Combustion Air
To maintain combustion (burning), you need three things: fuel, heat, and oxygen. If you have all three in the proper proportion, you can maintain a continuous state of combustion. Remove one (or reduce one sufficiently), and the triangle of combustion can collapse. In a common natural gas (NG) furnace, the heat is the igniter, the […]
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Furnace Air Temperature Rise
Every gas furnace data plate/tag has a specification for the temperature rise through that furnace. It is shown in a range like 50-80° or 45-75°. Those two numbers are the lowest recommended temperature rise; the highest allowed temperature rise through the furnace is usually a 30° difference. When possible, we want to get the rise toward […]
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A Story We Know
Marley was dead, to begin with. There is no doubt whatever about that. That's the way Charles Dickens begins his “A Christmas Carol,” one of the most well-known pieces of literature in the modern world. A short story that can be read aloud in a few hours has to start memorably, and this one certainly […]
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The Diagnosis Game (and Why Van Sleeping Bothers Me)
The Sleeper  The year was 2002, and I was 20 years old. I had a helper named Clay, and he was a really nice guy, probably 15 years my senior, already with streaks of grey in his hair with a way of making you feel at ease—so very at ease. OK, he was sleeping most […]
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The “Approach” Method of Charging and Condenser Efficiency
We have discussed many methods for checking a refrigerant charge without connecting gauges over the last few years. Recently, I've been thinking about the “approach” method of charging that many Lennox systems require. What is the Approach Method? The “approach” simply refers to the temperature difference between the liquid line leaving the condenser and the […]
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Is it too cold to set the charge?
I've heard the phrase, “It's too cold to set the charge!” for as long as I've been in the trade. I've also heard some variations of, “We need to come back and set the charge,” or, “We need to come back to do XYZ [some other thing].” Granted, there are cases where you do actually […]
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A REALLY Loud Compressor
A while ago, I walked up on one of our managers who was talking to a junior tech diagnosing an intermittent controls issue on a pool heat pump. In the background, you could hear an EXTREMELY loud compressor. The junior tech had just been moving some wires around, and the next thing he knew, there […]
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4-20ma Control Basics
Back in the “good old days,” controls were all analog and mechanical; that simply means they acted in a directly connected and variable manner based on a change in force. Both pneumatic (air pressure) and hydraulic (fluid pressure) systems are examples of mechanical or analog controls. When the pressure increases or decreases on a particular […]
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Pool Heater Water Flow Issues
As you may already know, we work on pool heaters at Kalos as a way of opening ourselves up to some extra business during the winter. We find that it's a worthwhile line of work, and it may be something that other residential HVAC companies may want to consider doing. This tech tip by Bert […]
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