Handover Under Pressure on a Frozen Store

No. The readings do not reconcile with a healthy system, and pull-down conditions are never a valid basis for handover anyway.

• Superheat 1.5 K is below any acceptable minimum (typically 5–8 K at the evaporator outlet). Liquid is reaching the compressor.
• Discharge 108 °C is far beyond normal (roughly 70–90 °C). Combined with low superheat, that is a floodback/damage signature - the oil is being diluted and the compressor is the component that pays for a signed certificate.
• Subcooling 2 K says the liquid line is not properly condensed or charged; a clear sight glass with 2 K subcooling means the glass is telling you less than the gauges are.
• Room 6 K off design after 14 hours may be normal for pull-down, but it cannot be demonstrated either way while the refrigeration circuit is behaving like this.
• TEVs hunting on both circuits with 1.5 K superheat is a control instability, not a settling-in phase.

To the client: the system is not ready to take product, the reason is measurable, and here is what I am doing about the stock - a contingency plan (holding space in an adjacent store, or a rental unit with temperature logging) rather than a false certificate. A signature tonight buys a compressor failure in six weeks and a far bigger claim.

I would work from the cheapest and most common error outwards, because the combination is internally contradictory and one bad measurement would explain it.

1. Verify the measurements. Probe calibration, clamp position, insulation, and - most likely culprit - the TEV bulb: is it on the evaporator outlet, clamped tight, on a horizontal run, insulated, and not on a header or a vertical? A bulb sensing the wrong point produces exactly this picture.
2. Weigh the charge. Compare actual charge against nameplate plus calculated line charge. Low subcooling with a clear glass points to a marginal charge or a liquid-line restriction; check for a temperature drop across the filter drier and any sharp pressure drop.
3. Check the TEV against the duty. An oversized valve hunting on a pull-down load, wrong orifice, incorrect MOP setting, or a valve selected for the design condition rather than the pull-down will all overfeed.
4. Check evaporator airflow. Fan speed, coil condition, ice build-up, and whether defrost termination is set correctly.
5. Check condenser side. 29 °C ambient - confirm the condenser is rejecting what the gauges say it is.

Then set the superheat, re-check subcooling, and record the readings that prove it.

Demonstrated, not asserted:

• A stable 24-hour run with the room at −25 °C and superheat in the 5–8 K band, subcooling at the design figure, discharge within the compressor manufacturer's limit.
• A full defrost cycle: initiation, termination on temperature or time, drain heater, drain free-flowing, no ice on the floor.
• Controls and alarms proven one by one - high/low pressure, high discharge, door alarm, product-simulator alarm, remote dial-out to the client's monitoring.
• Door heaters, curtains, strip curtains, air-flow path, and the anti-sweat control.
• Power failure and restart behaviour.
• Everything witnessed by the client's representative and, where the specification requires, the consultant.

Documented: as-built drawings, charge weight and refrigerant record, pressure-test and evacuation records, electrical test certificates, O&M manuals, control schematics, the commissioning sheet with actual readings rather than ticks, training record for the client's staff, and a clear statement of any outstanding item with a date.

I would not accept "outstanding: none" unless it is true. A dated defects schedule is a professional document; a false clean sheet is a liability that follows you for twelve months.