OPERATION
08
TECHNICAL DOCUMENTATION
OPERATION
The Rapide Extreme utilises a conventional simple storage cylinder, with a cold water feed connection at its
lowest point and a hot water draw off connection at its highest point, in addition there is a plate heat
exchanger draw off connection situated diametrically opposite to the cold water feed connection, both
connections extend within the cyinder, thus reducing the gap between them within the cylinder (see
diagram). Similarly at the top of the unit there is a plate heat exchanger flow connection diametrically
opposite the hot water draw off connection, again the connections are extended within the cylinder. A
secondary hot water return connection is situated around midway up the cylinder.
The plate heat exchanger draw off is connected to the secondary side of the plate via a bronze “loading”
pump, with the secondary flow side of the plate being connected to the connection at the top of the
cylinder. The primary connections of the plate heat exchanger are extended outside of the casing and made
available for connection to a Mikrofill Ethos condensing boiler or other suitably sized boilers.
To ensure only the correct minimum temperature is loaded and stored in the cylinder, the primary
temperature sensor (TT4) will look for a minimum primary temperature before releasing the loading pump to
allow the loading process to begin. The minimum required primary temperature is the storage set point (see
page 16) + 5°C.
Requested Storage Set Point 60°C: Minimum Primary Temperature Requirement: 65°C
Requested Storage Set Point 65°C: Minimum Primary Temperature Requirement: 70°C
Requested Storage Set Point 70°C: Minimum Primary Temperature Requirement: 75°C
Once the loading process has begun the loading pump will receive a “pulsed” voltage to ensure that the
temperature of the domestic hot water measured entering the storage vessel is kept at a minimum
temperature of the requested set point, the unit will display “nL” and the temperature during this process. The
loading process will continue until the stop temperature sensor (TT2) has registered the requested minimum
storage set point. The Rapide Extreme will then register “nR” and the cylinder temperature (TT1) to indicate
the requested set point has been achieved.
When domestic hot water is drawn from the top of the storage vessel, it is replaced by mains cold water at the
bottom of the storage vessel. Once there has been a sufficient temperature drop, the start temperature
sensor (TT1) will register the drop in temperature due to the ingress of the mains cold water and the loading
cycle will commence again providing primary temperature is available.
