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  • FIRST POST
    • richardc1983
    • By richardc1983 4th Feb 09, 2:03 AM
    • 1,928Posts
    • 1,014Thanks
    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 68
  • Littlenel
    Ecodan Air Source Heat Pump - U1 error code
    I hope someone can offer me some advise please?

    I have an ecodan air source heat pump which was installed in December 2012. We keep getting a U1 error code on the panel. The radiators upstairs don't seem to be getting hot, the underfloor heating seems to be working fine and the water is always hot.

    I've had someone out to look at it and he has replaced a sensor as he thought it may be faulty but the problem is still occuring, sometimes more than once a day.

    Has anyone experienced this error before and if so what fixed it?

    Many thanks
    • hebridean
    • By hebridean 2nd Jan 14, 10:04 PM
    • 87 Posts
    • 31 Thanks
    hebridean
    Have a look at these two links:

    http://www.refrigeration-engineer.com/forums/showthread.php?41146-Ecodan-2-zone-system-U1-Error

    http://forums.moneysavingexpert.com/showthread.php?t=1464827&page=58
    • deano72
    • By deano72 3rd Jan 14, 10:05 PM
    • 782 Posts
    • 130 Thanks
    deano72
    I hope someone can offer me some advise please?

    I have an ecodan air source heat pump which was installed in December 2012. We keep getting a U1 error code on the panel. The radiators upstairs don't seem to be getting hot, the underfloor heating seems to be working fine and the water is always hot.

    I've had someone out to look at it and he has replaced a sensor as he thought it may be faulty but the problem is still occuring, sometimes more than once a day.

    Has anyone experienced this error before and if so what fixed it?

    Many thanks
    Originally posted by Littlenel
    U1 is the most common fault on the eco dan, it is a high pressure fault which usually occurs when poor flow rate at the dan.if the dan see's a u1 fault 3 times it will shut down,then you have to perform a full reset.from what I understand you are saying that yours never shuts down, but you just loose the heating to the rads and an u1 fault code appears?strange if it does.
    List of checks for you to to
    1.check the flow setter , mitisi recommend that it needs to be set 12.5l>15ltrs , if you don't know what the flow setter is it is brass fitting with glass window with a white tab in it, the bottom of the white tab should be with in 12.5> 15l mark, turn all the heating on and see what flow rate you are getting.
    2.loss of pressure in heating system. There should be pressure gauge somewhere and that should be between 1bar > 2bar but they should run as low as 0.6 bar.
    3.i take it you got 2 zones for heating, ifso check both pumps are running.one of pumps could appear to be running but might not be running to its full pottential.
    4.frozen pipes can cause it also but I doubt it as it's not really been that cold.
    5.iv come across some where software needs updating
    6.poss might have air in the system, check your air bleed valves, undo the little caps to see if any air comes out.
    7.check no valves have accidentally been turned off, especially the outdoor ones by the dan, kids love to play
    9x10 it's usually loss pressure, which is just case of topping up the system and seeing if the pressure holds up.

    I'm not sure why the chap changed any sensors,that's probably one of the last things to go, there's not a lot to wrong with a sensor.which one did he change

    Anyway see how you get on, if you can give a bit more info then might be able to pin point it.
    • matelodave
    • By matelodave 4th Jan 14, 11:27 AM
    • 3,893 Posts
    • 2,452 Thanks
    matelodave
    Not having the same system as you (Daikin) I can only suggest what happens when mine goes into a low-flow shut down.


    The heatpump requires a minimum flowrate through it and it's possible that the zone valves are closing the flow in your upstairs zone and restricting the flow below the minimum level.



    My system has 8 thermostatically controlled zones (probably overkill) and it's possible for them to reduce the flow to several zones thus reducing the boiler flow below it's shut-off point. Sometimes just our bathroom wants heat and there's insufficient system flow when just that zone is open. To combat this there's an adjustable by-pass valve in the system which is designed to maintain a minimum flow rate even when only one zone is operating.
    Have a look at your thermostat settings and check that all valves are operating correctly and that nothing has been inadvertently turned off or adjusted.




