"HeatMan" wrote in message news:KRMdd.38579
http://www.crownboiler.com/products/warm_gas/90up2.asp

First off, I didn't know Crown made FA furnaces. You learn something new
every day.

Yup. Model UCA 108 NH5R.

Some units can't use the rear returns. I don't have the manual and can't
open it on this computer.

I have the manual. It says a bottom or side filter cabinet is the way
to go, but it doesn't mention what NOT to get, so I don't know if a
rear filter cabinet CAN'T be used.

I have seen water in the pressure switches before and it does cause a
problem.

Is this problem usually due to a furnace being tilted away from the
drain, or are there other explanations for this?