The system uses Rinnai continuous gas fired water heater units incorporated with solar water heating for a new stand- alone classroom and facilities block for 75 children, their staff and helpers. Solar heating was required to meet the Council's policy of reducing their carbon footprint and to comply with Part L2a of the Building Regulations.  Hot water is provided for hand washing and utility sinks.

Mark Lowe, the mechanical design engineer, chose a Rinnai HD 50i water heater and this was linked to an evacuated tube solar array mounted on the plant room roof.  The solar array feeds into a 500 litre storage tank.  The effect of this arrangement is that the incoming cold water supply passes through the solar tubes and is stored in the 500 litre tank.  If there is a hot water demand, water preheated by the solar system is drawn from the tank, and the water heater has only to raise the water from the stored temperature to that set by the system controls. 

For example the system is set to deliver hot water from the Rinnai heater at 60ºC (to avoid legionella risks).  This water is blended to provide a safe 43ºC at the outlets.  On a typical day with sunny periods the store could well be at 45ºC, leaving only a 15º rise to be made by the heater.  Compared to an average cold main temperature of 10ºC, the solar is saving 70% and on very sunny days could mean virtually no gas input is required.

"The Rinnai system is simpler," says Mark, "Any solar input is made use of, even if the solar input is only a few degrees.  Also there is no conflict, as there is with a storage and boiler approach, of the boiler pre-empting the solar panels and heating a whole tank of water which then cannot accept any solar contribution."

Rinnai UK Ltd
9 Christleton Court
Manor Park
Runcorn 
WA7 1ST
Tel: 01928 531870

Email: davidhayhurst@rinnaiuk.com
Web: www.rinnaiuk.com

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