New Combi: Change Washing Machine Plumbing?

[Neal]

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.

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.

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

Advice? Opinions?

Neal

[Phil]

Some WM are cold fill only. Hot fill only any use if pipework not full of a slug of cold water!

[dmc]

Yes. In fact, many new washing machines are cold fill only.

Do you regularly wash hotter than 40 deg? If not, you'll probably find your washing machine isn't actually using the hot feed anyway.

Also, unless the pipe run is short you are more likely filling the machine with the cold water that has been standing in the pipe and just warming up the feed pipe...

You use the hot water tap in the kitchen that frequently? Fair enough if true.

Darren

[Rod]

Most new WM are cold fill only. So any chance of using gas-heated water will probably disappear when you need to replace your current machine.

[Andrew Gabriel]

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.

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

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.

It's been covered lots in the past.