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General: R4 - NIBE investigation....?

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    • CommentAuthorDarylP
    • CommentTimeSep 10th 2012
     
    ... NIBE systems not performing properly....?:confused:
    • CommentAuthorDarylP
    • CommentTimeSep 10th 2012
     
    .... not sized properly it seems?... 'not well' insulated British homes are not suitable for these pumps:cry::cry:
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 10th 2012
     
    Leaky houses as well.
    Seems to be lack of understanding on how the system works and should be run.
    Is this a sales issue or a technical/educational one?

    Have none of us got anything better to do than listen to the radio all day :bigsmile:
    •  
      CommentAuthorfostertom
    • CommentTimeSep 10th 2012
     
    Wot's NIBE? - puleeze!
    • CommentAuthorDarylP
    • CommentTimeSep 10th 2012
     
    A bit like the Seven Dwarves, but not quite, I listen while I work.... :bigsmile::bigsmile:

    NIBE - Swedish producer of exhaust air - water heat pumps amongst other things.

    The upshot of the article is that they work if specified correctly, in a well insulated-to-spec dwelling.
    They don't work well in a spec built UK standard developer box, it seems :confused:

    At least the concept of well-insulated homes got mentioned! :wink:
  6.  
    • CommentAuthorRobinB
    • CommentTimeSep 10th 2012
     
    two threads running on this now -

    listening while I work of course - but sitting here typing this? Not really working now am I?
    • CommentAuthorwavy
    • CommentTimeSep 10th 2012
     
    I've seen these installed in a Social housing scheme. The ones I saw had open (as in you could see daylight through 'em) inlets into the habitable rooms. It seems to me that they rely on large fresh air movements through the dwelling in order to get access to enough low grade heat for the heat pump in very cold conditions(The collector is situated in an exhaust duct)
    Using air from the dwelling does give preheating and possibly solves heat pump icing problems but the downside is large air movements and draughts. If the air movements are limited the system appears to switch over to all-electric.
    Not sure about the detailed physics but I am skeptical!
    • CommentAuthorDarylP
    • CommentTimeSep 10th 2012
     
    ... the PR guy from NIBE sort of alluded to that without saying it outright, if the system is not sized correctly for the property, it will revert to grid electricity as the pump cannot provide enough energy.

    Perhaps the problems were down to the building fabric not being as was envisaged when the systems were first specified?

    I hope the true facts are eventually laid bare, but I am not holding my breath........:confused:
    • CommentAuthorRobinB
    • CommentTimeSep 10th 2012
     
    (copied from other thread)

    It seems that because the unit was undersized* the immersion, supplied to allow the occasional top-up in extremely cold weather, was doing most of the work and negating any benefit of the heat pump.

    *undersized not necessarily for the building per se, but for the way the heating system was used by the occupants. Also seems as if the insulation levels in the buildings may have been overestimated - meaning the system couldn't cope.

    The piece also said housing associations are "ripping them out" even though only a few months old. There may be bargains to be had.

    Sad story really and I don't know who is responsible.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 10th 2012
     
    Posted By: RobinBSad story really and I don't know who is responsible.

    Maybe
    Posted By: SteamyTeaIs this a sales issue or a technical/educational one?
    • CommentAuthorqeipl
    • CommentTimeSep 11th 2012
     
    A friend of mine who's in her 70s had a NIBE Fighter 200 fitted by the housing association. Her electricity bills rocketed.
    The NIBE website says it is designed for small flats and houses with a heating demands of up to 4kW.
    It has a 550W heat pump and a 3kW immersion heater.
    When it was installed Chrissie refused to have the open fire closed off.
    The 1990s build of her house and the open flue means that the heat demand is probably much greater than 4kW.
    I suspect the 550W heat pump is unable to cope with the demand so the 3kW immersion takes up the slack, hence the big bills.
    A case of poor specification coupled with poor installation and poor education, I think.
    Chrissie uses it for DHW only and burns coal on her fire.

    I have an Ecocent, which is a similar machine, drawing air from inside the house like the NIBE.
    It has an 800W heat pump and a 1kW immersion heater that only kicks in for periodic bug killing.
    My house is relatively new and well insulated.
    The heat pump is very economical and I have never been aware of draughts.
    The concept works fine but only when the house is built for it and the equipment is of a suitable size.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 11th 2012 edited
     
    Does seem that one bad report can kill a technology, shame as using waste air/heat is a sensible thing to do.
    I used to work near a factory that made large wood working machinery that had several very large orders from Barrats, there was a TV program about how useless their timber frame houses were and that killed the company next door. Though having worked with builders, I am appalled at the attitude to 'doing a good job'.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 11th 2012
     
    Does anyone know/have a link, to the program about it?
    • CommentAuthorseascape
    • CommentTimeSep 11th 2012
     
    It's called Rip Off Britain on BBC 1 I think - Angela Rippon is the main presenter.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 11th 2012 edited
     
    OK, thanks, shall see if I can watch it now, got to be better than Woman's Hour

    What a rubbish report, can see why I got rid of my TV nearly 20 years ago. Just seemed to blame the heating system, and that 'independent heating engineer' said very little 'they work best in well insulated homes'. well all systems do. Really makes me mad that sort of biased reporting. Why don't they do a program about how things should be done and work, oh I know, it would be boring.
    • CommentAuthorEd Davies
    • CommentTimeSep 11th 2012
     
    It'd be interesting to see the results of a blower door test on those houses.

    Also, it'd be interesting to have some idea of the usage profile. I can easily imagine people turning the things off for much of the day in the belief that'll save money when all it really does is force the system to use the immersion.

