Grandee Combi offers the best
flow rate - or your MONEY BACK!*

What is the Flow Rate?

……… a familiar question because so many ‘combis’ seem to produce less hot water than a conventional copper cylinder.

How is Hot Water produced?

Either DIRECTLY from the heat source to the domestic water – as with an instantaneous gas or electric water heater or shower. Or, INDIRECTLY by heating primary water (within the boiler) which is then used to heat secondary (domestic) water as in a copper cylinder or via a plate heat exchanger.

The maths

A kW (Btu/h) is the amount of heat needed to raise .45 litres (1 lb) water by .55 degrees C (1 degree F). Therefore a 17.6 kW/h (60,000 Btu/h) output boiler, in ideal conditions, can only raise 4.5 litres (1 gallon) a minute by 38 degrees C (100 F) which, in our opinion, is neither hot enough nor sufficient for most people. In order to increase the temperature and volume of hot water it is necessary to:

Either increase the boiler output substantially (and risk excessive ‘cycling’ when in heating mode) or provide a thermal store or ‘battery’ of heat.

The Spurious Claims

One leading manufacturer claims "…. 15 litres (3.3 gallons) per minutes at 37 degrees C" which is almost blood temperature. We consider this inadequate and that hot water needs to be at least 50 or above.

The Options:

1) Standard Boiler with copper cylinder

Primary water is heated by mere coil of copper pipe, often situation a long way from the heat source – the boiler. Much heat can be lost as the heat moves from the boiler to the cylinder.

2) Boiler with no thermal Store

This is an efficient means of producing hot water but unless the boiler output is substantial then the amount of useful hot water available can be severely limited.

3) Boiler with separate thermal store

Can produce primary hot water efficiently but is then similar to the copper cylinder method - the domestic water is heated a step away from the main heat exchange. The larger the thermal store, the slower to heat and ‘recover’ after use.

4) The Grandee Method

An efficient method of producing the primary heat store – no secondary tanks to heat. The boiler output is sized appropriately to the heating load and the thermal store pro-ra tat. Much more efficient than methods 1 and 3 and produces more hot water than method 2.

*Conclusion – We claim that the Grandee Combi, output for output, produces hot water better than any other oil combi known to us – or your money back!