#metering device

Tech Tips:

Electronic Expansion Valve Troubleshooting

Electronic expansion valves (or EEVs) are metering devices that you’ll find in a variety of modern HVAC equipment, including heat pumps, VRF units, inverter mini splits, and chillers. This valve is electronic rather than mechanical and can precisely control the flow of refrigerant into the evaporator and optimize efficiency for heating and cooling units. Other […]

TXV External Equalizers and Distributors

This is a quick tip from the “Expansion Valves – What Does and Doesn't Matter?” livestream on our YouTube channel featuring Joe Shearer, Matthew Taylor, and Corey Cruz. You can watch it on our website HERE. Equalizers get their name because they provide a closing force to equalize against the bulb pressure (an opening force). […]

Piston vs. TXV Metering Devices

The piston (fixed orifice) and TXV (thermostatic expansion valve) are the two most common metering devices in use today, though some modern systems utilize an electronically-controlled metering device called an EEV (electronic expansion valve). It should be noted that there are other types of fixed-orifice metering devices, like capillary tubes; however, their use is not […]

HVAC/R Refrigerant Cycle Basics

This is a basic overview of the refrigeration circuit and how it works. It isn't a COMPLETE description by any means, but it is designed to assist a new technician or HVAC/R apprentice in understanding the fundamentals. First, let's address some areas of possible confusion: The word “condenser” can mean two different things. Many in […]

The Basic Refrigeration Circuit

In this episode of HVAC School, we discuss the entire basic refrigerant/compression refrigeration circuit. We are in the business of moving heat. Heat refers to motion in the molecules. Temperature is the average velocity of those molecules. Heat needs a temperature differential to move. So, HVAC systems absorb heat when the refrigerant is colder than […]

Understanding HVAC Metering Devices

Demystifying TEVs

NOTE: If you cannot view the recording, the video may still be processing. The maximum wait time is 24 hours. We apologize for the delay and appreciate your patience.

How to Evacuate an AC system, Full Vacuum Procedure

Our latest Podcast

HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

In this short podcast, Bryan talks about evaporator coil placement based on a question submitted by a listener, John. Evap coil placement differs in furnace applications versus air handlers.

When we use air conditioners with furnaces, we usually put evaporator coils on the positive side to protect the heat exchanger from rusting out during the summer (due to condensation and the chemical reactions that can occur with the metal heat exchanger). However, when it comes to air handlers, they’re usually on the negative side. The coil is usually on the negative side of a fan coil or air handler because it keeps the blower motor cooler (though that doesn’t make a huge difference in terms of performance).

The HVAC system will lose fewer BTUs to leakage when the coil is on the negative side, which is better for energy efficiency; those BTUs can reach the conditioned space rather than the closet, garage, or wherever it is stored. Pulling air over the evaporator coil on the negative side, however, could potentially lead to greater turbulence.

We run into challenges with evap coil placement on gas furnaces when we have dual fuel systems (a heat pump and furnace working together). You can’t run gas heat over a heat pump coil due to the high head pressure, so a parallel setup would avoid the risks of high head pressure (downstream) or rusted-out heat exchangers (upstream).

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.