dishwashers

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Re: dishwashers

Postby bpratt » Mon Nov 15, 2010 10:33 am

Just to prove the point, perhaps if possible, you could do the same test graph with just cold water running in to your dishwasher.


It's not that I don't believe, because I do, but it's more to show that it really does make a big difference.

:)
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Re: dishwashers

Postby Gordon-Loomberah » Mon Nov 15, 2010 11:01 am

OK, cold water via a hose through the door and a few fittings to the dishwasher underway now :)

...should be finished by the time I get back from picking some of my organic cherries and mulberries :mrgreen:
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Re: dishwashers

Postby bpratt » Mon Nov 15, 2010 11:27 am

Gordon-Loomberah wrote:OK, cold water via a hose through the door and a few fittings to the dishwasher underway now :)

...should be finished by the time I get back from picking some of my organic cherries and mulberries :mrgreen:


Sorry, wasn't saying you had to go out of your way, but a cold hard comparision would be undeniable proof of how much is wasted by a dishwasher having to heat up the water by itself.

It's great that you have gone out of your way to do that.
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New house build :-
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Re: dishwashers

Postby Gordon-Loomberah » Mon Nov 15, 2010 12:15 pm

It seems the 52min cycle takes quite a bit longer when the dishwasher heats the water from cold. The water temp was around 22C, and its clear a lot more power was used to wash the dishes.

hmm, buggered if I know why the image handling in here is so inconsistent, this one has been made non-fuzzy with annoying scroll bars...
dishwasher20101114a.gif
click to de-fuzz
dishwasher20101114a.gif (10.32 KiB) Viewed 6093 times
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Re: dishwashers

Postby lad » Mon Nov 15, 2010 12:31 pm

Tassie water is a wee bit cooler, I think I will keep feeding in hot :o
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Re: dishwashers

Postby Gordon-Loomberah » Mon Nov 15, 2010 12:35 pm

OK, I've put both graphs in one GIF, so the forum software cant treat them differently!

The 2nd heating stage must be heating rinse water as well as air for drying, the area under the "curve" is clearly massively larger when the dishwasher is supplied with cold water, representing wasted energy if you have solar, or even heat pump, hot water. Its been rather warm to hot in recent days, so the cold water is warmer than usual. In winter with colder cold water (~10C here), the difference would be greater still.

dishwasher20101114b.gif
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Re: dishwashers

Postby bpratt » Mon Nov 15, 2010 1:37 pm

Wow, she sucks a whole lot more juice when you supply it with cold water.


Comparison? there's no comparison ... they are just so much different.

I know what I'll be doing if I ever get a dishwasher here !!!


Thanks for going to so much effort. :)
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Re: dishwashers

Postby Gordon-Loomberah » Mon Nov 15, 2010 2:02 pm

No worries, I was keen to see the direct comparison myself ;)

I'll whack the power meter on it to see what the difference is in kWh over the next few days.

I've organised a slightly more sophisticated arrangement on the washing machine- the hot water take-off is before the tempering valve, so water up to ~90C sometimes is available at the tap, but our fairly new Bosch only has 1 inlet pipe, and they say to connect it to cold (it would be a bit difficult to do a cold wash otherwise!). Apparently they do this for the energy ratings- the only way energy usage can be accounted for- by doing the heating internally.
Anyway, I have an adjustable, 25-55C, tempering valve with an easily turned knob between the hot and cold, and the washing machine takes its water from the tempering valve outlet.
For a cold wash- adjust it to 25C, 1.75 turns for a 40C wash, and 3.5 turns to max for a 50 or 60C hot wash. If its a sunny/windy day and I have plenty of power excess to requirements, I might do a hot wash with cold water coming in, but the option is there to set the inlet temperature to whatever I want it to be.
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Re: dishwashers

Postby andykidd » Mon Nov 15, 2010 8:21 pm

Hi everyone,
I appreciate all of your input and advice. I have now installed our Samsung dishwasher, with the gas boosted solar hot water plumbed into the only inlet in the back, and am happy top say that it works well and gives us a welcome break from hand washing everything.
I learnt from all this research that basically what matters is to have your hot water going in (with the thermostat set at or above the dishwasher's cycle temp.), rinse off the egg and cheese and anything else very messy, and keep an eye on the solar power levels of the batteries! For us, we can run it most days if we want, preferably during the day when sun is on the panels, and at all goes well. The shortest cycle doesn't always clean everything so I tend to go for the 'daily' cycle which uses water at 65* C.
So all's well that ends well. Thanks. With best wishes, Andy
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Re: dishwashers

Postby munter » Tue Nov 16, 2010 12:48 pm

Excellent comparison data - Thanks Gordon. This is just the data I need to convince the missus that we should plumb our solar/gas hot water in to the dishwasher when we renovate. We will probably take the water from the downstream side of the tempering valve to try to avoid hot water damaging seals but still making a good contribution to reducing the energy requirements. I would guess that the first rinse will typically just use cold water between the gas boost and the washing machine and that it will use hot water from there onwards. Given that our household consumption is about 5 kwhrs/day and our dishwasher uses about 20% of that we could make a 10% reduction in our overall power consumption through this change!
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