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  • FIRST POST
    • richardc1983
    • By richardc1983 4th Feb 09, 2:03 AM
    • 1,889Posts
    • 1,006Thanks
    richardc1983
    Air to Air Heat Pumps/Air Con - Full Info & Guide
    • #1
    • 4th Feb 09, 2:03 AM
    Air to Air Heat Pumps/Air Con - Full Info & Guide 4th Feb 09 at 2:03 AM
    With all the posts ongoing here regarding heat pumps etc I have decided to start a new post I have put together with information on reverse cycle air conditioning (heat pumps), where people can ask questions, chat about heat pumps, discuss experiences, installs, electricity usage & anything else heat pumps related.
    Theres a lot of info here to take in, please do read it all as this may just


    How does it work?

    It's actually quite simple. Air conditioners work in much the same way as your refrigerator except there are two separate, but integral, parts to the system. There is an outside unit housing the compressor that is similar to the exterior back of your fridge. It draws warmth from the outside air in even the coldest of weather. That warmth is then transferred inside the home using a refrigerant process through a piping system powered by an indoor fan unit that is typically mounted to the wall. This is why the system is also often referred to as a heat pump rather then air conditioning. Both are in fact the same. Similarly, in summer, the reverse happens. Warm air is drawn from the interior room and expelled by the outside unit.

    Heat Pumps are capable of transferring up to 4kW of heat into a space while only consuming 1kW of electrical energy. The energy efficiency of a heat pump will decreases as the temperature difference between inside and outside becomes greater, even at low temperatures a heat pump can provide 3 times as much heat as a normal electric space heater would provide with the same amount of electricity input. This makes Heat pumps extremely energy efficient.

    "Not all Heat Pumps are designed to continue working where temperatures fall below freezing point"

    The principle of air conditioning always comes down to the same:

    absorb energy in one place and release it in another place

    The process requires an indoor unit, an outdoor unit and copper piping to connect both. Through the piping the refrigerant flows from one unit to another. It is the refrigerant that absorbs the energy in one unit and releases it in the other.
    Cooling mode (Heating mode is the same but in reverse)

    1 Indoor unit
    A fan blows the hot indoor air over a heat exchanging coil through which cold refrigerant flows. The cold refrigerant absorbs the heat from the air and cooled air is blown into the room.
    2 Copper piping
    The refrigerant circulates through the units and the piping and takes the heat from the indoor unit to the outdoor unit.
    3 Outdoor unit
    Through compression, the refrigerant gas is heated and its boiling point increases. In the outdoor unit the obtained heat throught compression is released to the outdoor air by means of a fan which blows the outdoor air over a heat exchanging coil.
    4 Refrigerant
    The liquid refrigerant flows back to the indoor unit.
    5 Indoor unit
    Back in the indoor unit, the refrigerant is decompressed and thus enabled to extract heat form the indoor air.



    Comparison of 2400w fan heater & Heat Pump Running Costs:

    http://www.bdt.co.nz/comfortmaster/data/guides/WinterRunningCostsComparison.pdf - this is for Mitsubishi Electric but savings made on other manufacters however these will vary.

    Inverter Technology:

    Here's some info about inverters, the same applies across all manufacturers however efficiency levels are different but the operation side of things is the same. There is an article at the bottom from Mitsubishi Electric where they have done a comparison test for a fan heater and heat pump. This is not unique to Mitsubishi Electric, similar costs will be seen across all heat pumps... its a very efficient technology. Different manufacturers will have different efficiencies. The best manufacturers are Mitsubishi Electric, Daikin, Mitsubishi Heavy Industries, Fujitsu, Sanyo, LG, any other manufactures are entry level and will not offer as good quality systems or efficiencies.

    Inverter systems save energy by using a variable controlled Compressor. The output is controlled to only provide the energy required to keep the room to the set temperature. By reducing the output required less power is used and this substantially reduces power consumption. Inverter control not only saves you money but also keeps you more comfortable.


    Inverter System or Fixed Speed System?

    What is a Fixed Speed Split System?

    This system only has a single speed compressor motor that is either on or off.

