FieldBench
How To

Charge · 12 min

Weigh in a new split (any refrigerant)

Nameplate plus liquid-line feet. The charging chart is a trim, not a substitute for the scale.

Safety

Match the cylinder to the nameplate. R-32, R-454B, and R-410A are different jobs.

A2L: max charge / mitigation limits still apply on a ‘standard’ 15-foot line set if the indoor is in a small space.

Do not start the compressor to ‘pull the charge in’ from a vacuum. Weigh in with the system off, then start.

Tools: Charging scale · OEM I/O: factory charge and oz-per-foot adder · Core tools, vacuum already passed · Thermistors and the Charge screen for SH/SC trim

  1. 1. Calculate before you open the bottle

    Factory charge on the outdoor plate is for a stated line-set length (often 15 ft — read it). Extra liquid-line feet × the OEM oz/ft. Some brands subtract for a short set. Write the target pounds on the ticket before the valve opens.

    Expect: A target weight, not a feeling.

    If not: No adder on the plate → open the I/O or the install book attached to this model in FieldBench.

  2. 2. Weigh in liquid with the system off

    Passed decay. Cores out or tools on. Liquid from the cylinder into the liquid line (restrictor / liquid valve per OEM). Zeotropes (410A, 454B, 407C): liquid only. R-32: OEM path. Watch the scale to the ounce.

    Expect: Target weight in the system. Cylinder closed.

    If not: Weight will not move → a closed king valve or a frozen hose. Do not start the compressor to force it.

  3. 3. Run and trim on the device, not on suction pressure

    Cool call, 10+ minutes (longer on 454B). TXV: hit published SC. Piston: published SH from indoor WB + outdoor DB. High SH + low SC is still a starve. High SC + high head is still overcharge or non-condensables. Put the final charged weight on the ticket.

    Expect: SH/SC in the OEM window. Final weight written.

    If not: If you added more than a few ounces of trim, you either missed the adder or you have a leak / restriction. Recover and weigh the whole charge — do not keep topping.

  • HVACR School: if you do not use a scale every time you add or remove refrigerant, start today.
  • A piston system charged by ‘beer-can cold’ is how you bury a restriction.