[BP1972]

I was always told before that running traps are for AHs and P traps are for package units. Now yesterday I was told the opposite is true. Yes 99% of the time either will work but which is actually correct?

 

[Tech Rob]

"Running traps" are good for nothing as far as I'm concerned.

 

[BP1972]

"Running traps" are good for nothing as far as I'm concerned.

Can you give a reason as to why you think that way?

 

[Tech Rob]

Sure. They're shallow enough that a little bit of increased negative static pressure due to a blocked coil, filter, duct, or damper will cause water to be held in the drain pan, causing it to eventually overflow. This is naturally only on a draw-through AHU configuration, but If the coil is downstream of the fan, why have a trap at all?

 

[ckartson]

The install is what determines running trap or p trap. You may have to make your own depending on system static pressures. If you have 2.00" static at the condensate (negative or positive) drain then you will have to build a trap about 3.5" deep running trap or p trap. All AHU's require traps, careful though some manufacturers provide them inside their equipment already. You don't want to double trap. If the coil is downstream of the fan it is still required. I have heard tis argument many times. Read the manuals with the equipment. Never have I read don't trap the condensate line (except on the above situation).

 

[RACMT]

http://0323c7c.netsolhost.com/docs/Trane_-_Trapping_Design_Flaws[1].pdf

 

[BP1972]

http://0323c7c.netsolhost.com/docs/Trane_-_Trapping_Design_Flaws[1].pdf

That is exactly what I was looking for thank you.

 

[RACMT]

That is exactly what I was looking for thank you.

No Problem, although you should always follow manufactures specifications for each install you do.