35
Mixing of a heating medium with a four-way valve allows to adapt the tempera-
ture in the system to changes in the temperature outside. It is necessary to install
a mixing valve when the boiler set temperature would be below 60 °C.
To protect the boiler against "low-temperature corrosion", the temperature of
water returning from the heating system is increased in the four-way valve installed
on the return connection, by mixing it with water heated in the boiler.
To prepare domestic hot water, connect the heat exchanger (domestic hot
water). A heating system for domestic hot water should be equipped with the
following components: circulatory pumps and a domestic hot water temperature
sensor, connected to a supply terminal strip on the boiler side. The system should
be constructed by a qualified person, according to current regulations.
7.5.1. OPEN VENTED SYSTEM
Water-based open vented heating systems should be equipped with protec-
tive devices in accordance with current specific regulations in force in a country
of destination (PN-EN 12828:2013-05E Heating systems in buildings. Design for
water-based heating systems). The expansion vessel volume should correspond
to at least 4% of water volume in the whole heating system.
NOTE:
No valves can be installed on ascending and descending safety pipes and
on a circulatory pipe, and these pipes and the expansion vessel should be
protected against freezing of water in them.
SAS AGRO-ECO boilers can work with gravitational or forced water flow. When
a circulatory pump is installed in an open vented system, a differential pressure
control valve should also be installed on a supply/return pipe, so in the even of
power outage or pump failure the valve opens and the system automatically starts
to operate in a gravitational mode.
An example of the boiler installation in an
open vented central heating and domestic hot water system with a forced
water flow is shown in Fig. 9.
SAS AGRO-ECO boilers can also work with a water based central heating
system through a heat exchanger. Due to a small water capacity of the open vented
system, installation of a thermal protection valve is recommended as protection
against overheating. A sealed heating system is located downstream from the
exchanger.
An example of the SAS AGRO-ECO boiler installation in a central
heating and domestic hot water system with a heat exchanger is shown in Fig.
10.
The standard boiler equipment includes a connector for a temperature sensor
with a capillary tube (item 2); the temperature sensor is installed in the hottest part,
at the top of the boiler. A Regulus thermostat valve type BVTS (optional)(item 8) is
thermal protection device for the boiler installed in an open vented system working
with the system through a heat exchanger. During normal operation the valve
protecting against overheating is closed and blocks supply of cold water from
the water supply system to the heating system. When boiler is overheated (jacket
