Water Pipe Work; Hot Water Pipework; Cold Water Pipework; Pipework Connections - Mitsubishi Electric ecodan EHST20 Série Manuel D'installation

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installation

4.3 Water Pipe Work

Hot Water Pipework

the cylinder unit is UnVented. When installing unvented hot water sys-
tems building regulations part G3 (England and Wales), P3 (Scotland) and P5
(Northern Ireland) should be adhered to. If outside of the UK please adhere
to your own country's regulations for unvented hot water systems.
Connect the flow for the DHW to pipe A (Figure 3.1).
The function of the following safety components of the cylinder unit should be
checked on installation for any abnormalities;
• Pressure relief valve
• Temperature and pressure relief valve (EHPT20X-VM2HB ONLY)
• Expansion vessel pre-charge (gas charge pressure)
The instruction on the following pages regarding safe discharge of hot water from
Safety devices should be followed carefully.
• The pipework will become very hot, so should be insulated to prevent burns.
• When connecting pipework, ensure that no foreign objects such as debris or the
like do not enter the pipe.

Cold Water Pipework

Cold water to the suitable standard (see section 4.2) should be introduced to the
system by connecting pipe B (Figure 3.1) using appropriate fittings.
Hydraulic filter work (ONLY EHPT series)
Install a hydraulic filter or strainer (field supply) at the water intake ("Pipe G" in
Fig.3.4, Fig.3.5)

Pipework Connections

Connections to the cylinder unit should be made using the 22 mm or 28 mm
compression as appropriate.
Do not over-tighten compression fittings as this will lead to deformation of the olive
ring and potential leaks.
Note: To weld the pipes in the field, cool the pipes on the cylinder unit using wet
towel etc.

Sizing expansion Vessels

Expansion vessel volume must fit the local system water volume.
To size an expansion vessel for the heating circuit the following formula and
graph can be used.
When the necessary expansion vessel volume exceeds the volume of an built-in
expansion vessel, install an additional expansion vessel so that the sum of the
volumes of the expansion vessels exceeds the necessary expansion vessel
volume.
* For installation of an EHST20C-*M*EB model, provide and install an expansion
vessel in the field as the model does not come fitted with an expansion vessel.
ε × G
V =
P ¹ + 0.098
1 −
P ² + 0.098
Where;
V : Necessary expansion vessel volume [L]
ε : Water expansion coefficient
G : Total volume of water in the system [L]
P ¹ : Expansion vessel setting pressure [MPa]
P ² : Max pressure during operation [MPa]
Graph to the right is for the following values
ε : at 70 °C = 0.0229
P ¹ : 0.1 MPa
P ² : 0.3 MPa
*A 30% safety margin has been added.
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insulation of Pipework

• All exposed water pipework should be insulated to prevent unnecessary heat loss
and condensation. To prevent condensate entering the cylinder unit, the pipework
and connections at the top of the cylinder unit should be carefully insulated.
• Cold and hot water pipework should not be run close together where possible, to
avoid unwanted heat transfer.
• Pipework between outdoor heat pump unit and cylinder unit should be insulated
with suitable pipe insulation material with a thermal conductivity of ≤ 0.04 W/
m.K.

Filling the System (Primary Circuit)

Filling
1. Check all connections including factory fitted ones are tight.
2. Insulate pipework between cylinder unit and outdoor unit.
3. Thoroughly clean and flush, system of all debris. (see section 4.2 for
instruction.)
4. Fill cylinder unit with potable water. Fill primary heating circuit with water and
suitable anti-freeze and inhibitor as necessary. Always use a filling loop with
double check valve when filling the primary circuit to avoid back flow
contamination of water supply.
• Anti-freeze should always be used for packaged model systems (see
section 4.2 for instruction). It is the responsibility of the installer to decide
if anti-freeze solution should be used in split model systems depending
on each site's conditions. Corrosion inhibitor should be used in both split
model and packaged model systems.
• When connecting metal pipes of different materials insulate the joints to
prevent a corrosive reaction taking place which will damage the pipework.
5. Check for leakages. If leakage is found, retighten the screws onto the
connections.
6. Pressurise system to 1 bar.
7. Release all trapped air using air vents during and following heating period.
8. Top up with water as necessary. (If pressure is below 1 bar)
expansion vessel sizing
25
20
15
10
5
0
0 50 100 150
System water volume [L]
<Figure 4.3.1>
200 250 300 350 400