FieldBench

Bosch

BOVA 2.0

Heat pump · Bosch IDS 2.0 · inverter ducted split · BOVA outdoor + BVA/BAA AHU

Bosch IDS 2.0 / BOVA 2.0 inverter outdoor paired with a BVA / BAA air handler. The indoor–outdoor pair is communicating. The wall thermostat on many jobs is conventional 24 V at the AHU. Charge is weigh-in / the Bosch chart — not piston superheat. Do not apply Daikin U4 or Carrier 31 to this system.

Not Daikin DZ20VC (U4/L5). Not Mitsubishi MXZ. Not a 24V piston 14-SEER with a contactor-only outdoor. Not Climate 5000 ductless (different code set).

Walk this in Diagnose

This plate

Outdoor
BOVA20 / BOVB inverter HP · R-410A · 2–5 ton class
Indoor
BVA / BAA air handler · electric-heat kits with their own limits
Pair wiring
Communicating cable indoor–outdoor. 24V stat typically at the AHU (Y/B/G/W/C)
Charge
Weigh-in + Bosch IDS chart. Not a piston SH target
Example SKU
BVA-36N1 indoor · BOVA20 outdoor

This board

BOVA outdoor inverter PCB + BVA indoor board

  • Faults show on the outdoor display (C3, E4, E5, E6, E7, E9, H0, H8, P0, P1, P2, P3, P4, ATL, and inverter L-family). Read the IDS sticker in THIS outdoor.
  • Indoor–outdoor comm is the dedicated pair between BVA and BOVA. The wall stat is 24 V at the AHU on most residential jobs. Techs mix these two cables constantly.
  • Do not translate these as Daikin U4 or Carrier 31. Bosch letters are Bosch.
  • Electric-heat limits live on the AHU heat kit (mechanical limits / sequencers), not as a Daikin E3.

Sequence

  1. Stat call. 24 V at the AHU (Y cool, B/O reversing, G fan, W strips). The AHU then talks to the outdoor on the comm cable. No Y at the outdoor like a contactor unit.
  2. Outdoor start. Inverter ramps after the comm handshake. H0 / E9 / blank display with a good 24 V stat is almost always the indoor–outdoor cable, not the stat.
  3. Heat pump heat. B (or O, per Bosch diagram) must be correct or you get ATL / no HP heat and the strips take over.
  4. Defrost. Outdoor coil sensors (T3/T4) and the IDS defrost routine. Failed sensors are E4 / C3, not a furnace rollout.

Faults on this IFC

  • ATL

    Ambient temperature limited

    warn

    Outdoor T4 outside the allowed window (cool: T4 ≥125°F or <15°F; heat: T4 ≥86°F or <−4°F on IDS 2.0), or the reversing-valve call is wrong so the outdoor thinks it is in the wrong mode.

    • Idle ≥5 min, compare T4 on the board to real outdoor temp (10K sensor, ~10 kΩ at 77°F).
    • Heat call must energize B per the Bosch diagram. Y-only in heat, or B stuck on in cool, produces ATL.
    • 18–28 VAC B–C at the outdoor during a heat call.
  • C3 / C4

    Condenser coil sensor seating

    warn

    T3 reads implausible vs T4 (T3 < T4 − 3°F for 10 min).

    • T3 on the outdoor coil U-bend per the diagram, not hanging in air.
    • T3/T4 10K ohms. 18 SEER has one T3; some 15/20 SEER have T3 and T3L.
  • E4

    Temperature sensor fault

    lockout

    T3, T3L, T4, T5, or TF out of range.

    • Identify which sensor the display names.
    • T3/T4/T3L: 10K. T5/TF: 5K class — use the IDS ohm chart. Open/shorted harness vs failed bulb.
  • E5

    High / low voltage protection

    lockout

    Line voltage out of band (IDS: operate ~180–270 V; typical run ≥210 V).

    • L1–L2 at the outdoor. A just-pulled disconnect can E5 on the inrush — wait and recheck.
    • This is line voltage, not a 24 V stat brownout. Still verify 18–28 VAC Y–C at the AHU so you do not chase the drive for a dead transformer.
  • E6

    Outdoor DC fan motor

    lockout

    Outdoor fan failed or the board is not driving it.

    • Blade free? Ice/wind lock?
    • Motor vs board: resistance and drive voltage per the 5-wire or 3-wire diagram on THIS BOVA.
    • A dead outdoor fan becomes P1/P0 next.
  • E7

    Discharge sensor seating

    warn

    T5 not tracking (T5 < T3 − 5°F in cool, or similar band in heat, for 10 min) — plug not on the discharge or a real high-discharge event.

    • T5 fully on the discharge tube. 5K sensor.
    • If T5 is seated and hot, that is charge / restriction / P4 territory — do not just reseat forever.
  • E9

    EEPROM fault

    lockout

    Outdoor control EEPROM / memory chip.

