M thermal Mono
74 202005
Midea M thermal Mono Engineering Data Book
3 Water Pipework
3.1 Water Circuit Checks
M thermal Mono units are equipped with a water inlet and outlet for connection to a water circuit. M thermal Mono units
should only be connected to closed water circuits. Connection to an open water circuit would lead to excessive corrosion
of the water piping. Only materials complying with all applicable legislation should be used.
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 automatic release of air in the water circuit is possible.
3.2 Water Volume and Expansion Vessel Pre-pressure Checks
Outdoor units are equipped with an expansion vessel (8L) that has a default pre-pressure of 1.5 bar. To assure proper
operation of the unit, the pre-pressure of the expansion vessel might need to be adjusted. Refer to Table 3-3.1. The total
volume of water in the system must be at least 25L(for 4/6/8kW unit, the minimum volume is 15L) and should not exceed
the limits specified in Figure 3-3.1.
Table 3-3.1: Expansion vessel pre-pressure adjustment
Installation height
difference
1
No pre-pressure adjustment required
Actions required:
• Pre-pressure must be decreased, calculate
according to "Calculating the pre-pressure of the
expansion vessel"
3
•Check if the water volume is lower than maximum
allowed water volume (refer to Figure 3-3.1)
Actions required:
• Pre-pressure must be increased, calculate
according to "Calculating the pre-pressure of the
expansion vessel"
2
•Check if the water volume is lower than maximum
allowed water volume (refer to Figure 3-3.1)
Expansion vessel in the outdoorunit too small for
the system. An external expansion vessel (field
suppied) is required.
Notes:
1. 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 difference is considered to be zero.
2. For 1-phase 12~16kW and 3-phase 12~16kW units, this value is 72L, for 5~9kW units, this value is 30 L.
3. 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 Pg(bar)=(H(m)/10+0.3) bar
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