Section 3: Water Pipe and Fittings
There are several types of pipe we can use for the water piping:
1. Black carbon steel pipe
2. Copper pipe
3. PVC pipe
Do not use galvanised iron (GI) steel pipe! This is because the zinc coating on the GI pipe will
have an electrolytic reaction with the copper components of the system, e.g. the brazed plate heat
exchanger and fan coil unit heat exchanger.
The zinc will be the sacrificial metal and deposit itself on the copper surfaces.
a) The pipe wall thickness will slowly eat away and cause leakages
b) The zinc deposit on the copper surfaces will retard heat transfer process. It may also
reduce the gap between plates in the BPHE and slows the water flow rate.
The mini chiller water piping connections is for a pipe size of 1-1/4". For a single run installation,
the recommended maximum pipe length is 150 meters, but this will depend very much on the
method of installation and the fittings used. The more complex the piping network is and the more
fittings there are, the higher will be the friction losses. This will limit the piping length available.
Always calculate the friction losses in the system and compare this with the capability of the water
pump in the chiller unit. See Section 4
1. Black Steel Pipes
The black steel pipes are the most commonly used in chiller installations. It is relatively cheap and
by far the strongest among the 3 types mentioned above.
However, these pipes are heavier and requires more extensive work to join and install.
The common pipe sizes are determined from the ASME (American Society of Mechanical
Engineers) standard B36.1 OM which specifies the pipe dimensions. See Appendix 1.
Generally, steel pipes are sold in lengths of 6 meters each. The dimensions of importance which
we need to know is the nominal pipe size (NIPS) and schedule number (wall thickness).
For pipes 14" (350mm) and larger, the nominal diameter is the same as the actual outside
diameter.
For pipes between 3" (80mm) to 12" (300mm), the nominal diameter is close to the actual inside
diameter.
However, for pipes smaller than that, the nominal value does not correspond to any actual
dimension.
Steel pipes are manufactured with different wall thickness. The ASME standard has defined
schedule numbers to identify these specifications. A pipe with a nominal pipe size may have
several schedule numbers. See also Appendix 1
Section 3 Page 28
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