Q&A - Drain Traps & Static - Short #209

HVAC School - For Techs, By Techs

Bryan Orr

Training, Careers, Airconditioning, Self-improvement, Hvac, Business, Education, Refrigeration, Heating, Ac, Apprenticeship

4.8 • 985 Ratings

🗓️ 10 September 2024

⏱️ 6 minutes

🔗️ Recording | iTunes | RSS

🧾️ Download transcript

Summary

In this short Q&A podcast episode, Bryan answers a question about drain traps and static pressure. This question was sent by Stephen with The Comfort Squad when he noticed an uptick in nuisance calls on retrofit systems that kept having their secondary drain pans filled.

In negatively pressurized systems (i.e., straight-cool or heat pump units, not gas furnaces), air can pull water back into the drain line. The evaporator coil is under negative pressure because the blower is on top of the evaporator coil.

The rule of thumb for trap depth is that it should be greater than or equal to twice the return static pressure (which is why a 1" deep trap is typical for systems with 0.5" return static pressure). However, return static can have some variation, and it's also not a great idea to use the TESP for this measurement because the return static could be greater than the supply. It makes most sense to account for the highest possible return static you will see.

1" is only sufficient if 0.5" return static pressure is the most you will see, so bigger is usually better in all cases. If you can install a 2" or 3" trap, you'll typically have your bases covered without having an excessive trap.

We also wrote a tech tip about this topic: https://hvacrschool.com/drain-trap-depth-and-negative-pressure/

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

Purchase your tickets or learn more about the 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

Subscribe to our podcast on your iPhone or Android.

Subscribe to our YouTube channel.

Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android.

Transcript

Click on a timestamp to play from that location

0:00.0	Yep yep yep yep yahouly this is a short h-vac-school podcast episode you probably knew that because you probably
0:09.3	already read the description but it is also a Q&A episode and this is from Stephen at Comfort Squad. He asks about
0:16.5	trap depth on residential negative pressure systems and we're gonna hopefully do our best to answer the question, but before we do that,
0:26.0	we're first going to thank our great sponsors.
0:28.6	Refrigeration Technologies at refriggedech.com. Field Piece in the SR 47 wireless refrigerant charging scale.
0:38.0	At only 7 pounds, it still rains as the heavyweight champion of refrigerant scales.
0:44.0	The Field Piece SR-47.
0:47.0	Navac and Navac Global.
0:50.0	And the Break-Free Power Flaring tool model NEP 6 LM.
0:56.0	carrier and carrier.com.
0:59.0	Hey Brian this is Stephen with the comfort squad and Charles Hill Virginia and I have a question regarding condensate traps so the situation here is we've had a number of nuisance calls in the last couple weeks on retrofit jobs where we just
1:16.1	couldn't get the static below, like one inch.
1:19.0	So what appears to be happening is the high static pressure in the air handler is creating a high
1:24.9	negative pressure at the drain trap and that's pulling enough water into the pan to
1:29.6	overflow the secondary switch. We're currently using the rector seal easy traps. They're a one inch
1:36.5	trapped up but the solution to this seems to be fabricating a deeper trap so there's formulas online and some info but I find it would be kind of confusing. So a dive into the effect that negative pressure has on trap depth I think would be really awesome especially this time of the year.
1:56.2	Thanks man.
1:57.2	All right Stephen so you bring up a really good point and I think it's quite
2:01.8	incredible that I haven't written about this or talked about this before.
2:04.6	Maybe we did. I think Roman Baw actually did some content on this a while back, but this idea of
2:10.0	trap depth and its relationship to static pressure and negatively pressurized systems.
2:14.8	So to be clear, we're not talking about gas furnaces or systems where the evaporator
	...

Please login to see the full transcript.

Previous episode | Next episode

Disclaimer: The podcast and artwork embedded on this page are from Bryan Orr, and are the property of its owner and not affiliated with or endorsed by Tapesearch.

Generated transcripts are the property of Bryan Orr and are distributed freely under the Fair Use doctrine. Transcripts generated by Tapesearch are not guaranteed to be accurate.