Airedale Condensing Units (CU) 3kW - 80kW - Manual (Page 15)

Condensing Units
CUS 15 - 60 / HCU 20 – 30D
Chillers & Condensing Units
Installation & Maintenance:Part No: 6259592 IM 07/14
15
Refrigeration System
HOLDING CHARGE All units are shipped with a holding charge of dry nitrogen. This is to ensure that there
is no risk of internal contamination or moisture entering the units during shipping or
storage.
Before the units are evacuated prior to the charging process, the condensing unit
should be checked to see that the holding charge has been retained. If it appears to
be either partially or totally lost, then the unit concerned should be carefully checked
for signs of physical damage.
PIPEWORK SIZING/OIL
ADDITION. It is MOST IMPORTANT that the correct size refrigeration pipework is used to ensure
that the pressure drop in the system is kept to a minimum, and also so that proper oil
return will take place under all normal operating conditions.
Accepted Good Practice should be followed in the design and installation of the
refrigeration pipework system.
Oil should be added to the pipework installation in accordance with the compressor
manufacturers recommendations where applicable.
PRESSURE TESTING When installation is complete, fill the system with dry nitrogen to a pressure of 17
bar/250 psig. Record the pressure over a period of time (a minimum period of 60
minutes should be sufficient to detect any major leaks, however, ideally 24 hours
should be allowed). If there is any reduction in pressure, trace the leak and repair
before conducting a further pressure test.
EVACUATION Evacuation should be carried out with a high vacuum pump. The pump should be
connected to the high and low pressure sides of the system via a gauge manifold
fitted with compound gauges. A high vacuum gauge should be fitted to the system at
the furthest point from the vacuum pump.
Triple evacuation should be used to ensure that all contaminants are removed or at
least reduced to significantly low proportions.
There are no hard and fast rules when applying this method. However, the following
has proved effective for general installation and service work.
1. Recover system charge and pressure test.
2. Replace filter drier.
3. Evacuate to (10 Torr) 13 mBar and maintain for 20 minutes.
4. Break vacuum with OXYGEN FREE dry nitrogen to 0.5 Bar (7psi) and hold for 15
minutes.
5. Evacuate to (5 Torr) 7mBar and maintain for 20 minutes.
6. Break vacuum with OXYGEN FREE dry nitrogen to 0.5 Bar (7psi) and hold for 15
minutes.
7. Evacuate to (½ Torr) 0.65 mBar and maintain for 1 hour.
The plant should now be sufficiently dehydrated and suitable for recharging.
Note: During installation keep all pipes capped to prevent dirt and moisture
ingress. If polyolester oil becomes contaminated with moisture then it is
advisable to change the oil and filter drier.
ALTERNATIVE
REFRIGERANTS There are now an increasing number of transitional refrigerants as well as the
traditional ones and if any refrigerant other than R 22 is used care must be taken in all
aspects of installation and charging.
This is especially important with regard to the type of compressor oil used, and care must
be taken to ensure that the correct oil is used with the correct refrigerant.
IMPORTANT:- If an alternative refrigerant is used, then this must be with the
approval of Airedale International Air Conditioning Ltd. Use of an alternative
refrigerant without the approval of AIAC Ltd could invalidate the warranty.