Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



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.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

Buy individually or both books together. Delivery is free!


powered by Surfing Waves




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




    • CommentAuthordickster
    • CommentTimeApr 6th 2021
     
    So when we built our small well insulated house, we went for emergency only LPG underfloor heating via boiler (never used) in case of infirmity or lack of logs , but have used a 5 kW log burner since day 1. That was 10 years ago, now getting older, due to retire, if I go first, how will "her outdoors" manage?

    GSH pumps and the like were, at the time, well beyond our pocket and we didn't have a proper electricity supply, so a no-no.

    Now we are slightly more fluent in cash and have a new electricity supply, but all the heat pump stuff tends to want to heat water up in a tank for the underfloor heating. We have no space for a hot water tank, full stop, but it slowly occurred to me that an air con unit might possibly be used instead for heating in the winter months and doesn't involve hot water tanks.

    I think I'm right in thinking that aircon works the same way as an air source heat pump with a COP of around 3.5. Having studied a few you tubes on same, it looks like it might be a possibility. Our stove is never used in earnest apart from very cold times, just on gentle tick over throughout the day, so nowhere near 5 kW per hour, let's say 3.

    An aircon unit outside with an internal blower the other side of the wall in front room could be just the job.

    Could it?

    Your thoughts please, oh mighty Forum.
    • CommentAuthorowlman
    • CommentTimeApr 6th 2021
     
    The air to air, ( A2A ) air source heat pumps to which you refer are certainly capable of providing a warm interior. Modern digital inverter R32 units can exceed a COP of 3.5 and are extremely quiet in operation both inside and out. they have the added advantage of Summer cooling should you wish.
    The come in single or multiple "splits" i.e. one outdoor condenser unit and several indoor units. Although the indoor units can be individually controlled/output they obviously have to be in the same mode; either heating or cooling.
    Once internal temperature is reached they modulate and just tick over to maintain that level, - very efficient.
    The outdoor unit can be remoted from the indoor and 20 metres plus is not unusual.
    The controls are generally excellent.
    The indoor units come in various configurations not just " the wall blower" to which you refer, - the term tends to put people off BTW.
    Its possible to have ceiling cassettes, ceiling hung, ducted, low level which looks not dissimilar to a storage rad, and the wall units are many and varied.
    They are reliable and generally trouble free.
    They need to be fitted by an "F" gas qualified fitter, not as onerous as you may think.
    •  
      CommentAuthordjh
    • CommentTimeApr 6th 2021
     
    Posted By: dicksterCould it?

    FWIW, I share owlman's views though I haven't seriously thought about getting one installed just yet. So 'yes'.
    • CommentAuthorEd Davies
    • CommentTimeApr 6th 2021
     
    To back up what Owlman says, and as I've mentioned on here before, there are a number of well-insulated small houses in New England (where winters tend to be a bit more fierce than in old England) which use these mini-splits for heating. Though a single unit usually gives enough kW [Âą] to heat the house it's common to have one at each end of the house mainly to get the heat evenly spread because, as we've also discussed often, air is fairly poor at moving heat around due to its low volumetric heat capacity. Multiple units also give quicker warm up on the odd occasions that's needed and a degree of redundancy.

    I'm not clear, though, why a suitably modulating ASHP really needs a tank.

    [¹] not “per hour”.
    • CommentAuthordickster
    • CommentTimeApr 8th 2021
     
    Thanks for your confirmations.

    Ed, I try my best and understand what I mean, but I'm so wary of messing up my units in front of audience, I always seem to get it wrong!
    • CommentAuthormarkocosic
    • CommentTimeApr 17th 2021
     
    Can you?

    Yes.

    Do you want to?

    Maybe.

    What's are catches?

    Control. Airflow. Buoyancy. Noise. Fugliness.


    1) These things are designed to be "turned on" and "turned off" - they cannot sense what the indoor temperature is unless the indoor fan is running; and they have a limited range within which they can modulate and next to no thermal mass, so they do a fairly bad job of being "set at 20 and ignored" especially when the heating / cooling loads are below their minimum range.

    If you expect them to work like a fan heater (blasting at 1 bar or two) then fine. If you expect them to "chuck a bit of heat into the floor to keep it at a setpoint" whilst the mass of the floor means you the human are oblivious to when they're running then no.


