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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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  1.  
    I have my dishwasher connected to my hot water tank, fed in at 50c. Is this likely to be a problem? This way I take advantage of the COP of the heat pump
    • CommentAuthorHollyBush
    • CommentTimeOct 6th 2017
     
    do you know how much water will stand (and be cold) in the pipes before getting the hot water actually inside the dishwasher?
    I can't believe it is worth connecting to the hot, unless this is much smaller that the dishwasher will use
    • CommentAuthorGaryB
    • CommentTimeOct 7th 2017 edited
     
    I connected my dishwasher to hot to take advantage of solar hot water.
    HollyBush is correct - you have to check the amount of water used in the wash cycle vs the volume in the hot pipe, but this is very easy - just run the hot tap on the kitchen sink into a measuring jug until warm water comes through.
    In my case the volume run-off is just 2 litres (my system was completely re-piped as it was 9 litres originally) vs 12 litres for the wash cycle so it is well worth it. In winter there is still a benefit as the water is heated by oil rather than electricity.
    • CommentAuthordpmiller
    • CommentTimeOct 7th 2017
     
    what is the maximum temperature the deioniser resin in the dishwasher can take, and what precautions are you taking against Legionella?
    • CommentAuthorGaryB
    • CommentTimeOct 7th 2017 edited
     
    My dishwasher can take 60 deg C hot water.
    I store at up to 85 deg C in the cylinder on sunny days and have a TMV set at 55 deg C on the cylinder outlet, no issues with Legionella anticipated. Before fitting the safety TMV my son once made me a cup of tea straight out of the hot tap and I didn't notice...
    Also, all dishwashers seem to run the rinse cycle at 65 deg C to assist with drying, even if you use the 'economy' low temperature (55 deg C) wash.
    • CommentAuthorTimSmall
    • CommentTimeOct 7th 2017
     
    I've previously run dishwashers from solar preheat for years without problems. Bosch state that this is OK in their manual for the last model I installed (about 7 years ago?), but some give a max temperature.

    To reduce losses I used 10mm PEX pipe (but you could even go down to 8mm PEX or copper).
    • CommentAuthorTimSmall
    • CommentTimeOct 7th 2017 edited
     
    Internal diameter of 10mm PEX is typically about 6.5 to 7 mm (brands vary). The volume of water in a 10 metre run of 10mm PEX is 0.38 litres.

    For the same reason I run my kitchen hot tap from 10mm PEX. It brings the maximum flow rate down (probably breaks WRAS guidelines), but you get hot water at the tap far sooner.

    Whether it's greener to run from oil (or gas) heating in the UK vs. electric depends on how windy it is. Gas (including boiler losses) is about 250 g CO2 / kWh, and oil is 300+ I think? Last night the grid was down to under 150 g CO2 / kWh in the UK in the small hours (including transmission losses).

    http://www.earth.org.uk/_gridCarbonIntensityGB.html

    Tim.
  2.  
    Posted By: TimSmallFor the same reason I run my kitchen hot tap from 10mm PEX. It brings the maximum flow rate down (probably breaks WRAS guidelines), but you get hot water at the tap far sooner.

    Off Topic, but.. how far?
    I ask as I'm thinking of doing the same (~9m run in our case).
    • CommentAuthorTimSmall
    • CommentTimeOct 7th 2017
     
    The pipe run to the kitchen tap is approx 15m at the moment (it will be shortened to 10 m when I get around to replacing the kitchen). Flow rate is 6.5 litres per minute.
    • CommentAuthorTimSmall
    • CommentTimeOct 7th 2017 edited
     
    That's actually higher than I thought it was, and the combi boiler has a 9 l/m flow restrictor in it. The mains peerage here is normally about 3 bar, but dross to about 2 at peak times.

    Ahem. The joys of replying on your phone in a hurry. Need to be careful about that, could accidentally start a war or something...

    "The mains pressure here is normally about 3 bar, but drops to about 2 at peak times."
  3.  
    Posted By: TimSmallThat's actually higher than I thought it was, and the combi boiler has a 9 l/m flow restrictor in it. The mains peerage here is normally about 3 bar, but dross to about 2 at peak times.

    Thanks. Sounds like we should be fine (shorter run, higher mains pressure).
  4.  
    ''The mains peerage here is normally about 3 bar''

    Oh Lord!
    • CommentAuthorowlman
    • CommentTimeOct 8th 2017
     
    Posted By: Nick Parsons''The mains peerage here is normally about 3 bar''
    Oh Lord!


    Is that predictive "dross"?:wink::bigsmile:
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