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    • paulstar
    • By paulstar 10th Mar 17, 10:47 AM
    • 177Posts
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    paulstar
    Replacement conventional heat-only gas boiler
    • #1
    • 10th Mar 17, 10:47 AM
    Replacement conventional heat-only gas boiler 10th Mar 17 at 10:47 AM
    We have an ancient Glow-worm Space Saver 45-60 which works fine but we're thinking of replacing it.

    Its rated output is 17.59 kW. Would a Worcester Bosch Greenstar 18Ri be a good replacement? Is there a better alternative?

    We have a 4 bedroom bungalow with 13 radiators (4 of them small). Pumped hot water system with a cylinder, cold water tank and F&E tank in loft. The good old Glow-worm does the job just fine so we're assuming the 18 kW Worcester would also?
Page 1
    • Alex1983
    • By Alex1983 10th Mar 17, 11:31 AM
    • 675 Posts
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    Alex1983
    • #2
    • 10th Mar 17, 11:31 AM
    • #2
    • 10th Mar 17, 11:31 AM
    The Worcester would need a permanent live which is likely your current boiler doesn't.
    Most modern boilers req permanent lives as they normally control the pump and pump over run. I think baxi make a boiler that doesn't req permanent live.
    You should get someone to workout your boiler size requirement as modern boilers are more efficient if they are correctly sized.
    • paulstar
    • By paulstar 10th Mar 17, 11:54 AM
    • 177 Posts
    • 103 Thanks
    paulstar
    • #3
    • 10th Mar 17, 11:54 AM
    • #3
    • 10th Mar 17, 11:54 AM
    The Worcester would need a permanent live which is likely your current boiler doesn't.
    Most modern boilers req permanent lives as they normally control the pump and pump over run. I think baxi make a boiler that doesn't req permanent live.
    You should get someone to workout your boiler size requirement as modern boilers are more efficient if they are correctly sized.
    Originally posted by Alex1983
    Thanks for the reply. By permanent live, do you mean a mains electricity connection? My existing boiler does have a mains lead going into it. But I've no idea why.

    I've been reading about pump overrun. At the moment the pump only runs when the CH or water thermostat tells it to. Presumably with a condensing boiler there is a control from the boiler to the pump to manage overrun and I guess that's the same with all makes of new boilers.
    • Alex1983
    • By Alex1983 10th Mar 17, 12:07 PM
    • 675 Posts
    • 380 Thanks
    Alex1983
    • #4
    • 10th Mar 17, 12:07 PM
    • #4
    • 10th Mar 17, 12:07 PM
    The mains cable you have is probably a switched live and only becomes live when there is a demand for heating or hot water.
    Most manufacturers req permanent lives, I do think baxi make one that doesn't need it.
    With pump over run a cable will need to be ran from the boiler to the pump.
    • getmore4less
    • By getmore4less 10th Mar 17, 2:22 PM
    • 30,854 Posts
    • 18,453 Thanks
    getmore4less
    • #5
    • 10th Mar 17, 2:22 PM
    • #5
    • 10th Mar 17, 2:22 PM
    wiring diagram says mains supply for the GW.

    supplying 24v switch feed for the gas valve.

    http://www.upperplumbers.co.uk/PDF/Manuals/Boilers/Glowworm/Spacesaver-45-60.pdf

    one site say 65% efficient decent new should be better.
    • Alex1983
    • By Alex1983 10th Mar 17, 2:31 PM
    • 675 Posts
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    Alex1983
    • #6
    • 10th Mar 17, 2:31 PM
    • #6
    • 10th Mar 17, 2:31 PM
    From the diagram it shows no switch live so very likely your boiler has no permanent live.
    • paulstar
    • By paulstar 10th Mar 17, 3:28 PM
    • 177 Posts
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    paulstar
    • #7
    • 10th Mar 17, 3:28 PM
    • #7
    • 10th Mar 17, 3:28 PM
    Alex and Getmore - thanks. Shouldn't be too much of a problem running wires across the loft and down through the ceiling.

    But I see condensing boilers need a pipe to take the condensate away. That could look very untidy coming down from the boiler, through the kitchen worktop and down into the sink outflow pipe. If it went out through the wall there's no outside drain for it to go into - the nearest cistern overflow drain cover is round the corner and the other side of the back door.

    EDIT - unless the condensate pipe could go into a rain gutter downspout?
    Last edited by paulstar; 10-03-2017 at 3:41 PM.
    • Alex1983
    • By Alex1983 10th Mar 17, 3:41 PM
    • 675 Posts
    • 380 Thanks
    Alex1983
    • #8
    • 10th Mar 17, 3:41 PM
    • #8
    • 10th Mar 17, 3:41 PM
    Depending on what's outside you could dig a soak away into the ground. It's a plastic fitting that you put into a hole in the ground and then fill the hole with lime chippings. If the top of my head I think it needs to be 500mm away from house.
    • Alex1983
    • By Alex1983 10th Mar 17, 3:43 PM
    • 675 Posts
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    Alex1983
    • #9
    • 10th Mar 17, 3:43 PM
    • #9
    • 10th Mar 17, 3:43 PM
    The best option though is to keep it internal to take away the risk of freezing.
    • paulstar
    • By paulstar 10th Mar 17, 3:54 PM
    • 177 Posts
    • 103 Thanks
    paulstar
    Depending on what's outside you could dig a soak away into the ground. It's a plastic fitting that you put into a hole in the ground and then fill the hole with lime chippings. If the top of my head I think it needs to be 500mm away from house.
    Originally posted by Alex1983
    Interesting. The gutter down pipe leads to a soak away, so I guess having the condensate pipe going into the down pipe would be OK.

    I take the point about freezing. We live right on the south coast so I'd hope that would not be too much of a problem. Think I'd rather run the risk than have it coming out of the boiler, down in front of the wall tiles and through the worktop.
    • Alex1983
    • By Alex1983 10th Mar 17, 6:07 PM
    • 675 Posts
    • 380 Thanks
    Alex1983
    Some manufacturers are ok with some not. Worcester say it ok if it terminates below the grating level but above water level.
    • MX5huggy
    • By MX5huggy 10th Mar 17, 7:42 PM
    • 4,074 Posts
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    MX5huggy
    You need a Gas Safe Registered Engineer to work all this out for you, but you can have a condensate pump fitted if you don't have an easy route to say pump it into the loft and across to the bathroom.
    • paulstar
    • By paulstar 11th Mar 17, 12:52 PM
    • 177 Posts
    • 103 Thanks
    paulstar
    You need a Gas Safe Registered Engineer to work all this out for you, but you can have a condensate pump fitted if you don't have an easy route to say pump it into the loft and across to the bathroom.
    Originally posted by MX5huggy
    Thanks.

    I guess another option would be to go out through the wall from the back of the boiler, have a 3 ft vertical pipe on the outside wall, then in through the wall underneath the worktop and into the sink outflow pipe.
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