    Finally has it been working OK and suddenly started playing up, if so it's worth having a think about what has changed since it started behaving abnormally - have you (or anyone else) tweaked any radiators, thermostats or settings
  • Littlenel
    Thanks everyone. Apparently it was a valve not a sensor that was changed.
    • deano72
    • By deano72 8th Jan 14, 9:31 PM
    • 782 Posts
    • 130 Thanks
    deano72
    He could of tested the valve to see if it works or not, if it did not that would explain no heat to that zone,but if it was a faulty valve it should not cause u1 fault providing you have a bypass valve fitted and set correctly...

    Anymore info you can give
  • dons19791
    Hi - I'm a newbie here looking some advice on heating my home (size 150m squared on ground level with attic conversion). I had underfloor heating powered by an oil boiler. Each zone is thermostatically controlled and this also heats my hot water tank. My house is 10 year old and fairly well insulated although not fully airtight. I have solar panels generating electric only and the excess feeds into the grid. My boiler has died and I have been told that the boiler and burner needs replaced. Rather than put in another oil boiler I am tempted to look at other greener and cheaper methods to heat the house and the water. I have no access to mains gas and geothermal is not an option. Presently I am looking at air source heat pump but I am reading conflicting reports on the forums and have become confused - can anyone offer me any advice on what I need?? Thank you in advance.
    • jeepjunkie
    • By jeepjunkie 22nd Jan 14, 12:54 PM
    • 1,453 Posts
    • 1,362 Thanks
    jeepjunkie
    Hi - I'm a newbie here looking some advice on heating my home (size 150m squared on ground level with attic conversion). I had underfloor heating powered by an oil boiler. Each zone is thermostatically controlled and this also heats my hot water tank. My house is 10 year old and fairly well insulated although not fully airtight. I have solar panels generating electric only and the excess feeds into the grid. My boiler has died and I have been told that the boiler and burner needs replaced. Rather than put in another oil boiler I am tempted to look at other greener and cheaper methods to heat the house and the water. I have no access to mains gas and geothermal is not an option. Presently I am looking at air source heat pump but I am reading conflicting reports on the forums and have become confused - can anyone offer me any advice on what I need?? Thank you in advance.
    Originally posted by dons19791
    I'm sure others will disagree and is subject to professional survey... If your system is not designed from the ground up for a heat pump then oil may still be the best bet...
    • Cardew
    • By Cardew 22nd Jan 14, 1:10 PM
    • 27,547 Posts
    • 13,516 Thanks
    Cardew
    Agree with the above.

    To achieve high efficiency, water from an ASHP runs at a considerably lower temperature than Oil/Gas central heating.

    Thus the radiators and UFH pipes are usually bigger with an ASHP. It is probable that water at 35C-40C from an ASHP will not provide sufficient warmth from a system designed for water that can be up to 80C.

    Who has condemned a 10 year old boiler?
    • matelodave
    • By matelodave 22nd Jan 14, 2:13 PM
    • 3,893 Posts
    • 2,452 Thanks
    matelodave
    Do you know what your u/f heating system temperature was - some have mixing valves to reduce the higher boiler temperatures from a convention boiler down to 35-40 degrees.


    As said above, if you are seriously thinking about a heat pump then learn as much about it as you can, get several (at least three) surveys and quotes done. You really do need to know if your existing u/f heating will deliver enough heat to your house at 35-40 degrees. Mine runs at 30-35 degrees and works fine as the pipe spacing is 6" (150mm) instead of the more usual 8" (200mm). Running a heatpump at much more than 40 degrees will increase your electricity consumption by quite a bit.


    Do the sums - you won't get much change out of £6-8k and even if you save £500 a year on your energy bills, that's a payback of 12-16years. You could buy three or four new oil boilers for that or get your existing one repaired a lot of times
  • dons19791
    Agree with the above.

