Hey Ryan,

We are located in Minnesota and primarily install our radon systems with fans in the house or garage attic. All piping in unconditioned spaces is wrapped in R6 insulated flexible ducting. I don't believe these systems are very susceptible to freeze-up, as we have never received a call about one being frozen.

We have been including an option for heat cable for the last few years for our customers where an external system is the only feasible solution. The homeowners with the heating cable don't seem to have freeze-up issues.

Here are a few videos we have about frozen radon systems.
Heat cable experiment- https://youtu.be/BunkB3zGgUw
Permanent heat cable install- https://youtu.be/ooWqGVEQEtY
Signs your system has frozen- https://youtu.be/huaZcBEjAxc

We have since changed to having the heating cable hard-wired with a switch rather than having a cord to plug in.

I believe fan manufacturers say to leave the fan running in the event of a freeze-up, but you may want to check with them.

I have heard that some mitigators disconnect the discharge piping above the fan during freeze-up conditions.

We also have noticed that critter guards tend to cause icing issues, so we only install them if there are trees that may drop debris down the discharge or if the homeowner has squirrel issues.

Using 4-inch PVC piping on external systems and on the discharge of internal systems also seems to help, as the system would take longer the freeze compared to a 3-inch system.

I hope this help!
Jesse

Does anybody have significant data on using the insulated pvc piping? I remember seeing it at a few AARST conferences.
If it costs a bit more but saves steps, is it a $ saver in man hours vs insulation wrap or heat tape?

It's called Polar Pipe. I've never used it.

It has been our experience that a significant issue with ice is not so much the pipe building up ice, but rather when the ice partially melts and falls into the fan housing. This will lock up the fan and cause it to get very hot and kick out on thermal overloads. The fan then cools down and tries to restart but it gets hot again since the ice chunk is still in fan housing. This cycle continues until the ice chunk melts out. This is not good for the fan and repeated high temps likely degrades the lubrication.
One approach has been to put one or two lengths of 3/8 inch stainless steel all-thread through a short length right above the fan. Use washers and nuts to secure it in place along with some caulk to seal it. If one looks through the short stub it looks like the cross-hairs of a rifle scope. So now when the ice chunk falls down, the bigger pieces get stopped before it hits the fan and it can slowly melt out.
Likely one length of all-thread is all you need for 3-inch pipe. And the presence of the all-thread does not degrade fan performance.

There are also pre-made devices with either venturi nozzles within them or a 45-degree directional change that can also preclude ice chunks.

Recognize that the air going through the pipe will be warmer than the outdoor air. 100% soil air would be at the mean annual temperature. Also, if there are slab leaks one is pulling in warmer, conditioned air. So, the air will eventually melt out the ice depending upon how cold it is outdoors.

Of course, this is not a concern in Canada as they have figured out how to install systems totally within the envelope of the house. But certainly, is a concern in North Dakota, Montana and Minnesota.

Hi Ryan,

Being in Minnesota, we never do an outside system if we have an interior route, but we have probably 800 to 1,000 exterior systems in operation. My guess is that 50% of the systems in homes without drain tile (meaning: low air velocity) freeze up after a couple days of below zero temps.

I've pulled a few frozen systems apart, and the pipe is packed tight with snow-like ice crystals. If we've had problems with falling ice inside the pipes, I'm not aware of it.

I've been told that a fan that is not moving air is not working, and not working- it's really happy and will live a long time. The small amount of heat from the running fan eventually melts the ice crystals. We tell our clients to leave the fan on and call us it the gauge doesn't go back to normal after a few days of temps in the teens. We rarely hear back from them.

In exterior systems with low air velocity, we'll pull tubes of 1/2 inch pipe insulation (normally used on the outside of pipes) through the inside of the pipe. I'm sure it helps, but they still freeze up.

Our interior systems rarely freeze up, but we insulate horizontal pipe runs and the pipe above the fan.

Thanks for the responses so far.

At this moment in time, I'm not familiar with any mitigators in PA that do anything like a heat tape or heat cable for any of their systems. Not sure that the regs would even allow for a heat cable to be installed on the inside of pipe.

I hadn't considered the possibility of large chunks of ice falling into the fan housing and clogging up the fan. Wouldn't that break fan blades? Also, in the event a large object was blocking the fan from spinning, would you expect there to be an unusual sound that would tell you something is blocking the fan?

I also didn't think about how systems moving more air are less likely to freeze compared to a system that relies on a low flow/high suction fan. So thanks for pointing that out.