Hach-Lange SIGMA SD900 Refrigerated Sampler and All Weather Refrigerated Sampler User Manual - Manual (Page 40)

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Installation
3.5.1 AC power installation
WARNING
Electric shock hazard. The temperature of the power supply
will increase when the sampler pump is operating. If the time
interval between sample cycles is too short, the power supply
can become overheated resulting in power supply failure or
loss of power supply safe guards.
In heavy industrial environments it is good practice to use a power
line filter or connect the controller to a quiet electrical branch circuit.
To prevent overheating the power supply when it is used with a
sampler, complete the following steps.
1. Determine the amount of time that the pump will run
continuously during a sample cycle. Include all stages:
pre-purge, intake rinse, sample, sample retries and post-purge.
Note: The programmed options for each sample cycle, in addition to
the purge states, affect the amount of time that the pump is on
continuously.
2. Use the graph in Figure 21 to estimate the amount of time that
the pump must be off between sample cycles.
Figure 20 Side view of controller—connectors
1 Power connector 4 SDI-12 connector
2 Auxiliary connector 5 Distributor/full bottle shut-off connector
3 Serial connector 6 Thermal connector (AWRS only)