Can I use my warm radon air to increase the COP of a heat pump in winter? – GreenBuildingAdvisor

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?