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  • FIRST POST
    • richardc1983
    • By richardc1983 4th Feb 09, 2:03 AM
    • 1,929Posts
    • 1,015Thanks
    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 86
    • helpjack
    • By helpjack 1st Oct 18, 11:02 AM
    • 40 Posts
    • 58 Thanks
    helpjack
    ASHP setup advice
    Hi all,

    I can't believe this thread has been going so long.

    I'm the proud owner of a Mitsu 8.5KW heat pump which I love but its not without its problems.

    We've recently been getting lots of U1 error codes. I thought there might just be air in the system but it seems connected to the hot water coming on and the hot water never gets up to temperature.

    I called the technical helpline and they checked the heatpump and refrigerant levels and after doing a few tests they diagnosed there was an issue with one of the heating zone valves which would need completing replacing (not just the motor) this was because during the hot water cycle, one the heating valves would open and divert hot water away from the cylinder.


    I can get a plumber in to replace the valve but it means draining down the system and refilling with glycol which is expensive so before I do that I want to check there's nothing else.


    I say this because the heating controls have always been a bit strange. We have 2 zones one for upstairs and one for downstairs both with wireless stats. I had an engineer in last year to refill the glycol after a leak and he looked at the wiring and in consultation with Mitsubishi made some changes and said the controllers had been wired wrong originally but we still don't seem to have any control over when the heating is on upstairs or downstairs - it just does its own thing and nothing really correlates to the control panel. Whichever zone is meant to be on, normally the radiators are on both upstairs and down stairs. I know this also points to zone valves but its a bit strange that both zone valves would have failed.

    Is there a way I can just check that the zone valves and thermostats are wired in correctly before getting anyone out?
    • verityboo
    • By verityboo 3rd Oct 18, 4:46 PM
    • 950 Posts
    • 1,173 Thanks
    verityboo
    Can you remove the motor from the valve and manually set the valve to the correct position and see if the water reaches the correct temperature?
    • Moorlander
    • By Moorlander 4th Oct 18, 10:07 PM
    • 9 Posts
    • 1 Thanks
    Moorlander
    Simple question...I hope
    Hi Folks,

    I hope I am doing this right by simply posting a reply, if not I apologise to HelpJack by highjakking his thread.

    Anyway we are building a conservatory which is about 70 cubic metres,and I'mplanning to heat and cool it with an ASHP.

    Bearing in mind its for the conservatory only , and we are already a little over budget, i was hopiong someone could recommend a brand other than the premier heat pumps but without resorting to a nameless chinese import on fleabay. I was thinking maybe Panasonic or LG etc.

    Any recommendations as to brand and output to help me through the ASHP minefied would be very much appreciated.

    Thanks for reading.
    • helpjack
    • By helpjack 4th Oct 18, 10:35 PM
    • 40 Posts
    • 58 Thanks
    helpjack
    Moorlander - if I can get our hot water working again that is the next project for the conservatory.

    You can get a big name invertor for around £500 may be a bit less depending on size. Some of them come with pre-gassed pipes so can be self installed.
    • helpjack
    • By helpjack 4th Oct 18, 10:46 PM
    • 40 Posts
    • 58 Thanks
    helpjack
    An update on my heating/hot water

    I've noticed that the flow gets hot but the return doesn't get warm at all so either the pump has gone or there is an airlock.

    The valve thing was a bit of a red herring.

    I've got some air out of the system but with no luck so far.

    It actually has 2 pumps. One on the flow and one on the return. I've bled the one on the flow but the one on the return doesn't have an easily accessible bleed valve. I don't want to mess too much.
    • Moorlander
    • By Moorlander 9th Oct 18, 11:27 AM
    • 9 Posts
    • 1 Thanks
    Moorlander
    Hi, could you give me some details for where I could get a decent inverter for £500, just some names to google would be fine. Especially pre-gassed.


    Cheers
    • helpjack
    • By helpjack 10th Oct 18, 8:14 PM
    • 40 Posts
    • 58 Thanks
    helpjack
    Can anyone help
    I guess this is a last ditch attempt to try an get some help and some heating and hot water. Does anyone know anyone who could come and help us. We are now in a complete mess. We have no heating or hot water. I have called Mitsubishi and they told me I just needed a plumber. We have had 2 plumbers out and they generally say they can't see anything wrong but didn't want to touch it because of the specialist nature. I called Mitsubishi and asked them if they could send someone out and they flatly refused saying they wouldn't send someone out to people without a service contract. I then called the only specialist within 50 miles who has come and replaced 2 pumps at god knows what cost and said that was the only thing they could think of. The result is I have spent probably £700 and we still have no heating or hot water. I have called Mitsubishi again who again have refused to come out and said it is now down to the engineer who came out and replaced the pumps. So we are stuck. He doesn't know what's wrong and I just can't afford to replace every single part at contractor rates.

