Hydrostatic Pressure - Short 108

HVAC School - For Techs, By Techs

Bryan Orr

Careers, Business, Self-improvement, Education

4.9 • 1K Ratings

🗓️ 19 January 2021

⏱️ 8 minutes

🔗️ Recording | iTunes | RSS

🧾️ Download transcript

Summary

In this short podcast episode, Bryan explains how hydrostatic pressure can build up in refrigerant cylinders and present a hazard to technicians.

Your refrigerant cylinders have tare weight and water capacity values stamped on the tank. You'll want to use these when weighing the refrigerant you recover because you don't want to exceed 80% capacity. However, capacity changes when the liquid density changes; that density will change with pressure and temperature.

Hydrostatic pressure builds up when you have overfilled refrigerant vessels. When those vessels get warm, the density will decrease, and the liquid refrigerant expands. At some point, the vessel will contain 100% liquid and can no longer expand, so hydrostatic pressure will build. When that happens, you have a dangerous situation on your hands; the vessel may even explode.

AHRI recommends using 77 degrees as a guideline for figuring out the vessel capacity. However, we recommend using 130 degrees out of an abundance of caution; the back of your van probably won't get much hotter than that, so we use it as an operational maximum.

We only get hydrostatic pressure when we recover refrigerant as a full liquid. When we recover refrigerants like R-410A in the liquid phase, we get a 45-PSI increase for each degree (Fahrenheit) of temperature increase. For R-22, that number is about 60 PSI; with R-134A, that number is about 40 PSI. When we get temperature swings from an ice bucket (~32 degrees) to the back of a hot van (~130 degrees), the pressure can build up within the vessel.

We also need to think about hydrostatic pressure when pumping down systems with microchannel coils. Hydrostatic pressure can build up in the receiver, and liquid can fill your condenser.

Learn more about Refrigeration Technologies HERE.

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Transcript

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0:00.0	Hey, this is the HVAC School podcast. This is a short episode and today's short
0:07.8	episode is about hydrostatic pressure, which is something that many of you may be
0:12.4	familiar with, but we're going to put a few numbers to hydrostatic pressure today, but before we do that, we need to give thanks to our sponsors.
0:20.0	carrier and carrier.com. I've been a carrier dealer for many years carrier has their new green
0:26.8	speed extreme super high efficiency heat pumps out on the market now. Find out more by going to carrier.com. Refrigeration Technologies is a sponsor and they make a new excellent product called Nylog White. Nylog White is used for air, water, glycol, thread sealing applications.
0:47.5	It is an excellent product. It is very smooth.
0:50.9	It's made from the very best materials in order to seal, but also to be really easy to work with.
0:57.0	If you've used other types of pipe dope, then you're definitely going to want to take a look at Nylog White for all of your water, air, or glycol applications.
1:06.7	Find out more by going to Refrig, Tech.com
1:10.3	Blue On and Blue On Energy, makers of the very innovative Blue On app, you can download it on
1:16.0	Android or iPhone. You can get 24-hour tech support manuals for multiple equipment as well as
1:21.6	learn how to retrofit systems from R22.
1:25.9	They make the TDX20 refrigerant, but there's so much more.
1:29.6	Find out more by downloading the Blu-on app or by going to Blu-on-energy.com.
1:34.7	Ultra-Air at Ultra-Air-A-I-R-E.com. Ultra-A-A-R makes all sorts of amazing
1:42.3	whole-home dehumidification products we use them all the amazing whole home dehumidification products. We use them all the time
1:45.2	everything from their 98H
1:48.4	all the way up to their SD 12 which is actually a split dehumidifier amazing products.
1:53.6	We use them in our own homes and our own projects every day, and we are so excited
1:57.4	to have them as a sponsor.
1:58.6	It's Ultra-Air, spelled with an E, dot com.
2:03.0	All right, so hydrostatic pressure, what is it?
	...

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