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Base for external oil boiler

Discussion in 'Plumbing and Central Heating' started by Cocat2517, 5 Aug 2019.

  1. Cocat2517

    Cocat2517

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    Hi
    Are there any restrictions on the siting if an external oil (combi) boiler? I understand there are for the flue/outlet etc, but what about the unit itself?

    In the photo I've marked a space that is approx 400mm from house wall at the side. Boiler will be installed against kitchen extension wall. Is this ok?

    Is a 50mm concrete slab ok for it to sit on?

    Thanks

    20190805_124908.jpg
     
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  3. muggles

    muggles

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    If it's this one, it needs turning round 90°. Some oil combis have service hatches at both ends, every external one I've seen has the screws which hold the lid on positioned at the ends, and I've only ever seen side exits for the pipes. Therefore, the long side needs to go against the wall.

    No, 50mm isn't deep enough, you want 75mm on a bed of compacted hardcore. An oil combi full of water can weigh a quarter of a tonne, and you don't want it to sink into the ground or crack the base.

    Be aware that oil combis only achieve around 65% efficiency when generating hot water. You're much better off having a regular boiler and a hot water cylinder if at all possible
     

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  4. Cocat2517

    Cocat2517

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    Thanks, I'll adjust the position. Boiler dimensions are 770x640, I'll make the base 800x800. The ground there is concrete already, but it slopes away from the house slightly, so I was going to lay a 50mm slab on it to level it. I'll do a 75mm slab though.

    Gone for an external combi to free up space and avoid the hot water cylinder running out scenario. It's a 4 bed house, sleeping up to 8 at any one time.
     
  5. muggles

    muggles

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    I certainly wouldn't put a combi in with that level of occupancy. Freeing up space is all well and good but a combi is highly unlikely to keep up with the hot water demands of an 8 person household. A properly sized hot water cylinder with the correct controls won't run out of hot water.
     
  6. Cocat2517

    Cocat2517

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    Too late, all ordered by fitter :/ Had 3 quotes from 3 heating firms, all recommended a W-B greenstar heatslave 18/25.
     
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  8. oilboffin

    oilboffin

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    18/25 good boiler one recombination though make sure one of your sowers is electric cos sooner or later all boilers turn their toes up when you don't need it with an electric shower you can still keep clean.Bob
     
  9. Cocat2517

    Cocat2517

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    Cheers. Got an electric shower in the ensuite and two regular showers in bathrooms, for that reason.
     
  10. muggles

    muggles

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    Fair enough, suppose they must have had their reasons, maybe your mains flow rate is poor? Just prepare to be disappointed if you try to run two showers at the same time
     
  11. Cocat2517

    Cocat2517

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    Thanks. Yeah, wasn't expecting great performance running two showers at once, will see how it goes.
     
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