HTW ECO-THERMAL PLUS -V18WD2RN8PLUS Manuel De L'utilisateur Et D'installation page 111

Before continuing installation of the unit, check the following:
The maximum water pressure ≤ 3 bar.
The maximum water temperature ≤ 70°C according to safety device setting.
Always use materials that are compatible with the water used in the system and with the materials used in the unit.
Ensure that components installed in the field piping can withstand the water pressure and temperature.
Drain taps must be provided at all low points of the system to permit complete drainage of the circuit during maintenance.
Air vents must be provided at all high points of the system. The vents should be located at points that are easily accessible
for service. An automatic air purge is provided inside the unit. Check that this air purge valve is not tightened so that automat-
ic release of air in the water circuit is possible.
9.4.2 Water volume and expansion vessel pre-pressure checks
The units are equipped with an expansion vessel (models: 8L) that has a default pre-pressure of 1.0 bar. To assure proper
operation of the unit, the pre-pressure of the expansion vessel might need to be adjusted.
1) Check that the total water volume in the installation, excluding the internal water volume of the unit, is at least 25L . Refer to
14 Technical specifications to find the total internal water volume of the unit.
In most applications this minimum water volume will be satisfactory.
In critical processes or in rooms with a high heat load though, extra water might be required.
When circulation in each space heating loop is controlled by remotely controlled valves, it is important that this
minimum water volume is kept even if all the valves are closed.
2) Using the table below, determine if the expansion vessel pre- pressure requires adjustment.
3) Using the table and instructions below, determine if the total water volume in the installation is below the maximum allowed
water volume.
Installation
height Water volume ≤230 L
difference(*)
≤7 m No pre-pressuread justment required.
Actions required:
• Pre-pressure must be increased, calculate accord-
ing to
"Calculating the pre-pressure of the expansion
>7 m
vessel" below.
• Check if the water volume is lower than maximum
allowed water volume (use graph below)
* Height difference is between the highest point of the water circuit and the outdoor unit's expansion tank. Unless the unit is
located at the highest point of the system, in which case the installation height differnce is considered to be zero.
Calculating the pre-pressure of the expansion vessel
The pre-pressure (Pg) to be set depends on the maximum installation height difference (H) and is calculated as follows:
Pg(bar)=(H(m)/10+0.3) bar
Checking the maximum allowed water volume
To determine the maximum allowed water volume in the entire circuit, proceed as follows:
NOTE
Water volume >230 L
Actions required:
• Pre-pressure must be increased, calculate accord-
ing to
"Calculating the pre-pressure of the expansion
vessel" below.
• Check if the water volume is lower than
mum allowed water volume (use graph below)
Expansion vessel of the unit too small for the
installation.
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