A.O. Smith Theta T Series, Installation, User And Service Manual

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Installation-, User- and Service Manual
63
2 Working principal
2.1 Introduction
2.2 General working
principle of the
Theta dual service
module
2.3 Heating cycle
This chapter covers the following topics:

General working principle of the dual service modules;

Heating cycle;

Safety of the dual service modules.
Dual service is a module that connects a Domestic Water system (DHW system) and a
heating system. By using a Theta dual service module, heat from a BFC, SGE or SGS
can be transferred, through a plate heat exchanger, to the heating system.
Through the use of an intelligent control there is an optimal use of the available hot water
supply. Without compromising on comfort the system can provide hot water demand
from both domestic hot water system and heating system.
The intelligent control controls the domestic hot water and heating system through a
number of sensors and directs the DHW-pump and 3-way mixing valve in order to
achieve the desired flow temperature on the heating side of the system.
Note
The maximum working pressure, on the DHW-side of the system, is 8 bar. The minimum
working pressure, on the heating-side of the system, is 1 bar and the maximum working
pressure is 3 bar.
At heat demand on the heating side of the system, from the room thermostat, the DHW-
pump(modulating) an heating pump will be activated by the controller. To reach the
desired supply temperature the 3-way mixing valve will also be activated.
In the 3-way mixing valve, the water that runs through the plate heat exchanger is mixed
with hot water from the water heater, in order transfer enough heat in the plate heat
exchanger, which will result in the desired supply temperature of the heating water. The
desired heating supply temperature (heating setpoint) can be set on the controller of the
water heater.
The desired temperature depends on the type of heating system. The heating supply
temperature is measured by temperature sensor S
5
which is mounted on heating supply
pipe.
Note
Temperature sensor S
5
has a control function and is not to be used as a safety for the
heating system. This kind of safety should be regulated separately and is the full
responsibility of the installer.
Note
The pressure protection must also ne provided separately and is the full responsibility of
the installer.