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Data and monitoring: Insulating fridge sides to save energy

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    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 22nd 2011 edited
     
    After reading the thread about about buying an AAA+++ rated fridge, I decided to monitor and improve mine. Seems I have improved it by reducing the energy use by a third (32W down to 21W).
    The sheet of 40mm PU cost £21.30 for a 2440mm by 1220mm sheet, £7.16/m^2. I needed 500mm by 870mm or £3.11 worth.
    If I assume all the cooling is done at the higher rate of electricity (£0.18/kWh), then every year from now on I will save 96.36 kWh or £17.35/year.
    I have charted all this and included the room mean temperature.
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    •  
      CommentAuthorJSHarris
    • CommentTimeOct 22nd 2011 edited
     
    You can't beat a good experiment when it comes to demonstrating something!

    Having read the long thread on using an Ecocent drawing warm air from the house to run DHW and UFH, and noted that someone suggested using the cold exhaust air from the Ecocent to cool a larder, I've been seriously thinking about building a cold box around the fridge freezer, sealed from the room, with cold air from the Ecocent pumped in then exhausted outside. My guess is that this would give a double whammy, as the insulation would have a lower delta T, so lower losses and the condenser on the fridge freezer would also operate at a lower delta T, so the fridge freezer heat pump would have a higher COP.
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 22nd 2011
     
    Yes, I think experiments show much more than calculations.
    I am still pondering your tiles and waste water heat recovery. Will have more data soon about tile temperatures to see if it is worthwhile.
    •  
      CommentAuthorJSHarris
    • CommentTimeOct 22nd 2011
     
    I've added a reply on the other thread to avoid drift on this one.
  5.  
    Good idea but this thread is 2 days too late! Just ordered new kitchen units for around F/F, incl unit for bridging the F/F on top. I'll see what flex there is between.....
    • CommentAuthorseascape
    • CommentTimeOct 22nd 2011
     
    Good result - did you stick insulation on with gaffer tape?

    I am thinking of doing similar thing with my electric oven - only use once week for bread, but lots of heat leaks out from sides, and into grill area. I've got some 100mm kingspan or lambswool - just slightly worried about flammability/fumes, but it's in stone pantry and won't be using the hotplates.
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 22nd 2011
     
    No tape, just wedged it into the 80mm gap, actually the 78mm gap as I had to think it a bit in places.
    Next trick is to try a fan to force cold air onto the element.
    Not sure what temperature PU softens at, it is not very high so would be reluctant to use it around a cooker. Would imagine they get to a similar temperature as radiators, about 70 C (or as hot as you want to put your hand on bu tnot leave it there long).
    • CommentAuthorJohn B
    • CommentTimeOct 22nd 2011
     
    Does it make any difference to the amount of noise the fridge makes (or appears to make)? Making mine quieter as well as more efficient would be useful.
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 22nd 2011
     
    Not really noticed, but it was pretty quiet anyway (only 6 years old this week). If it is an under worktop one like mine I think it would help as all the 'gubbins' is at the back.
  10.  
    ST said: ''Not sure what temperature PU softens at, it is not very high so would be reluctant to use it around a cooker. Would imagine they get to a similar temperature as radiators, about 70 C (or as hot as you want to put your hand on bu tnot leave it there long). ''

    I believe some manufacturers of flat-plate SWH panels use PIR board behind the collector. If it's used in that circumstance then presumably it ought to meet the BS requirement for being good for 230C (?).
  11.  
    Seascape, I've been thinking along the lines of insulating a cooker too, after hearing about hayboxes. Another thread really, but will post it here...

    You put your food into a well insulated box, after it's been heated up to oven temperature, then the retained heat cooks the food, with no added energy input.

    I've been dreaming of an American Chambers Stove, which produced beautiful fireless cookers from the 1920s to the 1950s, or so. They insulated their cookers with three layers of rockwool. Don't think they ever came over here and a bit heavy to import! But lovely nevertheless....
    •  
      CommentAuthorCitrus
    • CommentTimeOct 23rd 2011
     
    Haybox cookers are brilliant. We had one which was a wooden chest with a load of old woolly blankets in and it worked a treat. They are much more successful the bigger and fuller the saucepan is, so not so good for smaller quantities, but still useful. When we get a new house we are building one in to the kitchen so it gets used as much as possible.

