Washing machine deficiency

[sid]

I hadn't realised I had bought a washing machine with no hot water inlet. The silly situation where I heat up 50 gallons of water in the Heat Pump system, but cant use the hot water for the washing machine.

[The Natural Philosopher]

It's more ecoBollox innit?

[alan_m]

Washing machines start with a cold wash in order not to set certain types of stains (protein based stains).

With low water content machines the cold water in the pipes between the boiler/tank will often be enough for the wash and so there isn't any chance of the hot water actually reaching the machine.

You may also find that if you research some cold/hot water inlet machines they don't actually use the hot feed for many of the programs.

A machine without a hot feed may not be too much of a disaster.

[Alan Lee]

Welcome to the year 2000. Standard domestic washing machines have been like that for a long time.

[Fredxx]

3 reasons

1) Cost to make a machine of an extra valve

2) Cold soak start to stop fixing of some stains 3) The amount of water used in a wash is such that in many instances the initial slug of cold water before the hot is significant and is wasteful.

Most machines, with dual inlets, will only use hot water for a 90C wash. There is a risk that the water will be too hot for a 50 or 60C wash.

Nothing to do with eco desires and aims claimed by art students, but is a practical engineering solution covering many different installations.

[Andy Burns]

My previous three W/Ms had hot and cold fill, I would generally run off the cold leg of water from the sink before starting a program, the machine could decide for itself whether to use cold and/or hot fill depending on the wash, you could hear it alternated between hot and cold to get the temperature right.

Very probably the extra power consumed to heat the water in the machine is minimal, I haven't noticed a spike in electricity costs, but it does grate slightly that there is hot water available, not being used.

[whisky-dave]

I thought it was due to the plastic pipes and connectors expanding and contracting and causing leaks of hot water and the possible dangers it could cause.

and of course some people complaining that it used up the hot water in the cyclinder they wanted to use for a shower or other purposes.

[sid]

It didn't impact me with my previous dual piped Indesit machine. I also have an electric shower.

[Jethro_uk]

Our machine(s) (one just delivered and one just taken away) are cold fill only. When they fill the drop in water pressure causes the electric shower to fluctuate quite unpleasantly. As I have <ahem> gently pointed out to SWMBO.

[Fredxx]

The volume of initial fill hot water used by a washing machine is pretty small. I note Ebac claim 20 litres other sources suggest 5-15 litres.

[RJH]

If it's anything like my combi, that initial slug can be the best part of the water needed for the wash - taking up to a minute before hot water comes through.

[alan_m]

When the machine first fills not only does it have to have a minimum water level but it must also soak the washing. Often there is an initial fill, a few turns of the drum and then a top up fill (maybe two or three top ups depending on the type of load). The first part of the wash will likely be cold to prevent setting some stains so even after a pump out before the main wash the load in the drum will will still be damp/wet and so the amount of water subsequently required will be a lot less.

[Spike]

If you are so concerned, get a hosepipe tap fitting and a short length of hose, fill the machine from the hot tap.

Note that there are drawbacks to this approach, as have already been mentioned.

[SteveW]

Modern machines use less water and, in many cases, the length of pipe between a hot water cylinder or combi-boiler and the washing machine means that it will fill almost entirely with cold water anyway, leaving the pipework to lose heat from the hot water that has made its way through. It is more efficient to just heat the water in the machine and avoid those losses.

[Theo]

Is there a good reason not to insulate your hot water pipes to avoid that problem?

There's Legionella risk, but you're feeding the pipe with hot water so they'll get zapped, and Legionella will still lurk in a pipe with stagnant room temperature water in it (see the Bibby Stockholm saga).

Theo

[Andrew]

ebac make and sell washing m/c's that can have hot and cold input. I have posted this before, but for some reason ebac don't seem to market them very well and few white goods dealers seem to be aware of them.

[Theo]

Are they any good? I see various 'buy British' marketing but wonder how they compare with the competition.

Theo

[Theo]

Let's do some numbers on this. Suppose the initial fill is 10 litres from a

15mm pipe. If your fill takes a minute your flow rate would be 10 litres/min which is what mine is, so sounds about right.

CSA is pi r^2, so 0.75*0.75*3.14 = 1.76 cm2

10 litres thus needs 10000 / 1.76 = 5681 cm = 56.81m of pipe run

I wonder who has a 56m pipe run from the hot water cylinder in their house? Mine is about 7m.

Theo

[me9]

He's using a combi, so an initial burn to heat heat excahanger before hot water becomes available.

If from tank, 10L per min is virtually impossible with 15mm pipe and usual pipe runs, more like 2.5 L per min.

Theo <theom+ [e-mail]> wrote:

[alan_m]

It's unlikely that a machine will only use the hot supply. If the machine is mixing hot and cold it will probably still need to heat the water itself to get to the final temperature. On lower temperature washes the hot supply may not be used at all.

Although a 60c+ wash may be required to remove oil based stains modern detergents are claimed to work down to 15C and most people could get away with the majority of washes at 20, 30, or 40C.