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HVAC School - For Techs, By Techs


Jul 22, 2021

In today’s podcast, Trevor and Bryan discuss Copeland Scroll Compressor Multiples for Air Conditioning. “Multiples” refer to equipment setups with multiple compressors that have connected suction and discharge lines; they resemble parallel rack refrigeration setups. Multiples typically come in tandem (2) or trio (3) sets. Compared to having a single giant compressor, multiples are more efficient, more reliable, and have the ability to keep running in case if there’s a compressor failure. We often use multiples in rooftop units, makeup air units, and chillers. When you’re working on multiples or troubleshooting multiples, it’s okay to have sight glasses that indicate different oil levels. If you shut the compressors down and restart them, they should equalize. If you have a single compressor failure on a set of multiples, you may have to replace both compressors in a tandem set; the manufacturer does not make single replacements for some tandem models. Check the Application Engineering (AE) bulletin to determine your replacement needs. Multiples may contain compressors of different sizes. Compressors of different sizes have different mass flow rates. In these cases, you would use a flow restrictor to balance the mass flow across the compressors. On the refrigerant management end, the Copeland Scroll multiples will generally benefit from a crankcase heater. Correct location and installation of the crankcase heater are critical for proper functioning in multiples, and you can find that information in the manufacturer literature. Sometimes, you may also need an accumulator if there is a risk of refrigerant migration. Bryan and Trevor also discuss: Individual vs. multiple compressor manuals Oil equalization lines Compressor clamping Variable speed motors and compressor variability Sweating and flow restrictors Maximum tilt Adding oil Torque values Check out the AE-1430 bulletin HERE. Check out Emerson’s HVACR training HERE. Then, navigate to “Contractor Tool Box Talks with Emerson.” If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.