    To achieve high efficiency, water from an ASHP runs at a considerably lower temperature than Oil/Gas central heating.

    Thus the radiators and UFH pipes are usually bigger with an ASHP. It is probable that water at 35C-40C from an ASHP will not provide sufficient warmth from a system designed for water that can be up to 80C.

    Who has condemned a 10 year old boiler?
    Originally posted by Cardew
    Its a warmflow boiler and the boiler burst and flooded the burner. 2 Plumbers told me that it was not worth fixing and to put a better boiler in next time!
  • dons19791
    Do you know what your u/f heating system temperature was - some have mixing valves to reduce the higher boiler temperatures from a convention boiler down to 35-40 degrees.


    As said above, if you are seriously thinking about a heat pump then learn as much about it as you can, get several (at least three) surveys and quotes done. You really do need to know if your existing u/f heating will deliver enough heat to your house at 35-40 degrees. Mine runs at 30-35 degrees and works fine as the pipe spacing is 6" (150mm) instead of the more usual 8" (200mm). Running a heatpump at much more than 40 degrees will increase your electricity consumption by quite a bit.


    Do the sums - you won't get much change out of £6-8k and even if you save £500 a year on your energy bills, that's a payback of 12-16years. You could buy three or four new oil boilers for that or get your existing one repaired a lot of times
    Originally posted by matelodave
    Hi - The screen on the main control was always around 37 - 40 degrees and the house and water was lovely and warm. not sure what the spacing between pipes are - have given the plans to a company to get a price.
    • Cardew
    • By Cardew 22nd Jan 14, 11:12 PM
    • 27,547 Posts
    • 13,516 Thanks
    Cardew
    have given the plans to a company to get a price.
    Originally posted by dons19791

    This is the potential problem with fitting an ASHP in the UK.


    Many(not all) companies are unlikely to give you a frank and honest appraisal of the suitability of your system to have an ASHP fitted - and thereby lose a job.


    Indeed many of them simply don't know if it will work efficiently or not. ASHP manufacturers sell their units to anyone and take no responsibility if the property is unsuitable.


    As said above by matelodave:

    if you are seriously thinking about a heat pump then learn as much about it as you can, get several (at least three) surveys and quotes done.
    Quite honestly, if you have a reasonable technical background you can work out if your property is suitable - or at least be able to ask the right questions.
  • 3CLM
    More U1
    Hi all,

    I’d be eternally grateful if someone could share their expertise on this U1 error case that I’m having with my Mitsubishi Ecodan air source heat pump PUHZ-W50VHA-BS.

    The U1 that I’m experiencing occurs only when the water heating cycle is about to switch to the heating cycle. This happens most often after a lot of hot water has been used (e.g.. bath). The display on the boiler freezes after hot water cycle for about 15-20 mins, system is silent and then U1 kicks in.

    During the first part of 2013 the U1 occurred unpleasantly frequently, leaving the house unheated when we happened to be out. Mitsu engineers came, saying that a bypass had to be fitted because it seemed that the hot air had problems exiting the pipes after the water cycle and that’s what caused the U1. Bypass fitted, the U1 still kept coming back. Eventually we got on Mitsu “top engineer” on the phone who asked me to change two things:
    Extend the hot water cycle from 1,5h to 2h.
    Change settings on the panel so that the hot water aim was 55-60 degrees and not more.


    This seemed to do the trick with the U1 but we started to get random patches when there wasn't hot water after a cycle or it was tepid at best. Anyway, we were happy enough that the U1 was gone.
    This all changed few months ago when the Mitsu recommended service people came to check the systems (so that the guarantee would be valid). After their visit U1 came back. They had changed the flow gauge and didn’t turn it up to the recommended 12-15 level. We changed the level ourselves but U1 is still there, although not as frequently as before summer.

