Equipment
Heat pumps, furnaces, air conditioners, boilers and water heaters: how they work, what they cost, how long they last and which efficiency standards apply.
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Static Pressure in HVAC: What It Should Be, How to Measure It, How to Fix It
Most home HVAC equipment is rated at 0.50 in. w.c. of total external static pressure. Here is where that number comes from, how to measure TESP with a…
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Building Automation System (BAS): How It Works, Who Has One, Savings and Cost
A building automation system runs a commercial building’s HVAC from one network. Our EIA CBECS tabulation shows who has one by building size, plus PNNL measured savings, BACnet,…
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Air Handling Unit (AHU): Components, How It Works, Code Rules and Maintenance
How a commercial air handling unit works, section by section, how it differs from an RTU, DOAS and fan coil, the 62.1 and 90.1 numbers that shape it,…
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Fan Coil Unit: How It Works, 2 Pipe vs 4 Pipe, Code Rules and Maintenance
A fan coil unit heats or cools one room with water from a central plant. We explain 2-pipe vs 4-pipe, how FCUs compare with AHUs, VAV and PTACs,…
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Water Source Heat Pump: How the Loop Works, Federal Ratings and Maintenance
A water source heat pump trades heat with a shared water loop instead of outdoor air. Here is how boiler/tower loops work, what 10 CFR 431.97 and ISO…
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Steam Trap Explained: Types, Failure Modes, Testing and the DOE Cost of a Leak
A steam trap drains condensate and air while holding back steam. DOE data show 15% to 30% fail in neglected systems, and one stuck open can waste thousands…
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Manifold Gauge: How to Read and Hook Up HVAC Gauges, and What EPA 608 Requires
A manifold gauge reads both sides of an AC system. Here is the hook-up order, a worked R-410A and R-454B reading, analog vs digital specs, and the 40…
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VAV Box: How Variable Air Volume Boxes Work, Types, Minimum Airflow and Reheat Rules
A VAV box meters air from the air handler into one zone. How pressure-independent boxes measure airflow, the box types, what PNNL and ASHRAE 90.1 say about minimum…
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Duct Smoke Detector: When Code Requires One, Where It Goes and How It Is Tested
A duct smoke detector shuts down an air handler when it senses smoke in the duct. Here is when IMC Section 606 and NFPA 90A require one, supply…
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HVAC Dampers: Types, How to Tell Open From Closed, and When Bypass Is Needed
HVAC dampers set, switch or block airflow in ductwork. Here are the six types, how to read a damper handle, seasonal settings for two-story homes, and what Honeywell,…