Aircon DC Reactor: The Heavy Coil Fitted for the Mains

The part is a length of wire wound onto an iron core, with no electronics inside. Two leads go in and out. Daikin tells the technician in its RXS09 and RXS12 removal steps that the two reactor harnesses can go back either way. Very little else in that box tolerates reversal.

Position is the next useful fact, because the board does not carry it. Daikin gives the coil a removal heading of its own, Removal of Reactor / Partition Plate, and one screw holds it. Mitsubishi Electric writes the same arrangement into the PUZ-HA service steps, where the reactor and the capacitor attach to the rear of the electrical parts box. On Toshiba's larger multi-type outdoor units the coil gets a box to itself behind the inverter assembly.

Mass is why the mounting looks like that. A Toshiba outdoor inverter parts table lists a reactor for the compressor rated 5.8 mH at 16 A, and a second for the fan at 5.8 mH and 14 A on the MMY-MAP chassis. Hitachi Industrial Equipment Systems sells DC reactors as an inverter option and prints a weight against each; the smallest, matched to a 0.2 kW drive, is 0.8 kg. That is different equipment, quoted to show the class of object rather than the aircon part.

Some units carry two of them. Toshiba's wiring legend separates the reactor for the compressor from the reactor for the fan and lists both, and Carrier labels two reactors beside the compressor on its 18K size. On those machines, the phrase the reactor has already skipped a question.

Each maker labels it differently on the diagram, which is how one object reaches a homeowner under several names. Mitsubishi Electric marks it DCL alongside a diode bridge and a smoothing capacitor, while Daikin marks it L1R and expands that as REACTOR. Toshiba writes reactor for compressor and Hitachi's industrial catalogue calls the same idea a DC reactor. Of everything on those legends, the reactor is the one item bolted outside the electrical box.

The purpose is written down, and it points away from the machine. An inverter makes direct current out of the mains before it drives anything, and that conversion pushes current back into the supply at frequencies the supply never sent. Mitsubishi Heavy Industries names the consequence in a technical review of its own room aircon inverters. The converter causes an outflow of harmonic current to the power supply system, it writes, and that current can interfere with other equipment.

Reactors are the named remedy. Mitsubishi Electric publishes a harmonic suppression guideline for inverters, and its instruction runs to one sentence. Connect an AC reactor on the power supply side of the inverter, or a DC reactor on its DC side, or both, to increase circuit impedance and suppress harmonic currents. The same table states the effect: harmonic currents are suppressed to about one half.

A drive maker selling the component on its own says it in a line. Hitachi Industrial Equipment Systems describes its DC reactor option as suppressing harmonics generated on the inverter input side and being useful for power factor improvement. Two jobs, and neither is cooling a room.

Power factor is the second job and the easier one to picture: current drawn in step with the voltage is current the supply delivers without carrying extra. Mitsubishi Heavy Industries describes its converter working the reactors so that a sinusoidal current with a power factor of approximately 1 flows. A service manual built by Gree and sold under the Comfortstar name reaches the same idea from the repair end. It calls the PFC board a component for power factor correction and voltage boosting, with the reactor one of its core parts.

None of that makes the coil optional. In the designs these manuals describe it sits in the running power path, so a machine that loses one does not simply lose its manners. Mitsubishi Electric lists a disconnected reactor as a reason an outdoor unit never powers up at all. Why a maker fits the part and what happens when it goes are two separate subjects.

A harmonic limit applies to room aircon, and makers say so in writing. Mitsubishi Heavy Industries puts it flatly: every room air conditioner is required to meet harmonic regulation values such as IEC. Its own export models carry two chopper circuits in the converter to satisfy those limits.

Those limits live in IEC 61000-3-2. The fifth edition, published in January 2018, is titled Limits for harmonic current emissions. The bracket after that title carries the boundary: equipment input current at or below 16 A per phase, connected to public low-voltage distribution systems.

That boundary sits inside the domestic range. The three export models tabulated in the Mitsubishi Heavy Industries paper run on single-phase 220 to 240 volts, with maximum running currents listed as 14.5 A, 17 A and 17 A. An ordinary household split sits either side of the standard's figure.

One link in the chain stays general on purpose. No service manual read for this page cites a standard number against the reactor. Makers state a harmonic obligation, published guidelines name reactors as a way of meeting it, and the coil is in the unit. That is a reading of three documents, not a quoted instruction.

Supply quality changes the job the coil has to do. The same technical review notes that a distorted supply voltage distorts the current through the reactor with it. It is direct about the cost: the distorted input current causes extra harmonic current flow, which increases loss and deteriorates efficiency. The machine still cools, but less efficiently, for a reason with nothing to do with the refrigerant side.

Several makers document the coil failing, which sets it apart from most of the power stage around it. In the service diagnosis for Daikin's FTXS-L and RXS range, a disconnected reactor is one supposed cause of an H0; that code is raised when supply and DC checks taken before startup come back wrong. The branch that follows ends at connect the reactor properly or replace it, and H8 on the same range lists a defective reactor. The PUZ-HA self-diagnosis table lists a disconnection that leaves no power at the outdoor controller board; Carrier's manual reaches the coil through a communication error, an overload protection and a voltage protection.

One manual carries a warning worth taking into any conversation about this part. The Gree-built document named the reactor as one of the core parts of PFC, and it adds a flat prohibition: do not remove the reactor and replace with short circuit by no means. Bridging a coil out is the kind of shortcut that appears to work. The unit runs again and the fault clears, while the function the part was fitted for is gone.

No owner ever sees this coil, and no display names it. What appears is a code raised by whatever noticed the trouble. Across these documents that is a current reading outside its band, a voltage reading outside its band, a link that stopped answering, or no power at all. A code is evidence of detection; evidence of diagnosis is a separate thing, and only the code reaches the room.

Heat is documented too, which is why the manuals slow the technician down. Toshiba instructs that the breaker be set off and at least ten minutes allowed before the service panel is opened. The reason given is that the fan motor, reactor and inverter will be very hot to the touch. Daikin sets its own wait before disassembly begins, and this stage carries mains potential with stored charge in the smoothing capacitor beyond it.

This is one of the few items in an outdoor power stage that makers say to replace on its own. Daikin's branch ends at replace the reactor, Toshiba gives it a part number and a procedure, and the Gree-built manual lists it as a stocked item. A quote naming this coil is not automatically a board price, and it should not read like one. The same documents hold endings where nothing is replaced, such as connect the reactor properly or check the connection of the reactor.

Matching the label on the paper to the label on the diagram is worth the minute. DCL, L1R and reactor for compressor are three makers describing one object, and the model on the outdoor unit plate settles which document applies.