Overview
Reactivation air filter, 9" × 11-3/8" × 1/4". Phoenix part number 4027168.
This is the filter on the reactivation air stream — the air that is heated, drawn through the desiccant wheel to drive moisture off it, and exhausted.
What it fits
- Phoenix D850 Desiccant — named in the manual as Reactivation Air Filter Replacement 4027168, 9" × 11-3/8" × 1/4" Pre-Filter (Standard), and in the parts list as Air Filter, Regen, one fitted
It sits behind regen filter door 4035669, ahead of regen blower 4028254 and the regen inlet thermal overload 4036114.
Process air and reactivation air are different filters
- Reactivation air — filter 4027168, 9" × 11-3/8" × 1/4". This part.
- Process air — filter 4022636, 20" × 20" × 2" MERV 8.
Both need changing. Neither substitutes for the other. They are different sizes, sit in different parts of the machine, and do different jobs.
Why the reactivation filter gets neglected — and why that costs money
The process filter is the obvious one: it is large, accessible, and visibly dirty. The reactivation filter sits behind its own door and is easy to forget.
It should not be. The reactivation stream is heated air, and it passes over a thermal overload on the way in. A restricted reactivation filter reduces that airflow, and reduced airflow across a heater is how you trip the regen inlet thermal overload — which presents to the operator as a machine that runs for a while and then stops making water, with no obvious cause.
If a D850 is nuisance-tripping or its performance has fallen off for no apparent reason, check this filter before you go looking at anything else.
When to change it
Change it at the same interval as the process filter, as a matter of routine. It is inexpensive and the failure mode it prevents is not.
Check the regen filter door seals properly when you close it. Air bypassing a filter is the same as no filter.
Frequently asked questions
Is it the same as the process filter?
No. That is 4022636, 20" × 20" × 2".
Where is it on the machine?
Behind the regen filter door (4035669), ahead of the reactivation blower.
My D850 stops making water after a while. Is this the cause?
It is a very good place to start. A restricted reactivation filter can trip the regen inlet thermal overload.
Can I clean it?
No. Replace it.
Running a D850? Order the process filter and the reactivation filter together — both need changing and only one of them is obvious.
