Domestic Hot Water Operation - Bosch Buderus SSB399 Control Operations Manual

Control Operations Guide

6.2 Domestic hot water operation

The SSB Boiler onboard control can support domestic hot water production using an
indirect tank. The boiler can use either the supplied 10K ohm domestic sensor or a
aquastat (dry contact only, aquastat supplied by installer) to control the heating of
an indirect tank. The 10k ohm sensor or aquastat are wired to the #9 and #10 low
voltage terminal block of the SSB boiler. Parameter #35 (Domestic Hot Water Mode)
must be set to the appropriate value depending upon which type of sensor is used.
Follow the instructions below for the sensor type you have chosen to use with the
SSB Boiler.
Using the supplied 10k ohm Sensor:
1. Wire 10k ohm sensor to low voltage terminals #9 and #10 on the boilers
main control panel.
2. Within the "Boiler Settings" menu set Parameter #35 to "1".
3. Set desired domestic hot water temperature using Parameter # 48.
4. When the domestic hot water temperature falls 7.2 degrees below the
desired set temperature for hot water the boiler will begin to heat the
indirect tank. To change this switch-on diff erential adjust Parameter #36
to the desired value. The switch-off diff erential can be set separately using
Parameter #37. The default value for this parameter is zero.
Using a fi eld-supplied aquastat:
1. Wire your fi eld-supplied aquastat to the low voltage terminals #9 and #10
on the boiler main control panel.
2. Within the "Boiler Settings" menu set Parameter #35 to "2".
3. Adjust the fi eld-supplied aquastat to the desired tank temperature
according to the manufacturers instructions .
4. Upon a call for heat from the aquastat the boiler will target a supply
temperature of DHW Set point + DHW Extra. The burner will cycle on/off
based upon a +/- 3.6 degree diff erential of the target supply temperature of
176 °F.
Depending upon which DHW Mode is selected (Mode 1 = 10 K ohm sensor or Mode
2 = Aquastat) will then determine which of the following parameters can be used to
adjust the hot water operation.
DHW Parameter DHW Mode
35 -
36 1
37 1
38 1
42 1 & 2
43 1 & 2
44 1 & 2
48 1
Table 12
Bosch Thermotechnology Corp. | 03.2018
Description
DHW Mode
DHW Tank Hyst. Down
DHW Tank Hyst. Up
DHW Supply Extra
DHW Priority
DHW Max Priority Time
DHW Pump Overrun
DHW/Tank Setpoint
Bosch Buderus SSB255 | SSB399 | SSB512 Boilers | 17
Default Value
0
7.2
0
54
0
30
15
120
Range
0 - 2
0 – 36 °F
0 – 36 °F
0 – 54 °F
0 - 2
1 – 255 min.
0 – 255 sec.
104 – 140 °F
Data subject to change