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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthornbishara
    • CommentTimeDec 7th 2021
     
    Hi all,

    Finally bit the bullet and having a Daikin air source heat pump installed – with all the known caveats, but we’re off main gas so… anyway, I had a conversation with Company boss before we signed up about pipe sizing because my father had raised the issue rather helpfully – and he explained that they will be using 20 mil and how this was a much greater flow rate than the smaller piping and I think I also checked here. However, when I look at what they’re actually doing, they are largely using 20 mil – apart from when they are cutting into the old 12 mil piping.

    In fairness, there doesn’t appear to be a lot of it and I did raise it as an issue in the first place when I heard them talking about it and the boss says he wanted to use new piping where possible except where it was an accessible (i.e. it was a pain from their point of view).

    From what I can see, they are cutting into the smaller bore piping on the first floor to drop down into the downstairs bathroom. Also, they mentioned when they took out the old piping – which is really really old And we’re on a hard water area – that it was really sludgy and full of gunk.

    My partner says that I shouldn’t worry about this, it will all be fine and if it’s not we can take it up with them afterwards. He is the most unassertive person on the planet. I’m concerned because if the heat pump doesn’t work as planned, the most likely explanation will very reasonably be because we haven’t done the internal insulation yet and the most likely consequence of the heat pump working is not, in my opinion, as my partner thinks that the radiators won’t heat up, but that the bills will be that much more expensive – and it will be me paying them.

    So… I have texted the company post this morning politely to ask him what the implications of the smaller piping may be (in writing), but what do you all things? Am I being fussy and pedantic or right to be a bit concerned?

    I’ll be delighted if you think that I am being too concerned because obviously I don’t want any issues – but I would much rather address things when I have plumbers in the house then try and chase them down after I paid them and in fairness, the quote talked about using large bore piping throughout and there was no mention of except where it isn’t very convenient for us.

    Many thanks for any thoughts & advice :)

    Tania
    • CommentAuthorrevor
    • CommentTimeDec 7th 2021
     
    Posted By: nbisharaSo… I have texted the company post this morning politely to ask him what the implications of the smaller piping may be (in writing), but what do you all things? Am I being fussy and pedantic or right to be a bit concerned?

    No you are not being pedantic. You have real concerns that need clarification. If I am not mistaken you are talking here of 12 mm pipe feeding radiators what conventionally known as micro bore. Personally I would have the piping replaced you will I reckon struggle to get the temperature hot enough from the HP without sacrificing some COP to give you the levels of comfort you previously experienced. Did the installer do you a proper specification to calculate the heat requirement including the level of internal insulation you are planning to do? This would be needed to size the unit to install. Was there any mention of installing higher output radiators?
    • CommentAuthornbishara
    • CommentTimeDec 7th 2021
     
    Hmm, so spoken to plumber who’s installing the system and he says that they have to go to 15mm for the radiators. I questioned the fact that it was a 15 mm run of at least 5 metres, first horizontal, then vertical to the rad and he assured me that it was fine. He pointed out that they’d actually used 28 mm for much of the piping, with 28mm joints going to 22 to improve flow and, most importantly from my pov, that the heat pump would tell them if the flow was wrong and that they’d been doing heat pumps since 2008. I’m actually quite reassured…should I be? One way and another I have trust issues with tradespeople generally (we have history) and we all know how many companies are jumping on green tech incompetently so it makes me cautious!
  1.  
    I'm not totally clear what is being installed (15mm? 12mm?) but you mentioned it is to a bathroom radiator, is that the only run of small bore pipe?

    The bathroom is presumably a small radiator (?) so that might well be ok. Would be more of a concern if it was a big radiator or if it were 8 or 10mm pipe.
    • CommentAuthorphiledge
    • CommentTimeDec 7th 2021
     
    Weve got 8mm pipe feeding some radiators in parts of the original house without a problem at 50+ degrees depending on how much wood is on the fire. Cant see 12mm being a problem unless its feeding an enormous radiator.

    If youre not 100% trusting in your plumbers expertise/warranty dont pay him for a few days while you test the system and verify that all the rads get up to temperature.
  2.  
    Posted By: nbisharaFrom what I can see, they are cutting into the smaller bore piping on the first floor to drop down into the downstairs bathroom. Also, they mentioned when they took out the old piping – which is really really old And we’re on a hard water area – that it was really sludgy and full of gunk.

