Bosch GWH C 920 ES - Page 28

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Bosch applications manual
Bosch applications manual | 06.2009
BOSCH THERMOTECHNOLOGY CORPORATION
9.2.3 Solar DHW system with gas tankless water heater booster
and recirculation loop
Similar to 4.3.2 with domestic hot water recirculation added. The
tankless water heater only runs when solar heated water needs a
boost. Buffer tank provides small amounts of DHW instantly and
increases comfort by smoothing out DHW temperature.
Recommended appliances: Bosch GWH 715 ES, GWH C 800 ES.
 Thermostatic valve 1 ensures that warm solar water bypasses the
water heater and directs cooler water through the appliance
when reheating is needed.
 Thermostatic valve 2 acts as a tempering valve that brings
potentially hot water temperatures down to a level that is safe for
the users.
Water
supply
Hot
Cold
Solar
Pump
Station
Domestic
hot water
Thermostatic
valve 1
Thermostatic
valve 2
Solar
Controller
Collector
sensor
Tank
sensor
Symbols
Ariston GL8ti
mini tank
Bosch GWH 715 ES,
Bosch GWH C 800 ES,
Bosch GWH C 920 ES/ESC
Service
valve
Pressure
relief
valve
Honeywell
Am-1 series
thermostatic
mixing
valve
Solar
storage
tank
Flow
direction
Potable
water
expansion
tank
Well
thermometer
Circulator
Flow
check
valve
Drain
valve
System parameters:
 Honeywell AM101 Thermostatic Valves required for proper
operation;
 Remove check valves from Thermostatic Valve 1 as it is used as a
diverter valve;
 Thermostatic Valve 2 is a tempering valve;
 Recommended setpoint 120°F for both Valves;
 Set tankless water heater temperature to 140° F
 Ariston mini tank will provide increased temperature stability and
quicker hot water delivery. (recommended but not required)
 Choose size of the Ariston mini tank to match the volume of the
recirculation loop
See Chapter 5.1 for recirculation pump parameters