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VIII.

Troubleshooting

Circulation Pump

Water Switch Pump Nuisance Tripping (1)

There have been some nuisance tripping of thermal motor protectors on

three-winding circulation pumps for use with water switches (# 239129).

To prevent nuisance tripping, use pumps with upgraded thermal

protectors (# 437345). If upgraded pumps (# 437345) aren’t available,

use original circulation pumps (# 239129) with new (PTC) motor starters

designed to prevent nuisance tripping (# 423023).

IMPORTANT: Using new & original

pumps & motor starters:

• Use “new" circulation pump #

437345 (with 135ºC OVLP) only

with "original" motor starter #

182318 (4.7 – 4.8Ω).

• Use “original" circulation pump #

239129 (with 120ºC OVLP) only

with "new" motor starter # 423023

(15Ω).

TECH NOTES

: New motor starter # 423023 (15Ω) has a larger resistance to limit current

draw through pump motor start windings. Winding temperatures are reduced, but starting

torque is reduced as well. So, new motor starters (# 423023) should never be used with new

circulation pumps (# 437345).

HINTS: Typical repairs will involve either replacing “original" circulation pump # 239129 with

“new" circulation pump # 437345 (preferred) or replacing "original" motor starter # 182318

with "new" motor starter # 423023.

TECH TIPS

: All circulation pump motors use auto-reset thermal protectors. Once motor

windings cool below a preset temperature, protectors reset and pumps will work again. If

thermal protectors fail to reset, replace pumps.

Bosch SHX46B05 User Manual

Questions and Answers: