Manual of SR288 intelligent controller
34
Hysteresis switch on temperature difference is 5K.
OHDP Heat transferring by external radiator
Heat transferring by external radiator function is designed to transfer the excess heat which
is generated under the strong solar irradiation through an external heat exchanger (e. g. fan
coil); the purpose is to keep the collector’s or tank’s temperature within the operating range.
For this function, an extra output should be added (R2 or R3 as option)
Heat transferring by external radiator function can control either an additional pump or a
valve (
OTPM ON
= pump logic,
OTPM OFF
= valve logic)
Heat transferring by external pump:
If the collector temperature reaches the adjusted switch-on temperature, the allocated relay
for pump is energized with 100 %; if the collector temperature falls by 5 K below the adjusted
collector overheat-temperature, the relay will be switched off. When heat transferring is
achieved by pump, then the heat transferring function will be independent from solar loading.
Below is the example of this application for reference.
Collector heat transferring valve logic Collector heat transferring pump logic
Sign displays on the screen, it indicates that valve logic heat transferring is running.
Sign displays on the screen, it indicates that pump logic heat transferring is running.
Note:
1. When collector overheat temperature OTST is 10K below the CEM temperature of
collector emergency shutdown, then collector overheat temperature OTST is locked
2. Heat transferring function is only available when collector cooling function (OCCO) and
system cooling function (OSYC) are deactivated.