    My partner has been in contact with Mitsu by email and now they say that it has to be underfloor heating piping problem. As we have already used the free engineer callouts, we would need to fork out cash for their next visit + a plumber that would work with him.
    All of this (and reading other posts here) makes me think that all they are trying to do is to make us spend money on their service. We strongly refuse to do so because there’s absolutely no guarantee or evidence that it is a underfloor heating piping issue - it’s in the same boat with the “you need a bypass” claim.
    The whole saga has eaten dozens of hours out of our lives and it’s still not over.

    All help is more than welcome!
    • lovesgshp
    • By lovesgshp 29th Jan 14, 2:52 PM
    • 1,314 Posts
    • 731 Thanks
    lovesgshp
    3CLM
    I don't know if this will help, as have not got a Ecodan, but sounds similar to a minor problem I had recently.
    I would think there is a 3 way valve in the system, that switches between DHW/Heating. I do not know if you can check it manually for operation on that unit. It could be sticking on switchover from one sequence to the other. Mine was stuck in the DHW cycle. Luckily a spray of WD40 into the electric motor part of the valve seems to have cured the problem.
    Hope someone who knows more about the Ecodan can help.
    As Manuel says in Fawlty Towers: " I Know Nothing"
  • albyota
    Hi all,

    I’d be eternally grateful if someone could share their expertise on this U1 error case that I’m having with my Mitsubishi Ecodan air source heat pump PUHZ-W50VHA-BS.

    The U1 that I’m experiencing occurs only when the water heating cycle is about to switch to the heating cycle. This happens most often after a lot of hot water has been used (e.g.. bath). The display on the boiler freezes after hot water cycle for about 15-20 mins, system is silent and then U1 kicks in.

    During the first part of 2013 the U1 occurred unpleasantly frequently, leaving the house unheated when we happened to be out. Mitsu engineers came, saying that a bypass had to be fitted because it seemed that the hot air had problems exiting the pipes after the water cycle and that’s what caused the U1. Bypass fitted, the U1 still kept coming back. Eventually we got on Mitsu “top engineer” on the phone who asked me to change two things:
    Extend the hot water cycle from 1,5h to 2h.
    Change settings on the panel so that the hot water aim was 55-60 degrees and not more.


    This seemed to do the trick with the U1 but we started to get random patches when there wasn't hot water after a cycle or it was tepid at best. Anyway, we were happy enough that the U1 was gone.
    This all changed few months ago when the Mitsu recommended service people came to check the systems (so that the guarantee would be valid). After their visit U1 came back. They had changed the flow gauge and didn’t turn it up to the recommended 12-15 level. We changed the level ourselves but U1 is still there, although not as frequently as before summer.

    My partner has been in contact with Mitsu by email and now they say that it has to be underfloor heating piping problem. As we have already used the free engineer callouts, we would need to fork out cash for their next visit + a plumber that would work with him.
    All of this (and reading other posts here) makes me think that all they are trying to do is to make us spend money on their service. We strongly refuse to do so because there’s absolutely no guarantee or evidence that it is a underfloor heating piping issue - it’s in the same boat with the “you need a bypass” claim.
    The whole saga has eaten dozens of hours out of our lives and it’s still not over.

    All help is more than welcome!
    Originally posted by 3CLM
    Hi, I have an Ecodan (8.5kW) with UFH, I work in the renewables industry, fitted loads, willing to help.
    I would like to know more about your set up before making any comments.
    Al
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  • 3CLM
    Hi, I have an Ecodan (8.5kW) with UFH, I work in the renewables industry, fitted loads, willing to help.
    I would like to know more about your set up before making any comments.
    Al
    Originally posted by albyota
    Hi and thanks for offering help!

    What kind of info would you like me to give you exactly?

