Hitachi YUTAKI Series - Mixing; Bypass Valve Control; Mixed Heating Circuit Maximum Temperature Limit Protection; Mixing Valve Opening Delay

Controller pack
Service Manual
102
Mixing valve control functions
SMGB0066 rev.0 - 12/2009
 

Thisfunctiononlyappliestoconguration5(CONF5)

Whentheboilerisswitchedon,themixingvalvecontrolisenabledandoperatesinthesamemannerasdescribed
above (Mixing Valve Control).
Whentheboilerisswitchedoff,andthedifferencebetweenthesupplywatertemperature(TSUP)andmixedsupply
temperature(TMIX)issmall(lessthanEP3),themixingvalveisalwaysclosed(by-passoperation)sothatthehot
supplywaterfromtheheatPumpdoesnotcirculatethroughtheboilerheatexchanger,whichmaycauseunnecessary
heatlossandreductioninsystemefciency.Whilethewaterfromtheboiler(TSUP)ismuchhotterthanthemixedsupply
temperature(TSUP),themixingcontrolcontinuestooperate.

P9 Mixing Valve Runtime (default 120 sec)
EP3 Difference Supply water temperature (default 1.5K)
The value for EP3 has been chosen based on laboratory tests and it is not recommended to change it.

note
Engineering Parameters (EP) are only available for service engineers. -
 

Thisfunctiononlyappliestocongurations4and5(CONF4,5)

The secondary circulation pump is switched off and the mixing valve closed when the maximum supply temperature
(mixingcircuit)settingisexceeded.Thisfunctionhelpspreventdamagetooorheatingsystemsbyveryhigh
temperatures.
TMIX>P6  Pumpswitchedoff,mixingvalveclosed.
TMIX < P6 – 5K Returns to normal control.

P6 Maximum Supply Temperature

note
A fault code is displayed when the maximum limit is exceeded. -
 

Thisfunctiononlyappliestocongurations4and5(CONF4,5)