R407C Charging Procedure UK: Step-by-Step for HVAC Engineers
R407C is a zeotropic blend of R32, R125 and R134a. Its zeotropic nature means it must always be charged as liquid — drawing vapour causes fractionation, changing the blend composition and degrading system performance.
Key R407C Facts Before You Start
- Always charge as liquid — use siphon or inverted cylinder
- Temperature glide ~6–7°C — use dew point for suction, bubble point for liquid side
- Never use R410A PT data for R407C calculations
- POE oil required
Step-by-Step R407C Charging
- Recover existing charge (if system has leaked, recover all and recharge fully)
- Pressure test with dry nitrogen; evacuate to 500 microns
- Use siphon or inverted cylinder — attach to high-side liquid service port
- Open valve slowly; charge by weight to data-plate specification
- If charging via suction port: use liquid-charging device to vaporise before compressor inlet
- Run system 15 min; check dew-point superheat (5–10°C) and bubble-point subcooling (5–8°C)
- Log refrigerant type, quantity, engineer certification, date
Common Mistakes
- Drawing vapour from upright cylinder — causes fractionation
- Topping up a fractionated system without full recovery
- Using wrong PT data — R407C pressures are very different to R410A
R407C 10 kg from Refrigerant Gas Supplies Ltd — UK F-Gas compliant, next-day delivery. See also R407C R22 retrofit guide.
Frequently Asked Questions
Why must R407C be charged as liquid?
R407C is zeotropic — its three components have different volatilities. Vapour withdrawal preferentially removes R32, leaving an off-spec mixture. Liquid charging preserves blend composition.
What is the target superheat for R407C?
5–10°C suction superheat measured using dew-point saturation temperature. 5–8°C liquid subcooling using bubble-point saturation temperature.
Can I use R410A manifold gauges for R407C?
Only if they have an R407C scale. R407C and R410A have very different pressures. Use digital manifold with the correct refrigerant selection.