Other: General tips (part 1 of 2)

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

Absorption time delay

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Circulation waits for generator warm-up and continues after satisfy; don't mistake for a fault. Plastic pipe not directly on a furnace-mounted chilled water coil — use copper extensions; insulate drain lines.

Ask the customer three things

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What happened, when first noticed, how many times. Note previous problems and any interest in upgrades on the work order.

Check the economizer on every RTU call

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Stuck-open outdoor louvers wreck comfort and efficiency.

Class 2 circuits

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(NEC Art. 725) — some municipalities require a licensed electrician even for 24 V.

Closing a stat call

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Remove jumpers, replace covers, restore switches, offer the old part, leave manuals, show the customer.

Code applicability

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Adding AC to an unconditioned building, mixed-use, or heritage buildings changes which code applies; verify first.

Comfort trade-off

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High RH feels hotter; a lower temp plus more air movement compensates; in winter low RH needs higher temp.

Drain condensate from steam main before opening supply valve

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Avoids slugging.

Enthalpy control matters

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60°F/100% rh outdoor air holds more heat than 80°F/15% indoor air; sometimes better to just run the compressor.

Evaporator vs cooling coil

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"Cooling coil" properly means a brine/water coil that doesn't evaporate; useful when reading manuals for geothermal/secondary-loop systems.

GFCI locations

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GFCI required outdoors, garages, pools, kitchens/baths; trips at ~6 mA leakage and can be reset.

Heat stress

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OSHA: light clothing, 1 pint water (50–60°F) per hour, shaded rest breaks, avoid alcohol/caffeine.

Inspection mirror for hidden parts

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Telescoping mirror checks fan alignment, condenser dirt, evaporator; keep it away from moving parts.

Inverter soft start

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Low starting frequency = low torque = energy savings; inverter DC bus also powers EEV and fans.

Ionizers make ozone

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Some ionizing purifiers emit ozone; don't use ozone-generating cleaners.

Ladder diagram on the door

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Ladder diagrams show components in the order they energize (top first); usually glued inside the access panel. Each rung = one load circuit.

Life-cycle cost

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Purchase/installation is often < 10% of lifetime cost; sell on efficiency and maintenance.

Low-e windows can focus reflected heat

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Onto neighbouring objects/structures.

Lower indoor RH in extreme cold

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To stop window/wall condensation (see A26).

Mark fan hub before removal

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Scribe matching marks on hub and shaft so the new fan sits in the same position.

Master-slave zoning

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Slave can't call cooling while master is in heat; replace slave stats only with the manufacturer's part.

NC vs NO solenoids

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Most liquid line solenoids are normally closed (gravity/spring closes on power loss). Direct-acting vs pilot-operated: pilot valves use system pressure to move the main valve (reversing valves are pilot-operated).

Patio doors

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Can be 20% of a home's solar gain/leakage.

Record commissioning data

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On console/packaged units log inlet/outlet air temps, electrical load and pressures at install; give a copy to owner.

Replace the board, not the part

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When a device on a PCB fails, replacing the whole board is usually quickest; repair later or discard.

Service receptacle required

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NEC 210.63 requires a 125 V 15/20 A receptacle accessible at HVACR equipment for service tools.

Size by load, not by the old unit

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Windows, insulation, shade trees change loads; run a load calc on every replacement.

Smoke + stopwatch for drafts

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Time smoke puffs; >15–20 fpm = draft. Vane/swinging-vane/pitot are inaccurate at very low velocities.

Soda-can dew point test

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Half a shiny can, 2/3 water, add ice while stirring; when the outside fogs, water temp ≈ dew point.

Strainer ahead of every water valve.

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Strainer ahead of every water valve.