#carbon monoxide

Tech Tips:

If you’ve been following my writing for the last couple of years, you know that I like to blather on and on about combustion analysis. Now, I am by no means an expert on the subject, as I live in North Texas (which is not known for its intense heating season), but I love using […]

Combustion Testing Doesn’t Stop in the Summer

This tech tip was written by Casey Contreras. Casey is a field coach and instructor for the National Comfort Institute (NCI). Thanks, Casey! As HVAC technicians, our careers often focus on either cooling or heating. Because of this split view, we typically ignore gas-fired appliances during the cooling season. There are dangers lurking in any […]

Practical Uses of Combustion Analysis

This tech tip reviews the live stream by the same name aired on November 1st, 2023. You can watch the full live stream HERE. We want to give special thanks to the guests: Jim Bergmann, Jim Davis, Tony Gonzalez, Louise Kellar, Bill Spohn, and Tyler Nelson! Gas furnaces (or any combustion equipment) create a controlled […]

The Case for Buying a Combustion Analyzer

Last year, I bought my first combustion analyzer. I had just started my own company and felt the additional weight of responsibility to sit down and determine the best way to verify that the furnaces I was servicing were working safely. In the past, the most extensive testing I had done was a visual inspection […]

What Does “Air Free CO” (Carbon Monoxide) Mean?

Almost everyone knows that CO (carbon monoxide) is really nasty stuff and nothing to play around with. Humans will often begin exhibiting symptoms of CO poisoning at 200 ppm (parts per million) of CO in a space. Studies have also shown that the effects of CO exposure can accumulate over time, resulting in health […]

Combustion Analysis and Troubleshooting with Tyler Nelson

Why and How of Combustion Analysis w/ Tyler Nelson

Bryan Orr interviews Tyler Nelson, an HVAC expert with over 20 years of experience as a contractor. They have an in-depth discussion about combustion analysis and why it is becoming increasingly important for HVAC technicians to utilize this process. The conversation provides an overview of combustion analysis benefits and why HVAC pros should incorporate […]

Crystal G Cleveland
#air free co #carbon monoxide #CO

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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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