Rheem · Furnace

20 Twinning fault

Medium severity Rheem/Ruud 802P / 80MDP 80% two-stage furnace (UT 1028-928 IFC)R95P

What the control is telling you

Twinning was detected and then lost in the same power cycle.

Applies to: 802P/80MDP (802PA050-150); R95P (R95PA040-115)

Likely causes

TWIN wire broken or disconnected
Controls not identical (different part numbers)
24 VAC transformers out of phase
TWIN setting wrong on a single furnace

Test and repair steps

Check the wire between the TWIN terminals of both controls and the C and W connections (802P: also W2).
Confirm both IFCs have the same part number (R95P manual: UT 1194-200 board).
Check transformers are in phase (out of phase makes flame LED dim); both furnaces must be on the same power phase.
For a single (non-twinned) furnace make sure TWIN is set to single / nothing connected.
R95P see twinning wiring diagrams Fig. 43 (1-stage) and Fig. 44 (2-stage).

Settings for these units

Clearance to combustibles (all models) · R95P
Reduced clearance to combustibles, upflow/horizontal (Fig. 4) · Rheem/Ruud 802P / 80MDP 80% two-stage furnace (UT 1028-928 IFC)

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Source: 802P: 92-24161-146-02, Diagnostics and Fault Codes table, p.32, 40, 51; R95P: Twinning section and fault table, p.80 (PDF p.84). Summarized in our own words; check the original manual for your model.

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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.