Commissioning; Multipoint Gas Water Heaters; Combination Boilers - Mira Combiforce 415 Installation And User Manual

Section
8
All heater appliances must have a fully modulating heat output for the domestic
hot water, to provide a constant temperature of hot water to the Mira CombiForce 415
shower control.

Multipoint Gas Water Heaters

These notes are based on a heater with an effective output power of 23.5 kW. Heaters with
higher or lower effective output powers will proportionally affect the following information.
The Mira CombiForce 415 range does not compensate for water temperature
changes.
1. Use the heater appliance on a "high" or "winter" setting only.
2. A minimum maintained water supply pressure of 1.5 bar is required to the water
heater. This allows for a 0.5 bar pressure loss in the heater and ensures the
maintained inlet pressure at the shower is above 1 bar.
3. The maintained water supply pressure should not exceed 5 bar. A pressure reducing
valve will be needed for pressures over 5 bar to improve the system operation. It
should be installed to reduce both the cold feed pressure to the heater and the cold
feed pressure to the Mira CombiForce 415 to approximately 3.5 bar.
Additional benefits may be obtained by fitting the pressure reducing valve after the
premises internal stop valve, drain valve and if fitted, outside tap. The valve should
be correctly sized for the duty.
4. If the minimum modulating output of the heater appliance exceeds 14 kW with a
reducing hot flow rate, then the maintained minimum supply pressure will need to
be increased. This is to keep the flow rate through the heater sufficiently high in order
to ensure that the gas flame stays ignited. An extinguished flame will produce a cold
shower after a short period of time.

Combination Boilers

1. This information is based on a heater appliance fitted with an internal flow regulator
rated at 10 l/min hot water.
2. Use the heater appliance on a "high" or "winter" setting only.
3. Should it not be possible to get a hot enough shower it may be necessary to fit a
9 l/min flow regulator (available from Kohler Mira Customer Services) between the
shower control and hose to further reduce the flow. The "top hat" regulator should
fit into the hose recess such that the black 'O' seal is visible before attaching the
hose to the shower control.
4. A minimum maintained water supply pressure of 1.5 bar is required. This allows for
a 0.5 bar pressure loss in the heater.

Commissioning

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