    It works similar to a fan heater that switches off when the desired temperature is reached and on again when the temperature drops to a set level. It speeds up or slows down to calculate the heat loss from the space to be heated ensuring it is only putting in the same amount of heat that the space is losing.

    What does Inverter Mean?

    Inverter technology uses a variable speed compressor motor similar to a car. It simply slows down and speeds up as needed to hold a selected comfort setting.

    Inverter technology provides a more precise room temperature without the temperature fluctuations of fixed speed systems.

    Inverter vs Fixed Speed:

    Inverter Systems are Approximately 30% more efficient than fixed speed systems.

    Inverter systems reach desired room temperature quicker.

    The speed control of the outdoor unit also means quieter operation, this is important especially at night in residential areas.









    Inverter Systems
    • Increased output to achieve set temperature faster.
    • Then varies the output to maintain a constant room temperature.








    Fixed Speed Type
    • Slowly gets to temperature as output rating is fixed.
    • Then turns on and off to maintain room temperature.
    Sizing of units:

    Read the following guide for sizing info: Excuse the references to Australia and New Zealand this contains useful info:

    http://www.bdt.co.nz/comfortmaster/data/guides/heatpump_sizing_quideline.pdf


    What type of unit is best suited for your property:

    Heat Pumps / Air Conditioners are manufactured with various indoor unit options. High Wall Type, Ceiling Cassette Type, Floor Mounted Type, Concealed Ducted Type, and Under Ceiling Type.


    High Wall-mounted

    The most popular residential unit choice. These units tend to be the quietest as well as taking up no floor space.

    Compact Floor Console

    The floor mounted are more designed for heating applications. They are ideal for space heater or gas fire/fireplace replacement. They can be recess mounted into the wall cavity giving a shallow profile for hallway installation.

    Ceiling Cassette

    The ceiling mounted units take up no floor space. These units have four way air direction and have adjustable air flow patterns. These units are more suited to larger floor areas & commercial properties.

    Ceiling Concealed (Ducted)

    These units are mounted in the ceiling space and are unseen in the conditioned space. The only visible presence is the supply and return air grilles.

    Ceiling Suspended

    These units are more suited to high stud large room areas. They tend to have high airflows and are more suited to commercial applications.

    Multi-Split Systems








    Multiple Indoor Units can be Connected to a Single Outdoor
    • Connect from 2 to 8 Indoor Units
    • Many Combination Patterns to choose
    • Energy Saving and Quiet Operation
    • Five Multi-Split Systems from 6.4kW to 16.0kW (Heating)
    Inverter Multi-Split system models are designed to allow several indoor units (regardless of capacity or type) to be connected to a single outdoor unit. This allows you to select the model best suited to each and every room in your property.


    Example: 3x Bedrooms and 1x Office

    ~


    Location of units:

    Indoors:

    Don’t locate units with obstructions in front.

    Result:


    Short cycling of air back to units room sensor making the unit think its wamer/cooler than it actually is.
    Air is not circulated correctly leaving cold/hot areas in room.

    Try to locate the indoor unit where the airflow is pointing to the other areas of the house that may require residual heating/cooling.

    Outdoors:

    Avoid paved areas unless a drain kit is fitted. Result: Units condensate and drip water. May cause slime build up or ice. If no other place please advise customer.

    Noise:
    Outdoor inverter units are very quiet and have scroll compressors, watch the following video and you will see mine in action:
    http://www.youtube.com/watch?v=-mUzYHEfQEY


    Defrost Cycles & Correct Sizing of Outdoor Unit:
    Defrost will happen in all climates, however the lower the humidity the less frequent it will defrost as it takes longer for it to build up on the outdoor coil.

    You will probably not even notice it defrosting, if you buy a decent brand system you will find that the defrost strategy is very good so that it doesn’t take long to defrost.

    When they defrost you will find that the system goes into reverse, taking heat from the inside circuit to the outdoor unit so it defrosts. This will last about 5 minutes depending on how much ice has built up but you have to look at the unit to notice it doing it as it doesn’t start making things cold inside. The unit just doesn’t heat during that time.