    2) Airflow makes humans cold. Radiators at with indoor air at ~20C are as comfortable as underfloor with indoor air at ~18C or fan coil units at ~22C. The draughts are nice when it's hot and you want cooling. They are not so nice when you're cold and want warming.


    3) Hot air rises. if you have a bungalow then one unit is always fine. If you have a two floor house then one unit mounted in an open plan downstairs area is enough to heat the downstairs and the air going up the landing is enough to heat the bedrooms. Don't expect the bedrooms to be cooled in summer though.


    4) Noise. The indoor units are noisy. You can't have them in bedrooms. They're ok on the other side of a closed door though...as long as the unit isn't cycling on and off. If the unit is cycling on and off then it will be like a stove warming up and cooling down - click clack click clack as all the parts expand and contract with temperature.


    5) The indoor units aren't small or pretty. Unless your ceilings are high or there's stuffs on the floor anyway (sideboard / TV etc) you will sacrifice some usable floor space too.


    For chucking the odd bit of heat and odd bit of cooling into a home that holds temperature for a long time I think they're fine.



    Datasheet for the one I bought:

    https://www.saturnsales.co.uk/images/products/editor/CS-Z_Range.pdf


    The COP in heating mode in the shoulder season is good.

    e.g. 3.5 kW unit gives 0.8 to 5.8 kW of heat when it's 7C out with a COP of 3.9 to 4.4

    It must still be over 2 by the time you drop to -10C if the output is 3.2 kW and max power input is 1.5 kW. Probably more in practice as I don't think the compressor can run at full chat when it's that cold out.



    The Mitsi units perform better in the smaller sizes on paper and are pre-charged for pipe runs of up to 15 metres vs the 7.5 metres of the Pansaonic units:

    https://www.saturnsales.co.uk/images/products/editor/SRKZSX-W.pdf



    Strictly speaking these need to be fitted by an F-Gas person. Only they can make some flares, pressure test the lines, vacuum out the lines, then open up the valves on the outdoor unit. Good luck finding one that'll get out of bed for less than the price of the unit though.

    If you can make brake lines you can make the flares. A fridge compressor and a set of automotive A/C gauges let you clean the air and moisture from the pipework.


    Alternatively there el cheapo (and lower performance) hydrocarbon filled units available that don't need to be fitted by an F-Gas person. e.g.

    https://www.appliancesdirect.co.uk/p/eiq-9wminv/electriq-eiq9wminv-air-conditioner

    These come with fixed length pre-flared lines etc that almost any numpty can work with. Probably won't last as long and will use more electricity but if they're only for occasional use in a build that doesn't us much energy...
    • CommentAuthorcjard
    • CommentTimeApr 19th 2021 edited
     
    > all the heat pump stuff tends to want to heat water up in a tank for the underfloor heating

    I didn't understand this part - my ASHP has a motorised valve that flicks between DHW and UFH - in DHW mode the ASHP heats a 300 litre tank to 50 degrees. In UFH mode, the ASHP provides 26 degree water to the underfloor. The 300 litre tank is DHW only and never takes any part in heating the floor

    There's a buffer tank in the UFH circuit, but that's 10 litres and about the size of two 5 litre petrol cans (curiously enough!). I don't believe it's even necessary - we don't have any shut off valves on the UFH circuits so the ASHP is never short circuited for water but even if it was, it'd just turn off thinking the UFH had reached the target temperature. If you think about it, the entirety of the UFH can be a tank; there's a volume of fluid in the pipes, but the "tank" the ASHP has to heat is actually the volume of the screed too, because you're tasking the pump with "heat this 4000 litres of concrete using this X litres of circulating fluid". Just because the screed and the fluid don't mix, doesn't mean that it's not a "volume to be heated"
    • CommentAuthortony
    • CommentTimeApr 19th 2021
     
    Air to air heat pumps heat or cool air directly will always work so long as correctly sized
  1.  
    Our A-W ASHP was supposed to be connected to a buffer tank (iirc at least 30 litres) as a heat store for defrost cycles.

    The installer didn't bother as the un-valved volume of the CH circuit was greater than that and I can't say we ever missed having it.

