Chiller Diagnostic & Refrigerant Calculator

Two things. First, it calculates superheat and subcool from suction/discharge pressures and line temperatures for the common HVAC refrigerants (R410A, R32, R134a, R407C, R454B, R22) and tells you whether you're inside the manufacturer's typical target band. Second, it gives a manufacturer-agnostic fault-category lookup for the conditions chillers actually trip on — HP, LP, freeze stat, flow, oil, motor overload, short cycling — with likely causes ranked by frequency and a structured on-site diagnostic walk-through.

Superheat tells you whether the expansion valve is feeding the evaporator correctly. Too low (<3°C on most refrigerants) risks liquid slugging into the compressor; too high (>10°C) means the evaporator isn't fully wetted and capacity drops. Subcool tells you whether the condenser is performing and whether you have the right refrigerant charge. Together they let an engineer distinguish refrigerant problems (charge, expansion valve) from heat-exchanger problems (fouled coil, low flow) without disconnecting hoses.

The tool uses fitted saturation curves accurate to within roughly 1°C across the normal HVAC operating range (-20°C to +60°C evaporating/condensing). This is well inside the precision of typical field gauges and digital manifolds. For charging or commissioning decisions, always cross-reference the manufacturer's published PT chart for the exact refrigerant and condition.

R410A (still common on commercial AC and small chillers installed 2005–2024), R32 (modern lower-GWP replacement), R134a (large water-cooled centrifugal and screw chillers), R407C (R22 retrofit blend), R454B (newer A2L low-GWP chillers and heat pumps), and R22 (legacy plant — phased out, included for diagnostic work on remaining systems). Hydrocarbon refrigerants (R290, R600a) are not currently supported.

Manufacturer-specific alphanumeric codes vary widely between Daikin, Carrier, Trane, York, Mitsubishi, Climaveneta and others. The tool's categories cover the underlying conditions (high-pressure trip, low-pressure trip, freeze stat, flow switch, oil fault, motor overload, short cycling), which is what an engineer actually diagnoses against. Cross-reference the panel code with your manufacturer's O&M manual to map it to one of these categories.

No — and it isn't intended to be. The tool is for engineers and FM teams to think through what they're seeing before or during a site visit. All refrigerant work in the UK and EU must be carried out by F-Gas certified engineers under the F-Gas Regulation. Use this as decision support, not as a substitute for qualified service.

Yes, completely free with no signup required. The calculator runs entirely in your browser — pressure and temperature values are never sent to a server. The fault category content is static reference material. There is nothing to store and nothing to track.

This tool gives you generic, manufacturer-agnostic guidance. PM Assist lets you upload the specific chiller's O&M manual, manufacturer service bulletins, commissioning data, and historical service reports — then search them in plain English with source-cited answers (e.g. "What's the HP cutout setpoint on the level 3 Carrier 30RB?" returns the page reference from the actual manual). The two are complementary: use the diagnostic tool to think; use PM Assist to retrieve the OEM-specific values.