    Some units in New Zealand or other countries that have very cold winters have units optimised for that country, i.e. defrost cycles instead of stopping and going into reverse will inject hot gas into the outdoor unit whilst the unit is heating so that it doesn’t actually stop heating. Currently can only find info on Sanyo air to air heat pumps in this country that do this... not sure of a system that does this on a unit that will provide this on hot water but you can see the technology is there. As I say you don’t need it in the UK climate our winters are not as harsh as some countries.

    The best method for new builds is under floor heating, nice even temps throughout, however longer warm up times due to the lower water temperature but if left on during cold weather you will be fine.

    I personally prefer fan coil units as these double up as cooling/ac for the summer and provide very fast warm up times.

    Most air to water outdoor units can be used with fan coil units... you just use a fan coil instead of a water coil in the floor.

    Mounting of unit... must be installed in the open, no enclosure, so no garages, lofts or corners the unit must be in the open air.

    A user in another post:

    http://forums.moneysavingexpert.com/showthread.html?p=29040015#post29040015

    He installed it in the loft and it froze the loft in the cold weather and thawed and caused leaks into the house below, this happened twice and after this he decided to mount the unit outside and it performed better as it was effectively turning the loft into a giant fridge/freezer.

    Here’s some more info on heat pumps:



    Defrost Strategy

    When the outside temperature drops below zero all heat pumps must perform a “defrost cycle” to remove ice build up on their outdoor coils.

    Defrost strategy is determined by individual Heat Pump manufacturers. These strategies vary greatly between brands. Older style Heat Pumps initiated defrost by a fixed time or coil temperature. This system was not efficient as it often caused Heat Pumps to defrost too often or effected performance by not defrosting often enough. Defrost cycle is required when the outdoor coil is too cold or covered in ice preventing heat transfer and unit performance.

    All Heat Pumps must defrost. heats pumps utilise a Fuzzy Logic software program, a form of Artificial Intelligence contained in the chip of the outdoor unit and typically lasts between 3 to 5 minutes.

    The program measures and records:

    - Ambient Temperature
    - Outdoor Coil Temperature
    - Accumulated Continuous Heating Running Times
    - Defrost Initiation Time and Termination Times

    The program optimises this data based on history to produce defrost initiation only when absolutely required.

    This is important as Heat Pumps are unable to produce heat when they are in defrost mode. This is extremely important to real performance in low ambient conditions.

    Defrost Cycle Management

    Heat Pumps optimise its defrost cycle once selected in three ways:
    When the outside temperature drops below zero all heat pumps must perform a “defrost cycle” to remove ice build up on their outdoor coils.

    Defrost strategy is determined by individual Heat Pump manufacturers. These strategies vary greatly between brands. Older style Heat Pumps initiated defrost by a fixed time or coil temperature. This system was not efficient as it often caused Heat Pumps to defrost too often or effected performance by not defrosting often enough. Defrost cycle is required when the outdoor coil is too cold or covered in ice preventing heat transfer and unit performance.

    The program measures and records:

    - Ambient Temperature
    - Outdoor Coil Temperature
    - Accumulated Continuous Heating Running Times
    - Defrost Initiation Time and Termination Times

    The program optimises this data based on history to produce defrost initiation only when absolutely required.

    This is important as Heat Pumps are unable to produce heat when they are in defrost mode. This is extremely important to real performance in low ambient conditions.



    1. Compressor Control
    When a Heat Pump is defrosting it is not providing heat to the controlled space. It runs the compressor(inverter drive) at maximum speed during defrost to bring the outdoor coil up to temperature as quickly as possible. This melts any ice formed on the coil fins quickly and minimises defrost time. Minimising defrost time maximises heat output per hour real time.

    2. Dry Coil Defrost Cycle
    Once the outdoor coil is up to temperature and the compressor cycle has completed there is generally water between the outside coil fins. If the outdoor unit were to immediately resume heating the outdoor coil would freeze and prevent heat exchange. To prevent this the outdoor fan is run at maximum speed prior to resumption of the heating cycle. This is often characterized by steam blowing from the outdoor unit. This ensures the coil is completely dry before the heating cycle resumes.

