"Phil Sherrod" wrote in message
...

On 30-Mar-2004, "News" wrote:

Using high efficiency condensing water heaters will bring different
results.
The lower the return temperature the more efficient they are. If you
allow
a tank of water to cool and you re-heat it with a condensing water
heater
the re-heat is very efficient in fuel use.

I've never seen a water heater that was designed to condense water on the
outside. In fact, I can't understand how that could possibly happen since
the
shell of the water heater will be hotter than the surrounding air.

In the European market they are common. A condensing boiler is a separate
unit heating the water of a storage cylinder. Condensing boilers, or water
heaters, extract latent heat from the exhaust gasses. The lower the return
temperature the more efficient they are. A cylinder of hot water cooled
right down will have a lowish return temperature for a large part of the
re-heat. This is efficient. Just topping up the hot water when the odd
sink of water is drawn-off, as the cylinder stat has dropped a few degrees
is less efficient when using a condensing water heater, although still more
efficient than not using one.

I don't particularly like this company's products, but a decent
explanation.:

http://www.ravenheat.co.uk/productsCSIPRIMARY.htm