The screen says 72°F. The room says 78°F. One of them is lying.
Most controls calls go wrong in the first hour. A tech logs in, reads the graphic, trusts it and swaps a part. The other trade does the same. Two trucks, two invoices, and the room is still hot.
HVAC Controls Field Guide teaches a service tech, not a programmer, how to prove which version of the truth is real. You'll do it with a meter, a thermometer and a fixed order of checks that works on any building and any brand of controls.
What you'll be able to do
- Settle "controls or mechanical?" in the first hour, and leave with a written answer on which trade owns the fix.
- Prove a 10K thermistor against its maker's curve, and catch the Type II and Type III mix-up that started icing a coil while the screen read 56°F.
- Check 0-10 V and 4-20 mA signals with nothing to measure, and find the shared transformer that makes a reading jump.
- Follow a command from the controller's terminal to the damper blade or the valve stem, one link at a time.
- Find every override louder than the sequence, release it at the right priority, and leave life safety alone.
- Fix the schedules, holiday calendars and clocks that run a unit all weekend or leave an office dark on Monday.
- Corner an MS/TP trunk fault in five splits instead of paying for three days of new wire.
- Check the BAS against the chiller's own display, and find the mode or the mapping that's wrong.
- Measure a hunting valve before anyone retunes it, and catch heating and cooling fighting over the same air.
- Prove the fix with before-and-after trends, so the complaint stays gone.
Built from real service calls
Six chapters open on real calls from the author's company records, worked by his technicians in Burbank, the Valley, West LA, Santa Monica, Glendale and downtown LA. A coil icing up behind a sensor on the wrong curve. A damper shut tight while its actuator turned on a loose clamp. A surgery center running full cooling for three weeks on two forgotten overrides. A whole floor knocked off the network by one drywall screw. Every hard number traces to a published source you can check, from manufacturers' data sheets to standards and codes, all listed in the back of the book.
Inside
- 12 chapters, each ending in a named field tool you can copy and carry, from the Blame-Loop Shakedown to the Closeout Receipt
- 20 figures and 14 tool tables, drawn for the truck, not the classroom
- 168 knowledge-check questions with a separate answer key in every chapter
- A 52-term glossary and a full list of manufacturer and standards sources
Who wrote it
JD R. Lawson is a licensed mechanical engineer with more than 25 years in HVAC across the Philippines, Japan and the United States. He built his own HVAC company from nothing and grew it to a successful acquisition. He didn't make his living programming controllers, and this book doesn't pretend he did. He paid for the second truck, and the third, often enough to know what a tech with a meter and a method is worth.
Trust the meter. Then trust the screen.