    3. Time optimization through Fuzzy Logic
    Time between defrost cycles is continually being reviewed and optimized by the Heat Pump microprocessor software. Algorithmic calculations based on previous history is used to calculate the next defrost period.

    Fuzzy Logic or learning logic is a form of artificial intelligence. Defrost cycle termination is based on a combination of time and temperature. These parameters are used to calculate the next defrost period.

    Outdoor Humidity
    Outdoor humidity also effects heating performance. Areas that have a “dry cold” or low humidity such as “Mount Cook” will perform better at low ambient than say Taupo where ambient conditions can reach zero and “misty” moisture laden air conditions exists. The more moisture in the air the more moisture will freeze on the outdoor coil.

    Incorrect Unit Selection
    If a unit is selected that is too small the Heat Pump will run continuously and never reach set point. This continuous running will increase defrost requirements by reducing the outdoor coil running temperature and driving it into sub zero temperatures for excessive periods. The unit will defrost at the minimum intervals and may never catch up and achieve set point.

    Location of Outdoor Unit
    Location of the outdoor unit is essential for low ambient performance. Units located under houses, decking and in areas where airflow is impeded may create their own microclimate (i.e. giant fridge/freezer or in summer oven) and reduce the effective outdoor ambient temperature that the units operates in. Locating the outdoor unit too close to a wall and not observing clearances will also prevent the unit from delivering full output.


    Get the correct sized unit:
    Choosing the right sized Heat Pump is key to ensuring optimum comfort levels. Every home is as individual as its owner. The key to selecting the right Heat Pump for heating your home is choosing the correct unit size. Choosing the wrong size can cost you more in power consumption.


    Insulation and building orientation are key aspects in terms of potential heat loss a home is effected by. An older style home with poor insulation will lose indoor heat much quicker than a modern well insulated home that faces north.
    The quicker a home loses its heat, the bigger the Heat Pump system will need to overcome this heat loss.
    Last edited by richardc1983; 03-01-2011 at 4:00 PM.
Page 1
    • richardc1983
    • By richardc1983 4th Feb 09, 2:20 AM
    • 1,889 Posts
    • 1,006 Thanks
    richardc1983
    • #2
    • 4th Feb 09, 2:20 AM
    • #2
    • 4th Feb 09, 2:20 AM
    Manufacturer Websites & Further Info:

    http://www.bdt.co.nz/smarterheating/home.aspx : Contains all the info above plus lots more including sizing guide & running costs calculator on heat pumps... very useful however its an Australian site.

    http://www.mitsubishi-aircon.co.uk/ : Mitsubishi Electric UK Website -

    http://www.mhi.co.jp/en/aircon/index.html : Mitsubishi Heavy Industries Website

    www.daikin.co.uk: Daikin UK Website

    www.sanyoaircon.com : Sanyo Website

    http://www.fujitsu-general.co.uk/aircon/index.htm : Fujitsu Website

    http://uk.lge.com/products/category/list/airconditioning.jhtml : LG UK Website

    If you feel I have missed something out then let me know and I will add it to the main post.

    Mods it would be good if you can have this as a sticky topic so we can avoid duplicates and have all the info in one place.


    Air to Water Systems:

    Some users are looking to replace traditional gas heating & hot water for heat pumps:

    Heres some info on how this works:

    Many manufactures listed above are offering similar systems, so shop around to get the best prices, again however the efficiencies and capacities will differ.

    Here are 3 of the best systems:

    http://www.altherma.co.uk/for_the_home/default.jsp- Daikins Altherma

    http://www.altherma.co.uk/default.jspMitsubishi Electrics Ecodan

    http://www.mylg.co.uk/data%20for%20site/therma%20V%20databook%20%28AWHP%29.pdf - LG's Therma V
    Last edited by richardc1983; 16-06-2010 at 9:03 AM.
  • stevehead
    • #3
    • 6th Feb 09, 2:06 AM
    Tech-Talk, ASHP Technology Improvements
    • #3
    • 6th Feb 09, 2:06 AM
    Here are the developments made 2000 - 2007 to ASHP's which have resulted in a constantly improving performance:

    (1) Compressor

    a) High-efficient compression technology
    The Compressor is the heart of an air conditioner and requires high-precision
    processing technology.
    Although a rotary compressor with rotary method was widely adopted before, a
    twin rotary method or scroll method with better compression efficiency has now been
    developed and adopted.

