UTICA BOILERS UCS-380 Installation, Operation & Maintenance Manual page 84

13 - TROUBLE SHOOTING
Troubleshooting Chart 9
E40 - HRU/URC Unit test error
Is HRU terminal being used
on the auxiliary SCU board
(see section 8) ?
NO
YES
Is wiring connection to HRU Is wiring connection from
terminal secure? SCU board to main board
secure?
NO
NO YES YES
Fix Wiring Fix Wiring
Is Parameter P42 set
Connection
Connection
to 1?
NO YES
Is P42 parameter set
to 0?
Set P42 to 1
NO
YES
OK Not OK
Set P42 to 0
Replace SCU board
OK NOT OK NOT OK
Done OK
Done Done
Replace Main
Control Board
Is HRU accessory
operating properly?
NO YES
Correct HRU
Accessory
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P/N 240011662, Rev. D [06/30/2017]