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blow-through system, an untrapped drain on a draw-through
system is an efficiency issue. But more importantly, the air
being sucked through the drainpipe can prevent the pan from
draining, causing it to run over.
Without proper trapping, air pulled back into the equipment
can lift the water up from the condensate pan much like an
aerosol spray. Often, this results in a good soaking of the
liner material and many of the components located nearby.
As I noted earlier, if a condensate pan is contaminated it can
become a health issue. If the pan water becomes airborne as
a result of improper trapping, it is even more likely to be one.
TraP ProblEmS
When a trap seal is too shallow, it can be sucked or blown
dry at each cooling cycle startup. Running traps are prone to
fail in this way. Some manufacturers specifically recommend
against the use of running traps.
If the seal is too deep, it actually can cause condensate to be
held in the pan. A trap with an excessively deep seal also is
prone to clogging. Because fan speed, duct size, coil condi-
tion or other issues that affect the static pressure around a
cooling coil can be as varied as each HVAC system instal-
lation, trap design should be as varied as well. Based on my
experience as an installer and service tech, I believe little
consideration actually is given to static pressure issues, and
though traps might appear to be somewhat different from
unit to unit, this almost certainly is from happenstance and
almost never by engineering or design.
Today in my area, many installers seem to favor manufac-
tured traps, but site-built traps still are common. Home
inspectors should know that equipment makers often recom-
mend a drop from the pan at a minimum of 2 inches and
then a minimum of a 2-inch trap seal
(see illustration bottom
left)
. Anything outside of these parameters, either excessively
short or long, should cause a home inspector to look more
closely for signs of moisture concerns in or around the equip-
ment. Without the supporting evidence of an overflow or
similar failure, you might not want to call out
the system as defective, but do suggest moni-
toring. Be sure the secondary measures
employed to prevent moisture damage are
in order, too.
There are a number of piping mistakes
made when installing a condensate trap.
In my opinion, an open clean-out be-
tween the trap and coil is the number
one mistake. I believe it’s made be-
cause installers think leav-
ing the pipe open will help
the system drain, working
much as a vent does on the house plumb-
ing. When in fact, an open clean-out at
this location allows air to bypass the trap
altogether. This mistake is easily corrected
by placing a cap over the clean-out
pipe and only removing it for cleaning
purposes. It should be easy to remove,
so gluing is unnecessary
(see photo at
right).
Running traps.
Photo TS Hart.
Recommended trap configurations.
Illustration from Trane installation manual.
Recommended by some
equipment makers, the
translucent EZ Trap
®
Kit
includes a tee and a cross
with removable caps and ise
packaged with a flexible
brush for cleaning.
Photo Gerry Spanger, Airtec Products
Corporation & Marketair, Inc.
Opened clean-outs or vents
between the trap and coil should
be covered. An easily removable
cap or plug should be installed.
Photo TS Hart.
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T H E C A N A D I A N
HOME INSPECTOR
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