6. As a result of the reverse cycle, the finned tube heat exchanger coil will now act as an
evaporator in the heating cycle. Therefore, moisture removal will occur at this coil and the
water will flow down to the ground. Care must be taken for proper drainage of this water.
Do not allow this condensate water to drip onto live wire parts. Do not allow this water to
form puddles and submerge wire cables.
7. As mentioned in Section 9, scaling of the BPHE becomes more prevalent with hot water
systems (temperature >50°C). A more regular monitoring of the pressure drop across the
BPHE is required to check for fouling. A better periodic maintenance programme may be
necessary.
8. Check the pump specifications whether it can operate at the required operating temperature.
The GRUNDFOS CH pumps have a maximum fluid temperature of 90°C. It is also a good
practice to counter-check again the NPSHA for the pump with the higher water temperature.
This is because the vapour pressure of water will increase and will reduce the NPSHA.
Refer to Section 5.
Therefore, the risk of cavitation occuring in the pump is higher with hot water systems.
Adjustments to the system may be necessary for a safe operation.
9. The hot water will cause expansion of the pipes. The linear thermal expansion for carbon
steel and copper changes as follows:
Temperature.°C
Linear thermal expansion, mm/m
Carbon
steel
Copper
0 0.2 0.31
10 0.32 0.47
49 0.76 1.14
Increase with respect 2.8 2.7
to 0°C times times
Therefore, it is important that the piping installed with the supports must have sufficient
flexibility to allow for the expansion. A general practice is to never anchor a straight pipe
run at both ends. Pipe bends and loops are excellent to absorb such "shape changes" due
to expansion and contraction. Rubber expansion joints can also be installed along the
piping for the same purpose.
During operation of the heating cycle, check for any piping deformation. Check also for
failure of any pipe supports and leakage due to cracking.
Section 10 Page 116
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