Low ambient temperature operation
It is recommended that oil separators are insulated as a minimum requirement to preserve
the heat generated by the oil heaters. It is important that the coalescer end of the separator is
insulated to prevent refrigerant condensation.
On systems located outdoors, or in unheated buildings, where the ambient temperature may drop
below 0° C, insulation and heat tracing of the compressor lubricating oil systems, including oil lines,
oil filters, oil pumps, and oil coolers, is mandatory. Freeze-up protection must also be provided for
all water-cooled equipment.
SABROE heat pumps always have insulation and heat tracing.
Heating element
To keep the compressor lubricating oil warm during a period of standstill, a heating element is built
into the oil reservoir. Before start-up, you must switch the heating element on for 6 to 8 hours to
ensure that only a minimum of refrigerant remains in the oil. If there is too much refrigerant in the
oil, the oil loses its lubricating properties.
WARNING
The heating element must not be switched on if the oil level in the reservoir is below minimum in the
sight glass. Normally, it must be turned off when the compressor is in operation.
Remember to turn off the heating element before draining the oil through the compressor service
valve and before opening into the oil reservoir for inspection.
ATEX
On ATEX-executions, the heating element(s) are ATEX-approved. Heating elements from Johnson
Controls Denmark have a thermostat with manual reset. If the thermostat drops out, only
competent personnel should reactivate it.
Start-up
Preparations before start-up
1. Turn on the power voltage and the control voltage. Check the emergency stop button.
2. Check the oil level in the oil separator, see
3. Check that all valves are positioned in accordance with
,
,
including the secondary side of the oil cooler.
4. Reset all alarms according to the control system instructions.
5. Check on the control display that the compressor capacity control system is in minimum slide
position 0 to 4%.
WARNING
On ATEX-executions, you must always respect the limits in Table
.
57
SAB 283-355 A-Frame OHU 6042 and OHU 7650 (including ATEX) Screw Compressor Unit
