Low flow rate solved for Vaillant 937 installation
July 6th, 2010
Our customer, in Woldingham, Surrey, had recently purchased a property with a conventional tank fed water system.
They wished to remove a couple of shower pumps and the water tanks and install a direct fed pressurized water system. The problem was that the water flow rate into the property was around 9-10 litres per minute. There was also a limited space to fit the entire boiler plant into.
It's easier to plumb the accumulator in this position
We had to boost the flow rate as well as provide the new boiler plant, all within a single cupboard. We chose to fit a wall hung Vaillant ecoTEC 937, which is a ‘hybrid’ condensing combination boiler. Most combination boilers heat water as you use it, but this restricts the available flow rate to around 15l/m for most units. Hybrid combination boilers store some hotter water in preparation for usage, and then mix this with the water they ‘heat on the fly’ when a tap is opened……in the case of the Vaillant 937, this delivers the equivalent of 20 litres per minute of hot water for the first 10 minutes.
As we use hot water in bursts of activity, and then the system lies dormant, the hybrid combination boiler is a versatile solution.
But of course, we can’t get 20 litres a minute of hot water out of a water main only supplying 10 litres/min – so we also specified a Trent Clyde Mainsboost accumulator. This stores water at pressure and enables a highly boosted flow rate when required.
Commissioning checks underway
With the accumulator, flow rates including cold and hot water of 30 litres per minute are easily achievable.
The finished hot and cold water/heating solution
We added a secondary heating expansion vessel, as the unit in the Vaillant boiler is only suitable for a modest volume of radiators.
The flue aperture was made good outside, and the decking lifted to provide a neat direct condense drain into the external drainage.
External discharge shown
As is usual with our installations, our customer has an extended Vaillant boiler warranty, from 2 years to 5 years.
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