    The heat pump outside is making strange noise now so it looks like the problem lies there rather than the plumbing.

    We are pretty desperate now
    • pd001
    • By pd001 10th Oct 18, 8:43 PM
    • 865 Posts
    • 239 Thanks
    pd001
    I guess this is a last ditch attempt to try an get some help and some heating and hot water. Does anyone know anyone who could come and help us. We are now in a complete mess. We have no heating or hot water. I have called Mitsubishi and they told me I just needed a plumber. We have had 2 plumbers out and they generally say they can't see anything wrong but didn't want to touch it because of the specialist nature. I called Mitsubishi and asked them if they could send someone out and they flatly refused saying they wouldn't send someone out to people without a service contract. I then called the only specialist within 50 miles who has come and replaced 2 pumps at god knows what cost and said that was the only thing they could think of. The result is I have spent probably £700 and we still have no heating or hot water. I have called Mitsubishi again who again have refused to come out and said it is now down to the engineer who came out and replaced the pumps. So we are stuck. He doesn't know what's wrong and I just can't afford to replace every single part at contractor rates.

    The heat pump outside is making strange noise now so it looks like the problem lies there rather than the plumbing.

    We are pretty desperate now
    Originally posted by helpjack
    Cant help with the heatpump situation and hopefully someone else will be along to help you with that.

    How did you pay your plumber?
    By the sound of it you have been charged for work that didn't fix the fault?
    If you paid by credit card could you not try and get the money back because the work was unsatisfactory?
    • lovesgshp
    • By lovesgshp 10th Oct 18, 9:31 PM
    • 1,314 Posts
    • 731 Thanks
    lovesgshp
    Are there any alarms showing in the heat pump info?
    Have you checked the filters on the flows?
    What is the strange noise you are hearing. Is the fan blocked?
    As Manuel says in Fawlty Towers: " I Know Nothing"
    • helpjack
    • By helpjack 11th Oct 18, 6:23 AM
    • 40 Posts
    • 58 Thanks
    helpjack
    I have paid yet I'm waiting for the invoice.

    We get a U1 alarm which is high pressure at the Ecodan normally associated with poor flow. There is poor flow you can feel the flow get hot and the return stays cold and then the system shuts down.

    Where are the filters? The flow setter is broken see we can't see what the flow is. I mentioned this to the guy yesterday and he said it wouldn't make any difference as its open so won't impede the flow. It could be gunked up but the Ecodan was making such strange noises last night we just switched it off. The fan only comes in for a short time and was making a rattling whining noise. It just didn't sound right

    The immersion is also not working so we can't even get hot water that way.
    • lovesgshp
    • By lovesgshp 11th Oct 18, 8:53 AM
    • 1,314 Posts
    • 731 Thanks
    lovesgshp
    There is supposed to be a filter on the water input side of the system, from what I have read. Have you got the exact model details?
    You need to get the flow setter replaced to be able to see what is actually happening.
    It could be a problem with the zone valves, possibly a faulty thermistor. Had a similar problem with a gshp, where one zone was not heating.
    You do need to get at the other pump, as it may have air in it if just replaced. Has the Ecodan got a function in the menu to manually check operation of all functions (pumps, valves etc)?

    With the external unit being noisy, fan could be out of balance. Check the vanes are clean.
    As Manuel says in Fawlty Towers: " I Know Nothing"
    • helpjack
    • By helpjack 11th Oct 18, 8:49 PM
    • 40 Posts
    • 58 Thanks
    helpjack
    There are definitely no water filters.

    There's a manual operation setting and in there it has Pump1, pump2, pump3, 3 way valve and mixing valve.

    The mixing valve is flashing which I think indicates an error but I don't know which one is the mixing valve.

    The system has 3 zone valves, one for each heating zone and one for the hot water.

