On Mon, 15 Mar 2004 23:14:31 GMT, Martin Angove
wrote:

Since dishwashers have some quite hot programmes, why is it that they
usually only have a cold feed? Washing machines rarely come without a
hot feed, why not dishwashers?

I still can't see how filling the machine with cold water and
electrically heating it is going to be any more efficient than tapping
off a little of the already-heated water from my gas-fired HW storage
system.





There are three main reasons:

1) If you put hot water directly onto anything where a protein is
present e.g. egg or egg containing foods, it will set it onto the item
and make it harder to remove. Therefore rinsing with cold water and
then starting a wash cycle with cold water will remove much of the
protein first.

2) Modern dishwasher detergents are designed to work based on contact
time with the contents, whereas older detergents were essentially an
abrasive that was blasted onto the contents. Thus heating from cold
gives a longer cycle. It also allows machines to be designed to run
more quietly because they don't need such high pressure blasting the
contents.

3) Modern dishwashers use very little water , so much of what will
come from a DHW cylinder will be the contents of the pipes and cold
anyway. Since the water volume is smaller than it used to be,
electricity consumtion is reduced anyway.


For washing machines with modern detergents and fabrics, most washes
are fairly cool as well, so there is less and less need to fill them
with hot water either.




..andy

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