IV404E Rev.000 SIEL S.p.A.
Issue date: 2017-06-05 Pag. 75 di 90 + FR
4.7
By-pass for maintenance
observe the following precautions when operating SWMB
SWMB must not be closed on a UPS that is off and that is connected in parallel with other units
operating normally. This operation may cause a fault on the UPSs which may create a
dangerous voltage at the output. SWMB may be closed with the SAFEPOWER EVO HFT
operatin
g by following the procedure described in the section “Operating modes” .
operation not to be executed
If disconnector SWMB is closed on any unit, the whole system switches onto by-pass.
If all the switches are then opened to allow maintenance operations to be carried out, all the
power required by the load will switch onto the maintenance by-pass line of the unit in which
SWMB has been closed.
WARNING: both the automatic and the maintenance by-pass line of each UPS is sized for the
rated power of the single unit.
N.B. To carry out maintenance on all the UPS, the switches SWMB of all the units must be
closed.
maintenance on a single unit
This is the procedure to carry out maintenance operations
on a single unit
(e.g. UPS1):
open switches SWBY, SWOUT, SWIN and the battery cabinet disconnector on unit 1 only.
If the active UPSs can power the load, the system remains in normal operation, and the maintenance can
be carried out on UPS1.
