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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorcubbs
    • CommentTimeDec 1st 2015
     
    Hi,

    Can I please have some more advice.

    For first fixing electrics what size and how many cables are needed to run from loft to consumer unit?
    Allowing for future PV and possible wind turbine?

    What cables and where to for Immersun too please.

    Thanks for your help
    •  
      CommentAuthordjh
    • CommentTimeDec 1st 2015
     
    Put some ducts in so you can put in whatever cables are required once you know exactly what that is.

    PV presumably will be to underneath your roof somewhere, assuming it is a conventional roof. DC cables for a conventional inverter, AC for microinverters; your installer will decide what size.

    Wind turbine will be outside somewhere so needs an underground duct through the foundations.

    Immersun will be between the hot water tank and the CU, so you could just run some 2.5 T+E between the two for now.
    • CommentAuthorDarylP
    • CommentTimeDec 1st 2015
     
    as above...... put in ducts, flexible conduits, or similar, and future-proof yourself!
    40mm dia. should do it, with no nasty 'street elbows' but nice swept bends....

    Good luck:smile:
    • CommentAuthorcubbs
    • CommentTimeDec 1st 2015
     
    Brilliant

    I've just put in some ducting now.

    Would wind turbines(small) be able to power immersion heater(s) in a thermal store?

    Thanks
    • CommentAuthorcubbs
    • CommentTimeDec 1st 2015
     
    Plenty of wind here in port Erin on Isle of Man
    • CommentAuthorringi
    • CommentTimeDec 1st 2015
     
    wind turbines hardly ever make sense fixed to a house unless at the top of a big hill with no other buildings close by.

    The return on investment (and carbon saved) is more if you buy into a company that does full size wind farms.

    A small wind turbine that is 5% of the size of a large one, will give a lot less than 0.1% of the output of the large one in most cases.
    • CommentAuthorcubbs
    • CommentTimeDec 1st 2015
     
    Ok. Back to PV? Will it power immersion heaters to a useable water temperature?

    Thanks
    •  
      CommentAuthordjh
    • CommentTimeDec 1st 2015 edited
     
    Posted By: cubbsOk. Back to PV? Will it power immersion heaters to a useable water temperature?

    Yes. Obviously the answer is more complicated depending on PV and tank size but generally you can get hot water over the summer and probably a large proportion of spring and autumn, but not much in winter.
    • CommentAuthorcubbs
    • CommentTimeDec 1st 2015
     
    Sound. Still undecided on a thermal store size. Do you know how many m2 of PV are recommended for say 750litre store?

    Also you're a regular on this forum, is there a way of being notified by email if someone posts replies on here?

    Thanks
    • CommentAuthorringi
    • CommentTimeDec 1st 2015
     
    Don't have a thermal store without a VERY good reason. A normal unvented DWH works a lot better if you have a normal boiler or are heating it on E7.

    Thermal stores come into their own if you are heating them with a log burner for example.
    • CommentAuthorcubbs
    • CommentTimeDec 1st 2015
     
    I already listed my heating sources in heating and cooling section" blank canvas " post.

    The manufacturer of the boiler stove recommends min size 1000litre. To me when the fire is not lit that sounds like a huge volume of water to heat with the existing standard efficiency oil boiler.
    •  
      CommentAuthordjh
    • CommentTimeDec 1st 2015
     
    Unvented cylinders require regular inspections which vented thermal stores don't. Cylinders require regular heating to 60 °C which thermal stores don't. Mine appears to work just fine for us.

    The PV size depends more on how much water at what temperature you plan to draw. Tank size is more to do with how long you want the tank to last before it needs recharging. Work out the energy needed to heat the amount of water you need, and compare it against the predictions from PVGIS for the amount of energy you will get from the PV at different times of year. Then add a fudge factor; it's not an exact science.
    • CommentAuthorskyewright
    • CommentTimeDec 1st 2015 edited
     
    Posted By: djhThen add a fudge factor; it's not an exact science.

    ... for example, many people (on Navitron) are reporting this November as their "worst ever month" for PV, seeing only 60% or so of their PVGIS November estimates.

    Our worst (in 5 years so far), was December 2013 which only managed 40% of our PVGIS December estimate.

    The angle of the sun through the year is very easy to predict, but actual PV generation is essentially a weather related thing & thus very variable.

    Consider also that whilst you can only get 100% less than the daily mean (you can't generate less than zero), you can (especially in winter) get days that provide more than 100% above the daily mean. As a result it can easily be the case (especially in winter) that most days in the month are below the mean for the month. :confused:

    So yes, if you were relying on it then a big fudge factor would be a good idea.
    • CommentAuthorringi
    • CommentTimeDec 1st 2015 edited
     
    Posted By: cubbsThe manufacturer of the boiler stove recommends min size 1000litre. To me when the fire is not lit that sounds like a huge volume of water to heat with the existing standard efficiency oil boiler.


    The boiler stove is yours very good reason for a thermal store. However lots of people with thermal stores have a separate much smaller DWH tank, so they don't need to heat the complete TS all year. Apart from anything else, just the heat loses from the TS may overheat your home in the summer.

    You can set it up so that the existing standard efficiency oil boiler can run the heating without having to heat up the FS.
    • CommentAuthorringi
    • CommentTimeDec 1st 2015
     
    Posted By: djhUnvented cylinders require regular inspections which vented thermal stores don't. Cylinders require regular heating to 60 °C which thermal stores don't.


    Not an issue if you have a gas boiler, as you can get find someone that can check the unvented cylinder at the same time as servicing the boiler. As soon as you don't have mains gas, lots more options become sensible.

    However using a thermal store as a pre-heat for a combi boiler, then heating the thermal store with PV is a very nice setup if a combi boiler can give you enough hot water flow.
    • CommentAuthorcubbs
    • CommentTimeDec 1st 2015
     
    We're going off the subject a bit here but all great info anyway.

    Sounds good! How is that piped up and what brands and sizes for a smaller dhw cylinder?

    I'm am also going to run ufh off the proposed heating system?
    • CommentAuthorCWatters
    • CommentTimeDec 1st 2015
     
    We have a vented thermal store heated by an oil boiler and UFH.

    Positives: Oil boilers cannot modulate down so the thermal store stops the oil boiler cycling when there is low demand from the UFH. The boiler runs flat out until the store is heated, then shuts off until the store has cooled. Loads of mains pressure hot water.

    Negatives: The thermal store leaks a lot of heat into the room it's in.

    UFH works well if one of you is home most days. If you both work 9-5 then I'm not so sure.
    • CommentAuthorcubbs
    • CommentTimeDec 1st 2015
     
    <blockquote><cite>Posted By: CWatters</cite>We have a vented thermal store heated by an oil boiler and UFH.

    Positives: Oil boilers cannot modulate down so the thermal store stops the oil boiler cycling when there is low demand from the UFH. The boiler runs flat out until the store is heated, then shuts off until the store has cooled. Loads of mains pressure hot water.

    Negatives: The thermal store leaks a lot of heat into the room it's in

    What size is your TS? You have a log burner connected too?
    What size F&E tank is needed for such large water content?

    Thanks
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