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  1. #1

    Ashp or gas boiler

    Hi everyone


    I'm think of rebuilding my garage and change my pond heating system


    At the moment I have a hydropro Ashp a few years old and could quite easily install a gas boiler in the new build


    Is gas more a efficient than a ashp


    Another option would be to run the heating pipe work from the house?


    But think this would have a lot of heat loss as about 30 m run outside from my house boiler

    Cheers



  2. #2
    Extreme Koi Member Rank = Gosai sammy66's Avatar
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    Hi , i use gas as its the cheaper of the too. Heat only boiler up to 18kw dose a good job for my 25,000 pond and got rads in the filter house , you will need a pool heater with that . i use two on mine.

  3. #3
    Senior Member Rank = Rokusai Simon Fish's Avatar
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    LPG or natural gas?
    If its gas of the grid there are lots of things to plan out.
    The electric option of ashp could be the easy option

  4. #4
    It would be gas off the grid, I need to plan to heat the garage as it's going to be a office so introducing a boiler would help heat the office and provide some hot water for a small kitchenette

    I would need to move the Ashp to a new location which may prove awkward

  5. #5
    Senior Member Rank = Adult Champion Gazkoi's Avatar
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    Hi,

    ASHP would be easier but they are less efficient on the colder temperatures due to lower ambient heat to work off - which you probably recognise.

    From a gas perspective, consideration would need to be put towards supply amount and whether this is enough to feed both the house and the pond. I am not a Gas Safe Engineer so would be worth checking. The other major consideration regarding gas will be pipework. To legally install you would either need to bury the compliant gas pipes at a specified depth below ground to protect or run water pipes (which risk losing heat so would need to be heavily insulated)

    some of my customers have gas heated ponds which were installed years ago and would no longer be ‘legal’ installations. Distance from the house makes gas a more complicated install, however in winter the most efficient

    Cheers

    Gaz
    Hobby and business gone but when you’re hooked you’re hooked.

    Always happy to help!!

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  7. #6
    Senior Member Rank = Jussai Tom Koi's Avatar
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    The greater the distance the boiler is from the meter the less gas pressure you'd get at the boiler, you can adjust the gas regulator [gas safe engineers can do that], but even then you may be struggling. As a minimum you need 19mbar working pressure at at the boiler, any less can alter the flame picture when burner is running, which can be dangerous and much less efficient, you'd probably get away with 18mbar, but that's debatable and against Gas Safe rules/guidelines, boiler manufactures instructions are the key in all situations.

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  9. #7
    Moderator Rank = Supreme Champion Feline's Avatar
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    The ultimate would be to have gas and ASHP
    In colder temps gas wins by some margin on efficiency, but if heating to keep summer growth temps for a few months of the year then the ASHP comes into its own.

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  11. #8
    Extreme Koi Member Rank = Gosai sammy66's Avatar
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    Hi , its a good point on the gas , i put 25mm pipe down to the filter house to feed my 18kw boiler and its runs to the meter outlet to a 22mm tee that goes to the house boiler . its down to the size coming in from the road . So if your new boiler is going in your garage and you use 22mm or 28mm pipe you should be ok .

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  13. #9
    Senior Member Rank = Jussai Tom Koi's Avatar
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    Quote Originally Posted by sammy66 View Post
    Hi , its a good point on the gas , i put 25mm pipe down to the filter house to feed my 18kw boiler and its runs to the meter outlet to a 22mm tee that goes to the house boiler . its down to the size coming in from the road . So if your new boiler is going in your garage and you use 22mm or 28mm pipe you should be ok .
    I've run 28mm from meter under stairs into garage up wall and back into house under the floor boards and it run's to boiler in utility room, 12/13mters in a straight line and I had to adjust the regulator on meter and I've still only got just about 19mbar at boiler, nightmare, Wales & West are in area upgrading gas mains, may get a few more millibar then perhaps.

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    Member Rank = Nisai Mpathe's Avatar
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    No one except the gas service provider is allowed to adjust a gas meter regulator, not even gas safe engineer. To get the correct gas pressures to a boiler the pipework is designed around a 1mb loss from the meter to the boiler, if the pressure is correct at the meter but not correct at the boiler the pipework is not big enough

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  17. #11
    Senior Member Rank = Jussai Tom Koi's Avatar
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    Quote Originally Posted by Mpathe View Post
    No one except the gas service provider is allowed to adjust a gas meter regulator, not even gas safe engineer. To get the correct gas pressures to a boiler the pipework is designed around a 1mb loss from the meter to the boiler, if the pressure is correct at the meter but not correct at the boiler the pipework is not big enough
    Im a gas engineer/installer, I now fit meters and we are allowed to alter regulator pressures, I also stated above in a post that its the responsibility of the gas provider to alter regs unless authorised to do so, you're right about pipesize, that takes account of bends/elbows along the pipe run also.

    I've got 19mbar at boiler and its been fine, along with gas rate, I could run 35mm from meter through into garage and up wall to help I suppose.
    Last edited by Tom Koi; 15-11-2020 at 04:27 PM.

