Dishwasher on cold water!

[dj-gabriele]

a heater powerful enough (on an ordinary circuit of 15a or

Don't worry, 1 kWh is plenty of heating power for a dishwasher! Indeed Miele, SMEG, and even Ariston models for export can complete nicely a cycle starting on cold water in reasonable time while doing a wonderful job.

A theoretical example:
heating 4 litres of water plus 10 kg of dishes, considering the heat capacity for dishes at 2 J/(K*g)
Water enters at 15°C and we need to wash at 55°C and rinse at 70°C.

For the wash we'll need a dT of 40°C: around 0,41 kWh of energy.
A 1 kW heater will supply that in less than 25 minutes, a more than reasonable time frame.

 

[dj-gabriele]

Legionellosis "have spread through the pipes"

Don't worry, hopefully legionnaires bacteria can only thrive in still water so they can't survive in piping as water currents will destroy their colonies!
There even are boiler with specially designed coils to increase water currents to avoid this problem!

You would need to use water coming out of a faucet that was turned off for weeks at a time and that wasn't ever chlorinated nor previously heated over 55°C

 

[foraloysius]

I wish you were right. Only recently a senior citizen apartment block had to be closed down for a week to get the pipes cleaned again. It wasn't the water heater only that was the problem.

 

[dj-gabriele]

I have no idea of all this differences, here legionellosis is considered a problem only in wet HVAC apparatus like humidifiers and similar!
Residential and tertiary hot water application seem to be free of the problem and I'm telling you from the engineer's point of view. Could it be that chlorination/environmental condition might change the bacterial behavior? Just guessing!

 

[foraloysius]

The problem in larger hot water systems is the water that keeps sitting in unused parts of it. Besides that, the material of the system has influence too. Bacteria grow faster in RVS, PVC and PEX pipes. That in combination with the low chlorine bleach percentage in the water here, the problem is a serious one. Once in the pipes, the problem is very hard to solve, the bacteries seem to like to grow in the scale in the pipes. In order to solve the problem you need to run the system with 60*C water for at least 32 minutes, but it takes quite a while before the end of the pipes have reached that temperature. So most of the time it is done by raising the temperature of the water heater much higher.

 

[washer111]

@rolls_rapide

What you mention doesn't do anything for us in terms of water heating in this country. It sounds you are mentioning something that costs a fortune to setup too!!!

Topping up the system is because the lousy closed circuit leaks (hard water + empty house for 7 or so years _ no anode replacement), and sticking a garden hose on the air vent fills up the system, making really hot water again. Within minutes of me starting, the return from the collector panel (even in mild cloud conditions) will STEAM water off the pipe, and is too hot to touch.

In this country, thats how water is heated with solar, what you mention is used for electricity production, and where I live, they have stopped allowing you to sell anything back to the grid, as they have reached "quota," and any more self generated power may cause huge rises in power prices for us (not good! Too expensive already. Summer bills are HUGE).

The biggest problem with Solar heated water is that you get scalding hot (or BOILT) water in the Summer, when you can shower very easily in the cold and lukewarm, horrible water in the winter, when its needed most - but our winters are generally pretty sunny and aren't' too cold, so i think a heat pump boost would be a great option for people like us!

 

[jerrod6]

 I had a 1996 Miele DW and now a 2006 Miele DW and both said they could  be connected to cold water but that the cycle time would increase a bit.  The Dw is connected to hot water.   It is using the standard USA voltage. 

 

I have a gas whole house tank-less water heater- had one for over 13 years. I have a long pipe run(water heater on the other side of the house from the kitchen) running  through  insulated pipes in an unheated basement, the DW might as well be connected to cold water and it wouldn't matter if I had a tank water heater.

 

 Each DW fill takes between 32 and 37 seconds but It takes about 1 1/2 minutes before the water from the water heater will reach the kitchen, so if I am not using the kitchen before starting it the DW gets mostly cold water.  Even then by the time it gets to the last rinse it gets cold/cool  water because I am not around to run hot water in the sink. 

 

Given this my cycle times in the winter are about  2 hours 6 minutes and in the summer they are about  1 hour 45 minutes, and depending on the cycle the Dw is heating water for the wash between 120F and 170F and between 130F and 150F for the last rinse.

 

[combo52]

Hot Water Cooling Off In The Hot Water Line To The DW

This is a much bigger problem with the new low water use long cycle DWs. I wounder if they take into account all the additional electricity that running these new Energy Star DWs require to keep heating the water in the machine?.

