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.



Heating and cooling: Wood boiler stove with quench coil - no gravity circuit needed?

Bottom of Page

1 to 8 of 8

  1.  
  1.  
    Can a European style stove with integrated cooling coil and safety valve be used in a pumped only installation?

    If so it would greatly simplify adding such a stove to an existing fully pumped open vent oil fired CH and DHW system. It would need some extra valves, stats, relays, etc to isolate the unused appliance but is the quench coil sufficient to cope with any component/power failures and satisfy building control?
    • CommentAuthorcrusoe
    • CommentTimeAug 4th 2010
     
    Theoretically, the quench coil is designed to take temps down quickly, if its working, a valve isn't stuck, and if you are not in a high-wind, full-firebox condition with a piece of clinker jamming the thermostat open. Extreme problems only usually happen in extreme circumstances - often a combination of unusual events combined.

    Some manufacturers I have used like a degree of thermosyphon with any WS boiler for this reason. And a power-back-up if possible. And don't forget, if you have a widespread power cut - and according to the ex-controller at the national grid, these are set to happen with increasing frequency and severity - (another recent thread), then depending where you live, even your mains water pressure could be affected for a while.

    To be safe, ask your specific question of your supplier regarding your specific choice of boiler - the techie, not the sales guy! And don't rely on BC saying its all OK - they are ticking boxes and often have no clue why things are done a certain way.
    • CommentAuthorowlman
    • CommentTimeAug 4th 2010 edited
     
    When combining two systems eg. wood stove and oil boiler I believe its usual to run them through a central neutral point,( neutraliser ). Your wood stove would be open vented as is the current oil system, with it's own header tank, and therefore the header tanks are the safety nets. Is it not simply a standard back boiler scenario? The quench coil is only a coil through which cold water runs to transfer heat from the boiler to drain. I can't quite see why you need it in this instance. I assume they are more relevant in a pressurised system.
    • CommentAuthortrw144
    • CommentTimeAug 6th 2010 edited
     
    If the boiler has a thermal safety device (quench coil), then it can go on a fully pumped closed (sealed) system. Be careful if you try and use one of these boilers/stoves on a gravity system - some of them have both the flow and return at the bottom of the boiler, threfore making it somewhat difficult.
    • CommentAuthorbillt
    • CommentTimeAug 6th 2010 edited
     
    Could you clarify why air should collect in a boiler if it is vented, rather than closed?

    I'm rather at a loss to see the difference from the boilers point of view.

    Edit - question doesn't make sense now, as TRW144 has edited his post.
    • CommentAuthorowlman
    • CommentTimeAug 7th 2010
     
    billt;
    If the boiler is "vented " it always has access to fresh water from the header tank. That fresh water brings with it dissolved air which, when heated is released, and in the type of appliance that trw144 describes, ( bottom flow and return, gravity system ), could result in air gathering and forming a pocket in the top of the back boiler itself.

    On the other hand if the system is "sealed," and pumped, that sealed, constantly circulating water eventually loses all its air via the AAV and any more dissolved air is only re-introduced whenever the system is topped up with fresh water via a filling loop. That's why on a sealed system you need to pay particular attention that the whole system is well sealed and you are not dragging air in through radiator bleed valves for instance. I've heard of some systems having to be topped up almost weekly, if that's the case the system is faulty in my book.

    To go for a back boiler wood stove you would have to check of course, that it is capable of being used on a closed/pressurised system. ie. pressure tested.
    • CommentAuthorcrusoe
    • CommentTimeAug 7th 2010
     
    billt's point is a valid one. Boilers with bottom F&R will, by design, have an AAV attached. They won't function otherwise. Sealed system or OV, that's as pertinent to the system function as the pump.

    Entrainment of air in a boiler caused by oxygenated water from an open-vented system is a different argument, one touted by sealed system mfrs especially but which has failed to materialise as a problem in my own heating career (1978 onwards).

    But as the boiler in question would - sensibly - have at least one top tapping, there is no air problem there. Even if the tappings were at the bottom, as noted, the AAV takes care of it. No problem in either event, as far as I'm concerned.

    Keep it as simple as possible if you want reliability - and low maintenance in this context... where's a luddite when you need one? :smile:
    • CommentAuthorsune
    • CommentTimeSep 7th 2010
     
    Hi Megacycles - the answer is yes.

    We spec a lot of systems like this and we like to see a heat leak rad as well as the coil even on a sealed system. Gravity circulation does work on a sealed system. In terms of regs part G says that you need 2 overheat safety devices on a sealed system like this. The overheat coil is one, the PRV is another.

    A stove with overheat coil can probably be used on a pressurised system but only if it is designed to take the pressure - the manufacturer's specs will tell you.
    A lot of these coils (well the valve thermostat actually) kick in at around 95 - 97 degrees C and so you can set the heat leak to come on before that.
    Some people spec systems which introduce mains cold water directly into the system - as far as I'm concerned this should be avoided.

    Hope that helps somewhat

1 to 8 of 8

  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