  18. #12
    Member Rank = Nisai Mpathe's Avatar
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    Im also a gas engineer and ive only raised concern because you was coming across as tho anyone can adjust the gas regulator, also you only said gas safe engineers can adjust which is not correct only esp engineers can adjust a regulator

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  20. #13
    Senior Member Rank = Jussai Tom Koi's Avatar
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    Quote Originally Posted by Mpathe View Post
    Im also a gas engineer and ive only raised concern because you was coming across as tho anyone can adjust the gas regulator, also you only said gas safe engineers can adjust which is not correct only esp engineers can adjust a regulator
    Fair point. when we change meter we change the reg as well. when we re-light boiler we check at meter for working pressure, a lot of times it needs altering, normally its because pressure is above 23mbar. Strangely we're not allowed to test at the boiler itself, which its there where it counts.
    Last edited by Tom Koi; 15-11-2020 at 04:58 PM.

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    Senior Member Rank = Jussai Spongebob's Avatar
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    Hmmm I think I’d question whether gas has so much edge on an ASHP. Ok yes when it’s very cold, but how often is that nowadays? November and December are pretty much always warm and mild now, that only really leaves Jan and Feb. For me an inverter ASHP all day long not sure I’d go with gas for such a short period, especially if as most your only going to 15 for those months, a good ASHP will nail that at little cost.
    Fibreglassed/5000 gals/4.5 m Tunnel/Spindrifter/Twin drums/Bio chambers/Beads/Showers/Remora ASHP

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    Senior Member Rank = Jussai Tom Koi's Avatar
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    Quote Originally Posted by Spongebob View Post
    Hmmm I think I’d question whether gas has so much edge on an ASHP. Ok yes when it’s very cold, but how often is that nowadays? November and December are pretty much always warm and mild now, that only really leaves Jan and Feb. For me an inverter ASHP all day long not sure I’d go with gas for such a short period, especially if as most your only going to 15 for those months, a good ASHP will nail that at little cost.
    I've been wondering if an inverter would be better and more efficient than a Dura Tec type ASHP and if its worth changing, be interesting to know, at least.

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  26. #16
    Moderator Rank = Supreme Champion Feline's Avatar
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    The COP in deep winter sub zero temperatures will be pretty much 1 on an ASHP. So you’re effectively heating directly from electricity. So this is basically the equivalent of using an immersion heater for hot water rather than the gas boiler. I think we all know which of those is cheaper don’t we?

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  28. #17
    Senior Member Rank = Jussai Tom Koi's Avatar
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    Quote Originally Posted by Feline View Post
    The COP in deep winter sub zero temperatures will be pretty much 1 on an ASHP. So you’re effectively heating directly from electricity. So this is basically the equivalent of using an immersion heater for hot water rather than the gas boiler. I think we all know which of those is cheaper don’t we?

    Gas be cheaper through winter months but over the yr, it may just about even itself out , I'd have to use LPG as I'd struggle to supply gas to boiler where filter house is.

  29. #18
    Senior Member Rank = Jussai Spongebob's Avatar
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    Quote Originally Posted by Feline View Post
    The COP in deep winter sub zero temperatures will be pretty much 1 on an ASHP. So you’re effectively heating directly from electricity. So this is basically the equivalent of using an immersion heater for hot water rather than the gas boiler. I think we all know which of those is cheaper don’t we?
    Over the full twelve months I’d say the ASHP would win comfortably. Can’t see the point in fitting gas heating for a koi pond nowadays.
    Fibreglassed/5000 gals/4.5 m Tunnel/Spindrifter/Twin drums/Bio chambers/Beads/Showers/Remora ASHP

  30. #19
    Extreme Koi Member Rank = Gosai sammy66's Avatar
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    All of whats has been said on gas pressures is ok as you test at the meter at 20mlb , i worked for british gas for 20 years in them days your gas service was a 20mm pipe as boilers now have a higher demand for gas ie combi , they now put in service lines at 25mm or 35mm to give extra at the meter .Boiler pressures can be as low as 10.5 burner pressure , so its all down to your boiler make .

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  32. #20
    Senior Member Rank = Jussai Tom Koi's Avatar
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    Quote Originally Posted by sammy66 View Post
    All of whats has been said on gas pressures is ok as you test at the meter at 20mlb , i worked for british gas for 20 years in them days your gas service was a 20mm pipe as boilers now have a higher demand for gas ie combi , they now put in service lines at 25mm or 35mm to give extra at the meter .Boiler pressures can be as low as 10.5 burner pressure , so its all down to your boiler make .

    10.5 burning pressure goes back to system boilers rather than Combie's you'd struggle to find an A band Combie with pressure that low, the old FFBU [fire,front back boiler units] used to run a variable pressures at low rate, medium and high rate, I think high used to be around 14mbar, combie's work at full rate when supplying hot water, pressures need to be 21+ or - 2 mbar

 

 
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