    • L1–L2 in range. If E9 remains, the outdoor board — not a Daikin indoor IFC.
    • Do not ‘reprogram’ this like ComfortBridge shared data.
  • H0

    Comm / main control chip

    lockout

    Communication fault in the main control / EEPROM seating. Field: indoor–outdoor handshake and the outdoor board itself.

    • Dedicated comm cable BVA↔BOVA landed on the comm terminals — not the 24 V stat cable.
    • EEPROM chip fully seated / not backwards on boards that have a plug-in chip.
    • L1–L2 in range. H0 that survives a good comm cable and good power is the outdoor board.
  • H8

    Pressure transducer

    lockout

    Suction PT failed or disagrees with gauges.

    • PT wiring. Idle PT vs manifold (±50 psi class on IDS).
    • Supply ~5 VDC on the transducer reference. Bad PT vs bad board.
  • P0

    High outdoor coil temp

    lockout

    T3 outdoor-coil overtemp.

    • Outdoor coil and inverter heat sink clean. Fan running (see E6).
    • T3/TF readings in the parameter list.
  • P1

    High pressure switch

    lockout

    HPS opened (airflow, overcharge, restriction, or failed switch).

    • Outdoor fan and coil. Indoor filter/coil.
    • HPS (2 yellow leads on IDS) ohms closed when idle and cool.
    • Charge is weigh-in / Bosch subcooling chart — not piston SH.
  • P2

    Low pressure / heating discharge SH

    lockout

    Low-pressure protection in cool, or high discharge superheat protection in heat (IDS: <44 psi for 5 min cool; high discharge SH band in heat).

    • Service valves open. Indoor blower on a cool call; outdoor fan on a heat call.
    • Weigh-in. Restriction / TXV / drier. Then the PT (H8) before you add gas.
  • P3

    Compressor overcurrent

    lockout

    Inverter current out of band (tonnage-specific trip on the IDS card).

    • Valves open, coils clean, outdoor fan running, outdoor <125°F.
    • Overcharge and a locked compressor both P3 — weigh-in and windings before you order a drive.
  • P4

    High compressor discharge temp

    lockout

    T5 overtemp (IDS trips in steps up to a 230°F-class shutdown).

    • Weigh-in / Bosch chart (undercharge is the usual P4).
    • Valves open, indoor blower, outdoor coil, T5 seated.
  • AHU heat limit

    Electric heat limits on the BVA

    warn

    Strip kit opened a limit / sequencer. This is AHU airflow or a bad element, not a BOVA P-code.

    • Filter, blower, heat-kit size vs the BVA nameplate.
    • W at the AHU calling strips because HP failed (RV, sensors, ATL) — fix the HP before you upsize strips.
    • No Carrier 33 and no Daikin E3 on this limit string.

Workflows

Outdoor not starting

AHU alive, outdoor silent. Techs mixed the comm cable with the 24V stat.

  1. 24 V stat lives at the AHU. Y/B/G/W/C there should look like a conventional heat pump.
  2. Indoor–outdoor is the dedicated comm cable on the Bosch comm terminals. It is not R/Y to the outdoor contactor — there is no contactor.
  3. If someone landed the stat on the outdoor and the comm pair on the stat, H0/E9/blank outdoor is the result. Fix the landings before you order a board.
  4. Then E5 line voltage and E6 fan. Then inverter codes on the door card.

No heat in HP mode

Strips run or the house is cold; outdoor idle or ATL/EA-class.

  1. Is B (reversing) actually energized on a heat call at the AHU and present where Bosch wants it? Wrong O/B is ATL or cool-mode outdoor in January.
  2. Outdoor sensors T3/T4/T5 (E4/C3/E7) and PT (H8) before you condemn the 4-way.
  3. If the AHU is on W strips, find out why the HP gave up — do not leave it as an electric furnace.
  4. Charge is weigh-in / Bosch chart. A ‘2 °F SH piston’ top-off is how these P4/P2.

Test points

Stat vs comm
24 V at the AHU. Communicating pair indoor–outdoor only. Never 24 VAC on the comm pins.
Charge
Recover and weigh. Bosch IDS chart / nameplate + line-set. Not piston SH.
Sensors
T3/T4 10K, T5 5K class, PT ~5 V reference. Use the IDS parameter list.

Gotchas

  • Do not invent Daikin U4 or Carrier 31 on a BOVA display.
  • BOVB / BAA / BVA-36N1 are this IDS 2.0 pair, not a different code family.
  • Inverter L-family codes (LO–L9 on some boards) are on the outdoor drive — read the IDS card; they are not Daikin L5.

Related plates

  • mitsubishi-mxz-sm — Another communicating inverter outdoor, different brand and a multi-zone branch box. Do not share codes.