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Siemens Building Technologies Basic Documentation RVD110, RVD130 CE1P2381E
HVAC Products 17 Function block D.h.w. actuator 2 27.05.2004
17.5.2 Measuring the d.h.w. temperature
A sensor or control thermostat is always required. The type of measurement is to be
entered on operating line 53. When using a thermostat, consideration must be given to
the following criteria:
• The free sensor will automatically be assigned to the differential temperature meas-
urement
• Frost protection for the d.h.w. is not possible
• The thermostat is to be connected to terminal H5
Supervision of faults is not possible, since short-circuit and open-circuit are permitted
states.
When setting the temperature on the thermostat, it is recommended to use the mean
value of the fresh water temperature and d.h.w. temperature setpoint.
17.5.3 Feeding the circulating water into the heat exchanger
Feeding of the circulating water into the heat exchanger can be configured on operating
line 55.
The following settings can be made:
Setting Circulating pump Feeding the
circulating water
Function, action
0 Yes or no If used: into the storage
tank
No control, no compensation
of the heat losses
1 Yes Into the heat exchanger Partial compensation of the
heat losses (80 %)
2 Yes Into the heat exchanger Full compensation of heat
losses (100 %); the d.h.w. flow
temperature setpoint is con-
stantly aimed for
A flow temperature drop of 20 % is accepted. On completion of a d.h.w. heating cycle,
the circulation circuit will first be charged for about 5 minutes before the demand for
d.h.w. heating becomes invalid.
The behavior is the same as that with d.h.w. heating directly via heat exchanger (set-
ting on operating line 54 = 2) as described in subsection 17.4.4 “Offsetting the heat
losses”.
17.5.4 D.h.w. heating
• Plant type no. 6: The d.h.w. flow temperature (B3) is controlled by adjusting two-port
valve Y5 in the d.h.w. primary circuit. The storage tank is charged via charging
pump Q3
• Plant type no. 7: The temperature of the secondary d.h.w. flow (B3) is controlled by
adjusting mixing valve Y5.
When there is a demand for d.h.w., pumps Q3 and Q7 will be activated only when
the common flow temperature (acquited with sensor B1) has exceeded the storage
tank temperature (B71) by 5 K. They are immediately deactivated (with no pump
overrun) when the common flow temperature (B1) falls below the storage tank tem-
perature (B71). This function can only be provided when using a d.h.w. temperature
sensor. When using a control thermostat, pumps Q3 and Q7 run at any flow tem-
perature and do not stop charging the tank as long as d.h.w. heating is required.
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