In this episode of the HVAC Know It All Podcast, host Gary McCreadie is joined by Jamie Kitchen, an HVAC expert, Training and Account Manager at Danfoss, to discuss refrigeration metering devices and how they control refrigerant flow. Jamie explains what a simple restriction is, how an orifice or piston works, and how flow is set by the size of the hole and the pressure difference across it. The conversation covers capillary tubes and why they self regulate through friction and flash gas, why cap tubes clog when a system runs hot, and why suction lines are sized larger than liquid lines. Gary and Jamie also explore how outdoor weather and humidity change the load, why pistons struggle with latent cooling, and how overcharging on a hot day can flood the compressor and destroy a scroll.

In this conversation, Jamie explains what a simple restriction is and how fixed metering devices control refrigerant flow in cooling and refrigeration systems. He discusses how an orifice or piston works, how the size of the hole and the pressure difference set the flow, and how capillary tubes self regulate through friction and flash gas. Jamie and Gary explore topics such as why cap tubes clog when a system runs hot, why suction lines are larger than liquid lines, and how oil must keep moving back to the compressor. They also discuss how outdoor weather and humidity change the load, why pistons cannot adapt to latent cooling needs, and how overcharging on a hot day can flood the compressor and wreck a scroll.

Expect to Learn:

What a simple restriction is and how an orifice or piston controls refrigerant flow.
How the size of the hole and the pressure difference across it set the amount of flow.
How capillary tubes self regulate through friction and flash gas, and why they can clog when a system runs hot.
Why suction lines are sized larger than liquid lines and how oil keeps moving back to the compressor.
How outdoor weather and humidity change the load, and how overcharging on a hot day can flood the compressor and wreck a scroll.

Episode Highlights:

[00:00] - Sponsor Ad: Factory Direct Filters

[00:42] - Intro to Jamie Kitchen in Part 1

[02:04] - Simple Restriction (Orifice & Pressure Differential)

[02:52] - Cap Tube vs. Orifice & How Cap Tubes Self-Regulate

[06:35] - Clogged Cap Tubes: Causes (Heat & Oil Breakdown)

[09:11] - Are Cap Tubes Still Viable? (Stable Loads Like Coolers)

[12:20] - How Orifice Systems Work & Charging Challenges

[17:58] - Scroll Compressor Bearing Failure & Failure Sound

This Episode is Kindly Sponsored by:

Cintas: https://www.cintas.com/hvacknowitall

Cool Air Products: https://www.coolairproducts.net/