    In our next house I'm interested in A-A heatpumps but am not yet convinced that they will be quiet enough for bedrooms. I would like to get one with a big indoor refrigerant radiator, rather than a small coil with a fan blowing over it. Or even an underfloor refrigerant pipe coil. Still looking for those...

    A-A units and many A-W units are primarily designed for cooling. I could be wrong but I think that one designed specifically for heating would be more efficient, by using a different refrigerant with lower boiling temperature/pressure.
    • CommentAuthorEd Davies
    • CommentTimeApr 19th 2021
     
    Good videos about heat pumps, biased a bit towards ground-source HPs because he's in the US upper mid west where winters are a bit chillier but if you take that into account…

    https://www.youtube.com/watch?v=7J52mDjZzto
    https://www.youtube.com/watch?v=7zrx-b2sLUs
    •  
      CommentAuthordjh
    • CommentTimeApr 19th 2021
     
    Posted By: WillInAberdeenI would like to get one with a big indoor refrigerant radiator, rather than a small coil with a fan blowing over it. Or even an underfloor refrigerant pipe coil. Still looking for those...

    I think the difficulty is twofold. Partly that a passive radiator is a lot less effective than a fan-powered one, but also and perhaps moreso that the quantity of refrigerant allowed in a building is regulated, and regular inspections are mandated. (according to e.g. https://www.gdhv.co.uk/why-pick-chilled-water-fan-coil-system-over-refrigerant-based-system ) So heated/chilled water systems are a lot simpler to install and manage.
  2.  
    I think those are fairly overcome-able. The heat transfer of a radiator is improved by having condensation happening inside it (latent rather than sensible heat transfer) but indeed a UFH could run cooler. An A-A system already has a big advantage of not needing to be hotter than the CH water (to transfer heat into it) and not needing a deltaT in the radiators (latent heat again) so could comfortably run at 50+ degC, same as air-conditioning does in countries where ambient gets to 40+ degC.

    The risk of refrigerant inside a building depends what refrigerant is used, and how likely it is to escape. Newer heat pumps are starting to use CO2 refrigerant (like in a CO2 fire extinguisher, which doesn't seem too dangerous). Others use HFCs, which is not conceptually worse than parking a 1-tonne LPG tank outside the house and connecting it up to the hob and lounge stove with a piece of pipe. You just install the pipe per regulation design with strong joints and pressure-test them, and perhaps add a bad smell to detect leakage.

    edit:R410 is actually not flammable and R32 is only mildly flammable as it is difficult to ignite. Refrigerant pipework is smaller and holds less system volume than water CH (low flow rate, latent heat again). But indeed an UFH design would be better as the refrigerant pipework would be protected under the floor from ever getting bashed.

    I think the third difficulty is that refrigerant radiators or UFH are not used for cooling (due to damp condensation) so the market is very small. As I mentioned, most A-A units are just bogstandard cooling air conditioners, for which there is a huge worldwide market.

    Edit: the link seems to be somebody selling chilled water systems - maybe relevant to offices not houses? Never heard of any 'regular inspection being mandated' for a household A-A heatpump or aircon.
  3.  
    After some searching, I can't find any actual limits on the quantity of refrigerant allowed in a house, other than some about global warming potential.

    Do you have a proper link to any real regulation or limit?
    • CommentAuthorEd Davies
    • CommentTimeApr 20th 2021
     
    Posted By: WillInAberdeenThe heat transfer of a radiator is improved by having condensation happening inside it (latent rather than sensible heat transfer)…
    Why does what's happening inside the radiator make any difference to the transfer of heat outside it by conduction/convection and radiation?
    • CommentAuthorLF
    • CommentTimeApr 20th 2021
     
    Would HVHR spread the heat around the house gently enough to have a few heating units centrally. Our bedroom does not have a radiator these days and it is OK. In a morning we open the door and it heats up again.

    The mass market is for split units, the sort you see in hotel rooms. With fans and filters in them.Presumably this also makes amount of refrigerant lower than passive exchangers?

    Picked a random one and found it used propane as it only has Global Warming Potential of 3
    Nice and flammable so gives a feel for what we are handling.

    If you were to risk assess it then is there enough to create low oxygen levels ? Does not look an issue though.
    3.5 kW heating unit using propane has 290g of propane. 0.16 m3 at 1.8 kg/m3.
    This gives 0.7 % propane in a 24 m3 bedroom with no air changes when fully dispersed all coming out in one go. This would struggle to ignite as 2% is lower limit.