    My partner says that I shouldn’t worry about this, it will all be fine and if it’s not we can take it up with them afterwards. He is the most unassertive person on the planet. I’m concerned because if the heat pump doesn’t work as planned, the most likely explanation will very reasonably be because we haven’t done the internal insulation yet and the most likely consequence of the heat pump working is not, in my opinion, as my partner thinks that the radiators won’t heat up, but that the bills will be that much more expensive – and it will be me paying them.

    First off the sludge and gunk in the old pipes has nothing to do with being in a hard water area and more to do with the age of the system. (hot water tanks and kettles fur up in hard water areas because new hard water is continually introduced. CH water is not changed so hard water should make no difference). But any old piping that is retained for the new system should be flushed through properly to clean them.

    Who designed and sized the system and against what criteria ?
    If the installers designed the system on the basis of yet to be installed insulation then you can't expect the system to work properly until the design standard is met (i.e. after the insulation). If the system was designed with the house as is - then it should work now. The key would be to tell the installers what you want in terms of heat and not how to do it. That is tell them you want 21deg here and 20deg there etc. and let them give you a system that works. Don't tell them what size pipe to use because if you do and the system performs badly then it will be because you told them to use that pipe (what ever the real reason for failure is!)

    It is a misconception that heat pumps don't work unless the house is well insulated, any more than a gas boiler won't work in a poorly insulated house. All poor insulation means is that you will need a bigger heat source (either heat pump, gas boiler or what ever) and it will use more fuel so be more expensive to run.

    Come payment time (providing you have done any work that you said you would do for the design criteria e.g. insulation, then withhold some payment until you are satisfied with the performance. As a suggestion offer to pay for the materials but withhold the labour costs until all is OK.

    With regard to pipe size, many years ago I installed a CH system using 6mm nylon pipe work (a manifold system) I had no problems with getting the heat from the rads, the only problem was that one rad would gravity circulate so was impossible to switch off, often plumbers will say that gravity systems don't work to day or you need 22mm pipe etc. but pipe size is all about flow rates, temperature and demand and all have to be balanced. Today's plumbers are spoilt by combie boilers that are sized for a couple of showers so vastly over powered for CH so if a rad doesn't get hot enough rather than fix the problem they just turn up the pump speed (which generated more noise)
    • CommentAuthornbishara
    • CommentTimeDec 7th 2021
     
    Thanks everyone; that’s really helpful. Yes we did have a conversation about oversize radiators and I would’ve been quite worried if we hadn’t.

    I’m slightly wondering what size piping isn’t being used in the house? So far I know there is 28 mm, 22 mm, 15 mm and I’m sure I measured 12 mm!

    Thanks for all the tips and information – we worked out today that the old boiler is probably about 50 years old so I’m guessing that the pipes are probably 1970s as well! :-0

    I’ve just realised that, despite numerous conversations with the boss of the company, having it all written down on paper and actually writing on the actual walls – they’ve still managed to take the old radiator off and put a new radiator on, using all the existing small bore piping very conveniently for them – but on precisely the wrong wall for us!

    Aaargh…I can see a conversation tomorrow..

    Cheers!

    Tania
    • CommentAuthorrevor
    • CommentTimeDec 8th 2021
     
    Posted By: nbisharaI’m slightly wondering what size piping isn’t being used in the house? So far I know there is 28 mm, 22 mm, 15 mm and I’m sure I measured 12 mm!


    This is quite normal. Larger bore from the heat source e.g. 28 mm then if you have say 2 floors split into 2 x 22 then use this size to take to the radiator loop then 15 mm to rads. Often smaller bore is used but personally never have, other the use 12 or 10 mm to feed towel rails. If the pipe size is insufficient to take heat from the "boiler" it will affect the efficiency of it. The pipe sizes approximate quite closely to halving the flow capacity and amount of heat carried. 28 mm is half 35mm 22 half 28 and so on. If you work out the cross sectional area of each pipe you will see what I mean. There are tables that any decent heating engineer will have to calculate the pipe size needed for a given heat requirement in each heated area at a flow rate designed not to generate noise. I must state here I have no knowledge of HP installations but the principles of distribution of heated water is basic physics and very well documented in many heating publications.
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