Packaged terminal air conditioner (PTAC) under a window with its control door open, showing the set temperature and mode buttons
5 components covered

Field manual · Air Conditioner

Friedrich ZoneAire Select PZE / PZH PTACs: quick sheet

Covers: Friedrich ZoneAire Select digital packaged terminal units: PZE (cooling with electric heat) and PZH (heat pump with auxiliary electric heat), 42 in wide x 16 in high chassis in a 13-3/4 in deep PDXWS sleeve. Model pattern: PZ + E or H + nominal capacity (07, 09, 12, 15 = 7,000-15,000 BTU/h) + voltage letter (K = 230/208 V, R = 265 V in Friedrich's tables) + heater digit (2 = 2.5 kW, 3 = 3.6 kW, 5 = 5.0 kW in the submittal) + chassis S (standard) + design-series letter, e.g. PZH09K3SB, PZH12K3SB, PZH15K5SB, PZH12R3SC. Later SC-suffix PZH units are listed by Friedrich as R-32; earlier SB units are R-410A: read the label. Friedrich PDE / PDH digital PTACs use a different control and code set (the R-32 SG chassis has its own sheet), so the code list below does not apply to them. Search terms: PZH09K3SB, PZH12K3SB, PZH15K5SB, Friedrich PTAC E2, Friedrich PTAC E9, ZoneAire Select.

Single sourceBrands: Friedrich5 components

ZoneAire Select is Friedrich's hotel/apartment PTAC line. It runs from the chassis 'Smart Center' keypad or from a 24 V wall thermostat (selectable), has front-desk control terminals, stores service error codes, and uses a slinger ring on the outdoor fan to throw condensate onto the outdoor coil. Most calls are LCDI cord, filter/airflow, sensor codes and sleeve drainage.

Safety first

  • Unplug before opening the control area; do not use the LCDI as a switch.
  • Keep water off electronic parts during cleaning.
  • Refrigerant work is blocked: refer to an EPA 608-certified technician. R-32 units contain a mildly flammable refrigerant; no open flame near the chassis.

How it works

230/208 V units ship with an LCDI power cord; 265 V units ship with a non-LCDI cord for a subbase or hard-wire kit.

Heat pump (PZH): the board runs the compressor in heat; when the outdoor coil is below 26 °F for 3 minutes it switches to the electric strip, and it allows the compressor again once the outdoor coil is back to 41 °F (Friedrich IOM).

Indoor coil frost sensor: the compressor is disabled when the indoor coil reaches about 33 °F and re-enabled at about 59 °F; the fan keeps running on demand.

Random compressor restart after power returns: 120 to 240 seconds delay, so a whole building does not start at once. A normal 3-minute compressor delay also applies.

Room freeze protection runs fan and strip heat in an empty room regardless of mode. Friedrich's own documents disagree on the trip point: the IOM says 50 °F up to 55 °F, the 2024 submittal says 40 °F up to 46 °F. It can be disabled with a DIP switch.

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Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Packaged terminal air conditioner (PTAC) under a window with its control door open, showing the set temperature and mode buttons by Central Avenue, CC BY 4.0

Diagnostic guides for this appliance

Guide · Air Conditioner

PTAC not cooling (fan runs, air not cold)

Most PTAC no-cool calls are airflow (filter, coils), a wrong control setting or a failed compressor start component. Rule those out before suspecting the sealed system.

6 steps ~60 minmoderate
Guide · Air Conditioner

PTAC not heating (electric heat or heat pump)

PTACs heat with electric strip heat, a heat pump, or both. Heat pump models switch to strip heat in cold weather. Check settings, then the heater element and its limits, then the reversing valve.

5 steps ~60 minmoderate
Guide · Air Conditioner

PTAC error codes: how to read and clear them

Most PTAC brands store fault codes that can be shown with a button combination on the control (for example, on GE Zoneline (2019 technical service guide) you hold FAN and the red AUX button together while the unit is OFF, and AUX clears stored faults; other models use other sequences, so use the model's tech sheet). Read the active code, fix the cause, then clear it.

4 steps ~20 mineasy

Other air conditioners manuals

Manual · Air Conditioner

Carrier Infinity Greenspeed 24VNA6 air conditioner and 25VNA4 heat pump (variable speed): quick sheet

Carrier Infinity Greenspeed Intelligence variable-speed outdoor units: 24VNA6 air conditioner (up to 26 SEER) and 25VNA4 heat pump (up to 24 SEER, up to 13 HSPF), 2-5 ton. Nomenclature from the service manual: 24 = AC, 25 = HP; V = variable speed; N = Infinity series; A = Puron (R-410A); 6 / 4 = SEER tier; two digits = nominal capacity (e.g. 36 = 36,000 BTU/h); voltage digit 3 = 208/230-1; compressor ID 4 = variable-speed scroll, 5 = variable-speed rotary. Serial format: week + year + plant letter + sequence (e.g. 0118E00001). Other 24VNA families (24VNA0, 24VNA9) use different software and code lists.

5 components4 common failuresCarrier
Manual · Air Conditioner

Trane XV20i / XV18 variable-speed outdoor units (4TTV0 AC, 4TWV0 heat pump, ComfortLink II): quick sheet

Trane variable-speed TruComfort / ComfortLink II communicating outdoor units: 4TTV0 air conditioners (XV20i family, e.g. 4TTV0024A1000C, 4TTV0036, 4TTV0048, 4TTV0060, 4TTV0061) and 4TWV0 heat pumps (Service Facts 4T-V0-SF). They use an Integrated Variable Speed Control (IVSC) board and a Communicating Display Assembly (CDA) in the outdoor unit. Distributor listings note several 4TTV0 revisions; confirm the full model on the nameplate before ordering parts. Single-stage XR14/XR16 units are on a separate sheet.

4 components3 common failuresTrane
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Lennox XC21 air conditioner and XP21 heat pump (Dave Lennox Signature, iComfort-enabled): quick sheet

Lennox XC21 (air conditioner, service literature Corp. 1007-L2) and XP21 (heat pump, Corp. 1031-L7), 2, 3, 4 and 5 ton, R-410A, expansion valve indoor coils only. Both use an A175 main control (outdoor control part number 101798-xx) that works in communicating (iComfort) or conventional 24 V mode, plus a separate fan motor control. The XP21 literature describes a two-stage scroll compressor; the 2018 XC21 literature describes the compressor as one-stage while the same control section covers two-stage units, so confirm staging on the nameplate. For ML14XC1/EL16XC1 single-stage units see the separate sheet.

4 components3 common failuresLennox
Friedrich ZoneAire Select PZE / PZH PTACs: quick sheet · OnCall Tech