I'm the maintenance guy for a 22 unit apartment building HUD/MISHDA. I have 3 units that the concentric vents exhaust (center pipe) freezes over whenever the temp drops below 0. Here in the central UP of Michigan that's fairly often.
The ice plug at the termination point is ice, not frost and is about 4-5 inches back
Into the pipe.
The company that installed them (3 yrs ago) says to cut the exhaust pipe and vent into the attic or basement area. Sorry, but this just has problems written all over it. The 2 in the attic run vertically through about 15 +- feet of unheated attic, the exhaust is insulated up to the concentric vent. The exhaust in the basement (horizontal) has 3 90s about and 16-17 feet of pipe in between.
Does anyone have a way to keep them from freezing?