On Tue, 16 Mar 2004 08:22:12 GMT, Martin Angove
wrote:

In message ,
Andy Hall wrote:

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?


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.

I must apologise for causing you to rewrite something you only wrote a
few days ago! I don't know how I missed the other thread - I'd been
looking out for one :-/


That's OK.

Please note that I'm not suggesting, as the other poster did, that a
dishwasher should only fill with hot, but that there should be both hot
and cold feeds available. A washing machine's pre-wash for example, uses
cold, but the main wash might use hot. Does a dishwasher only fill
once, or does it do as a washing machine does and fill several times,
at different temperatures?

Several times. Could be a pre-wash, a wash, and 2-3 rinses. It
depends on the model and program.


If I have already heated water I feel a bit
cheated that I have to heat more, particularly if I have gone to the
trouble of lagging the hot supply pipes or installing a HW loop.

OK, but that is pretty unusual. Most people don't bother.

The water consumption is also very low.

If modern detergents are so good in cold water, why do we need hot at
all? Design the darned machines without a heater, or at least without a
programme hotter than 30C.

That isn't it. For dishwasher detergents the main issue is contact
time, but temperature is important as well - but not instantly at the
higher temperature. On mine for example, there are wash programs at
55, 65 and 75 degrees. The higher ones tend to get used for heavier
soiling because contact time is longer and the higher temperature,
after a time at cooler temperatures helps as well.



But (to return to washing machines for a second) I for one would not
feel entirely happy washing my children's nappies at 30C - I *need* that
90C wash :-)

That's true, but once you get beyond that stage the number of high
temperature washes drops dramatically.



Hwyl!

M.

..andy

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