Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



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.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.
Buy individually or both books together. Delivery is free!


powered by Surfing Waves




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
 Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.

The AECB accepts no responsibility or liability for any errors or omissions in the content of this site. Views given in posts are not necessarily the views of the AECB.



General: I'm abandoning oil & electric

Bottom of Page

1 to 12 of 12

  1.  
    • CommentAuthorNeil
    • CommentTimeNov 12th 2007 edited
     
    Planning to replace the oil and electric central heating / hw system in our 1950's house in the coming month, before winter bites and our fuel bills bankrupt us...

    240m2, reasonably well insulated, retaining 16 radiators.Considering an Aarrow Stratford TF90 wood stove (24kw water / 4.5kw room) and a 350l Gledhill 'Torrent RE' thermal store and 2x Navitron 20 tube collectors (in the spring time), with an ageing Worcester oil boiler as back up.

    Going to speak with manufaturer's and my green plumber friend who'll be helping, and who's open to experimentation, but would appreciate any other comments / ideas to put on the table...

    My first question's going to eb whether the 24kw stove rating (intended for a primary pumped heating circuit?) is suited to the store size / strategy, next will be controls / thermostats / designs to set an alarm clock off when store temp is falling towards an oil boiler firing, giving time to stoke a fire up.

    Saw a 1500l accumulator tank for sale on a thread here & got me thinking about strategies to store enough hot water to only power up the wood burner sparodically (say alternate /3 days in deep winter?)
    • CommentAuthorJohan
    • CommentTimeNov 13th 2007
     
    You can store ~30kWh in 500l of water (DeltaT=50C). Hence, in 350l you can store ~21kWh. Assuming the UK averange of 10-12kW heat loss for the house should give you a couple of hours of heating when the stove is swithed off. With 1500l that goes up to 9h. 350l for a wood boiler is way too small, 1500l sounds better.

    It all depends on the heat loss of the house though. Is it possible for you to estimate how much energy you use per hour?

    Insulate and draught proof as much as you can first!
  3.  
    Have a look at http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=342&page=1#Item_17 for some cross-over. We decieded in the end to go for 2 stoves (and no boiler) only. We have a SEVERE downdraught prob with the first one. The flue comes up at the eaves and has been lowered, I think. It performed fine when the installers tested it, on a fine, still day, but it's been like living round a camp-fire (only smokier) since!! I've temporarily added a metre and a half of galvanised duct to the stack, and that helps. Think I can only change this to 2m stainless, and rebuild the stack.

    Nick
    • CommentAuthorNeil
    • CommentTimeNov 13th 2007
     
    Thanks Nick & Johan.
    Not able to quantify heat loss Johan, but fuel costs are truely astronomical!
    The house a long term project, some minor upgrading done by previous owner - wall cavitys filled with polystyrene beads, 200mm warmcell in horizontal ceilings. Also antique plumbing looking in places like it was installed by heath & his mate robinson. I'm tackling the sieve-esque airtightness at the moment.
    Been here a year and used two oil tanks (3700 litres - £1200) for heating. A couple of electric storage heaters & (recently realised) the majority of hot water's off immersion, so c£250/month electric as well, the situation's unsustainable in every sense!
    I see the idea of 1500l in winter when the stove's stoked up and the accumulator running fully charged doing well, but I'm worried mid-season & summer heating / dhw demand won't be met by a (2 panel) solar powered accumulator and the oil boiler will still see significant use maintaining the temp of the 1500l (when lighting a fire is a non-starter). I guess adding more solar is one strategy? Or maintaining a separately powered dhw cylinder for the summer (non central heating) months?
    • CommentAuthorJohan
    • CommentTimeNov 14th 2007
     
    Adding more panels is an option, but I would suggest putting an immersion heater in the tank for top up. Or you could use your old oil boiler as a back up source connected to the tank as well. The nice thing with an accumulator tank is that you can plug several heat sources into it! The immersion heater/oil boiler would connect higher up on the tank and so wouldn't heat the whole 1500l. I suggest you locate a local heating engineer and have a chat with him/her about what you want to do.