    I'd love to insulate the cooker and fridge too. Any issues with causing the oven to overheat if the sides were insulated? Thanks for the thought provoking thread, SteamyTea :)
    •  
      CommentAuthordjh
    • CommentTimeOct 24th 2011
     
    Nick Parsons wrote: "I believe some manufacturers of flat-plate SWH panels use PIR board behind the collector. If it's used in that circumstance then presumably it ought to meet the BS requirement for being good for 230C (?)."

    I think a link to a manufacturer's data sheet stating this would be more valuable than 'I believe' and 'if' and 'presumably'.

    http://www.recticelinsulation.co.uk/faq/general-what-maximum-temperature-resistance-eurothane-purpir-building-insulation
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 24th 2011
     
    That is good enough for me, though I suspect that it ages the material pretty fast at those temperatures. Has anyone 'stuck some behind a radiator' to see what happens, though it does last OK on a copper cylinder and they often used to run up to 85C.
  15.  
    DJH. Point taken. I *know* that one manufacturer used PIR at the back of their panel in 2001. I believe they still do. As they definitely did, I (still) presume.... :)
    • CommentAuthorseascape
    • CommentTimeOct 24th 2011
     
    Haybox sounds interesting - will look into for my build - thanks. Having looked at ST's boiling kettle graph (can't remember thread) I got pan of potatoes up to boil, turned off ,took off ring and wrapped in 2 oven cloths - after about 20 mins they were cooked and still warm. Looking at it as a kind of 'heat bank', as money saved will inevitably go into storage heater on economy 7 in depths of winter - still, every little helps.

    For my oven (old and cheap) experiment I've got kingspan phenolic insulation so will look up max temps - site slow today. I cook bread at 230C. Tomorrow I will see how many units it uses and temps on sides of oven. Next time I will insulate sides to see difference. I'm hoping oven gets to temp quicker - don't think I will insulate at back because there are air vents.

    Can't do my fridge - more's the pity!
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 24th 2011
     
    More to be saved from fridge as that is 'always on', but will be interesting to see what oven does all the same.
    Don't you just love simple experiments, quick, easy, cheap and definitive answers.
  18.  
    Posted By: SteamyTeaDon't you just love simple experiments, quick, easy, cheap and definitive answers.
    especially when someone else is doing the work...!

    :whorship:

    J
  19.  
    Posted By: seascapeFor my oven (old and cheap) experiment I've got kingspan phenolic insulation so will look up max temps - site slow today. I cook bread at 230C. Tomorrow I will see how many units it uses and temps on sides of oven. Next time I will insulate sides to see difference. I'm hoping oven gets to temp quicker - don't think I will insulate at back because there are air vents.


    Phenolic is much more temperature resistant than just about any other kind of insulation short of mineral/glass wool. I was enquiring about pushing a stove flue through EWI made of phenolic and there is no need for a barrier of any sort. If it's good enough next to a hot flue, I can't see it being a problem for an oven.
  20.  
    Just found out I have a 25mm gap either side of my F/F, just as well as in both the adjacent towers is an oven. I know, I know: I asked and asked and asked - "It is normal practice"; "It's OK" etc. Anyway, so what to put in the space - got some left over XPS, hence, cost nothing. Anyone really think it is worth investing money in something else over using leftover XPS?
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 24th 2011
     
    I like leftovers, can call it 'bubble and squeak' if it is a tight fit :bigsmile:
    • CommentAuthorbrig001
    • CommentTimeOct 24th 2011
     
    While insulating a fridge is a good idea, I'd be a bit wary of insulating an oven - especially from the outside. I would think that the cavity between the oven itself and the outer metal case would get hotter and overheat the cables etc. in that space. Happy to be proved wrong on this though.

    Cooling fan is a good idea, and I always wondered about insulating between the hottest bit - the element on the back, and the back of the fridge itself. Might only fit bubble wrap in there without reducing the air flow too much, but it might work.

    Brian.
  23.  
    The ovens will be inside the carcasses, the insulation will be on the outside of the carcasses - ie the insulation is the minimise the heat from the ovens getting to the F/F rather than improve the efficiency of the ovens.

