I've got a 2018 3950BR. We're full timing in the Seattle area.
I've been running the furnace in the evenings for a few weeks. I try to use the heat pump during the day, but it doesn't happen every time. Furnace has been fine until today.
Today the blower would start, but the burner wouldn't even try to engage. After a short while the blower would stop.
Short version, the board is blinking 1 red with a 3 second pause. This is the error code for Air Flow / Limit Fault. Hmm, that wasn't what I was expecting, but ok.
Basic troubleshooting didn't resolve anything. (Flipping the reset switch...the 5th wheel equivalent of staring under the hood at the side of the road.) Dug out the manual, but it was lacking in any kind of troubleshooting suggestions.
However, this is something I did see:
Quote:
REQUIRED DUCTING
All ducts in the table are four-inch ducts except for bottom discharge as
noted. Two-inch ducts cannot be used in place of four inch. .
A bottom discharge requires no additional ducting; one additional duct
can be added if required. Vertically installed units can also be bottom
discharge when right side cover panel has been removed one
additional duct can be added if required.
FOR OPTIMAL PERFORMANCE use the following instructions for
ducting. (Two top ducts are only to be used in addition to the below
installations and are not allowed to be used until these requirements
have been met). Additional ducting added will reduce the air flow and
could cause poor heating.
- Horizontal or Vertical 4” Ducting: when using 4” ducting one
duct from each side must be used. When using side ducts,
utilizing rear duct openings as the other duct will yield the best
performance.
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It goes on to state that the 35k BTU units (mine is AFMD35131) require 36 square inches of discharge and specifically outlines that as three 4" ducts.
I found various forum posts from other sites talking about how folks had issues with the ducting being bent or restricting airflow, so into the basement I go. Take a look at my image here and tell me if I'm loopy for thinking that the factory install wasn't to spec.
So instead of using the mandated three 4" ducts, they used one 4" and two 2". All of which are mounted in the rear, none on the side and no bottom discharge.
It strikes me that this is a likely cause of an airflow issue. Am I wrong?
This isn't my strongest area, so I'd like to hear from those with more experience here. Should I push back on Keystone to make them re-duct this unit to spec? Is this a likely cause of my error?
Other data: Plugged into 50amp service and have been for a while. In the end I used compressed air to try to clear any potential build up or obstructions. The vents were getting air from the blower consistently. After I did the blow-off I did get to a point where the igniter was kicking on, so that's good. However, it wasn't staying lit. I was doing this in a heavy rainstorm with moderate wind today and I suspect that the wind was an issue with the cover off and that I got more water in there than was good. Drying it out in those conditions was doing more harm than good, so I sealed it back up and am running on heat pump right now. I'll test more when it dries up a bit. (I'm in Seattle, so, you know, June...) I'm more concerned at the moment with the ducting.
Thanks,
Jeremy
Linear Mode
