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  1.  
    We've got a cylinder that is losing more heat than desirable and a lot of surplus bubblewrap from deliveries - would it make sense to use it for insulation or is there any risk of it melting or catching fire? Or would it just be ineffective and worth while buying something?
    It's a 191l capacity Worcester Bosch cylinder with gas boiler and immersion heater. The hot water is currently all from PV via an immersion diverter, but I expect we'll need the boiler in winter.
    Thanks for any advice
  2.  
    Well, if its already an insulated cylinder, It won't harm. If its not already insulated, I'd get some proper stuff.
    One area to focus on is to carefully and fully insulate all the in and out pipes, especially the one out the top.
    • CommentAuthorMike1
    • CommentTimeAug 27th 2017 edited
     
    According to one particular manufacturer (http://horizon-sites.com/horizonsites/ssi/MSDS/2012/SEALED%20AIR%20BUBBLEWRAP%20MSDS%20092012.pdf), their bubble wrap melts at 95°C. That's much hotter than your water temperature should be, unless you have a thermostat failure.

    Personally I'd probably avoid putting it directly against the tank or pipes, just to be sure, though I wonder what the melting temperature is of a traditional plastic-encased mineral wool insulation jacket...
    • CommentAuthortony
    • CommentTimeAug 27th 2017
     
    Are you sure you don't want to use foil faced bubblewrap? and really get us going
  3.  
    Or a m---if--l/bubblewrap sandwich?

    But seriously, if you possibly can access all of the primary pipework (pipes to/from boiler to cylinder) to insulate it you will save far more than the cost of insulation when you need HW but not space htg.
  4.  
    Thanks, everyone; I'll go for it.

    The pipework was reasonably well insulated by the installers (after a bit of nagging) but there are still some awkward shaped hot bits which I hope to include in the bubblewrapping.

    The cylinder is insulated, ostensibly to a good standard, but I'm shocked by how much the PV monitoring site shows that it is taking to reheat, even when there's not been any hot water used. We'll see if this makes a difference.
    • CommentAuthortony
    • CommentTimeAug 28th 2017
     
    I have had my thermostat set at 50C for 30+years and that represents significant savings

    Note that nothing saved when the heating is running though
    •  
      CommentAuthordjh
    • CommentTimeAug 28th 2017
     
    When the heat is being provided by PV it makes sense to run the cylinder as hot as possible to maximise the energy stored. A TMV is needed on the output to limit the flow temperature to something reasonable.

    For the sake of a few quid I wouldn't use bubble wrap, I'd just go and buy a roll of the recycled plastic wool which is nice to handle and wrap that round the cylinder. Always presuming that it is new enough to already have some foam insulation attached to it already. Otherwise a lot more care needs to be taken.
  5.  
    That would certainly make a neater job of it, djh. It's all brand new kit in our brand new house and the bubble wrap would lower the tone a bit! I just hate wasting anything.

    I've been keeping it at a lowish temperature, thinking that would minimise the heat loss; so far we haven't run out of hot water even with a houseful of guests, but I guess it'll be different in winter. At the moment we can heat the cylinder then charge the battery and still export about half of what we generate, but that won't last, and it might be better to have the cylinder full of hotter water to tide us through short dark days. Don't think we've got a TMV so can't go too hot.
    • CommentAuthorgravelld
    • CommentTimeAug 29th 2017
     
    It will minimise heat loss, but if the PV is free...

    Why not charge the battery, then heat the cylinder from the battery just before it is required?
  6.  
    That might reduce heat loss from the cylinder, but there'd be a loss of electricity by putting it in and out of the battery. I'm not techy enough to know how the amounts would compare. Also, would mean engaging brain before having shower, rather than just staggering out of bed and hot water being there.
    • CommentAuthorgravelld
    • CommentTimeAug 29th 2017
     
    Well you would normally time it 30 mins or 1hr or so before getting up...

    I think it depends on the battery chemistry as to the losses?
    •  
      CommentAuthordjh
    • CommentTimeAug 29th 2017
     
    Posted By: gravelldWhy not charge the battery, then heat the cylinder from the battery just before it is required?

    Because then you can't use what's stored in the battery for something else. To maximise energy storage it needs to be stored in all available places.
    • CommentAuthorgravelld
    • CommentTimeAug 29th 2017
     
    Correct - but that might be an argument for bigger batteries... Not sure how much headroom the OP has.

    Also, depends on the losses of the batteries as above.

    I was juggling these ideas in my head when thinking about the Powerwall vs SunAmp.
  7.  
    I found bubble wrap went all brittle after a few years. Also I think its insulation value is not actually very good compared to say closed-cell polyethylene foam sheet, or mineral wool, the 'bubbles' are too big.

    Every little helps when fitting any insulation, but to get an improvement that you will notice, I think you need at least to double the insulation value, this means more than doubling the existing thickness if using a less-insulating material than is already fitted.

    I wish bubble wrap was easier to recycle. Toddlers love stamping on it :)
    • CommentAuthorJeff B
    • CommentTimeAug 29th 2017
     
    yclairejenkins - I have successfully used the widely ridiculed aluminium/bubblewrap "sandwich" on my thermal store. I have absolutely no before and after data to prove how effective it is, suffice to say that whereas before the surface of the store felt hot to the touch (it only has about an inch of PU insulation) it now merely feels warm and the room in which it is situated no longer feels like a greenhouse on a hot summer's day!

    In other words, do it - it's cheap and at worst it won't do any harm! (Don't cover any immersion heater parts or motorised valve though to avoid localised overheating).
  8.  
    Thanks all.
    I've gone ahead with recycled plastic loft insulation, which is quite good for filling the awkward shapes around the pipework and the walls as it compresses and expands usefully. Because of the way I've had to bodge it into the inaccessible bits, one roll hasn't covered it, so will have to go out for another, which means it's not a particularly cheap option as it's £18 a roll. Also looks messy and won't be easy to keep clean.
    So not ideal, but hopefully will be effective.
    •  
      CommentAuthorjoe90
    • CommentTimeAug 30th 2017
     
    With regard the foil bubble wrap, foil is a good reflector of heat I am told but at a certain wavelength, is heat from a DHW tank the right wavelength to benefit from the foil ( got loads left over from another project, not building) so might do this myself.
    • CommentAuthorJeff B
    • CommentTimeAug 30th 2017
     
    <blockquote><cite>Posted By: yclairejenkins</cite>Thanks all.
    I've gone ahead with recycled plastic loft insulation, which is quite good for filling the awkward shapes around the pipework and the walls as it compresses and expands usefully. Because of the way I've had to bodge it into the inaccessible bits, one roll hasn't covered it, so will have to go out for another, which means it's not a particularly cheap option as it's £18 a roll. Also looks messy and won't be easy to keep clean.
    So not ideal, but hopefully will be effective.</blockquote>

    Sorry I was too late with my input into your thread. I think you would have preferred the aluminium foil thermal insulation option as it is easy to attach and has a smooth surface so ease of cleaning (should the need ever arise - I've never cleaned ours!) would be a doddle. And a lot cheaper too (8m roll from Wickes for £12).
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