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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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  1.  
    I need to run the flow/return from my ASHP underneath my 1m pathway into the house, what is the best depth to dig down and the best insulation method? Just the usual pipe insulation?
    • CommentAuthortony
    • CommentTimeSep 1st 2014
     
    I would do it 200mm down in a duct, the insulation they give you should be OK
  2.  
    The insulation who gives me?
    • CommentAuthortony
    • CommentTimeSep 2nd 2014
     
    it should come with the ashp pipes, otherwise good quality black flexible pipe insulation
  3.  
    Ah yes it comes with flexible pipes, but I will need to extend these, I presume Hep20 22mm will suffice?
    • CommentAuthortony
    • CommentTimeSep 2nd 2014
     
    no, needs to copper and either compression joints or brazed, NOT soldered
  4.  
    Why does it 'need' to be copper and not hep20 barrier pipe?
    • CommentAuthorbarney
    • CommentTimeSep 2nd 2014
     
    I suspect you two are discussing different things - one of you is talking about the heating system flow and return - the other the fridge and gas lines of the heat pump

    Barney
    • CommentAuthorTriassic
    • CommentTimeSep 2nd 2014
     
    Maybe a photo would help?
  5.  
    If you are talking about the water flow and return on a mono block air source heat pump hep 2o would be ok needs to be at least 28mm depending on the size of your pump and the flow rates required, though it is possible to buy the pipework in ducting pre-insulated
    • CommentAuthorDantenz
    • CommentTimeSep 2nd 2014
     
    This is what I would use
    http://www.gogeothermal.co.uk/product-detail.asp?c=5&p=55

    22mm should be good for only a 1metre run with ASHP output not exceeding 11kW
  6.  
    Well it's the older Ecodan 8.5kw that comes with 22mm piping as standard. They upgraded later models to 28mm
    • CommentAuthorGaryB
    • CommentTimeSep 7th 2014
     
    I'm pondering this issue myself at present. I have to locate my ASHP on the other side of my shed for reasons of noise / proximity to neighbours.

    There is underground pipework already to the external cabin oil boiler on the other side of the concrete path and I will be extending another 3m to the other side of the shed, but it has to be above ground as there is no room to dig.

    The standard 20mm black nitrile rubber won't be anywhere near enough insulation in my view. I am favouring running the pipework (plastic 20mm bore for 8.0 kW Hitachi Yutaki M monoblock unit) in the 100 clear gap under the shed. I have some 25mm thick EPS board and am planning to form a box duct of EPS around the insulated pipe, giving 50mm insulation thickness in all.
  7.  
    Posted By: tonyno, needs to copper and either compression joints or brazed, NOT soldered
    Can anybody explain why solder is a problem for ASHP pipes please?
    • CommentAuthorowlman
    • CommentTimeSep 6th 2020
     
    It depends whether you're talking about water or refrigerant gas.
  8.  
    Water, though I'd be interested to know for both.
    • CommentAuthorowlman
    • CommentTimeSep 7th 2020 edited
     
    Posted By: ComeOnPilgrimWater, though I'd be interested to know for both.


    My experience with soldering has been DIY fitting, a complete domestic water supply plus later additions, a CH system, and latterly fitting a complete biomass boiler and accumulator set up, so not a technical expert, but lots of hands on practical experience.
    My experience with brazing has been labouring for a knowledgeable and very experienced, and precise, HVAC engineer, I did this whilst fitting my own A2A heat pump system a year ago.

    Soldering and brazing are similar processes differing in the heat needed to join the metal together and melt the filler metals used.
    Soft solder melts at around 450C depending on makeup, but can be much higher if for instance you're using silver solder, e.g. 45% silver content, (AKA Hard solder);
    brazing rod filler metal melts above this temperature roughly 1200C, again depending on filler metal makeup.

    I don't hve personal experience of monoblock A2W heat pumps so my guess is that Tony's, (original ) advice NOT to use solder is possibly based on protecting the monoblock heat exchanger from soldering contaminants. IMO if you follow good soldering practice regarding contamination, eg use of flux, solder type, clean joints etc. there should be no problem with heat exchanger harm. The plate heat exchanger on my biomass system has been coping with soldered joints for nearly 10 years with no ill effects.
    Brazing joints, on for example refrigerant pipes when done correctly, require the pipework to simultaneously be flushed with nitrogen gas to prevent oxidation and with its potential contaminant damage to the heat pump innards,that can, I'm told, negate warranty. Cowboy HVAC fitters can omit this process in chasing speedy jobs. Also I'm not sure that soft soldered joints could withstand the very high pre-use test pressures, I may be wrong on that, ( again often omitted by cowboy fitters), that my HVAC engineer subjected my system to.
  9.  
    Thanks @owlman, that's very helpful and makes sense. I've subsequently found some advice about soldering / brazing that echoes what you say above:

    '1-5 Precautions for the brazing
    Clear any dangerous or inflammable materials in surrounding environment.
    Make sure to empty the remaining refrigerant in the product or pipe before brazing.
    – Brazing with the refrigerant still remaining in the product or pipe may cause poor result and generate harmful gas. Furthermore, pressure of the refrigerant may increase and cause damage to the leaking part. This may lead harmful refrigerant and oil to spurt out which can be dangerous for service personnel.
    Use nitrogen gas to get rid of the oxide forming during brazing.
    – Using other type of gas may cause damage to the product or the exterior.'
    • CommentAuthorSteveZ
    • CommentTimeSep 8th 2020
     
    Might be worth asking about Argon.

    If you have a MIG or TIG welder, you may be able to use the Argon gas instead of the Nitrogen. Argon cylinders easier to get, maybe?

    It is standard practice to flush/fill components with Argon during TIG welding either Aluminium or stainless to prevent Oxygen contamination.
    • CommentAuthorowlman
    • CommentTimeSep 8th 2020 edited
     
    Posted By: ComeOnPilgrimThanks @owlman, that's very helpful and makes sense. I've subsequently found some advice about soldering / brazing that echoes what you say above:

    '1-5 Precautions for the brazing
    Clear any dangerous or inflammable materials in surrounding environment.
    Make sure to empty the remaining refrigerant in the product or pipe before brazing.
    – Brazing with the refrigerant still remaining in the product or pipe may cause poor result and generate harmful gas. Furthermore, pressure of the refrigerant may increase and cause damage to the leaking part. This may lead harmful refrigerant and oil to spurt out which can be dangerous for service personnel.
    Use nitrogen gas to get rid of the oxide forming during brazing.
    – Using other type of gas may cause damage to the product or the exterior.'


    If you were considering brazing heatpump refrigerant pipes, my quick advice would be DON'T. Employ a HVAC fitter with all the right tools e.g. swaging tools, pressure test rigs, nitrogen gas, etc., and more especially experience. My heat pump and I guess all pre-gassed ones allow for all brazing to be done before final connection to the heat pump and releasing the refrigerant gas in the required amount for the system size.
  10.  
    @owlman, I'm not planning on brazing. I understand brazing is stronger, and therefore might be better for coolant circuits where I guess leaks are a big issue. For the water circuit of an ASHP, I'm sure a soldered (or compression) joint is fine.
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