Odd HVAC calls

Hey guys, got a question for the techs here.

I came across a ducted heater today that I don’t run into very often. It basically had two large electric heating elements, an external temperature sensor in the return duct, and a thermostat mounted outside the unit to set the temperature.

A coworker mentioned it was also tied into an HRV downstairs, which added another layer to the setup.

Most of my work is usually boilers, RTUs, heat pumps, and chillers, so I’m pretty comfortable with those. But for some reason these one-off systems like HRVs, ERVs, duct heaters, or other odd setups don’t come up much for me.

Just wondering how you guys deal with equipment you don’t work on very often. Do you usually