Midea MHC-V10W/D2N1, Installation & Owner'S Manual

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Be careful not to deform the unit’s piping by using excessive
force when connecting the piping. Deforming the piping can
cause the unit to malfunction.
>12 m
≤12 m
Calculating 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
Setting the pre-pressure of the expansion vessel
When it is required to change the default pre-pressure of the
expansion vessel (1.5 bar), keep in mind the following guidelines:
■ Use only dry nitrogen to set the expansion vessel pre-pressure.
■ Inappropriate setting of the expansion vessel pre-pressure will
lead to malfunctioning of the system. Pre-pressure should only be
adjusted by a licensed installer.
Connecting the water circuit
Water connections must be made in accordance with the outlook
diagram delivered with the unit, with respect to the water intake and
water outlet.
2. Check that the total water volume in the entire water circuit is
lower than this value.
If this is not the case, the expansion vessel inside the unit is too small
for the installation.
Checking the maximum allowed water volume
To determine the maximum allowed water volume in the entire circuit,
proceed as follows:
1. Determine the calculated pre-pressure (Pg) for the corresponding
maximum water volume using the graph below.
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.
(a) Installation height difference: height difference (m) between the
highest point of the water circuit and the unit. If the unit is located
at the highest point of the installation, the installation height is
considered to be 0 m.
pre-pressure = pre-pressure of the expansion vessel
maximum water volume = maximum water volume in the system
A1 System without glycol for 1-phase 10~16 kW and 3-phase
12~16 kW unit
A2 System without glycol for the 5/7/9 kW unit
Example 1
The unit(16kW) is installed 10m below the highest point in the water
circuit. The total water volume in the water circuit is 100 L.
In this example, no action or adjustment is required.
Example 2
The unit(16kW) is installed at the highest point in the water circuit.
The total water volume in the water circuit is 150 L.
Result:
■ Since 150 L is more than 110 L, the pre-pressure must be
decreased (see table above).
■ The required pre-pressure is:
Pg(bar) = (H(m)/10+0.3) bar = (0/10+0.3) bar = 0.3 bar
■ The corresponding maximum water volume can be read from
the graph: approximately 160 L.
■ Since the total water volume (150 L) is below the maximum water
volume (160 L), the expansion vessel suffices for the installation.
■ Because brass is a soft material, use
appropriate tools for connecting the water
circuit.
Inappropriate tools will cause damage
to the pipes.
If air, moisture or dust gets in the water circuit, problems may occur.
Therefore, always take into account the following when connecting
the water circuit:
■ Use clean pipes only.
■ Hold the pipe end downwards when removing burrs
■ Cover the pipe end when inserting it through a wall so that no dust
and dirt enter.
■ Use a good thread sealant for sealing the connections. The
sealing must be able to withstand the pressures and temperatures
of the system.
■ When using non-brass metallic piping,make sure to insulate both
materials from each other to prevent galvanic corrosion.
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(b) for 1-phase 10~16kW and 3-phase 12~16 kW unit, this value is
125L, for 5~9 kW unit, this value is 45 L.
Selecting the additional expansion vessel
If the expansion vessel of the unit is too small for the installation, an
additional expansion vessel is needed.
■calculate the pre-pressure of the expansion vessel:
Pg(bar)=(H(m)/10+0.3) bar
the expansion vessel equipped in the unit should adjust the pre-
pressure also.
■calculate the volume needed of the additional expansion vessel:
V1=0.0693*Vwater/(2.5-Pg)-V0
Vwater is volume of water in the system, V0 is volume of expansion
vessel which the unit is equipped(10~16kW,V0=5L, 5~9kW,V0=2L).