#blower door

Tech Tips:

The Ups and Downs of High-Performance HVAC

This tech tip recaps the livestream by the same name, featuring HVAC School contributors Matt Bruner and Adam Mufich and special guests Michael Housh, Chris Hughes, and Dustin Cole. You can watch that livestream on our YouTube channel HERE. “High-performance HVAC” is a term we hear quite a bit these days, but it’s not easy […]

Solving Comfort and IAQ Issues in a Vintage Home: A Case Study

This tech tip is a recap of the Santa Fe Dehumidifiers and Comfort Dynamics, Inc. case study about a 1941 vintage home in Miami, FL. You can listen to the podcast about that case study by clicking the play button below, and you can read the case study at https://hvacrschool.com/case-study. Special thanks to Nikki Krueger […]

What is the Difference Between ACH & ACH50?

This photo is of a blower door test we performed at my own house using a Retrotec blower door. You will notice the 15-passenger van outside the window, which is a dead giveaway. A blower door is used to measure the tightness of a building and is often discussed in terms of an ACH50 number. […]

Blower Door Testing, Building Performance & More w/ Corbett Lunsford (Podcast)

In this podcast episode, Bryan talks to Corbett Lunsford about blower door testing and the coming building performance revolution. Building performance and HVAC have been becoming much more closely linked lately. So, it's a good idea for HVAC techs to learn a bit about building performance. In the HVAC world, we often see homes with […]

Bryan Brantley
#blower door #building performance

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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).

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