Outdoor Air Handler - Condensate Drain Insulation/Heat Trace?

[John_187]

Hello,

For an outdoor air handler, there are small sections of outdoor condensate drain pipe that discharge to grade, roof, or storm. These are typically 1-2 feet of exposed pipe, often 3/4" pipe connecting directly into the air handler.

Do these pipes require heat trace and/or insulation? It is a climate with winters below freezing. Condensate will not typically be produced much in the winter, but I assume the need for freeze protection still exist.

The question is: Is insulation good enough, or is heat trace required?

Thanks for your time.

 

[Drazen]

"Tipically" there will be no condensate from indoor units at all if spaces are not cooled during outdoor minus temperatures.

 

[BronYrAur]

I'm near Chicago and have never seen and insulated or heat traced condensate drain line for a rooftop unit. I have seen plenty piped in PVC that have frozen and cracked. I have also seen installations where the PVC traps were NOT glued together. They were just fit together without glue. That way, they will pull apart as the water freezes and expands. You just have to reconnect them in the spring.

Copper is better but can still burst. I have seen them with unions so they can be disconnected and manually drained or simply removed for the winter. The problem with all of these approaches is that they require someone from the maintenance staff to do something. Usually it is forgotten until it is too late.

The geniuses who put an air conditioning unit in my attic didn't give any pitch for the drain line other than where it drops out of the coil. It is completely horizontal after than and doesn't totally drain. After a few frozen traps and drain lines (which of course I discovered the hard way during the next cooling season) i cut in a tee with a plug. Each Fall I blow it our with compressed air. Something I must remember to do before it is too late.

To answer your direct question, insulating without heat tracing will do nothing.

 

[Compositepro]

I just replaced some CPVC pipe in my house with PEX because the CPVC will almost always burst when it freezes. PEX Generally will not. Or use a rubber hose with a low spot for a trap.

 

[willard3]

This begs the question of why anyone would put water exposed to atmosphere on a roof in a cold climate.

One of the major problems with rooftop HVAC equipment.

 

[LittleInch]

why is anyone asking about 2 feet of heat trace and insulation - Just do it and then nothing bad will happen.

don't do it and it might not work when you want it to.

you only need to maintain 5C.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Compositepro]

Perhaps because there are millions of units operating out there without heat tracing for the last 70 years. This is the first time I have even heard this problem mentioned, although it probably is not that rare. HVAC is a field filled with cheap engineering.

 

[LittleInch]

But most of those millions of units are inside.

The OP seems to be refereeing to am outdoor AHU.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[GT-EGR]

I would say you don’t have to insulate or heat trace the condensate if it’s just discharging to the roof and continuously pitched (aside from the trap) to its termination point. The pipe is open to atmosphere and the freezing trap water minuscule expansion just spreads out in the available pipe space. While the trap is frozen, there should be no condensate coming out of the unit since if it’s lower than 32 outside you aren’t getting any condensing on your evaporator coil. By the time the condensate drain becomes active with moisture again the trap will have thawed out long ago.

Yes you run a small risk of damaging the pipe, maybe water sneaks into a joint, but it usually isn’t a critical pipe, and you already had it discharging to the roof so failure wouldn’t make a significant difference except losing the trap seal.

If its not cheap material cheap assmebly it will survive. If you’ve seen them damaged it’s more likely due to cheap installation since the details and specs of this are often overlooked - or just exposure to the elements over time

You also could run the condensate piping within the unit roof curb down into the conditioned spaces or plenum, then you aren’t exposed to the elements and freezing isn’t an issue, but now you do have to route it to a drain somewhere (and insulate it).

 

[chicopee]

All the air handling units that I have seen in the N.E. were indoor so I am wondering if the OP is not mistakenly referring to roof top mounted compressor-condenser units as air handling units?

 

[lukaiENG]

I would echo GT-EGR's comments.
Also, heat tracing an open pipe is a sure way to dry out a trap which depending on what your RTU is serving may cause issues with unfiltered air being infiltrated through the condensate drain. This is only important in some situations, but is a consideration nonetheless.
One other option for consideration would be replacing the trap with a water-less trap which would remove the freezing concern. There are a number on the market, here's a couple of options:

https://www.rectorseal.com/waterless/

https://hepvo.com/

 

[Drazen]

Unfortunately we cannot have terms agreed easily as many newbies post on the forum, now I'm unsure whether "outdoor air handler" refers to unit that treats outdoor air (which would be first implication) or it is just clumsy expression for outdoor unit which serves air handler.

Here is quite precise calculator to make a choice on insulation and calculate freezing time based on most of parameters:

http://armwin.armacell.com/Calculation.aspx

It's only kinetic energy of water that is missing in this calculation, but for sake of security factor, it can be neglected.