52 | FAULT FINDING AND DIAGNOSTICS
Product Name6 720 ... ... (YYYY/MM)
239 F0 Watchdog relay error
240 D1 Return sensor shorted
241 D1 Return sensor disconnected
242 to
256
F0 Internal error call Bosch technical help-line
257 b7 Internal error - replace control board
258 &
259
F0 Internal error call Bosch technical help-line
260 No temperature rise after burner start
261 EA First Safety timing error
262 &
263
F0 Internal error call Bosch technical help-line
264 C1 Airflow stopped during operation
265 Stand-by mode forced due to energy transfer limit
266 CE No pressure variation detected after switching pump
267 F0 Watchdog time out error
268 Component test mode
269 EA Ignition device activated too long
270 Power up mode
271 D4 Temperature difference between flow and safety
sensor exceeding limit
272 F0 Internal error
273 C4 Airflow present during last 24 hours
274 Ionisation signal present during last 24 hours
276 E9 Flow temperature exceeded 95°
277 E9 Safety sensor temperature exceeded 95°
278 F0 Sensor test failed
279 F0 AD converter error, unstable measurement
280 F0 Recycle timing error
281 A1 Pump stuck or running in air
282 H5 No feedback from pump
283 Burner starting
284 Gas valve(s) opened, first safety time started
285 E9 Return temperature exceeded 95°C
286 D1 Return temperature too high
287 F0 Ionisation sensor shorted
288 CF Water pressure sensor not connected or short-circuit
to supply
289 CF Water pressure sensor not connected or short-circuit
to ground
290 F0 AD converter reference error
305 Anti fast cycle mode
306 FA Ionisation detected after burner stop
307 Pump stuck
308 Pump running in air
309 CH & DHW system are being heated
310 CUS communication error
311 CUS locked
312 CUS blocked
313 CUS reported error condition
314 Mains disconnected during super lockout
315 Several times lack of water flow
316 E9 Flue gas sensor temperature too high
317 A3 Flue gas sensor shorted
318 E9 Flue gas sensor disconnected
Status
codes
Fault
codes
321 Self-test of flue gas supervision
322 Code error
323 A8 EMS communication error
324 DHW-NTC defect
325 DHW-NTC not correctly installed
326 Storage-NTC defect
327 Reset-key stuck or short-circuit
328 Internal error
329 CE No pressure variation detected after switching pump
332 E5 Supply sensor exceeded 110°C
333 Start temporarily not allowed due to flow error on CH
338 F0 Too many short burner starts without confirmation of
water flow
341 D4 CH: supply and/or return temperatures rising too fast
342 D4 HW: supply temperature rising too fast
343 ED CH: flue gas temperature rising but supply
temperature not
344 ED HW: flue gas temperature rising but supply
temperature not
345 EF Supply and/or return temperatures do not change
after burner start
346 EC Flue gas temperature rising too fast
347 E3 Return temperature higher than supply temperature
(some time after burner start)
348 EE HW: supply temperature too hot
349 EF CH: Boil Detect, large delta T despite minimum
burner load
350 E2 Flow sensor shorted 351 'E2' Flow sensor
disconnected
353 -- Burn temporarily blocked due to no 20 minute
continuous OFF time in last 24 hours.
354 Overpressure setting erased
357 Primary Heat Exchanger air venting program active -
approximately 100 seconds
358 Three way valve kick
359 DHW outlet temperature too hot
364 FA Gas valve EV2 leak test failed
365 Fb Gas valve EV1 leak test failed
372 Temporarily ignoring CH requests to limit
temperatures of the appliance components
373 8C SuperLock caused by too frequent thermostat
overheat detections during burning
374 8C SuperLock caused by too frequent ionisation loss
during burning
375 E4 Preheat sensor on DHW inlet Short Circuit
376 E4 Preheat sensor on DHW Inlet Open Circuit
380 Inlet temperature greater than DHW Outlet Set point
800 CC Outdoor sensor defect
808 A7 Domestic hot water sensor defect
810 Domestic hot water remains cold
828 Water pressure sensor defect
Status
codes
Fault
codes
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