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MAINTENANCE MANUAL
Mirage technical manual
page 34 of 65
Expansion valve on manifold
The coffee water heating system consists of 2 or 3 heat-exchangers inside the steam boiler. This
entire system is filled with water only, no steam, no air. At the entrance of the coffee water system a
one-way valve, or check valve, is installed to prevent hot water being pushed back into the fresh water
lines.
When water is heated it will expand. As there is no room for the expanded water (no air pockets, no
way out) pressure will increase. To keep this pressure within safety limits, an expansion valve is part
of the system. The expansion valve will release drops of water when pressure exceeds the set value,
the released water is directed into the discharge.
The expansion valve is mounted on the cold-water manifold on the left hand side of the Mirage and
thus works on all groups simultaneously.
Easiest is to temporarily increase the pump pressure during this procedure. However, be careful not to
exceed 15 Bar as this may damage the solenoid valves in the machine. Best is to work with 2 people:
one adjusting the pump pressure and the other watching the pressure gauge and adjusting the
expansion valve.
Note!
The solenoid group valves have a rating of 15 Bar. This means they will be pushed open when
pressure exceeds 15 bar. The group valves thus act as a second safety, should the expansion valve
fail to open.
It is also possible to check/adjust without increasing pump pressure but you only have 2 minutes for
the water to expand (then the group valve is shut automatically). The machine must be close to or at
operational temperature. Let both groups run without filter holders for about 30 seconds to let a lot of
cold water enter the coffee system, then swiftly lock the gauged filter holder in (drain tap closed) and
let group run again. When the cold water heats up it will expand thus leading to increased coffee
system pressure.
The expansion valve should start to expel drops of water when the gauge reads 12 Bar.
Check expansion valve
Materials needed
Spanner 11 mm, 12 mm or 16 mm, depending on valve model
Towel or sponge
Filter holder with pressure gauge (and drain tap)
Screw driver
Procedure
1. Remove left hand side panel.
2. Pull black silicone hose from expansion valve, place towel or sponge under expansion valve
opening.
3. Increase the opening pressure of the valve by turning the outer nut on the expansion valve 2 full
turns clockwise (see Figure M 15).
4. Make sure that the mains switch is
in position “1” (no power to heating element).
5. Mount filter holder with pressure gauge in left group
6. Activate left group, check pressure gauge on filter holder. It should read a little over 9 Bar. If it is
higher, activate another group shortly (cold water in the coffee system has warmed up and
expanded such that the pressure is higher than the pump pressure. The one-way valve prevents
water from flowing towards the pump).