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SYSTEM DESIGN RECOMMENDATIONS
The hot water header from the water heaters should be put into the middle connection on the hot
water cylinder
A drain point should be fitted on the pipework after the last heater but before the cylinder for
commissioning and testing purposes.
A non-return valve and an isolating valve on the cylinder side of the drain should be fitted so that
when the drain is opened the water flows through the heaters instead of draining out of the
cylinder.
The mains water should carry on past the branch to the pump and into the connection above the
drain on the cylinder, this is called a Bi-Directional flow.
There must not be a valve between the check valve from the unvented kit and the cylinders Bi
Directional pipework. The expansion vessel and safety relief valve must have a direct
uninterruptable path to the cylinder to guarantee the system has capacity for expansion this is a
regulation to keep the system safe.
The hot water supply from the hot water storage cylinder comes out of the top and goes off to the
outlets. There must be an isolation valve in the pipework.
The secondary return should be piped into the hot water primary pipework from the water heaters
to the cylinder. The pump should be sized to give a sufficient flow rate so that the retuning water
temperature is over 50°C. Rinnai do not supply or size this pump as it depends on the design and
size of the building flow and return pipework.
On both sides of the pump there should be an isolation valve. After the pump there must be a non -
return.
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