 

Jarrod it is too bad you don't have a tank style Gas Water Heater, I have had customers install a small recirculating pump on the kitchen hot water line and control its use with either a wall switch or a timer that can be set for up to 6 hours. You can buy these at Home Depot etc. These allow you to always have hot water at the kitchen sink, and DW when you are running the pump. Using this type of system can save electricity, cycle time and needless wear and tear on your expensive DW, to say nothing of reducing pollution caused buy burning dirty coal generated electricity.

 

111 You guys need more modern Solar Water Heater Systems, I have never heard of a system that could not produce at least 80% of the yearly hot water required even here in the cloudy northeast United States. And I have never heard of a system that either scalds you or leaves you with a cold shower. I have been to Australia and Australians are more clever than that, if you don't want to fix or replace your system that is your option but it is silly to give people the impression that Solar Water Systems have these problems. On any Solar System I have ever seen you always have hot water of the set temperature, I do like your idea of using Heat-Pump back-up, I installed a HP WH in my partners home a year and a half ago and it works great and has been saving 20-25 dollars per month in a one person household.

 

[pierreandreply4]

me i have a electric hot water thank and i can say that it suffice for the dishwasher model i have since the kitchen is kind of right under the water heater thats in the basement

 

[washer111]

@combo52

I probably was exaggerating a tad when I sad what I sad, but we don't have systems that "Control" the water temperature of the water unless you have a house thats too high up for solar, where you use a "split" with a tank on the ground and panel on the roof with a circulating pump that run off a thermostat and timer to keep water hot when it counts (overnight etc) and stop scalding. These (according to reviews) can be troublesome to get working correctly... But the closed circuit systems today do have "shutoffs" to prevent water boiling, and you can install tempering valves to help save hot water too
If we have a few good days of sun, then our hot water lasts for around a day (3-4 showers + running the Dishdrawer) Cloudy days will yield "lukewarm" results (warm enough, but not HOT).

We are planning on replacing our system before next winter, and I since our system is half dead, I'd expect better results from a new system. Our old unit that we had at our old house was good for 2-3 days of COLD, CLOUDY weather, but we generally used the booster for 2-3 hours in cold weather to lift the water temperature enough for a shower (which lasted overnight for any showers the following morning).

But in the end, our system scalds you in Summer, and in Winter, well, the best we get is around 48C (120F) by my measurements.
New systems can apparently BOIL water in the summer, and scald you in winter (with not fully cloudy days!)

P.S. I know of people who say they've never used the booster up here - thats with 2-3 people and 2-3 showers per day. People in this country still wash clothes in cold water with Solar heated water - so we generally don't need lots of hot water. Our solar tanks are around 80gallons for most 4bedroom homes - which is good for keeping hot water hot in cold weather.

 

[logixx]

The solar system installed by our landlord acts as a supplemental heat source. It kicks in when it's (more or less) sunny outside and when not, gas heats the 80 gal. storage tank. The temp inside this tank seems to fluctuate widely - sometimes from 115F to almost 190F. At our old house, the heater was set to 120F for years and I never had a problem with getting sick from showering. Guess I was lucky?

Our DW is connected to cold but since it's such as piece of ... I usually manually fill it two bowls (1.3 gal) of 140F water right from the tap. This makes the 15 minute main wash nice and hot and it cleans most items this way just fine using Aldi-brand powder - and without pre-rinsing. Now, if the programming of that POS dishwasher would only include an automatic interim rinse, I wouldn't have to reset the cycle for another Quick Wash each time to get streak-free dishes. :-(

 

[jerrod6]

Combo52 actually it is not too bad.  I replaced my tank water heater with the tankless.  The tank doesn't matter that much since it still took the same amount of time to get hot water to the kitchen and bathrooms and I was always running out of hot water after two showers where taken back to back.  That last shower got blasts of cool/cold water.  The difference was -  that the  summer month I installed the tank-less, my gas bill decreased by about 18 dollars so I actually have no plans to have another tank in the house.

 

[rolls_rapide]

Logixx

Which brand of dishwasher do you have?

 

[logixx]

The brand is called Bomann. Looks internally just like the re-painted 45cm Hotpoint posted in a recent thread. Mine is 60 cm, though. It washes well for what it is but the semi-automatic cycles suck, it's loud and thirsty.

http://www.bomann.de/startseite/index_en.php