Chiller circuits must incorporate various components and features in order to protect the chillers from damage and facilitate pre-commission cleaning, commissioning and maintenance. Recommended features are illustrated in Figure 1. The numbered features are described in the following notes:

1. A strainer should be fitted as close as possible to the water inlet connection to the chiller and should be provided with a means of local isolation to facilitate cleaning of the mesh. This strainer is required to prevent debris from entering the chiller where it could become trapped between the evaporator plates causing blockages.
2. A line size flushing by-pass should be installed so that the chiller can be by-passed during pre-commission cleaning. This will avoid dirty water passing through the chiller during the clean, and will help to maximise flushing flow velocities in the pipework. For multiple chillers, the isolating valve in the by-pass should be replaced with a double regulating valve. Regulating this valve so that its resistance matches that of the chiller will mean that the chiller can be isolated for maintenance purposes without disrupting the flows through the other chillers.
3. Pipework immediately adjacent to the chiller should be easily demountable to facilitate visual inspection of the inner surfaces of the heat exchanger.
4. Drain off cocks, line size or not less than 25mm should be located on both sides of the heat exchanger to facilitate flushing or draining of the chiller and pipework.
5. A fixed orifice double regulating valve should be installed on return pipes from chillers to enable the chiller design flow rate to be established and measured. If there is a possibility that the overall flow rate could vary under various part load operating conditions, then consideration should be given to replacing this valve with a constant flow regulator i.e. a valve that will ensure constant flow regardless of changes in pressure elsewhere in the system.
6. A chemical dosing pot should be located across the pump for the addition of water treatment chemicals. This should be kept isolated during normal system operation.
7. For all but the smallest of systems, a pressurisation unit is required as a means of filling the system, keeping it topped up and accommodating any expansion or contraction of the water volume. Pressurisation units are preferable to open vented tanks since they allow less dissolved oxygen into the water and hence reduce the risk of corrosion to steel pipes. A water meter on the inlet to the pressurisation unit is a useful means of checking system volume and for identifying whether water is draining from the system. The pressurisation unit should be located on the inlet to the pumps since this makes it easier to confirm that the water pressure at pump inlet is high enough to avoid cavitation induced noise or damage. This is particularly important for rooftop plant rooms where the static pressure in the system is lowest.
8. A strainer should be fitted as close as possible to the water inlet connection to the pump and should be provided with a means of local isolation to facilitate cleaning of the mesh. This strainer is required to prevent debris from entering the pump where it could cause damage to the pump impeller or excessive wear to pump seals.

Please don't hesitate to contact us on our free phone number 0800 801 819 or contact our Applied Products Division Manager on the email address given below.

Mike Slattery
E-mail: mslattery@axairclimate.co.uk »