    Which one would the mixing valve be?
    • helpjack
    • By helpjack 11th Oct 18, 8:52 PM
    • 40 Posts
    • 58 Thanks
    helpjack
    There is one of those magnetic filters by the water feed. I have checked that and cleaned it. To be honest it wasn't that gunked up.
    • lovesgshp
    • By lovesgshp 11th Oct 18, 8:59 PM
    • 1,314 Posts
    • 731 Thanks
    lovesgshp
    Can you give me the exact model, so I can look at a manual online. I may be able to see where it is from the installation instructions.
    I deal with IVT units, but there could be something similar.
    As Manuel says in Fawlty Towers: " I Know Nothing"
    • helpjack
    • By helpjack 11th Oct 18, 11:47 PM
    • 40 Posts
    • 58 Thanks
    helpjack
    Hi it's PUHZ-W85VHA2-BS

    Thanks
    • helpjack
    • By helpjack 12th Oct 18, 6:57 AM
    • 40 Posts
    • 58 Thanks
    helpjack
    With an FTC4 controller. Thanks
    • helpjack
    • By helpjack 13th Oct 18, 7:20 AM
    • 40 Posts
    • 58 Thanks
    helpjack
    A quick update. We have got to the bottom of the problem (hopefully). I managed to persuade Mitsubishi to send someone out who was brilliant and really know his stuff. He identified very quickly that it was a blocked heat exchanger. It will need a power flush and then refilling with glycol.

    I'm surprised that it has got clogged so quickly as its a newish system (4 years) with a magnetic filter but at least we have an answer and a plan.

    I haven't heard from the other company who changed the pumps. I guess their invoice will come through the post. I was thinking as a compromise could I just pay for the parts?
    • pd001
    • By pd001 13th Oct 18, 8:00 AM
    • 865 Posts
    • 239 Thanks
    pd001
    A quick update. We have got to the bottom of the problem (hopefully). I managed to persuade Mitsubishi to send someone out who was brilliant and really know his stuff. He identified very quickly that it was a blocked heat exchanger. It will need a power flush and then refilling with glycol.

    I'm surprised that it has got clogged so quickly as its a newish system (4 years) with a magnetic filter but at least we have an answer and a plan.

    I haven't heard from the other company who changed the pumps. I guess their invoice will come through the post. I was thinking as a compromise could I just pay for the parts?
    Originally posted by helpjack
    Did they give you wrong advice? Did you need those parts? Did you pay for something that you didn't actually need?
    They evidently should have known about, or been able to diagnose the problem, just like the Mitsubishi guy if they were so called engineers
    Last edited by pd001; 13-10-2018 at 8:07 AM. Reason: addition
    • helpjack
    • By helpjack 13th Oct 18, 9:41 AM
    • 40 Posts
    • 58 Thanks
    helpjack
    The other engineers came round said they didn't know but thought it might be the pumps. They said it was a guess but the only thing they thought it could be. They are accredited by Mitsubishi I did check with mitsubishi. Before he left he said that it was fixed but didn't have time to wait while the hot water heated up but 20 mins after he left the U1 error occurred again and the hot water hadn't even heated a degree.

    The problem is he said he couldn't prove it but he thought it was the pumps and asked me should he go ahead. Of course I said yes. Probably stupidily but we needed heating and hot water and there seemed no other option.

    Mitsubishi man said there was nothing wrong with the pumps.

    First engineer told me to call the office and let them know as he was leaving which I did twice and they said they would discuss it and I haven't heard anything since.
    • pd001
    • By pd001 13th Oct 18, 10:30 AM
    • 865 Posts
    • 239 Thanks
    pd001
    The other engineers came round said they didn't know but thought it might be the pumps. They said it was a guess but the only thing they thought it could be. They are accredited by Mitsubishi I did check with mitsubishi. Before he left he said that it was fixed but didn't have time to wait while the hot water heated up but 20 mins after he left the U1 error occurred again and the hot water hadn't even heated a degree.

    The problem is he said he couldn't prove it but he thought it was the pumps and asked me should he go ahead. Of course I said yes. Probably stupidily but we needed heating and hot water and there seemed no other option.

    Mitsubishi man said there was nothing wrong with the pumps.

    First engineer told me to call the office and let them know as he was leaving which I did twice and they said they would discuss it and I haven't heard anything since.
    Originally posted by helpjack
    Take their accreditation up with Mitsubishi.
    If the Mitsubishi guy found the problem without too much difficulty then doesn't it follow that one of their own accredited contractors should have done the same?

    It is still a fact that their 'fix' which you will be billed for, didn't actually fix it. I would certainly argue that point when the bill comes through
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