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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Marine Air Conditioner: How Boat AC Works, Sizing Math, Seawater Flow and Power
How a seawater-cooled boat AC works, Dometic’s square-foot sizing table with a worked example, pump flow by model, heating limits, start surge and breaker rules, and where R-410A…
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Spot Cooler: How It Works, Where the Heat Goes, Sizing and the DOE Gap
What a spot cooler is, where its condenser heat goes, how to size one from watts, maker specs for 115 V to 460 V units, and why DOE’s…
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Chimney Liner Rules: When Code Requires One, Which Type and How It Is Sized
When code requires a chimney liner, which type fits wood, oil, Category I gas and condensing appliances, how liners are sized, and why an orphaned water heater forces…
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Combustion Air: The IRC and IFGC Rules, Opening Sizes and a Worked Example
Combustion air rules from IRC G2407 and IFGC 304, quoted section by section: the 50 cubic foot method, the infiltration equations, every opening size, and a furnace plus…
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Hygrometer: How Accurate Yours Is and How to Check It With the Salt Test
What a hygrometer measures, how accurate each sensor type is according to maker datasheets and the WMO, and how to check yours with the NBS salt test values.
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Fireplace Insert Guide: Wood, Pellet, Gas and Electric Compared on Federal Data
Open fireplaces lose over 90 percent of their heat; an insert turns one into a real heater. We compare wood, pellet, gas and electric inserts on EPA and…
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Negative Pressure Room: CDC and ASHRAE 170 Rules for ACH, Pressure and Exhaust
How a negative pressure room works and what CDC and ASHRAE 170 require: air changes, the 0.01 in. w.g. differential, exhaust discharge, monitoring and temporary HEPA conversions.
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HVLS Fan: How Big Ceiling Fans Cool, What DOE Requires and NFPA 13 Sprinkler Rules
An HVLS fan is a large-diameter ceiling fan over 7 feet. Here are the DOE efficiency floor, the four NFPA 13 sprinkler rules, the fire test behind them…
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Fume Hood: Face Velocity, ASHRAE 110 Tests, Hood Types and Energy Use
How a lab fume hood works, why OSHA no longer prints a face velocity, what Z9.5 and Cal/OSHA require, how ASHRAE 110 AM, AI and AU tests work,…
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RV Air Conditioner: Amps, 30 vs 50 Amp Service, Generator and Battery Math
An RV air conditioner draws about 13 to 16 running amps in maker spec sheets. We tabulate Dometic, Coleman-Mach and Furrion data, then do the 30 and 50…