16
System Overview Multiple Units in Series Cascade
Connection
(1)
Heating working principle
To set two or more units in parallel operation, set the primary unit to the required
parameters, other units could have 2~5°C difference of ST01,ST02 and ST05 to allow
for energy stage control.
1.
When SF04=0:
a). if the RT (inlet water temperature) is lower than ST02-ST04 of the unit, then
the unit will start to heat. The unit with the lower ST02+ST04 will stop first, the
others will stop as well if the RT continues to rise and be over its ST02+ST04.
b). RT will drop when units stop. The unit with the higher ST02-ST04 will start
first again to heat . If this unit can meet the heating capacity then its RT will not
drop any further, only this unit will run as required. If the heating load is bigger
than the capacity of one unit then the RT will continue to drop to below the second
unit ST02-ST04 , the second unit will start increasing the heating capacity.
2.
When SF04=1:
ST02 is replaced by “Set temperature at heating” =ST05+ST06 *(ST05-OT).
Refer to page 36 “Heating compensation curve setting” and page 37 “Three curves
of different ST05 setting”
(2)
Hot water production working principle:
On hot water mode, Three way valve (VXV) will open AB-B.
When domestic hot water requirement calls, the three way revert valve ( VXV) will
have the priority to revert to the hot water tank (VVB ). After the domestic hot water
reach its set temperature ST09, the three way revert valve ( VXV) return to heating
circuit position. After HT<ST09 – ST10, three way revert valve (VXV) will revert to
hot water circuit again.
Important
The coil heat exchanger inside the hot water cylinder VVB should be well selected to
have big enough diameter and heat exchange capacity. Otherwise, heat pump will have
high outlet water temperature protection alarm AL05 frequently
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Systems Overview (Indoor side)
