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UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?
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Does anyone on the forum have any experience or opinions of Nibe ASHP?.0
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No experience, only opinions, the Nibe fighter only operates down to -15C so be careful as the recent cold snaps we are having..... -20C in some areas of the UK, this would struggle, depending on area safer to go with something that can cope with -25C like the mitsubishi or daikin. hope this helpsThere 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!0 -
My LG system operates down to -15C any colder in most areas and I would top it up with an electric heater as temps do not go below this for long.If you found my post helpful, please remember to press the THANKS button! --->0
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I have read through every page of this thread with great interest! I've been spending a good bit of time researching this option for the last while - and have yet to find the ideal solution (but i just know its out there!).
I'm in Ireland - and have access to a €2000 grant for heat pump install. Currently, the house (4 bed semi-d/approx. 150m2) has rads and an outdoor oil boiler.
I want to have an air-water system installed that can be integrated into the current heating system - and cut in and out within a preset temperature range. ie. I want to use it when its most efficient to use it (within certain outdoor temp ranges and outside the highest electricity tariff times, etc) and revert to oil at other times. Also, it may well be that i couldn't rely on a a(w)shp exclusively with my current rads....BUT if it can get them to a certain temp - and I can top up by falling back on the oil boiler, I would be happy with that.
Main objective is getting a system with low capital cost that doesn't have excessive running costs.
If someone could shortlist a few systems that I should be looking at, I would really appreciate it.
Also, have any of you had issues with units icing up - and the cost implications of the unit expending energy deicing itself?0 -
I have read through every page of this thread with great interest! I've been spending a good bit of time researching this option for the last while - and have yet to find the ideal solution (but i just know its out there!).
I'm in Ireland - and have access to a €2000 grant for heat pump install. Currently, the house (4 bed semi-d/approx. 150m2) has rads and an outdoor oil boiler.
I want to have an air-water system installed that can be integrated into the current heating system - and cut in and out within a preset temperature range. ie. I want to use it when its most efficient to use it (within certain outdoor temp ranges and outside the highest electricity tariff times, etc) and revert to oil at other times. Also, it may well be that i couldn't rely on a a(w)shp exclusively with my current rads....BUT if it can get them to a certain temp - and I can top up by falling back on the oil boiler, I would be happy with that.
Main objective is getting a system with low capital cost that doesn't have excessive running costs.
If someone could shortlist a few systems that I should be looking at, I would really appreciate it.
Also, have any of you had issues with units icing up - and the cost implications of the unit expending energy deicing itself?
Hi there
All units ice up in the cold weather below 3C however if they are properly sized to the property they wont spend forever and a day defrosting as they will not be running flat out all the time.If you found my post helpful, please remember to press the THANKS button! --->0 -
Hi Richard. My understanding is that this doesn't happen in climates where the use of air source heat pumps is more established eg. Scandinavia - whereas the relative humidity in UK/IRL is much greater? Just wondering though - for that period when conditions are such that they are defrosting, is it uneconomical to use them? I have also read accounts of people building diy 'housings' around the pump in order to reduce the likelihood of unit icing up. Is this a possible solution?richardc1983 wrote: »Hi there
All units ice up in the cold weather below 3C however if they are properly sized to the property they wont spend forever and a day defrosting as they will not be running flat out all the time.0 -
Hi Richard. My understanding is that this doesn't happen in climates where the use of air source heat pumps is more established e.g. Scandinavia - whereas the relative humidity in UK/IRL is much greater? Just wondering though - for that period when conditions are such that they are defrosting, is it uneconomical to use them? I have also read accounts of people building diy 'housings' around the pump in order to reduce the likelihood of unit icing up. Is this a possible solution?
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.
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 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.
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.If you found my post helpful, please remember to press the THANKS button! --->0 -
Thanks Richard for the detailed post. Just wondering if anyone has any specific system recommendations for the circumstances I described above?0
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Thanks Richard for the detailed post. Just wondering if anyone has any specific system recommendations for the circumstances I described above?
Are you still wanting underfloor heating or have the fan coils changed ur mind, much more adaptable and controllable.
I reccomend some air to water systems on the 2nd post of this:
They are the main guys: Mitsubishi is a very good system, Albyota on this post http://forums.moneysavingexpert.com/showthread.html?t=702257&page=18 has the Mitsi system and seems very happy with it.
http://www.altherma.eu/default.jsp - Daikins Altherma
http://www.mitsubishi-aircon.co.uk/d...?id=168227 - Mitsubishi Electrics Ecodan
http://www.mylg.co.uk/data for s...(AWHP).pdf - LG's Therma VIf you found my post helpful, please remember to press the THANKS button! --->0
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