    (2) Fan
    a) Indoor Fan
    Various types of fans are used for indoor units depending on unit form. A “cross
    flow fan” is used for most of the wall-hung type air conditioners.

    Although a cross flow fan was composed of blades that were processed metal
    sheets in the past, an attempt to increase air volume has been made through
    introduction of plastic blades having a wing-shaped section and growing size of fan
    diameter, while controlling noise.
    The layout and molding of a fan and blades have also been improved, by having
    random spacing between blades, angling a fan shaft, etc.

    b) Outdoor Fan
    In general, a propeller fan is used for an outdoor unit of an air conditioner.
    Although it was made of processed metal sheets in the past, it is now made of plastics.
    An attempt to increase air volume has been made by improving a blade shape, while
    reducing noise.

    c) Fan motor
    For fan motors for both indoor and outdoor units, an efficient DC brushless
    motor has replaced a conventional AC motor.

    (3) Electronically controlled expansion valve
    A decompressor is a component to create high-pressure and low-pressure states in
    a refrigerant circuit. Until now a capillary tube has been used primarily. A capillary
    tube refers to a thin and long copper pipe being about 0.2 to 2 m long and having an
    inside diameter of 1 mm to 2mm. This pipe generates pipe resistance and achieves
    throttling action (decompression).
    A capillary tube has been widely used for a room-air conditioner as it can be
    implemented with a simple structure. However, adjustment of appropriate degree of
    throttling according to number of revolutions is not possible because the degree of
    throttling is constant even when the number of revolutions of a compressor varies.
    Thus, an electronically controlled expansion valve has become used, which
    enables appropriate degree of throttling based on an electronic signal from a
    microcomputer determining the operating state of an air conditioner. The valve is
    structured so that a pulse motor rotates based on an electronic signal, and a gap
    between the valve and the valve seat is adjusted by converting the rotation into
    up-and-down motion, thereby controlling the degree of throttling.
    This could achieve efficient control of refrigerant flow, depending on the operating
    state, such as changes in number of revolutions of a compressor used in an inverter air
    conditioner. Thus, the electronically controlled expansion valve has become mainly
    used.


    Heat exchanger
    A heat exchanger is one of the important components of an air conditioner. It
    exchanges heat between indoor air and refrigerant in an indoor unit, and between
    outdoor air and a refrigerant in an outdoor unit.
    A fin-tube-type heat exchanger, in which a copper tube for refrigerant penetrates
    a plate-form aluminum fin for air, is used for this heat exchange.

    Shape of heat exchanger
    In separate wall-hung type indoor units that account for most of the room-air
    conditioners, a cross section of the conventional heat exchanger was molded like a
    plate. However, in order to expand heat exchange area in a limited space, those of
    bent type and those molded in a curved surface have been developed.
    In addition, heat exchangers in an initial indoor unit were arranged in two
    columns. However, improvement has been on the way to increase the heat
    transmission area and to augment the heat exchange capacity by means of partially
    arranging them in three columns, as long as an indoor unit structure can afford
    enough space for it.
    Last edited by stevehead; 06-02-2009 at 11:42 PM.
    • richardc1983
    • By richardc1983 13th Feb 09, 1:48 AM
    • 1,889 Posts
    • 1,006 Thanks
    richardc1983
    • #4
    • 13th Feb 09, 1:48 AM
    Noise from Systems
    • #4
    • 13th Feb 09, 1:48 AM
    A lot of people are asking in the forums how noisy the units are:

    The indoor unit is very quiet, quieter than a desk fan.

