In article ,
Neal writes:
I have just had a new combi boiler fitted, removing the old tank etc.
My plumbing bsuggested that I should change the Washiung machine to
run only off the cold water supply (T the cold pipe, cap the hot), to
avoid the bolier cycling every time the wasing machine wanted water,
and potentially interfering with the heat balance in the shower etc.

You will probably find your washing machine barely uses enough
hot for it to have run much hot through the pipe -- most of the
hot produced probably goes to waste cooling off in the pipe
afterwards.

Modern detergents don't work properly with hot fill. If you want
a hot wash, it has to start not hotter than 35C and warm up slowly
to allow detergent action through the range 30-45C before going to
higher temperatures.

New machines don't even have hot fill capability anymore.

I am not sure I can see the point of this. I would prefer to have the
WM use the cheaper gas heated water rather than use its own
electrically heated from cold source.

It doesn't use enough to matter, unless you are frequently doing
hot washes (which shouldn't be necessary).

There is a thermostatic valve on the shower, so scalding should not be
an issue (I hope)

You need a thermostatic shower specifically designed for multipoint/
combi boilers. These are fast response (bi-metal rather than wax
pellet) and know they can't adjust the output temperature by adjusting
the hot flow rate.

And the WM is only used when we are in the house, so any issue of
wasted hot water in the pipe network is moot (we are just as likely to
be using the hot taps at similar times)

I read over some old posts, and there was nothing definitive about
this.

It's been covered lots in the past.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]