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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 condition or other issues that affect the static pressure around a cooling coil can be as varied as each HVAC system installation, 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.


translation: Follow the manufacturer's instructions. D'OH

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

quote; If the seal is too deep, it actually can cause condensate to be held in the pan.

NOW, how could that happen. The difference in elevations between the inlet and outlet are what cause water to flow through a trap. The DEPTH of the seal is immaterial, because when water flows into it on one side, it raises the level on the other side, REGARDLESS of how deep the seal is and thus the same amount of water flows out of the trap. It is just NOT the same water that flowed in however, which it seldom is in any trap anyway unless it is a large flow.

the seal depth should be 2" + whatever maximum static pressure the unit can develop

since the 'typical' unit runs at .25" with a clean filter and up to 1" with a dirty filter

a typical trap 'should' have a 3" seal


no one can really explain how or why, but, from industry experience, a trap with a too deep seal WILL create problems

IMO: this is due to NOT increasing pipe size as soon as you 'drop' into the trap

ie. 3/4" tapping in unit should be piped horizontal 3/4 into a 1" trap (running full 1" thereafter)






wires on top are for alarm/cutout - shown being brush cleaned using vent port which is normally open to atmosphere on DISCHARGE side of trap


height difference between inlet and outlet is to allow for friction loss and to build a 'head pressure' for drainage in spite of static developed pressure (suction)

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 2 times.

whatever as long as you use your own laws of physics and hydraulics.

and you, of course, are more knowledgeable than EVERY HVAC manufacturer

check with

Trane

Carrier

York

Lennox

even Goodman

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

Is this really an issue? Most hvac installers use the preformed pvc traps that have about a 1.5" water seal on them anyhow, and many that I have seen a open Tee somewhere above them for air admittance or cleaning.

Not disagreeing with the recommendations, just YOUR interpretation of why it is done that way.

sorry, perhaps I was a wee bit 'touchy'

however

they are NOT recommendations

they are manufacturer's REQUIREMENTS

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638