    The outdoor unit noise has been captured in this video the best it can. Its in heat mode as this is when the outdoor unit has to work its hardest. In cooling mode the fan rotates much slower and the noise in general is hardly noticeable, I think you will agree in heating mode it is also very quiet...

    http://www.youtube.com/watch?v=-mUzYHEfQEY&feature=channel_page
    • aligloo
    • By aligloo 15th Feb 09, 4:43 PM
    • 16 Posts
    • 9 Thanks
    aligloo
    • #5
    • 15th Feb 09, 4:43 PM
    Aircon/heating for conservatory
    • #5
    • 15th Feb 09, 4:43 PM
    The unit we've had in the conservatory for 18 months has completely conked & have been told we need a new unit.
    Any opinions on Samsung units?
    Thanks
    • richardc1983
    • By richardc1983 15th Feb 09, 5:22 PM
    • 1,889 Posts
    • 1,006 Thanks
    richardc1983
    • #6
    • 15th Feb 09, 5:22 PM
    • #6
    • 15th Feb 09, 5:22 PM
    The unit we've had in the conservatory for 18 months has completely conked & have been told we need a new unit.
    Any opinions on Samsung units?
    Thanks
    Originally posted by aligloo
    There ok, the very best systems are mitsubishi, daikin, sanyo, samsung.

    Mitsubishi and Daikin are very expensive however Mitsubishi Heavy Industries are cheaper and not the same company. They are still good though but a cheaper range. Mitsubishi cannot be beaten really!

    Out of interest what make unit is it in your conservatory at the moment? Is it fixed speed or inverter?
    Last edited by richardc1983; 17-02-2009 at 10:36 PM.
  • stubedoo
    • #7
    • 18th Feb 09, 10:56 PM
    • #7
    • 18th Feb 09, 10:56 PM
    i have a biggish old house with poor insulation and limited cost effective opportunities to improve this.

    Does this mean ASHP are not for me ??

    :confused:
  • Hermann
    • #8
    • 18th Feb 09, 11:11 PM
    • #8
    • 18th Feb 09, 11:11 PM
    i have a biggish old house with poor insulation and limited cost effective opportunities to improve this.

    Does this mean ASHP are not for me ??

    :confused:
    Originally posted by stubedoo
    Its never as simple as that!

    What are you using now? If it 's electric resistive heating then a heat pump would use less electricity to give the same heat. But thats not the whole picture.

    Do you have mains Gas and currently have an efficient gas boiler?

    Also if you have uninsulated old house and limited budget then insulate and draughtproof first. Everytime.
    The more expensive your heating is the more you'll save by cutting your heat loss by 50%!

    Paying for more efficient heat source just gives you slightly cheaper energy to throw away. So stop throwing the energy away first!
  • stubedoo
    • #9
    • 19th Feb 09, 12:14 AM
    • #9
    • 19th Feb 09, 12:14 AM
    had ancient gas boiler that was condemed a while back (lovely cold winter living out of one room)so looking to replace/ install whole new system. have been advised that all plumbing will need replacement for a new gas boiler.

    looking at multi fuel with back boiler;, ASHP and any other innovative ideas for long term future proof option. no intention of moving for many years so will spend some but as always cash is tight

    cheers
    • richardc1983
    • By richardc1983 19th Feb 09, 1:55 AM
    • 1,889 Posts
    • 1,006 Thanks
    richardc1983
    i have a biggish old house with poor insulation and limited cost effective opportunities to improve this.

    Does this mean ASHP are not for me ??

    :confused:
    Originally posted by stubedoo
    They are suitable for all types of properties and installations. My installation is in a 1920s victorian semi. Large rooms hgh ceilings no insulation and thick cold walls.

    I have multi split system installed with 2 indoor units.

    What part made you think they are not for you? Just so I can amend something if it gave that impression?
    • TeeKay63
    • By TeeKay63 3rd Mar 09, 10:26 PM
    • 4 Posts
    • 1 Thanks
    TeeKay63
    Choosing an Air Con unit for heating?
    I've read this thread and others with great interest as I'm looking to install something like the Mitsubishi Heavy Industries SRK25-ZGX Air Con unit primarily for heating. They seem to give a much higher COP than most others. My preferred installer likes Daikin but these are all around 3.5 COP versus Mitsubishi's 5 though all are A/A energy rated.

