Hitachi YUTAKI Series - Refrigerant Cycle and Hydraulic Circuit; 5.1 Refrigerant Cycle and Hydraulic Circuit for Split System

Controller pack
Service Manual
90
DHW control functions
SMGB0066 rev.0 - 12/2009
 

AppliesonlytocongurationsCONF3,5

The boiler may also be used to raise the temperature of the DHW tank if the Heat Pump is not able to reach the DHW
supplysetpointbyitself.TheboilerwillonlystartafteratimedelaydenedbyparameterP19(waitingtimeforboiler)in
order to allow the Heat Pump time to satisfy the DHW loading demand by itself.

P19 Waiting Time for Boiler (default 30 min)
 

Since the heat pump only reads the control signal (mA) once every 20 minutes there can be a delay before the system
respondstotheDHWrequest.Inordertoimprovethisresponsetime,theSystemControllerusesafeatureoftheheat
pumpthatwhenthecontrolsignalissettoitshighestvalue,itrespondsimmediately.Soifthesupplysetpointhastobe
increasedduetoaDHWdemand,thenthesupplysetpointissettotheparameterEP29(HeatPumpmaximumsupply
temperature) for a certain time. This time is the Heat Pump Max Time High Setpoint (EP35). When this time period
expires,theSupplySetpointissettothenormalcalculatedDHWsupplysetpoint.

EP35 Heat Pump Max Time High Setpoint (default 180sec)

note
Engineering Parameters (EP) are only available for service engineers -
 

A DHW time program is not provided inside the controller. An external timer can be used by itself or together with a tariff-
switchdevice.Forexample,withanexternaltimeritispossibletoblockDHWloadingduringdaytimeperiods.
It is possible to use
only a external timer. Operates according to EP24 setting.1.
an external timer in series with a tariff-switch device. In this case: 2.
if EP24=3 both the external timer and the tariff-switch contacts must be closed to allow DHW loading
if EP24=4 either of the external timer or the tariff-switch contacts can be open to allow DHW loading.
an external timer in parallel with a tariff-switch device. In this case: 3.
if EP24=3 either of the external timer or the tariff-switch contacts can be open to allow DHW loading
if EP24=4 both the external timer and the tariff-switch contacts must be closed to allow DHW loading.
only a tariff switch device. Operates according to EP24 setting.4.
Dependingonthesettingofthecongurationoftariff/timerinputparameter(EP24),DHWloadingcanbeblocked
according to the status of the input (open or closed).