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General Combi Installation Questions

Discussion in 'Plumbing and Central Heating' started by cosmarchy, 28 Aug 2011.

  1. cosmarchy

    cosmarchy

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    Hello all,

    I will be installing the plumbing in my house soon and have some questions regarding what is best to do. BTW I am not looking to do any gas work - I am having a qualified plumber in to do this, I am only looking to do the water pipework :D

    1) I will be using a Bosch Worcester combi boiler situated in the downstairs toilet adjacent to the kitchen. These have a plumbing manifold and I was wondering whether it is accptable (and enough room) to put a 'T' piece on the pipe as it comes out of the manifold connection so the pipework can go upwards and downwards. I am looking to take the hot water pipe downwards and through the wall into the kitchen and upwards to feed the bathroom above. I also want to take the central heating flow and return in the same manner - to feed the downstairs radiators and also the upstairs radiators.

    2) The hot water output from the boiler is 15mm. Does anyone see problems with this feeding a downstairs kitchen sink and a upstairs bath, sink and shower (not electric!!).

    3) When I take the copper and soil pipes through a brick wall, what protection do I need, if any? Do I need to sleeve it perhaps?

    If anyone could help me with these I would appreciate it.

    Thanks
     
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  3. BGEngineer

    BGEngineer

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    1) You only have minimal room down either side of the expansion vessel as shown here:

    http://www.worcester-bosch.co.uk/in...boilers/greenstar-28i-junior/wall-preparation

    The space is usually only enough to get one 22mm pipe down either side at a push, also it would look like a shower of ****. Is there no space either side of the boiler to do the drops? If not can you not just do the drops in another part of the house?

    2) No

    3) Only copper running gas needs to be sleeved, but if you are cementing after you should protect the copper from being corroded either with sleeving or tape.
     
  4. Boilerman2

    Boilerman2

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    If you get the Worcester "Stand-off Frame" you can run pipes up or down behind the boiler, which should be a solution, however be mindfull of where the flue will go when installing your pipes!! ;)
     
  5. cosmarchy

    cosmarchy

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    When you say sleeving, does it have to be a particular material or diameter? I am not so sure plastic would do for heating pipe for instance (although I could be wrong :?:)

    Has anyone used one of these? I am looking at a Greenstar 42 CDI although I think this is overrated for a mid terrace measuring 16m by 6m? I have looked around on the internet for radiator calculators and have found 5, each giving wildly different outputs (between 10kw and 20kw). Basically I don't know whether I am over or under speccing the boiler. Does it matter if it is too big, I won't be heating water unnecessarily.

    Many thanks for your help guys, it is really appreciated :D
     
  6. mikej2005

    mikej2005

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    Combis tend to be rated on their hot water output, so that's what the 42 refers to - 42kW for hot water. The 30, 37 and 42 WB Greenstar CDI combis all have CH outputs of 30kW.

    The main benefits of having a more powerful combi are that you can fill a bath quicker, have a more powerful shower and (potentially) supply more than one HW outlet at once without affecting the flow rate too much.

    How many bathrooms/HW outlets do you have ?

    It's probably worth mentioning that, in order to get the full benefit from the faster HW flow rate the more powerful combis give, you will need to check that your mains cold water and gas flow rates/pressures are high enough (your installer should be able to advise on this).

    I just about got away with having a 37CDI installed without needing my gas pipework altering, due to it being fairly close to the gas meter in 22mm. If it had been sited much further away, or I'd have gone for the 42CDI, then it's likely that some, if not all of the gas pipework would have needed upgrading to 28mm. This may not apply to you but it's something to consider and, again, something which your installer should be able to take into consideration.

    Incidentally, I was able to run the HW pipework up and out of the top of the boiler for upstairs and down and out of the bottom for downstairs by using a 15mm t-piece where the jig pipework hits the wall.
     
  7. onlyfitidealboilers

    onlyfitidealboilers

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    not really your problem you registered gas engineer will do this when he fits the boiler
     
  8. DIYnot Local

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