RunTru
Trane Technologies’ value line (successor to Ameristar): single-stage, standard-efficiency, contractor-priced equipment built for volume replacement work.
The family: Trane and American Standard are the same iron with different paint; RunTru is the value line. Ductless arrives through the Mitsubishi Electric joint venture (METUS).
Same family: Trane, American Standard
What they make
Split system A/C (straight cool)
Covered in the simulatorOutdoor condenser plus an indoor furnace-and-coil or air handler — the most common machine in single-family homes and garden-style multi-family.
The whole sim is built on this machine: every wing of the board and the guided no-cool flow apply directly.
Start a guided call →Practice: whole system dead →Practice: outdoor unit dead →Practice: runs but won’t cool →Practice: no air inside →Practice: acting possessed →Practice: blows fuses →Practice: gauges on →Practice: wrong part, wrong size →A2L start-up guide →
Heat pump (split)
Lessons carry overA split system that also heats: one reversing valve decides which coil condenses. Everything a straight-cool split has, plus the O (or, on some brands, B) circuit and defrost.
The HEAT PUMP wing of the board works the reversing valve; the guided flow routes heat pumps to escalation until its playbook ships. The electrical side transfers one-for-one.
Open in the Copilot (reference) →Practice: heat pump →Practice: whole system dead →Practice: outdoor unit dead →Practice: runs but won’t cool →Practice: no air inside →Practice: acting possessed →Practice: blows fuses →Practice: gauges on →Practice: wrong part, wrong size →A2L start-up guide →
Gas furnace
Covered in the simulatorThe indoor half of most split systems outside the Sun Belt: burners and heat exchanger below, the A-coil above, the 24V control system inside.
The control side — door switch, transformer, board, blower, low-voltage fuse — is fully modeled as the sim’s indoor cabinet, and the guided flow applies on cooling complaints. Combustion-side diagnostics are on the roadmap.
Start a guided call →Practice: whole system dead →Practice: no air inside →Practice: acting possessed →Practice: blows fuses →
Air handler / fan coil
Covered in the simulatorThe all-electric indoor cabinet: blower, coil, and controls. In multi-family it hides in closets and mechanical rooms; hydronic fan-coil versions swap the coil’s refrigerant for water.
Modeled as the sim’s indoor unit: control power, blower circuits, condensate float, coil airflow. Hydronic (water-coil) versions add loop diagnosis the sim doesn’t model yet.
Start a guided call →Practice: whole system dead →Practice: no air inside →Practice: runs but won’t cool →Practice: acting possessed →Practice: blows fuses →Practice: gauges on →A2L start-up guide →
Evaporator coil
Covered in the simulatorThe indoor coil itself — cased or uncased, A, N or slab — often replaced separately from everything else, which is where mismatches are born.
Freeze-ups, restrictions, airflow starvation and mismatched-coil audits are all on the board, and the guided flow’s superheat/subcooling paths read straight through it. Match by capacity and metering device, never by badge.
Start a guided call →Practice: gauges on →Practice: runs but won’t cool →Practice: wrong part, wrong size →A2L start-up guide →
Package unit
Lessons carry overThe whole system in one outdoor cabinet — on a pad beside the house or on the roof. Gas/electric, straight cool, or heat pump.
Same parts, one cabinet: contactors, dual-run caps, PSC/ECM motors and the refrigerant circuit fail exactly like the board’s scenarios. The guided flow’s split-system routing doesn’t fit a single cabinet, so it escalates package units by design.
Open in the Copilot (reference) →Practice: runs but won’t cool →Practice: blows fuses →Practice: gauges on →
Tech support
Tech support here is the guided Copilot with your RunTru info already loaded — one question at a time, evidence before parts, and everything you enter rides into the service report.
Opens the guided Copilot with RunTru already on the equipment card.
Reading RunTru model numbers
The leading digit is the refrigerant era: 2 = R-22, 4 = R-410A, 5 = R-454B (2025 on — 5TTR5036 is the R-454B 3-ton). Then two letters for product, one for tier, then size: 4TTR4036 reads 4 (R-410A) / TT (split cooling) / R4 tier / 036 = 3 tons. Heat pumps are 4TWR/4TWX; American Standard mirrors with 4A7A (cooling) and 4A6H (heat pump); RunTru badges lead with a letter instead (A4AC4036-style, refrigerant digit second). Air handlers TEM/TAM/GAM use odd size codes (37/49/61); furnaces (TUD, S9V2, AUD) code heating input.
4TTR6036J1000A— Trane split A/C, XR16-class, 3 tons (036), R-410A.4A7A6048H1000B— American Standard split A/C, 4 tons (048), R-410A.TEM6A0C37H21S— Air handler, 3-ton class (37), variable-speed era.
Thirty years of these units
1990s–2000s: 2TTR/2TWR R-22 generations with Spine Fin coils. 2010s: 4TTR R-410A everywhere. 2020s: 4TTR7 two-stage and 4TTV variable-speed tiers, then the 5-prefix R-454B successors (5TTR4/5/6/7 and up) from 2025. Climatuff compressors (badged Duration™ on American Standard equipment) run through all of it.
Package units: 4YCC/4WCC-style — same leading refrigerant digit, size code inside.
Dating a unit from the serial
Since 2010, the first two digits are the year and the next two the week. From 2002–2009 the serial leads with a single year digit followed by the two-digit week; older units use letter codes. Serial 16154ABCD → week 15 of 2016.
Common rule — spot-check against the manufacturer’s table
Need the wiring? The practice board’s ladder diagram is live and interactive — the same circuit these units share, with a meter on it. Open the board →