A heat pump is an air conditioner that can run in reverse, and that one feature changes how you service it. Refrigerant flows one way in cooling and the opposite way in heating, the outdoor coil has to defrost itself all winter, the thermostat has to tell a reversing valve which way to go, and backup heat waits for the compressor to fall behind. Parts that work fine on a straight-cool condensing unit can cause real trouble on a heat pump, and the filter drier is the classic example.
This category covers heat pump specific replacement parts: Supco bi-flow heat pump filter driers in flare and sweat connections (HP083, HP083S, HP163, HP163S, HP164S and HP165S), plus single-stage heat pump wall thermostats. Techs buy bi-flow driers on nearly every heat pump sealed-system repair. Homeowners usually shop here for the thermostat and leave the refrigerant side to a licensed tech.
A standard liquid line drier is built to flow one direction: in through the desiccant core, out through a screen that holds back debris. On a heat pump, the common liquid line carries refrigerant toward the outdoor coil in heating and toward the indoor coil in cooling. A standard drier in that line runs backwards for an entire season. Debris collected in one mode can be flushed out the inlet side when flow reverses, sending it straight to a metering device, and filtration and pressure drop in reverse are unpredictable.
A bi-flow heat pump drier uses internal check valves to route refrigerant so it is filtered correctly in either direction, keeping contaminants trapped in both modes. The rule is simple: on a heat pump's common liquid line, use a bi-flow drier. A standard drier belongs only where flow runs in a single direction.
| Situation | Drier Type | Notes |
|---|---|---|
| Heat pump common liquid line | Bi-flow heat pump drier | Filters correctly in heating and cooling |
| Straight-cool AC liquid line | Standard one-way drier | Flow arrow toward the metering device |
| Heat pump compressor burnout | Bi-flow liquid line drier plus suction line drier | Follow the compressor maker's burnout procedure |
| Brazed copper line set | Sweat connection (S models) | Flow nitrogen while brazing |
| Existing flared line | Flare connection | Use a proper flare tool and refrigerant-rated flare oil |
Light frost on the outdoor coil in heating is normal, and so is steam rising from the unit during defrost. These are not:
Before condemning a reversing valve, confirm 24 volts at the solenoid in the mode that should energize it, check coil resistance, and compare line temperatures across the valve. Low charge, a restricted drier and dirty coils can mimic defrost failures, so check the basics first.
A conventional thermostat has no reversing valve output and treats W as primary heat, which on a heat pump means heat strips doing all the work while the compressor sits idle. A heat pump thermostat, like the single-stage models in this category, runs the compressor (Y) for both heating and cooling, controls the reversing valve, and brings on auxiliary heat as a second stage.
Set wrong, the system heats when it should cool and vice versa. Go by the outdoor unit wiring diagram, not the old thermostat, which may have been miswired. A single-stage heat pump thermostat suits a single-stage compressor with one stage of auxiliary heat; two-stage, dual-fuel and variable-speed systems typically need a control designed for them.
Supco has been making HVAC and refrigeration replacement parts since 1945. Each HVAC365 product page lists specifications, cross-references and manufacturer spec sheets where available, so you can confirm connection size, capacity and compatibility before ordering. These items ship in 3-5 business days.
Not on the common liquid line. It carries refrigerant both ways, so a standard drier would run backwards half the year and could release trapped debris toward a metering device.
Bi-flow driers are designed to filter in both directions, so direction is not critical the way it is on a standard drier. Follow any markings on the specific drier.
Yes. Any time the sealed system is opened, install a new drier. After a burnout, add a suction line drier for cleanup as well.
Both use the same backup source. Auxiliary heat comes on automatically when the heat pump can't keep up or during defrost. Emergency heat is selected manually and locks out the compressor.
Possibly. A reversed O/B setting makes the system cool on a heat call. A stuck reversing valve, failed solenoid, defrost in progress or low charge can do the same. Check thermostat setup and solenoid voltage first.
Yes, during defrost. A coil that stays solidly iced for long periods is not normal and needs a service check.
Fast Shipping
Easy Returns
Warranty Coverage
Financing Available
