Floating vs. Fixed Suction and Head - Short #163

HVAC School - For Techs, By Techs

Bryan Orr

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

4.8 • 985 Ratings

🗓️ 16 May 2023

⏱️ 13 minutes

🔗️ Recording | iTunes | RSS

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Summary

In this short podcast episode, Bryan talks about compression ratio and efficiency, particularly how floating or fixed suction and head pressure affect those things.

Compression ratio (absolute head pressure divided by absolute suction pressure) closely correlates to efficiency in all sorts of compression-refrigeration HVAC/R systems; the most efficient systems have high mass flow with less compressor work. High compression ratios indicate a greater differential between the head and suction pressures. A lower compression ratio is desirable, but the number has to be realistic; a compression ratio of 1 indicates that the system is off. Medium-temp refrigeration compression ratios are typically around 3:1, whereas low-temp refrigeration can have higher compression ratios (6:1).

In commercial refrigeration applications, we can help control the compression ratio with floating suction and head strategies. Floating the suction and head pressures allow the equipment to achieve lower compression ratios and higher equipment efficiency. Old strategies for controlling compression ratio would involve having a fixed evaporator temperature and suction pressure. In a parallel rack system, floating suction allows the suction pressure to float up when the case maintains temperature; this strategy helps close the gap between the absolute suction and absolute head pressures and reduces the compression ratio.

Floating suction strategies allow the suction to "float" up by allowing the evaporator coil temperature to rise a little bit when the box temperature is under control. Floating head strategies, on the other hand, allow the head pressure to float down in low-ambient conditions. We can look at ambient temperature and discharge pressure to determine how much we can float down the head pressure.

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Transcript

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0:00.0	Yeah, dabbadab ado now, this is the HVAC School Podcast, the podcast, Foretext, and Bitex.
0:10.0	I'm your host, Brian. In this episode, we're going to talk about compression ratio, but specifically
0:16.1	we're going to talk about floating suction and a floating head.
0:21.5	How that relates to efficiency talk about some of the challenges. This is kind of a
0:25.2	supermarket refrigeration thing, but it actually applies to all of us. Some simple principles here.
0:29.8	If you want to take a deep dive on this floating suction, floating head thing,
0:33.6	Jeremy Smith and I talked about this many, many episodes ago, so good luck finding it.
0:37.8	The easiest way to find really old episodes is to go on the website,
0:41.4	HVCR School.
0:42.2	Use the search
0:43.0	bar and then just search podcast you'll definitely find it there
0:45.4	but I don't number the podcast because I don't care about that okay
0:49.5	okay okay?
0:50.5	It feels like in my mom or, always telling me what to do. Anyway, before we do that, we're going to hear from, or actually know, we're going to talk about some of our great sponsors.
1:01.0	Big thanks to White Rogers. Check out the White Rogers
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1:20.0	Choose from the 70 or 80 series, all in stock and ready to ship.
1:24.0	Install in five minutes or less and don't forget to join the logo challenge on social media.
1:28.0	To find the contractor branding landing page and to get started go to HVacr school
1:33.0	dot com slash sensei that's HVacr school
	...

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