18
Model
Differential - K
Flow – l/s
Total System Pressure
Loss - Metre H
2
0
MCW91CE
3
1.9
2.44
MCW136CE
4
1.9
2.44
MCW181CE
5
1.9
2.44
MCW226CE
6
1.9
2.44
MCW271CE
8
1.9
2.44
MCW316CE
9
1.9
2.44
MCW361CE
11
1.9
2.44
MCW401CE
12
1.9
2.44
MCW501CE
15
1.9
2.44
TABLE 10.2
WATER HEATER FLOW RATES
To ensure proper velocity through the heat exchanger, it is necessary to balance the temperature rise across the
heat exchanger from inlet to outlet. Excessive scale build up in the tubes is a result of too little velocity; excessive
pitting or erosion on the inside of the tubes is caused by too much velocity. Care should be taken to measure the
temperature rise and maintain a constant velocity as follows:
1.
Thermometers are installed on the inlet and outlet of the equipment to measure water temperature
entering and leaving.
2.
The pump should run continuously.
3.
With the pump in operation and the burner “off”, both thermometers should read the same temperature.
4.
Switch the burner on and allow the temperature to stabilise. Record the difference between the inlet and
outlet temperature. The difference will be the “temperature rise”.
5.
Compare the temperature rise with the required figure shown in Table 10.2.
A.
If the temperature rise is too high, water velocity is too low. Check the following:
1.
No restrictions in the outlet of the heater.
2.
All valves are open between the heater and the storage vessel.
3.
Pump is running in the proper direction.
4.
Pump size is correct.
5.
Pipework size is correct.
B.
If the temperature rise is too low, water velocity is too high. Adjust accordingly.
1.
Throttle the valve on the outlet side of the heater, until temperature rise is steady and at correct
value shown in Table 10.2.
2.
Periodically check the temperature rise to ensure proper operation.
10.1.9
PIPEWORK SIZE
The pipework for the primary circulating loop should be in accordance with the following table. If more than one
water heater is to be connected to common circulating pipework, the common sections need to be sized in
accordance with the following table:
1 x MCW
2 x MCW
3 x MCW
Pipe Size
54mm
67mm
76mm
TABLE 10.3
PIPE SIZES
