Can I use my warm radon air to increase the COP of a heat pump in winter?
I have radon in my house, my radon fan runs all year long to keep the radon at safe levels. The air that comes out of my radon system exhaust is 52.7F at 40% RH in the winter. The exhaust is 4″ in diameter and the airspeed is 1,300 Ft/min which if I am calculating that correctly is 113 CFM.
My radon fan location is close to where I would locate my new heat pump. What if I changed the radon exhaust to blow into the air input side of the heat pump?
I have no idea what CFM of air is running through a 3-ton heat pump outdoor unit is, but I must be higher than 113 CFM. For now, I will guess it is 800 CFM while running at 100% load. So, if it is 5F outside the 113CFM air entering the heat pump would be at 52F, and the 687 CFM would be coming in at 5F.
Let’s say the 86% of the air is coming in at 5F at a COP of 1.2 and 14% of the 52F air is coming in at COP of 3.7. If I did my math correct you would get a resulting COP of 1.8.
Raising the COP from 1.2 to 1.8 might be worth the effort of trying this.
I realize that the radon exhaust 10-foot rule would make me violate code unless I lifted my heat pump 10 feet above the ground on the side of my house.
Since the radon air is coming out at 40%RH I don’t think that would make the unit defrost more often. For the past month the RH has average 55.5%RH where I live near Boulder CO.
I would have to read the warranty info from the heat pump manufacturer, but I doubt this would void the warranty.
Also, I would need to locate the heat pump temp sensor that measures the incoming air and make sure I do not aim the radon air at that sensor.
Crazy idea?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
3ton unit is around 1200cfm. That is still a reasonable fraction of it, so it would help.
I think the better solution is to reduce that 100CFM of exhaust. Do you need that much to maintain the right sub slab pressure? Might be worth a bit of elbow grease and seal up your slab better. Usual big leaks are around any sump pits.
Akos, I do not have a normal basement, because of our soil I have a wooden basement floor, below the wooden floor I have a few feet of air, that is where the radon system is pulling from (at the sump pit).
As you can see in the graph my radon system keeps my radon to a safe 1.3 pCi/L over the past year. In the summer I only run it 6 hours a day, but in the winter my testing shows I need to keep it at 113CFM 24/7.
Getting back to my idea, I might give it a try when I get my new heat pump.
My guess the air velocity at the HP fan is about the same as in the pipe.
The 4 inch pipe has an area of 12.5 the 24 inch fan has an area of 452 inches or 36 time greater.
If you pee in the ocean does the water level change?
Consider the unintended conquest that when this moist air hits the very cold coil -20 sometimes. It will deposit a lot of moisture on the coils requiring more defrost cycles.
Walta
Thanks Walta100, sounds like it is a waste of time from your calculations.