Mitsubishi Electric EHST20C-VM6HA Service Manual page 27

Filling the cylinder unit
1. Check all connections including factory fitted ones are tight.
2. Insulate pipe work between cylinder and outdoor unit.
3. Thoroughly clean and flush, system of all debris. (see section 4.2 of Installation Manual for detailed instructions.)
4. Fill cylinder 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 package systems. It is the responsibility of the installer to decide if anti-freeze solution should be used in split systems
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depending on each site's conditions. Corrosion inhibitor should be used in both split and package systems.
When connecting metal pipes of different materials insulate the joints to prevent a corrosive reaction taking place which will damage the pipework.
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5. Check for leaks. If leaks are found, retighten the screws on 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 falls below 1 bar)
Filling the cylinder unit (Potable/DHW circuit)
Initial fill procedure:
1. Ensure all pipe joints and fittings are tight and secure.
. Open the most distant DHW tap/outlet.
3. Slowly/gradually open the mains water supply to begin filling unit and DHW pipework.
4. Allow most distant tap to run free and release/purge residual air from installation.
5. Close tap/outlet to retain fully charged system.
Initial flush procedure:
1. Energise system to heat-up cylinder contents to a temperature of approx. 30 – 40°C.
2. Flush/drain the water contents to remove any residue/impurities resulting from the installation works. Use the cylinder drain cock to safely discharge the warmed
water to drain via a suitable hose.
3. On completion, close drain cock, re-fill system and resume system commissioning.
Draining the cylinder unit
WARNING: DRAINED WATER MAY BE VERY HOT
1. Before attempting to drain the cylinder isolate from the electrical supply to prevent the immersion and booster heaters burning out.
2. Isolate cold water feed to tank.
3. Attach a hose to the tank drain cock (No. 17 on Figure 4-1 to 4-4). The hose should be able to withstand heat as the emptied water could be very hot. The hose
should drain to a place lower than the tank bottom to encourage siphoning.
Open a hot water tap to start draining without a vacuum.
4. When the tank is drained close drain cock and hot tap.
5. Attach hose to booster heater drain cock and water circuit drain cock (No.13 and No. 16 on Figure 4-1 to 4-4). The hose should be able to withstand heat as the
emptied water could be very hot. The hose should drain to a place lower than the booster heater drain cock to encourage siphoning. Open the pump valves and
the strainer valves.
6. Water remains in the strainer still after the cylinder unit was drained.
Drain the strainer by removing the strainer cover.
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