    It is about 1/2 a litre of propane liquid, which would be cold.

    In reality if you had a leak it would sit as a liquid or cold fog at low level till it was heated enough to mix in the room. Area around the pool would be dangerous till it disperses.

    All above is an instant leak, most likely very slow and not noticeable.

    Data from manual on here

    https://www.aircondirect.co.uk/Files/pdf/eIQ-9_12WMINV_R290%20Split%20user%2020200426.pdf
  4.  
    My granny had a 1-tonne LPG tank piped to her 1960s coal-effect lounge gas-fire. If the pipe had leaked, eventually all the propane would all have leaked into her bungalow and might have got ignited.

    Being that way inclined, she calculated the blast radius and deflagrative debris projection for that scenario. She told me it would have been impressive, but she had blown up much bigger things in her career and wasn't very concerned. Plenty of her friends at the gardening club had the same setup and the incidence of leaks was very low. The narcotic effect was more interesting. :bigsmile:
  5.  
    Posted By: Ed DaviesWhy does what's happening inside the radiator make any difference to the transfer of heat outside it by conduction/convection and radiation?


    It doesn't. But the heat transfer depends on the total resistance (the inside plus the outside). For a water radiator it's convective on the inside and convective/radiative on the outside.

    If you could improve the heat transfer on the inside (by condensing instead of convecting), you'd need a lot less area/volume of channels filled with fluid, but you'd still need most of the same area of fins to transfer the heat into the air.

    'Most of' because a CH water radiator is hot at the top and colder at the bottom, because the fluid has to give out sensible heat ('deltaT'), so the average temperature of the radiator surface is lower than what leaves the boiler, and the radiator is oversized to allow for this. The pipes are big, eg 15/22mm, to supply a large volume of CH water to minimise the deltaT. Not so for a aircon unit where there's little sensible heat or deltaT and the pipes are much thinner, eg 1/4" is enough for multi kW.

    A passive A-A refrigerant radiator would look more like the one on the back of a fridge, rather than like a water CH radiator.
    • CommentAuthordickster
    • CommentTimeApr 20th 2021
     
    All this information is most useful. My gradually evolving concern, (as it is to provide heating, not cooling) was that at say -10C outside I would be using more energy to heat the house than getting out of the unit. Effectively a negative COP (I think). However the data sheets posted optimistically suggest otherwise.

    A new project is on the cards, methinks.
  6.  
    Dickster, you want the SPF or SCOP rather than the CoP.
    The CoP is averaged over the whole heating season to give the SCOP, which accounts for the cold days you mentioned and also the milder days in autumn/spring, the SCOP should be on the datasheet.

    For an A-W heatpump, in milder months you can probably run your radiators cooler (weather compensation), which further improves efficiency, this is factored into the SPF for your particular house. I don't know if anyone does that for A-A.
    • CommentAuthorowlman
    • CommentTimeApr 20th 2021
     
    @ dickster,
    Richard where do you live? How many -10C days do you get each year.
    • CommentAuthordickster
    • CommentTimeApr 20th 2021
     
    I've got a bit more googling to do, it seems, thanks.

    Owlman, New Forest, bitter memories of starting build in -14C. Obviously not that cold and very infrequent, maybe -5 a few times these last few winters, but best to think of worst case scenarios and work backwards, I'm possibly a pessimistic optimist.
  7.  
    Posted By: dicksterAll this information is most useful. My gradually evolving concern, (as it is to provide heating, not cooling) was that at say -10C outside I would be using more energy to heat the house than getting out of the unit. Effectively a negative COP (I think). However the data sheets posted optimistically suggest otherwise.


    It's impossible to have a negative COP - air at -10C still contains extractable heat and air-to-air heatpumps are very common in Canada and can still pull heat out of the air down to below -20C. The problem with low temperatures is the capacity decreases, which is a shame as the heat load increases as the temperature falls. Eventually you reach a point where the unit cannot supply enough heat, even if the COP is still > 1.0.

    Paul in Montreal.
    • CommentAuthorLF
    • CommentTimeApr 20th 2021 edited
     
    Posted By: WillInAberdeenMy granny had a 1-tonne LPG tank piped to her 1960s coal-effect lounge gas-fire. If the pipe had leaked, eventually all the propane would all have leaked into her bungalow and might have got ignited.