    What I'm trying to find out is whether the Mitsubishi really does deliver a COP of 5, how that changes with loading (if at all) and how the COP falls as o/s temperature drops to around freezing. Or is this the A/C world's equivalent of the car fuel consumption figures?
    • richardc1983
    • By richardc1983 3rd Mar 09, 10:34 PM
    • 1,889 Posts
    • 1,006 Thanks
    richardc1983
    The cop will fall as temperature drops below 5C but at -15C the unit will stll have 85% capacity in most instances. The cop is based on normal uk temps. MHI are not the same company as MITSUBISHI ElECTRIC. Both are different products with diff spec so make sure you are researching the right brand!

    Cop is much talked about on the heat pump posts. The most important part is how much capacity you have in the unit at -15C, cops of around 3.5 are good and the figure of 85% capacity is good at -15C. At -5C your still going to have full capacity. They are rated down to -15C and how often does it get to that in england during the day or evening?

    Daikin is excellent, mitsubishi electric is excellent, MHI is also good but Mitsubishi Electric comes before MHI or Daikin on the COP figures and efficiency.
    • Cardew
    • By Cardew 4th Mar 09, 2:31 AM
    • 27,114 Posts
    • 13,225 Thanks
    Cardew
    What I'm trying to find out is whether the Mitsubishi really does deliver a COP of 5, how that changes with loading (if at all) and how the COP falls as o/s temperature drops to around freezing. Or is this the A/C world's equivalent of the car fuel consumption figures?
    Originally posted by TeeKay63
    Welcome to the forum.

    I really don't think you are going to find out a realistic overall COP.

    I suspect, rather like you, that a COP of 5 will not be realistic in practical situations, and most of the independent publications talk of 3 to 3.5 as achievable.

    Even then a heat pump needs to be working all day in cold weather as it simply does not have the 'muscle' to warm up quickly a house that has been empty all day.

    That said, IMO any system the will give an overall COP of, say, 3 is excellent and will be competing with gas.

    I also think that there is too much emphasis on performance at low temperatures of -5C etc. If you have an ASHP and on the very few occasions it cannot cope with the low outside temperatures, you won't freeze to death - you simply turn on a £10 fan heater for a few hours.
    • richardc1983
    • By richardc1983 4th Mar 09, 12:12 PM
    • 1,889 Posts
    • 1,006 Thanks
    richardc1983
    Welcome to the forum.

    Even then a heat pump needs to be working all day in cold weather as it simply does not have the 'muscle' to warm up quickly a house that has been empty all day.
    Originally posted by Cardew
    Or you could do as I do and just set the set points to about 18C when your not in or in bed during very cold weather so that when you get up you can just put it back up again and it will not have a struggle to get back upto temp.

    Cardew I have to point out that our huge central heating system took longer to heat the house up from 13C than the air con did. The air con took about 2.5hrs whereas the central heating 5hrs later the house was still cold!
    • Cardew
    • By Cardew 4th Mar 09, 7:53 PM
    • 27,114 Posts
    • 13,225 Thanks
    Cardew
    Or you could do as I do and just set the set points to about 18C when your not in or in bed during very cold weather so that when you get up you can just put it back up again and it will not have a struggle to get back upto temp.

    Cardew I have to point out that our huge central heating system took longer to heat the house up from 13C than the air con did. The air con took about 2.5hrs whereas the central heating 5hrs later the house was still cold!
    Originally posted by richardc1983
    I can only suggest that there is something wrong with your house insulation or your previous CH system and/or you have 40ft ceilings!!

    From 13C my gas CH will take less than 30 minutes to bring some large rooms up to temperature.

    An ASHP system capable of a 9kW output should not take 2.5 hours to raise a flat to an acceptable temperature from 13C.
    • richardc1983
    • By richardc1983 4th Mar 09, 10:57 PM
    • 1,889 Posts
    • 1,006 Thanks
    richardc1983
    As pointed out previously Cardew, the house has no insulation, we have 12ft high ceilings and an open cellar beneath the floors. Thick solid walls and no insulation at all in the walls or the floors, or the attic. Its a victorian house built in 1900 The house can drop to about 8c in about 5 hours if its been very cold. The central heating in winter is set on 80C and the radiators are large double ones and correctly sized.