    Have you got free access to logs or will you be buying them?

    Here's a quick calculation if you're buying them.

    For every liter of oil you use you need roughly 8 liters of dry, stacked logs. I.e., it your case you'll need ~30000l = 30m3 per season of stacked dry wood to replace the oil. That's a lot of wood!

    Assuming you pay £50/m3 gives you a total cost of 50*30 = £1500 per annum in fuel cost, which is more then your oil...

    Hope it's useful!
    • CommentAuthortony
    • CommentTimeNov 14th 2007
     
    Insulate. Spending time and money on insulation and draft proofing would save you heating costs.
    • CommentAuthorsteveleigh
    • CommentTimeNov 14th 2007
     
    Neil,

    I totally agree with Tony. Surely it is better to put your money into externally insulating your house to Passiv Haus standard and getting rid of your heating requirement altogether?

    Cheers

    Steve
    • CommentAuthorNeil
    • CommentTimeNov 14th 2007
     
    I'd agree Steve & Tony, insulate to the max and strive for zero heating, which IS our long term vision.

    The vision's expensive - however I look at it. In time we'll need to re-roof, and an infill GFL extension and a remodel upstairs is planned, which will be the most opportune time to upgrade insulation all around [external insulation with render below / local timber cladding over]. We've very large and numerous wall openings which will be expensive to upgrade with passivehaus standard products. Budget for all planned building work going to be c£50k self build which we don't have in near future. Electricity generation is also planned - pv and [ideally] a wind turbine [but the area's draconian planning currently prohibits].

    So we need a fix for hemmoraghing cash on fuel, investing in things that will play a part in the future plan. Luckily wood is easily come by. Thanks johan for the timber volume calculation. I'd been guessing up til now, and this is about double what I thought required! How sure are you of the 8 to 1 ratio?

    I'm hoping we can make the switch to timber & solar for under £5000 (with assistance from a good green plumber friend, overtime paid in 'Sheppys Dry'!) and doing most the work ourselves, which (conservatively) gives <4year payback assuming we'll have to buy a certian amount of wood each season.

    My plumber's suggesting a shorter term approach using the 350l thermal store, which I'm minded to agree with - much simpler with our house layout / construction and compatible with the longer term vision of lower demand. I guess we have to accept if we want heat from wood on cold mornings we'll have to stoke the stove & wait.

    Thanks all, starting to piece a strategy together...
    • CommentAuthorJohan
    • CommentTimeNov 15th 2007
     
    Neil,

    You get roughly 10kWh out of 1l of oil and roughly 1.3kWh out of 1l of stacked logs, which gives you 10/1.3 = 7.7 => 1:8 ratio.

    Burning wood is fine if you get it for free, but insulating and drought proofing first is easier and cheaper!
  10.  
    It looks to me like the boiler on the Stratford stove is behind the combustion chamber. If it is it will cool the fire and cause tar deposits in your chimney. If you are determined to burn wood, then I suggest looking at stoves which are specifically designed to heat water with wood. These generally have boilers above the combustion chamber.

    T
    • CommentAuthorJohan
    • CommentTimeNov 16th 2007
     
    To optimise loading of your accumulator tank and make the stove burn efficient use a Laddomat 21 or a Termovar unit. You shouldn't get any (or very little) tar deposit then.
  12.  
    What difference does it make what the boiler is connected to? If the combustion chamber is cooled as it is in just about all "multifuel" stoves, the volatiles won't all burn. If you are relying solely on wood, this can be a problem. Properly designed wood stoves and boilers extract heat after secondary combustion has taken place.

    T

1 to 12 of 12

  1.  
Add your comments

    Username Password
  • Format comments as
 
Back to Discussions Top of Page
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press