    3clm
    • thenudeone
    • By thenudeone 30th Jan 14, 1:33 PM
    • 4,402 Posts
    • 1,909 Thanks
    thenudeone
    ...
    Thus the radiators and UFH pipes are usually bigger with an ASHP. It is probable that water at 35C-40C from an ASHP will not provide sufficient warmth from a system designed for water that can be up to 80C.
    Originally posted by Cardew
    ... which is exactly why this sort of product has been designed: http://www.daikin.co.uk/binaries/AlthermaHT_UKEPLEN13-724_tcm511-277337.pdf

    and, if installed before 31st March, it will be eligible for RHI which could well pay for the ASHP installation cost over the 7 year life of RHI.

    ASHPs operating at over 53C won't be eligible for RHI if installed after April 1st.
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    • deano72
    • By deano72 31st Jan 14, 10:43 PM
    • 782 Posts
    • 130 Thanks
    deano72
    3clm. One I posted earlier

    U1 is the most common fault on the eco dan, it is a high pressure fault which usually occurs when poor flow rate at the dan.if the dan see's a u1 fault 3 times it will shut down.
    List of checks for you to try
    1.check the flow setter , mitisi recommend that it needs to be set 12.5l>15ltrs , if you don't know what the flow setter is it is brass fitting with glass window with a white tab in it, the bottom of the white tab should be with in 12.5> 15l mark, turn all the heating on and see what flow rate you are getting.
    2.loss of pressure in heating system. There should be pressure gauge somewhere and that should be between 1bar > 2bar but they should run as low as 0.6 bar.
    3.i take it you got 2 zones for heating, ifso check both pumps are running.one of pumps could appear to be running but might not be running to its full pottential.
    4.frozen pipes can cause it also but I doubt it as it's not really been that cold.
    5.iv come across some where software needs updating
    6.poss might have air in the system, check your air bleed valves, undo the little caps to see if any air comes out.
    7.check no valves have accidentally been turned off, especially the outdoor ones by the dan, kids love to play
    9x10 it's usually loss pressure, which is just case of topping up the system and seeing if the pressure holds up.

    Is your heating on constant and your hot water on auto?ifso program heating to come on/off 5mins before and after your hot water cycle and put dhw and heating to auto. So in other words a 5min time lag between the heating and hot water ,Bet that will cure it if this is the case
    Last edited by deano72; 31-01-2014 at 10:47 PM.
  • 3CLM
    3clm. One I posted earlier

    U1 is the most common fault on the eco dan, it is a high pressure fault which usually occurs when poor flow rate at the dan.if the dan see's a u1 fault 3 times it will shut down.
    List of checks for you to try
    1.check the flow setter , mitisi recommend that it needs to be set 12.5l>15ltrs , if you don't know what the flow setter is it is brass fitting with glass window with a white tab in it, the bottom of the white tab should be with in 12.5> 15l mark, turn all the heating on and see what flow rate you are getting.
    2.loss of pressure in heating system. There should be pressure gauge somewhere and that should be between 1bar > 2bar but they should run as low as 0.6 bar.
    3.i take it you got 2 zones for heating, ifso check both pumps are running.one of pumps could appear to be running but might not be running to its full pottential.
    4.frozen pipes can cause it also but I doubt it as it's not really been that cold.
    5.iv come across some where software needs updating
    6.poss might have air in the system, check your air bleed valves, undo the little caps to see if any air comes out.
    7.check no valves have accidentally been turned off, especially the outdoor ones by the dan, kids love to play
    9x10 it's usually loss pressure, which is just case of topping up the system and seeing if the pressure holds up.

    Is your heating on constant and your hot water on auto?ifso program heating to come on/off 5mins before and after your hot water cycle and put dhw and heating to auto. So in other words a 5min time lag between the heating and hot water ,Bet that will cure it if this is the case
    Originally posted by deano72

    Thanks for that! I did read this post earlier but thought that maybe someone has a similar issue. It's now clear that U1kicks in after the 3rd hw cycle after running the bath full.
    I've now set up the 5 minute thing that you mentioned - hope it does the trick. . .
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