Skyline Energy SX-20BZA, Installation Manual, Page: 7 / 51

Water flow-rate in the primary circuit:
Before anything else you MUST plan to achieve the required water flow rate in
the primary circuit between the heatpump and buffertank.
Adequate water flow-rate is critical to achieve maximum efficiency.
(Just because a unit is heating does not mean its running efficiently)
Avoid restrictive plumbing. Use large diameter pipes for the primary flow and
return, and limit elbows and sharp bends.
The temperature rise across the heatpump inlet and outlet ports is directly
proportional to the water flow-rate.
Lower the temp rise = higher flow rate = higher efficiency
Use enquiry code “A5” and “A6” to read the temperature rise which should be
4
o
C or lower for all models.
Example:
A model V35ZA with close-coupled buffertank with a GPD32-12 circ pump
produces a flow rate of 49Lt/min on our test rig, and at 10C ambient the unit
produces an average of 23.7kW power output.
If we increase the pump size to a GPD25-16 adding another 245Watts to the
power draw, this increases the flow rate to 64Lt/min, and increases the power
output to 24.7kW. The result is that we spend another 245Watts to gain
another 1000Watts output.
Note:
If your primary circuit is long and/or complex, an additional circulation pump
may be required to boost the flow-rate.