Rheem · Furnace

46 Low pressure switch open - inducer low speed

High severity Rheem/Ruud 802P / 80MDP 80% two-stage furnace (UT 1028-928 IFC)RGPE/RGLE

What the control is telling you

Low pressure switch opened while the inducer was on low speed (low-fire operation). RGPE/RGLE: Table 16 text LPC OPEN; meaning per 802P - verify on unit. Not stored back-to-back in the RGPE fault buffer.

Applies to: 802P/80MDP (802PA050-150); RGPE/RGLE 2-stage 80+

Likely causes

Weak inducer at low speed
Hose leak or water in hose
Partial vent blockage
Wind

Test and repair steps

Check inducer operation and wiring; RGPE/RGLE: check inducer low speed and 115 VAC on P2, replace inducer if weak.
Check hoses and switch for moisture.
Check vent for blockage and wind effects.
Check switch wiring.

Settings for these units

Filter sizes as shipped, upflow (Table 19) · RGPE/RGLE

Cabinet width	Input	Bottom filter	Side filter	Quantity
17-1/2 in.	50, 75 (000 Btu/h)	15-3/4 x 25 in.	15-3/4 x 25 in.	1
21 in.	75, 100 (000 Btu/h)	19-1/4 x 25 in.	15-3/4 x 25 in.	1
24-1/2 in.	125 (000 Btu/h)	22-3/4 x 25 in.	15-3/4 x 25 in.	1

Use one filter location only - do not double-filter or filter the supply side.

21 in./100K: cut 3-1/2 in. off filter and frame for a side filter; 24-1/2 in./125K: cut 7 in.

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

Model size	Cabinet width (A)	Right side	Top	Front	Vent
050 (5)	14 in.	4 in. (note 2)	1 in.	3 in.	6 in. (note 3)
075 (7)	17-1/2 in.	3 in. (note 2)	1 in.	3 in.	6 in. (note 3)
100 (10)	21 in.	0	1 in.	3 in.	6 in. (note 3)
125 (12)	24-1/2 in.	0	1 in.	3 in.	6 in. (note 3)
150 (15)	24-1/2 in.	0	1 in.	3 in.	6 in. (note 3)

Note 2: right side may be 0 in. with type B vent.

Note 3: vent clearance may be 1 in. with type B vent.

Reduced clearance to combustibles (Fig. 3 and 4) · RGPE/RGLE

Models that show this code

15 models in Rheem/Ruud 802P / 80MDP 80% two-stage furnace (UT 1028-928 IFC), RGPE/RGLE

R802PA050314MSAR802PA075417MSAR802PA100521MSAR802PA125524MSAR802PA150524MSARGLE-05(-)BMKRRGLE-07(-)AMKRRGLE-07(-)BRQRRGLE-10(-)BRMRRGLE-12(-)ARMRRGPE-05(-)BMKRRGPE-07(-)AMKRRGPE-07(-)BRQRRGPE-10(-)BRMRRGPE-12(-)ARMR

Other codes on the same units

23 HALC limit open (HALC LIMIT OPEN)
26 Line and neutral reversed
33 Rollout switch (MRLC) open
44 Low pressure switch closed (stuck)
45 Low pressure switch open - inducer high speed
55 Pressure switch stuck closed
57 Pressure switch stuck open
60 Blower fault - running (BLWR FLT-RUN)

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Source: 802P: 92-24161-146-02, Diagnostics and Fault Codes table, p.40, 51; RGPE/RGLE: Table 16 p.49 / Table 20; Fig. 45 p.63. 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.