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Heat output of a range rated appliance

Discussion in 'Plumbing and Central Heating' started by Fallout, 6 Jul 2017.

  1. Fallout

    Fallout

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    If a boiler is range rated. What information is require to work out the heat output of the appliance on a given installation?
     
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  3. Dan Robinson

    Dan Robinson

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    Your gas engineer will know what is required.
     
  4. Fallout

    Fallout

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    Am trying to find out for my course work
     
  5. Fallout

    Fallout

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    The boilers output is between 15/20 kw
     
  6. Dan Robinson

    Dan Robinson

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    This is a diy forum.... We're not going to be giving out this advice here. Besides, you should have this already in your text books.
     
  7. Steelmasons

    Steelmasons

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    Heat input rating as opposed to output rating.
     
  8. AGAS

    AGAS

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    wheres your text books if doing the course ;):cautious: , plus i offered you the book;)
     
  9. Agile

    Agile

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    The FAQ on this site show how to measure the input !
     
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  11. picasso

    picasso

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    Why would the op need to work out the input ?
     
  12. PullerGas

    PullerGas

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    Oh!!..............Here's trouble!!
    Steely, get your readers on, they're on the top of your head!! The OP stated output.
     
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  13. Steelmasons

    Steelmasons

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    So how you gonna calculate heat OUTPUT then Dickie?
    The gaps in my knowledge are getting more and more...
     
  14. ericmark

    ericmark

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    I have found, be it a simple fridge one is brewing beer in, or a whole house, and calculations are just a start point, to find size of heater to keep my beer as correct temperature I calculated I would need around 20W, then I set it all up with a energy meter, and in fact 5W was ample.

    My son tells me the boiler in my mothers house is too small, however it never seems to get cold, so it would seem the heating guy who fitted it knew his stuff, as an electrician I can have a good guess as to cable size required so volt drop is not a problem, because I have measured the results so many times, I can work it all out, but rarely need to. I am sure it is the same for heating engineers.

    My job was to heat things raising the temperature by 100°C per hour, then holding at 700°C for an hour, then cool at 50°C per hour, forget the calculations, one can never include all the drafts and other factors, I used experience, after setting up stress relief on 50 pipes you got a feel for what was required.

    The only way to size a boiler spot on is to monitor the old boiler for a couple of years to see what that house needs. There is always some thing which you had not allowed for, use of washer drier, use of oven, adding dish washer, having servers running, the list goes on. There is just experience.
     
  15. PullerGas

    PullerGas

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    There's the damning statement........'as an Electrician'.
    What do wire pullers now about central heating?? Most couldn't even wire a two way switch!!
     
  16. AGAS

    AGAS

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    Really???
     
  17. ericmark

    ericmark

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    Be it electric or gas there are two basic ways to control a boiler output, one is the analogue control the other is digital the latter using a mark/space ratio, however with electric that mark/space can be a rather short time, possibly seconds or even shorter, however with gas, the time is a lot longer, so with gas one has to be careful not to use a unit which is too big. There is it seems a minimum flame height. So where possible the gas boiler should be controlled by the return water temperature and only when the flame is at a minimum setting should the electric control take over.

    I was taught the wall thermostat is there to turn off the heating when no longer required, it is not there to control the room temperature. To control room temperature with a wet system you need to measure the temperature very close to the radiator and measure both air and water temperature the latter used to compensate for the air temperature being measured close to the source.

    As an industrial electrician I have been required to heat all sorts, wax, steel, and rooms. Using not only gas and electric but also oil and solid fuel, one of my jobs was to write the software to control the heaters and reduce the hysteresis to a minimum. Using solid state contactors easy enough with electric heaters the time between each pulse can be short, but using heat pumps one has to allow the pressure to equalise before a restart, so using inverters and altering motor speed instead of simple on/off works better, like gas there is a limit minimum and maximum speed.

    I have tried many times to design the system. And straight from Uni out came the slide rule to work it all out. However quickly I realised too many variables, it actually works better looking at the task, and saying this is similar to the job I did at xxxx but half or twice the size so it will likely need a heating unit of xKW, one considers the last one proved too big, or too small.

    In the main we have to use units of 3kW, 6kW, 12kW etc, working out it needs 4.25kW is rather pointless if you can't buy a 4.25kW unit, one uses experience, you look at the room, and you say to ones self 3kW will be too small think it with need a 6kW, yes you could work it all out, but why?

    If you buy a car to get to work, you don't work out what size of engine is required to get you to work in 1 hour, you use experience, and you say I'll have that one, you have considered all the pros and cons but you have not worked out the engine size, even with wagons you clearly have to satisfy the so many BHP per ton rules, but you look at reliability more than engine size.
     
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