Oil Acid Testing and Burn-Out Clean-Up — Procedure from Test Kit to Clean System

Using acid test kits on POE and mineral oil systems, interpreting results, and the full burn-out clean-up sequence — suction and liquid driers, oil changes, retests — that lets a replacement compressor survive, with the stocked ETK/TKO kits and drier families.

Why acid appears

Two chemistries sour a refrigeration system: moisture hydrolysing POE ester oil into organic acids (slow, from poor evacuation or a wet drier), and motor burn-out cracking oil and refrigerant into acids and soot in seconds. Both attack motor insulation and copper-plate bearing surfaces; both are measurable at the oil, cheaply, before they are measurable as a dead compressor.

Testing

The stocked kits cover the chemistry split: ETK for ester (POE) oils and the TKO universal kit for mineral and synthetic oils. Method: draw the sample from a live oil point (sight-glass drain or oil valve) into the kit vial, mix per instructions, read the colour change against the card — the kits resolve 'acceptable' from 'acid present' at the thresholds printed on the kit. Test: at commissioning (baseline), at every service on plants with a history, after any moisture event, and on schedule for critical plants. Record results on the plant card; the trend is the diagnosis.

Mild acid (wet system, no burn-out)

1. Fit/renew an oversized liquid-line drier (DML/DCL selection); run; retest in days.
2. Persistent acid: oil change (correct grade per the oil guide) plus a second drier change; find the moisture source — chronically wet systems have a leak on the low side or a service-practice problem.
3. Verify with the sight-glass moisture indicator dry and an acid retest after a week of normal running.

Burn-out clean-up — the sequence that works

1. Diagnose first: megger the old motor, read the protection module's memory (Kriwan Diagnose) — a burn-out has a cause, and the new compressor inherits it unless found.
2. Recover and inspect: acrid refrigerant and black oil = severe burn; flush the worst from accessible low points.
3. Replace compressor, liquid drier (step a size up), and install a suction burn-out drier (DAS family: 164s, 305s, 309s) with gauge access to watch its pressure drop.
4. Expansion device and strainers: clean/replace inlet strainers (EEVs: E2V 150 µm strainer); severe burns justify TEV/orifice replacement.
5. Evacuate deep, charge, run 24–72 h, then: oil sample acid test, suction-drier ΔP reading, oil change if dark.
6. Swap the suction drier cores / remove the DAS once two consecutive tests pass clean; a forgotten suction drier is a standing capacity tax and will eventually plug.
7. Document: tests, driers, oil batches into the plant file — the warranty inspector's first request.

What clean looks like

Clear oil at the sight glass (glass and O-ring stocked), acid tests passing on two dates, moisture indicator dry, suction drier ΔP stable and low, and compressor current/discharge temperature at commissioning values. Keep one ETK and one TKO kit on the van permanently: the five-minute test before quoting a compressor exchange routinely changes what gets quoted.

Compiled by cBallast for identification and cross-reference. Part numbers, designations and trademarks belong to their respective manufacturers. Confirm ratings and dimensions against the manufacturer's current documentation and the nameplate of the installed equipment before ordering or installation.