Refrigerant handling: General tips (part 2 of 2)

Short, practical technician tips on refrigerant handling for general. Check each one against the manual for your exact model before acting.

Magnetic-bearing centrifugals

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Need no oil; 60–300 tons; indoor non-freezing only.

Maintenance check sheet items

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Leak test, head & suction pressures, oil level, water valve/drain, motor lube, belts, clean both coils, straighten fins, V & A readings, fans, filters, tighten electrical connections, lube moving parts; note wear parts (belts, filters) to bring next visit.

Manifold valve positions

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Both closed = read pressures; both open = evacuate (pump on center); one open = charge that side.

Mercury spill

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Evacuate 15 min, ventilate, shut HVAC, never touch/vacuum/wash down drain; send old mercury stats to an authorized recycler.

Never just reset a tripped protector (Pro Tip)

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A tripped overload, pressure switch or oil safety is a symptom of a system problem; find the root cause rather than replacing the device.

Never put system pressure into a vacuum (micron) gauge

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Water/ice/pressure ruins it. Don't leave compound gauge on the high side continuously either.

Nozzle handling rules

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Never clean, never swap internals, hold by hex flats, keep boxed, use nozzle tool, exact replacement (gph/angle/pattern), replace yearly.

Oil deaerator install

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One-pipe needs bypass plug installed in the pump; two-pipe already has it; filter goes between tank and deaerator, never between deaerator and burner (clog → pressure → blown seals). Cap the old return line.

Oil nozzle cleaning on boilers

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Cloth and solvent only, never a wire brush (scratches orifice).

Oil nozzle size errors

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Too small = weak flame; too big = smoke/soot and short cycling. Replacing with higher-capacity nozzle = overfiring (red flue pipe, high stack temp). Never raise pump pressure to "fix" a problem.

Only a high-side gauge on a nitrogen test

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Compound gauge gets wrecked.

Re-zero gauges for elevation; never adjust psia gauges

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Open gauge to air, set needle to 0 with calibration screw.

Replace burner motor with same rotation, frame and rpm

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; pump speed = motor speed (3450 or 1725).

Required safety devices (most codes)

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High-pressure control, spring relief valve or rupture disc, fusible plug where fire exposure; outdoor access ports need locking caps (IMC 1101.10); refrigerant lines across walkways ≥ 7'3" above floor unless at ceiling; no refrigerant piping in elevator shafts, public stairways or exits (IMC 1107.2).

RTU curb gasket

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Resilient gasket between base rail and curb is the leak barrier; acoustic lining and 2" fiberglass in the curb for noise.

RTU oil tank

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Never more than 10' below the burner.

Smoke test

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Run 5 min until flue temp stabilizes, pull sample through filter paper, compare to scale.

Sooty electrode insulators short the spark

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Carbon conducts; clean porcelains.

Stack relay must see flue gas

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No damper between it and the gas; trips if no ignition in ~15 s. Stack-relay furnace = probably time to replace.

Sulfuric acid in cold flues

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Noncondensing oil flue must stay warm; low-sulfur oil or additives reduce yellow-red crust; biocide additive for sludge; dual filters (bypass at tank, no-bypass at burner) on wet-tank jobs.

Thermistor vacuum gauge tube cleaning

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Fill with solvent, rock, dump, repeat 2–3×, alcohol rinse.

Traditional CO2 fluid test needs temperature correction

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Cooling sample reads CO2 high.

Troubleshooting discipline

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Get the complaint and recent repair history, pick a probable cause, verify with pinpoint tests, repeat until found, then pick the remedy; fixing the symptom (e.g. just adding gas without finding the leak) guarantees a callback. Write down the exact model number and use the maker's chart for that model.

Unattended evacuations: solenoid on the pump inlet wired parallel to the motor

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Power loss closes it, so system vacuum can't suck oil out of the pump.

Underground oil tanks

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Check for water with water-finding paste before each fill/annually; seal plugs with temperature-resistant compound, never Teflon tape. Pitch tank to fill end; silver paint outdoor tanks; keep full in summer to limit condensation.

Upgrade transformer to 14 kV

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When replacing a 10/12 kV unit — helps with cold oil/cold air/low voltage. Solid-state igniters (20 kHz) can't be tested with a 60 Hz transformer tester; don't short their terminals.

Use a pipe nipple on heavily-used gauges

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Saves the gauge threads from repeated on/off.

Use gauge boots

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Cheap protection against drops.

Vacuum/barometric draft regulator

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Counterweight adjusts how much room air bleeds into the flue; thermostatic and electric vent dampers also exist.