Install a Heat-Pump Outdoor Unit

Set on risers/a stand above snow with room for defrost meltwater to drain, level on a pad with clearances, run the line set, then verify reversing-valve (O/B) operation, defrost, and configure auxiliary heat + balance point.

Approx. 300 min

Before you start

•Indoor section (air handler with electric heat kit, or furnace as dual-fuel) and its backup-heat capacity are known, plus the thermostat type (heat pump aware, O vs B reversing-valve energize).
•Refrigerant type, line-set sizing/length, and low-ambient operating range for the unit are known.
•Site allows raising the unit on risers/a stand for the local snow depth, with a clear path for defrost meltwater away from the unit.

Tools & materials

Equipment stand/risers or wall brackets rated for the unit weight · Level, pad (composite/precast) or stand hardware · Refrigerant/brazing or press tools, nitrogen for purge · Digital manifold + clamp temp probes, clamp meter · Heat-pump aware thermostat / control with O/B + aux-heat + balance-point settings

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Set above snow & defrost water

Raise the unit on risers/a stand above expected snow
Unlike a summer-only AC condenser that can sit low on a pad, a heat pump runs through winter and goes into defrost, shedding meltwater out the bottom. Set it up on risers, a tall stand, or wall brackets so the base is above the expected snow line and the coil draws clean air, not packed snow.
Target: Base elevated above local snow depth (commonly 6–18 in or more in heavy-snow regions)
⚠ Do not set a heat pump directly in a low pan/dish where defrost meltwater can collect and freeze into a block of ice around the coil.
Give defrost meltwater a path to drain away
Defrost dumps water at the unit base repeatedly through the season. Make sure that water drains and runs away (gravel bed, slope) instead of pooling and re-freezing under the unit, which heaves the unit and ices the lower coil.
Target: Free-draining base (gravel/slope) so meltwater leaves the unit and cannot pond/refreeze
Level the unit and honor clearances
Set level on the stand/pad and keep the maker's clearances around the coil and above the fan for airflow and service. Tight clearances starve the coil — worse in heating, when the outdoor coil is the evaporator and frosts.
Target: Level; coil/service clearances and overhead fan clearance per the install manual

Line set & low ambient

Run, support, and connect the line set
Route and support the line set, insulate the suction (vapor) line, and make the connections (braze under flowing nitrogen, or approved press fittings). In heating, the lines carry different temperatures than in cooling, so keep insulation intact end to end.
Target: Suction line fully insulated; line-set length within the maker's max + per-foot charge adjustment
Account for low-ambient operation
Confirm the unit's rated low-ambient heating range and that the defrost strategy/controls suit the climate. Charge by weight (the metering and capacity shift with outdoor temp, so a charging chart at one condition can mislead), then verify per the maker's heating/cooling method.
Target: Charge weighed in to nameplate + line-set adjustment; verified per the maker's heat-pump charging procedure

Reversing valve, defrost & aux heat

Verify the reversing valve and O/B setting
Confirm the thermostat energizes the reversing valve in the correct mode for this unit (most brands energize O in cooling; some — e.g. older Rheem/Ruud — energize B in heating). Verify the system actually reverses: in cool the outdoor coil rejects heat (hot), in heat it absorbs heat (cold) and the indoor coil gets hot.
Target: Thermostat O/B configured for the unit; system reverses correctly between heat and cool
Verify defrost operation
Force or observe a defrost cycle: the reversing valve flips to cooling to send hot gas to the outdoor coil, the outdoor fan stops, and backup/aux heat tempers the indoor air so the supply doesn't blow cold. Confirm it terminates on coil temp/time and returns to heating.
Target: Defrost initiates, outdoor fan off, aux heat tempers supply, terminates and returns to heat
Configure auxiliary/backup heat and the balance point
Set up the electric strips (or dual-fuel furnace) as auxiliary/emergency heat and configure the balance point / lockouts so backup heat only assists when the heat pump can't keep up, and (dual-fuel) the heat pump locks out below its economic/effective temperature. Avoid wiring that runs strips and compressor wastefully at the same time outside of defrost/recovery.
Target: Aux/emergency heat staged correctly; balance point / outdoor lockouts set so backup engages only when needed
⚠ On dual-fuel, ensure the heat pump and gas heat never run simultaneously — sequence one then the other.

Verify heat & cool

Run and verify both heating and cooling
Run cooling and heating in turn: confirm refrigerant operating readings, compressor amps vs RLA, and a reasonable temperature split in each mode, plus aux-heat staging in heating. Document the readings before leaving.
Tools: Digital manifold, Clamp meter
Target: Amps ≤ nameplate RLA; reasonable split in each mode; aux heat stages on demand