R-290 Undercounter Freezer in an Open Store
A grocery store has a built-in undercounter freezer with a nameplate charge of 5.3 oz (150 g) of R-290. A bubble test shows a slow leak at an evaporator pinhole. The store wants the repair done in place after closing, between 10 p.m. and 2 a.m., because the unit is built into a cabinet. The aisle contains a floor-scrubber charging station and an electric pallet jack, and the store's main electrical panel is 15 ft away. The technician's recovery machine is rated for A2L only. Available equipment also includes a nitrogen regulator, a 1-gram-resolution scale, and a standard halide torch. Ambient is 74°F and the aisle has no mechanical ventilation.
1. Is an in-place repair acceptable? What conditions must be met before any refrigerant is touched?
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In place is possible only if you control ignition sources and remove the refrigerant safely. The decisive problem is equipment: your recovery machine is rated for A2L, not A3. A2L-rated machines are not listed for flammable A3 refrigerants, and R-290 must not be recovered with one. Stop and get an A3-rated recovery unit or follow the OEM service procedure.
Before work: lock out and tag out the freezer and the scrubber charger, remove the pallet jack from the aisle, and establish an exclusion zone of at least 10 ft (more if the OEM or AHJ requires). R-290 vapor is heavier than air and its lower flammability limit is about 2.1% by volume, so ventilate at low level with a fan and keep sparks, relays, and open flames out of the area. Have a dry-chemical extinguisher at the work point and a second person present. If the cabinet cannot be opened enough to ventilate and work safely, pull the unit to a service area. Notify the store in writing that the area must stay clear until you release it.
2. Outline the repair, evacuation, and charging steps, and identify which tools listed in the setup cannot be used.
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Sequence: isolate power; recover the 150 g charge with an A3-rated machine into a DOT cylinder, staying within the cylinder fill limit; do not vent it in the store. Break vacuum with dry nitrogen, then cut out or replace the leaking evaporator section. Nitrogen-purge the line while brazing with a flow regulator - no air in the line and no flammable gas. Pressure-test with dry nitrogen only, never oxygen or compressed air. Leak-check with an electronic detector rated for flammable refrigerants.
The halide torch stays in the truck: it is an open flame and does not reliably detect hydrocarbons. Use the 1-gram scale for the final charge. Triple-evacuate to 500 microns and hold a decay test. Charge by weight to exactly 150 g, charging liquid, and confirm you do not exceed the nameplate charge. Start up, verify superheat and the frost pattern, and leak-check again.
3. What do you document, and what do you tell the store about the limits of this repair?
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Document the recovered and installed weights, the leak location, the repair method, evacuation levels and hold time, the detector used and its calibration, and the final charge versus nameplate. Mark the unit R-290 only and confirm the cabinet ventilation openings are clear and unobstructed.
Tell the store: the 150 g limit is a condition of the unit's listing; no other refrigerant can be used; and the unit cannot be topped off or recharged above the nameplate. Also note that a second evaporator failure on a unit like this usually means replacement rather than another repair, and that this repair does not change the unit's safety classification or ventilation requirements. If local code or the insurer requires notification before A3 service work, send it before the unit goes back in service.