Is the refrigeration process reversible?

The refrigeration process is used in air conditioning to dehumidify and control temperatures in homes and buildings. The heating industry preceded the air conditioning business and many evaporator coils were placed on top of furnaces to create split systems and utilize existing ductwork. The heating industry welcomed the advent of modern refrigeration until heat pumps started to emerge. It wasn't a serious threat at first because heat pumping was an underdeveloped, immature and poorly marketed alternative. A heat pump is a refrigeration system with a reversing valve.
Here is a typical refrigeration diagram

From the perspective of a property owner with a furnace and an air conditioner that is not a heat pump from the factory, would it be advantageous to install a reversing valve to make the system reversible and more beneficial environmentally?
Refrigeration.png
 
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Heat pumps are the standard where I live (US-FL). While a reversing valve is the 'headline' difference between an air conditioner and an AC/Heat pump, there are several other differences. My take is that simply adding a reversing valve could easily result in a damaged compressor (liquid at the inlet).

More generally: Heat pumps are great if it's not too cold. If it gets near freezing, they are pretty near useless (icing). My system switches to resistive heat ($ouch!) at that point. If heat pumps aren't already common where you are, there's a good chance that they don't make economic sense.
 

russ_watters

Mentor
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From the perspective of a property owner with a furnace and an air conditioner that is not a heat pump from the factory, would it be advantageous to install a reversing valve to make the system reversible and more beneficial environmentally?
For the property owner, the primary issue is operating(energy) cost vs equipment cost. To a certain extent, energy cost is related to environmental impact, though that is complicated.

The issue with air source heat pumps is their capacity and efficiency goes down as outside air temperature goes down. So in a cold climate they need a backup source of heat. So the energy benefit is limited to a certain number of hours of the total. Add to that the recent drop in natural gas prices, and I think you will find that in most places a natural gas furnace is cheaper to run than an electric backed-up heat pump.
 
Heat pumps are the standard where I live (US-FL). While a reversing valve is the 'headline' difference between an air conditioner and an AC/Heat pump, there are several other differences. My take is that simply adding a reversing valve could easily result in a damaged compressor (liquid at the inlet).

More generally: Heat pumps are great if it's not too cold. If it gets near freezing, they are pretty near useless (icing). My system switches to resistive heat ($ouch!) at that point. If heat pumps aren't already common where you are, there's a good chance that they don't make economic sense.
In the case of reciprocating compressors, a suction accumulator would be beneficial. Heat pumps benefit from scroll compressors and R410a and crankcase heaters. Scroll compressors don't need suction accumulators. A Sporlan biflo txv is needed to feed the outside coil. The brazing is not too complicated once you have the refrigerant out. If POE oil is added, the r22 can be replaced with r 407c for an environmentally friendly refrigerant. You might be surprised at how many furnaces are out side the modern heat pump norm in Florida especially along the coast. The fossil fuel industry has game all along the seaboard.
As far as getting too cold, its still a furnace. the heat pump replaces the furnace for stage one and the furnace takes stage two , an out door temperature lock out and the defrost cycle . The savings are down from 40 percent but the ROI is less than three years. Most people who would have it done would do so for environmental conservation and be surprised on the savings. One should consider the savings of the upgrade in comparison to unit replacement.
 
For the property owner, the primary issue is operating(energy) cost vs equipment cost. To a certain extent, energy cost is related to environmental impact, though that is complicated.

The issue with air source heat pumps is their capacity and efficiency goes down as outside air temperature goes down. So in a cold climate they need a backup source of heat. So the energy benefit is limited to a certain number of hours of the total. Add to that the recent drop in natural gas prices, and I think you will find that in most places a natural gas furnace is cheaper to run than an electric backed-up heat pump.
I agree with you on the complication of the environmental impact. A study is warranted in my opinion. I think when something is better, it should be done. A hybrid heat pump is better than a heat pump with electric back up and a furnace alone. Most package gas are only 80 percent efficient. The heat pump can carry the load with renewable electricity depending on the weather with very little help from the furnace. It is nice to know that it is there. It is cheaper to move heat than to create it when all costs are considered. It is always cheaper to improve what you got than to buy new.

To replace a gas pack with a heat pump, one would need to run a 6 awg circuit and disregard te gas line. Factory hybrid units are available but they are pricy.
 

Averagesupernova

Science Advisor
Gold Member
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The feasibility even varies short distances within an area. In my area there are two main electricity suppliers. One is a cooperative and the other is not. The cooperative offers many incentives that the privately held company does not. If you do not live where natural gas is available you have to rely on fuel oil or propane. Heat pumps are quite common and electric resistance heat as a backup is not uncommon with a heat pump especially if your electricity supplier is the cooperative.
 
Thank you for your reply. I am speaking of adding a reversing valve to a straight air appliance. These are normally coupled with a furnace as package or split. The very reason they are not heat pumps. I say they can and should have been heat pumps all along and if we upgrade them they will be hybrid or dual fuel. My bet is they would stay hybrid into perpetuity in many instances. Since air conditioner is reversible, I have determined most components are the same or OEM equivalent as factory heat pumps. A great time to upgrade the refrigerant as well. I am looking into BLUON.
I would appreciate any cooperation with a co-op I can get. Thank you for your encouragement.
Sometimes the solutions to climate change are many. This one is in many back yards.
www.hybridpgrade.wordpress.com
 

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