    But getting that sort of thing covered on television is probably pretty hopeless.
    • CommentAuthorwavy
    • CommentTimeSep 12th 2012
     
    These systems rely on 'leakiness'
    You can see all the open vents on the drawing here:
    http://www.nibe.co.uk/Home-Owner/NIBE-Heat-Pumps/Exhaust-air-heat-pumps/Exhaust-Air-Heat-Pump-Function/
    It appears that you can either have a howling gale through the dwelling (much more vent than is required for health) in order to feed enough energy to the heatpump or restrict the airflow and have it switch over to electric heating!
    • CommentAuthorwavy
    • CommentTimeSep 12th 2012
     
    Any comments on the energy balance from the scientists out there?
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 12th 2012 edited
     
    Would the 'howling gale' be a crude summer bypass?

    Wavy
    When you say 'energy balance' do you mean the COP of the unit or something else?
    • CommentAuthorEd Davies
    • CommentTimeSep 12th 2012
     
    Posted By: qeiplIt has a 550W heat pump

    Is that 550 W electrical input or is it thermal output? I'd assume electrical input but it's as well to be clear.
    • CommentAuthorwavy
    • CommentTimeSep 12th 2012
     
    Its not a bypass. The untempered air comes straight into the rooms summer & winter.
    The drawing shows open vents into the rooms from outside bringing in fresh air. This mixes with the warm air in the dwelling and is then sucked out via the heat pump. This tallies with what I saw on site.
    The bit that concerns me is that the ventilation rate is being set by the needs of the heat pump (which is doing the space and water heating) rather than by the occupants requirements for health.
    It should be possible to calculate the maximum output of the heat pump when the ventilation rate is at a minimum reasonable level (knowing the COP, specific heat capacity of air, outside & inside temperature etc). My suspicion is that the output would be very small and that the ventilation rate would need to be increased dramatically (the 'howling gale') to get enough heat output.
    HTMS
    • CommentAuthorqeipl
    • CommentTimeSep 12th 2012
     
    Posted By: Ed Davies
    Posted By: qeiplIt has a 550W heat pump

    Is that 550 W electrical input or is it thermal output? I'd assume electrical input but it's as well to be clear.


    Electrical input, as far as I understand.
    • CommentAuthorqeipl
    • CommentTimeSep 12th 2012
     
    Posted By: wavy
    It appears that you can either have a howling gale through the dwelling (much more vent than is required for health) in order to feed enough energy to the heatpump or restrict the airflow and have it switch over to electric heating!


    I worried about the howling gale when designing my system and decided that the air supply had to come in at floor level via a longish pipe with a few bends in it.

    It works. I have a 300mm dia intake that splits into three to feed the the bedrooms.
    Never a problem with draughts even when the heat pump is pulling 450m^3/hour through the building.
    • CommentAuthorwavy
    • CommentTimeSep 13th 2012
     
    If you look at the NIBE drawing they show throught the wall vents at high level. The occupants of the house are sitting in the cold air stream on its way to the heatpump!
    So extra heat is required to counteract the draught.
    The dwellings I saw had this arrangement and I'm pretty sure they weren't design to take advantage of passive solar gain.
    Referring to comments on the other thread ('...cautionary tale') It is very difficult to get the tenant occupants of the houses in the report which caused this thread to understand an unfamiliar system and change their lifestyle. (Hope that didn't sound condescending)
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 13th 2012
     
    I agree that getting people to change ingrained ideas is difficult, probably why there are still MAC computer buyers.
    Posted By: wavy(Hope that didn't sound condescending)
    :bigsmile:
    • CommentAuthordjh
    • CommentTimeSep 13th 2012
     
    Posted By: wavyIf you look at the NIBE drawing they show throught the wall vents at high level. The occupants of the house are sitting in the cold air stream on its way to the heatpump!

    I believe this to be true even for MVHR inputs. Even though heat is recovered, the incoming air is still cooler than the air in the room, due to < 100% heat exchanger efficiency. The people at Hockerton warned me against having air inlets directed over anywhere people might be sitting. Unless you have a preheater ('heat battery') in the ventilation system.

    Low level inputs in bedrooms is an interesting idea. Are there any drawbacks?
    • CommentAuthorqeipl
    • CommentTimeSep 13th 2012 edited
     
    Posted By: djh
    Low level inputs in bedrooms is an interesting idea. Are there any drawbacks?


    None that have become apparent over two years of living with them.

    There are high level vents going from the bedrooms to the shower rooms.
    The heat pump sucks air from the shower rooms when occupied or when the humidity is high.
    So you might think there would be a draught across the bedroom but when the heat pump is running, if you hold your hand over the vent you can just feel the air movement but I've never noticed it chilly on the ankles or felt that there's a draught in the room.
    • CommentAuthorwavy
    • CommentTimeSep 14th 2012
     
    This is worth a look if you are following this thread (or the parallel one):
    http://www.aecb.net/forum/index.php/topic,2801.0.html
    (I assume its OK to post links to other forums)
    What is clear to me is that EAHP needs to be part of an integrated system and is definitely not just a 'bolt-on' or (worse) a simple replacement for a heating system!
    I still can't quite get my head around the physics.
    • CommentAuthorwavy
    • CommentTimeSep 14th 2012
     
    Just re-read the above link. If I understand correctly the maximum an EAHP can do is recover all the energy from the air passing through the dwelling and use that to keep the dwelling warm (i.e: reduce the ventilation losses to zero)
    If you want more energy (for water heating or to counteract fabric losses) the extra air (containing energy) has to come from somewhere else.
    Does that make sense?

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