    Should have overflow protection for a line break

    Being that way inclined, she calculated the blast radius and deflagrative debris projection for that scenario. She told me it would have been impressive, but she had blown up much bigger things in her career and wasn't very concerned. Plenty of her friends at the gardening club had the same setup and the incidence of leaks was very low. The narcotic effect was more interesting.http:///newforum/extensions/Vanillacons/smilies/standard/bigsmile.gif" alt=":bigsmile:" title=":bigsmile:" >



    An inspirational character ... Propane is a solvent ! - never thought of "those" type of effects.
    Line break protection that shuts off or limits flow is typical on propane tanks I think.:shocked::shocked:
    • CommentAuthorRobL
    • CommentTimeApr 26th 2021
     
    Continuing on the R290 chat....

    Vaillant's Arotherm plus monoblock ashp is propane R290 based, the smaller 3.5 & 5kW models using 0.6kg of propane. The install manual says that the unit should be placed 1m away from drains:

    "When placing the unit you must be aware of drains and openings. In the unlikely event of a refrigerant leak the gas needs to be allowed to disperse to stop the risk of the gas igniting"

    Is this really necessary? I note that you're allowed to have a 1kg charge R290 heatpump indoors. How can an outdoor drain be that important in comparison?

    Can you tell I have a drain in the wrong place?
  8.  
    Posted By: RobLThe install manual says that the unit should be placed 1m away from drains:

    "When placing the unit you must be aware of drains and openings. In the unlikely event of a refrigerant leak the gas needs to be allowed to disperse to stop the risk of the gas igniting"

    Is this really necessary? I note that you're allowed to have a 1kg charge R290 heatpump indoors. How can an outdoor drain be that important in comparison?

    Propane is heavier than air. The requirement to have the unit away from drains is so that in the event of a leak the gas won't sink down the drain and create an explosion risk in the drain network.
    •  
      CommentAuthordjh
    • CommentTimeApr 26th 2021
     
    Posted By: Peter_in_HungaryPropane is heavier than air. The requirement to have the unit away from drains is so that in the event of a leak the gas won't sink down the drain and create an explosion risk in the drain network.

    Indeed. That's why there's a lot of emphasis on gas leaks on boats. The gas fills the boat and can rapidly reach dangerous concentrations. Apparently, you can bail the stuff overboard using a bucket just as you would with water. :bigsmile:
  9.  
    "Code of Guidance for the Storage of Full and Empty LPG
    Cylinders and Cartridges”

    This is aimed at the big red propane cylinders, 19 or 47kg. Minimum 2 metres from a drain, *unless the drain has a water seal* which can stop propane vapour sinking into it and passing through the drainpipe to somewhere unexpected. Does yours?

    Are you installing the vailant yourself? Interested how you find it, looks like a high CoP unit even at radiator temperature.
  10.  
    Posted By: djhThe gas fills the boat and can rapidly reach dangerous concentrations. Apparently, you can bail the stuff overboard using a bucket just as you would with water.

    This is exactly what I was taught during my time in the GPO (telephones). You did a gas test before entering a manhole and if it showed positive you bailed it out with a bucket taking the bucket some meters away from the manhole and then emptied it. We were warned that this would generate comments from passers by who probably would not understand why 'empty' buckets were being emptied.
    • CommentAuthorJeff B
    • CommentTimeApr 28th 2021
     
    Posted By: Peter_in_Hungary
    Posted By: djhThe gas fills the boat and can rapidly reach dangerous concentrations. Apparently, you can bail the stuff overboard using a bucket just as you would with water.

    This is exactly what I was taught during my time in the GPO (telephones). You did a gas test before entering a manhole and if it showed positive you bailed it out with a bucket taking the bucket some meters away from the manhole and then emptied it. We were warned that this would generate comments from passers by who probably would not understand why 'empty' buckets were being emptied.


    Sounds like a sketch from "Monty Python" (for those of a certain age who remember them!).
    •  
      CommentAuthordjh
    • CommentTimeApr 28th 2021
     
    Yes, it's the sort of thing that you wonder about when being taught. A bit like being asked to go ask for a 'long weight' from stores.
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press