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Toshiba
8-3.
Hydro Unit
Control
8-2)Piping freeze prevention control 2
TC and TWO activates freeze prevention regardless of a heat pump operation mode.
1)Determination condition: TWO>20°C, 2*TC+TWO<-12°C is continuously detected for 30 seconds or longer. Or
TWO 20°C, TC+TWO<4°C is continuously detected for 30 seconds or longer.
2)Determination cancellation conditions
• The stop or operation mode is changed by the remote controller
• The mode is defrosting at the time of determination
At the next time of defrosting, the start condition is not met.
• The mode is other than defrosting at the time of determination
After cooling, heating, hot water heat pump restarts, the start condition is not met for 10 minutes.
3)Error display
• If freeze determination cancellation condition is not met, A4 error is displayed.
8-3)Piping freeze prevention control 3
This control applies only when defrosting is in operation.
1)Determination condition: During defrosting, TWI 15°C is continuously detected for 30 seconds or longer (After
the stop, the unit restarts.)
2)Determination cancellation condition
• At the next time of defrosting, the start condition is not met.
3)Error display
• If freeze determination cancellation condition is not met, A4 error is displayed.
8-4)Piping freeze prevention control 4
When the value of Ps sensor is low, freeze prevention is activated regardless of a heat pump operation mode.
1)Determination condition: Lo pressure sensor detects PS < 0.2 MPa and 30 seconds passes (defrosting and
cooling) (During a defrosting operation for cooling and heating, or hot water supply)
Lo pressure sensor detects PS < 0.2 MPa and 10 minutes passes (heating and hot water
supply operation)
2)Determination cancellation condition
• After a restart, the start condition is not met for 30 minutes.
• At the next time of defrosting, the start condition is not met. (Defrosting operation for heating or hot water supply)
3)Error display
• If freeze determination cancellation condition is not met, A8 error is displayed.
9)High return water protect control.
The hydro unit protects against high return water which made by separate boiler system.
When A02 error appeared, the built-in pump will stop.
Item Operation flow and applicable data, etc.
70
TWI, TWO, THO
(Diff : 2K)
A02 error detect
Normal operation
+00A09-002_01EN_SVM_ALL_Air_to_Water.book Page 55 Monday, October 5, 2009 2:09 PM