40kw Boiler in 3 Bed Bungalow

Discussion in 'Plumbing and Central Heating' started by s00tie, 13 Jun 2018.

  1. s00tie

    s00tie

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    Not sure I follow - hard to work out from your comment if there is a typo in there somewhere or it's in a language I clearly don't understand.

    Are you stating that the digital read out on the boiler is not showing the flow temp of the tap water, but rather the heat within the boiler?

    There are two dials on the boiler, one for CH and one for DHW. If I adjust the CH dial, it alters the max temp that is shown on the display when the central heating is running.

    When I turn off the CH and just run the Hot Tap, the displayed temperature is directly affected by adjusting the DHW - only it's about 10-12 degrees out from it's setting to that shown on the display.

    In another property, we had a Baxi Duo Tech 28 with the same dials and the display correctly displayed the temp that the dials were set at when running.

    I haven't measured properly but when the dial is set to 45ish and the display shows 55 under load, I can just bare my hand under the tap. When I set the dial to 55 and the display shows 67 under load I cannot keep my hand under the tap which is what makes me think the dial is actually correct.

    Are you sure I'm reading it wrong? If so, could you explain further please?
     
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  3. Dan Robinson

    Dan Robinson

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    Sorry. ... Was typing and talking at the same time.

    Have edited accordingly.
     
  4. s00tie

    s00tie

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    Ok thank you for the quick reply, I think I understand now.

    The thing that alerted me to the water temp was the shower. When the DHW dial was up at 55 (and primary showing at 68 under load) the electric mixer on the shower seemed to struggle. It would get very hot, the go freezing cold - sometimes in the middle of a shower. When I saw the boiler showing the differences in the temp I was setting the dial to and the actual reading on the display, I made an assumption that the water was coming to the mixer way too hot and causing a problem. This is when I turned it down to about 45 and since then, the shower hasn't had a single problem and the water is lovely and hot - even when the shower temp dial is in the middle, it's too hot to stand under at full which is what made me think it wasn't 45 degrees.

    Could any of this indicate an issue with the boiler that could be influencing the amount of gas it's consuming or am I just seeing normal behavior and jumping to conclusions?

    I'm happy to get an engineer in to assess, was just trying to work out if I'm wasting his/her time (and my cash!) :)
     
  5. Dan Robinson

    Dan Robinson

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    Yes, or that the shower flow rate is too low.
     
  6. dilalio

    dilalio

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    What have I got to do with it :D
     
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  7. dilalio

    dilalio

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    Edit: double post coz forum went on one
     
  8. Dan Robinson

    Dan Robinson

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    You're still in the primary doughnut category :p
     
  9. Combicert

    Combicert

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    Wow - that’s a hell of a gas bill.

    Wonder if your engineer missed something/didnt do something. Did he scribble any numbers down in your service manual? Gas rates etc...?
     
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  11. dilalio

    dilalio

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    Sure your gas meter is not faulty?
     
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  12. dilalio

    dilalio

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    I resemble that!
     
  13. flameport

    flameport

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    That really is massive.

    1. Are there any other gas appliances?

    2. When the boiler is switched off, make a note of the gas meter reading (including all red digits), then later (preferably after several hours or overnight) is the reading the same?

    3. Take a reading at the gas meter (including all red digits), turn on a hot tap fully for 1 minute, turn tap off, how much gas has been used?
     
  14. s00tie

    s00tie

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    Sorry flame, must have missed this reply the first time around.

    1. No other gas appliances, just the boiler
    2. No change overnight when heating hasn't been on
    3. Readings as requested for 1 min of hot tap:

    Start: 02293.927 m3
    End: 02294.021 m3

    I did have an engineer come around and he said he thought the boiler was fine and he couldn't detect any leaks. He said it was burning very clean.

    I contacted my energy supplier (now Bulb instead of Npower) about checking the meter and whilst they are happy to do so, they will charge me £160 if the meter is not found to be at fault so I haven't gone for that (yet).

    Don't think I'm doing anything out of the ordinary with the heating controls but just in case:

    We have a Nest in the main living room area
    The radiators are balanced so that they all heat up together with approx a 10c drop from feed to return when fully on
    The TRVs are set as follows: Living Areas / Kitchen (3), Bedrooms (2), Hallway / Bathrooms (No Trv)
    The temp on the boiler CH is 65c and the DHW is 50c
    The Nest is set at 20.5c for 07:00 and down to 18.5c at 22:30 (usually always someone in the house)
    The True Radiant setting on the Nest is on but no other automation is used
     
  15. McCombi

    McCombi

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    Unless I'm getting something wrong here with the figures, the gas rate for the figures you provided for one min of hot water use is very high.

    With using 0.188 as my difference between two readings over 2 mins i get this as a gas rate

    Screenshot_20181001-100750.jpg
     
  16. s00tie

    s00tie

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    Thanks for the quick reply.

    Just realised the Mrs had put the washing machine on, which whilst doesn't take hot water - does mess with the flow rates which I'm guessing might have messed the figures up.

    I'll repost values for a few tests at 2 mins as soon as it stops! :)
     
  17. ianmcd

    ianmcd

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    washing machine will not make any difference
     
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