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Does combi have minimum mains pressure requirement

Discussion in 'Plumbing and Central Heating' started by andytw, 12 Apr 2018.

  1. andytw

    andytw

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    Hi,

    It's all happening at once. Let property has Baxi back boiler on LPG. It has provided stirling service and is still going strong. HOWEVER the property only has an EPC 'F' so cannot now be legally rented out. It needs to be an 'E' at least. Apart from digging up the solid floors and re-laying as insulated then the heating is the next port of call.
    I have arranged for an EPC assessor to re-assess and then we can work on heating options.
    The Baxi is due for a service and safety check the day after so I will get my engineer to discuss combi/system options and give me some boiler options. These options can then be given to the assessor to see what might be the best way to go.
    So...just wondering...do combis need a minimum cold feed pressure and flow rate as it is not very good at this property. It is a single bedroom annex next to my own property and an upgrade to the MDPE is overdue but as I have a long driveway this has been put off as we manage. If so then I would need to stay with system boiler but I would have liked to lose the header tanks and hot water storage etc.
    I realise my engineer will have the answers, I just want to be a few days ahead in the thought/planning process.

    Thanks
     
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  3. heatservice

    heatservice

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    Basicly the answer is YES, your installer should check your mains water pressure & flow rate before any decision is made.
     
  4. dilalio

    dilalio

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    The requirements will be stated in the MI’s of whatever boilers you are looking at... you will also need to check the suitability of your gas supply pipe.
     
  5. andytw

    andytw

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    Thanks, gas "shouldn't" be a problem as we are on a bulk tank with a high pressure regulator and a high pressure underground feed pipe and then the low pressure regulator is installed at the annex itself.
     
  6. oilboffin

    oilboffin

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    Usually you'll need at least 1bar water pressure which won't drop and at least 20ltrs a min that's the absolute min you'll get away with I do know that as I've just put a wooooster combi in my house and before anybody says shame on you,I was given it as a company ordered too many and I took this one as part payment for work I've done for them and it's worked out very well for me.Bob
     
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  8. ianmcd

    ianmcd

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    if it is a baxi bermuda back boiler the gas appliance for EPC is out of 5 and the Baxi BBU is a 4 so its not the fire and BBU that is bringing your EPC down. you may be able to keep the BBU if you upgrade controls and look at double glazing or other things
     
  9. andytw

    andytw

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    Yes it is a Baxi Bermuda but is on LPG which I think makes the difference. The property is fully insulated with UPVC double glazed windows but has solid floors.
    Also has room stat and TRV's.

    Here are a couple of screenshots of the EPC from 2013 and the recommendations.

    The EPC is being re-done next week.


    [​IMG]
    [​IMG]
     
  10. andytw

    andytw

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    Waiting for EPC result and waiting for gas engineer this afternoon. If water flow and pressure deemed low is Salamander pump on incoming main an option ? Thanks
     
  11. Have fitted them before,they have their limitations thou (n).
    Extract from the pump manual,
    If your installation is complicated or you have any questions, please
    consult the PumpWise Technical Helpline immediately (0191 516 2002).
    Additional help can also be found on the HomeBoostTM website
    www.home-boost.co.uk
     
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  12. andytw

    andytw

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    OK thanks. New EPC gives the property an F28, slightly worse than before. Replacing Baxi BBU and fire with condensing LPG combi and electric fire would take EPC to E42. Couple of points to be gained with attention to some insulation in ceiling void over lounge (single storey property), next step would have to be to rip up solid floors and re-lay with insulation. At least 'E' would allow it to be rented.
    Don't know result with non-combi i.e system boiler option.
     
  13. DIYnot Local

    DIYnot Local

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