valve, a common suction port. The defrost board is located in the same place as the low and high-voltage wiring underneath a panel, and it has a defrost sensor connected to the outdoor coil. The common suction port is located between the suction and liquid line coming out of the outdoor unit. A 4-way reversing valve has a solenoid that can slide the reversing valve and swap the suction and discharge lines when energized. That process reverses the flow direction and allows the heat pump to switch between heating and cooling mode. There will always be a common suction line and a common discharge line leading into the reversing valve.

There may also be an accumulator on the system, which prevents liquid refrigerant from getting into the compressor. In cooling mode, the refrigerant flows through the suction line and then passes through the reversing valve before the compressor. In heating mode, the refrigerant passes through the compressor before it reaches the reversing valve.

The defrost board depends on a defrost sensor to tell the unit when to defrost. (In this case, it's a pink wire.) In defrost mode, the defrost board will send a 24v call on the white wire to energize the backup heat inside (heat strips).

[rogerf]

Thank you! Great info. Looking forward to more.

[kirkprospector]

I really appreciate Jesse taking us inside the condensing unit. Really helped me demystify where the lines are going once they're ran inside the unit.

[BrendaMartinez-eetk]

Thank you so much for these videos. I struggle to pay attention, my mind will wander constantly as the instructor is teaching. These videos help me focus. Watching, listening and taking notes helps me retain the information better. Plus, I get to rewind when I become distracted. Thank for taking the time to educate me!

[deanburke]

We need a troubleshooting sequence to figure out what went wrong with heat pumps, besides typical operation sequence. Like with furnace operation. Trace what's supposed to happen, and find the defects. Like stuck or worn out reversing valve. What would you see, how would you know? What would your pressures be like?

[christopherpaul]

when the system goes into defrost it simply goes back into cool mode with the fan cycled off so the head pressure can go up and then a signal is sent to the indoor board to turn on the heatstrip so it can warm up the cold air while its in defrost. And the main reason you want to have a high head preasure is so the hot gas can melt the ice around the outside coil.

[chancecooper]

This is THE best HVAC channel out there. This dudes like a surgeon but only in the HVAC field....

[djkaiser]

Moved into a new-to-us house that had this system, from a home with a gas furnace, and had no clue how it all worked... now I do! thank you!

[rogerbettencourt]

Nice information guys. And since you guys put out the free videos I will do my part and not skip the commercials, only fair. Thanks.

[BillyN]

We’re starting to see alot more of these up in Connecticut. Thanks for the video!

[theprocessor]

ill give this 5 star. very good explanation.finally no more intros direct to the point.

[Balticblue]

Here in Colorado, heat pumps are usually connected to a furnace for a dual-fuel setup because NG is far less expensive and efficient compared to heat strips. If you buy an efficient enough heat pump, it will be less of a problem or requirement of NG furnace. But I love my Bryant Evolution Heat pump and high-efficiency Bryant Evolution furnace. The cost of electricity is skyrocketing but our solar panels produce plenty of power during the day to run the heat pump completely.

[MrGarcon]

wow ! nice review for this retired old man lol done guys ! now in 2020 first day, ,my heat pump is running in north florida like miami or ft laud here at all for just little over 4 hours away ! thank you

[davidhill]

Some of the best explained info ive ever heard. Thanks so much for the careful consideration of " wording"/ terminology because its very easy to become complacent of wording leading to a total misunderstanding of functions for those who are wanting and trying to be good techs but that are just not quite there yet. Great job guys!!

[davidhenderson]

Heat pumps are krazy tight and mind blowing yo.

[albertoreyes]

Really help I use to always wonder how did the heat pump work, but it’s amazing how the coils make that switch. 3 main things that he spoke was reversing valve defrosting board the common suction line how they rotate depending if it heat or cold air

[javeedazad]

Amazingly clear and precise video. Incredibly thorough video. Thank you so much!

[terrypritchett]

Pretty helpful thanks sir for simplifying it made a little easier to understand

[ying]

Ty brother! Informative, clear, loud and slow.

[rodkneed]

Does the compressor run during the Heat cycle just like during the Air Conditioning cycle? Will the electric consumption be just as high in the winter as it is in the summer?

[dhavalgajra]

Loved the video. It was very informative and he nicely explianed the concept practically.