Continuous flow is the way to go for hot water efficiencies


Distributors called on to help schools get ready for universal free school meals (UFSM) may also be called on to provide for hot water needs for kitchens in the design.

By installing condensing continuous flow gas fired water heater system instead of a wasteful and costly hot water storage system, schools (and other catering operations) could make a significant impact to running costs, with the potential of saving up to 30% on fuel bills, according to hot water expert Rinnai UK.

This especially impacts on commercial kitchens where there is a continual demand for hot water throughout the day.

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According to Rinnai UK, this is the only method that can ensure cost effective hot water, whenever it is needed and that will never run out, and that guarantees to save thousands of pounds in energy and water usage over its lifetime

For example, a school kitchen installation with three 300 litre sinks can save 29% in energy costs using a system comprising two Rinnai Infinity 1200 condensing gas fired continuous flow water heaters when compared with a similar capacity stored hot water system, and never risk running out of hot water even at peak times.

The cost of installation can also be considerably cheaper.

With a stored system heat loss calculations can be 5.7kW with gas usage for the loss calculated at 0.53m³ and daily gas usage at 2.19 m3.

The Rinnai gas usage is a miserly 1.71m3 and no worries over standing losses.

Over a year the stored system will use 624.52 m3 while the Rinnai system will turn in a frugal figure of 444.60 m3, a saving of 179.92 m3 or 28.8 per cent.

Carbon dioxide emissions, too, don’t compare favourably for the stored system as it will be responsible for emitting 1230.22 kg/kW per annum against 875.873 kg/kW for the ultra energy efficient Rinnai set up which offers a carbon saving of 354.45kg/kW (28.80 per cent).

Most emphatically, says Rinnai UK, these calculations show the most efficient way to generate hot water quickly and efficiently isn’t by housing a massive heat-leaking cylinder.

The downside with a stored system is that water has to be brought up to a minimum of 60 degrees celsius from cold and then maintained at that temperature 24/7 even when it is not being used.

When all the water is used up, potable water will be heated and then stored until it is needed, a wasteful and uneconomic outcome that will suffer from standing losses eating away at the budget.

At the design and specification stage, the continuous flow system makes instant sense as more often than not stored hot water systems are designed to over-capacity as calculating the amount of hot water likely to be needed daily is complicated by a lack of information related to running time.

So specifications often have oversized systems that use too much gas and too much storage.

With a gas fired continuous flow system the designer simply needs to count the outlets and calculate the flow rate.

A continuous flow system supplies endlessly so there is no fear of running out of hot water due to length of time the outlets are left running – it really is that simple.

The condensing process delivers up to 107% nett efficiency, which translates to significant energy savings.

Tags : hot waterinstallationnewsschools
Kathy Bowry

The author Kathy Bowry

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