    We have doulbe glazing but it is very draughty. As its a rented flat theres not much I can do about it!
    • Andy_WSM
    • By Andy_WSM 8th Mar 09, 5:21 PM
    • 2,087 Posts
    • 4,505 Thanks
    Andy_WSM
    Hi Richard!

    I posted in the other A/C thread that I have been using my Fujitsu heat pump system to warm the house this Winter after my boiler failed.

    Well...I took the plunge and replaced the old gas boiler - with an Air to Water Heat Pump!

    Best investment ever! It is only a 5KW pump, but is maintaining the temperatures in my 2 bed bungalow with no problems at all. I leave it running 24/7 and let it do it's thing. It is costing £1.50 - £2 a day to run which compares very favourably (cheaper to run!) with my Gas bills of approx £200 a Quarter. And I now have heat and hot water 24/7 which suits my chaotic (due to work) lifestyle.

    The unit is one of the cheaper ones - a Trianco, Activair and it's in the loft! It is only just audible is you stand beneath where it is mounted (above the bathroom).

    I plumbed it so that it heats the hot water tank as priority, then the return continues around the heating system before going back to the unit for reheating.

    The hot water tank is always hot and each room has it's own thermostatic valve.

    Living room set at 22C
    Master bedroom 21C
    Second bedroom 18C (not currently in use)
    Kitchen 21C
    Hallway 20C
    Bathroom 23C

    The unit cost £925 which is comparable to a boiler, but I now don't have servicing costs, didn't have to pay a CORGI engineer to fit it and will benefit from much lower bills going forward.
  • albyota
    Hi Andy, who advised putting it in the loft?, how did you drain the condense? and when it has pulled all the heat from your loft, how does it perform?
    There are three types of people in this world...those that can count ...and those that can't!

    * The Bitterness of Low Quality is Long Remembered after the Sweetness of Low Price is Forgotten!
    • Andy_WSM
    • By Andy_WSM 8th Mar 09, 9:02 PM
    • 2,087 Posts
    • 4,505 Thanks
    Andy_WSM
    Hi Andy, who advised putting it in the loft?, how did you drain the condense? and when it has pulled all the heat from your loft, how does it perform?
    Originally posted by albyota
    The manufacturer recommends this can be done. The advantage is that the loft is ALWAYS warmer than the outside temperature, more so in the Summer, so plenty of very cheap hot water coming up. The other night it was -4C outside and the loft never dropped below -1C (I fitted a remote thermometer so I can check this). Right now it's 2C out and 5C in the loft. On the other side of the coin, despite an outdoor temp of just 7C yesterday the Sun was warming the tiles meaning the loft was 15C, so the unit ran even more efficiently yesterday than it would have done if it was outdoors.

    You will never pull ALL of the heat out of the loft as the loft is ventilated (as it should be) and you can feel a draft up there.

    If at the very worst case the temp in the loft drops below -5C (very unlikely here) then the unit will shut down and I'll have to run the immersion for hot water and plug a fan heater in. I can't imagine that ever happening though as I am near the sea...

    Draining of the condense is easy as the unit has a tray built in to catch the condense and it's simply a case of connecting this to a drain, which I have up there anyway as I also have whole house ducted A/C. The other bonus is that the condense goes into my rain water harvesting system, which in turn is used to flush the toilet and run the washing machine!

    (You can tell I'm impressed with it, can't you?!)
    • richardc1983
    • By richardc1983 9th Mar 09, 3:47 PM
    • 1,889 Posts
    • 1,006 Thanks
    richardc1983
    Andy very good what you have done but all manufacters i know advise the outdoor unit to be installed in open air. For instance most peoples lofts are not big enough to have a unit installed in them. Lofts are draughty but they are not fully open to the outside air. YOu say your loft is always warmer than outside thats crazy... (not that i dont believe you) but I have heard customers have had those self install units and put them in the loft. In heating the loft starts of at 5C but then quickly after about an hour the loft is at -10C and the unit is unable to remove any more heat and over working.

    Lofts are ventilated but not enough airflow for a unit. However you must have a large loft if you have proved the air temp doesnt drop. You may find yoou have to clean your coil more as dust in lofts is quite fine and may clog the coils.
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