    Though I will investigate what opportunities there are to insulate the ovens too....probably not much for the reasons you have stated Brian.
  24.  
    Just stumbled on to this thread. Just wanted to warn people to check the details on their fridge before doing this. Some use their sides to dump heat rather than a rear heat exchanger. Others have heaters to heat the sides to prevent condensation. Neither would be good candidates for additional side insulation.

    Off to go check mine now, kitchen refurb on the tbd list :)
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 25th 2011
     
    Yes I checked mine as my old fridge used one side at the radiative surface. Fitting a fan in the wrong place coudl easily play havoc with the self defrosting feature (uses the heat from the pump/radiator to warm the rear of fridge on the one at work, simple and clever design).
    • CommentAuthorseascape
    • CommentTimeOct 26th 2011
     
    Started my experiment with oven yesterday, without insulation. Will post details next week, but it took 15 mins to get to 230C. I could touch sides ok, but in grill space above, much too hot. I will proceed with caution as regards how much insulation - not bothered about ruining oven - more concerned about electrical fire.
  27.  
    Hi,

    Very interested in all this tinkering with the white goods.

    It does drive me nuts to see how often oven/microwave units are placed close to fridge/freezers in design by kitchen experts.

    Generally these days customers want bigger fridges / ovens, so as the insulation technology improves that is offset by a likewise increase in the internal volume, rather than improved efficiency. Customers do judge the “what to I get for my money” based on volume, and then perhaps look at the energy, rather than the other way round.

    Adding insulation to the cooker/oven is in principal a good idea but that may increase the temperature inside and around the control areas. It may be a simple thermostat dial type or a complex digital thing, either way even if working within the max temp there is a downward effect on the life. Increased operating temps always shorten lifespans.

    If you have a free standing Fridge / Freezer then adding the insulation is good but you must maintain adequate air flow ventilation to the rear or wherever the heat exchanger is. Not all these days have the old fashioned grill so it may not be apparent. If its build in you can assist the ventilation, if it’s very near units and under the counter then they can be too close and that too can impact performance. Raising it up off the floor to assist air flow might help.

    You need two things

    1) – Stop the out side heat from going in (insulation) [stop the cold coming out!]
    2) – Transport the heat from the exchanger away quickly (ventilation and some coolness)

    This has been discussed on a previous thread (old forum). The concept of the motor/compressor at the bottom is wrong as heat rises and finds its way out past the grill heat exchanger at the back, ideally it would operate as a split unit taking in air and exiting warmed air into a different space. You could do this in an old-fashioned larder with a freezer. If you have a stone larder (perhaps with some evaporation cooling) you probably wouldn’t need a fridge anyway.

    Pity the manufacturers don’t take notice of this. If you lost 50mm per side of “internal” volume, perhaps some extra cost would it sell??

    Cheers

    Mike up North
    •  
      CommentAuthorjoe90
    • CommentTimeOct 26th 2011
     
    Yes I remember that old thread, we discussed if it was best to put fridge/freezer in kitchen or larder (cold) and after reading the thread decided to put freezer in larder but move the motor/compresser through the wall into the kitchen (extend the pipes). Less loss of cold to a cold room, utilise heat within house. (might play havoc with the warranty!).
    • CommentAuthorSaint
    • CommentTimeOct 29th 2011
     
    Posted By: MarkBennett
    Posted By: seascapeFor my oven (old and cheap) experiment I've got kingspan phenolic insulation so will look up max temps - site slow today. I cook bread at 230C. Tomorrow I will see how many units it uses and temps on sides of oven. Next time I will insulate sides to see difference. I'm hoping oven gets to temp quicker - don't think I will insulate at back because there are air vents.


    Phenolic is much more temperature resistant than just about any other kind of insulation short of mineral/glass wool. I was enquiring about pushing a stove flue through EWI made of phenolic and there is no need for a barrier of any sort. If it's good enough next to a hot flue, I can't see it being a problem for an oven.


    Maximum operating temperature of phenolic is 150C. For some grades the suppliers quote even lower 120C. Not sure if there would be a catastrophic failure at 230C, it would probably go crispy possibly degrade physically but its thermal performance would be massively compromised and be ineffectual. There are many options for high temperature thermal insulation
    •  
      CommentAuthordjh
    • CommentTimeOct 31st 2011
     
    Posted By: SaintThere are many options for high temperature thermal insulation

    I guess there're some surplus space shuttle tiles available now, as one possibility :shocked:

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