Air source heat pumps

[Earthstore]

I am not a total expert on this, but I do have an understanding and some knowledge,
The room temp you are trying to achieve is around 20 degrees, so the lower temp you can run a heatpump the better really,
If I remember correctly 45 to 50 degrees, a heatpump can rack it up to 60-65 but the COP drops like a stone.

By the sounds of you insulation, your house will be ideal, do you have PV, as that would help to reduce your running costs also, daylight hours only of course.

 

[Greenday]

The house sounds ideal for a heat pump. How many square meters is it? I guess the heat loss would be something in the region of 50W/m2 so 160m2 house would need a 8kW heat pump. Do not add in the hot water load as it is usual to heat the water first then switch over to heating. A heat pump works better if it operates on a 24/7 basis with set back temperatures at night and in the day if you are out. Higher COPs will be achieved operating like this.

 

[Earthstore]

Just to add, heatpumps run better on longer cycles, rather than stop start, this is why you may have heard of "buffer tanks",
these help a pump to cycle for longer, they are not always necessary, it is all down to good system design and install.
There again that is the difference between an average PV system and an excellent performing one.

 

[Greenday]

Agreed earth store and we try to fit a buffer if the customer will agree whether the manufacturer specifies or not.

Dimplex do a combined unvented cylinder with buffer that is a convenient way of installing it.

Bad installs have done a lot of damage for heat pumps and this can only get worse if misguided sales and marketing companies get involved as the RHI looms. Bull***t sales techniques and sell at all costs is not the right approach. We walk away from a job if the heat pump won't work for that particular application. Would a salesman on commission only?

 

[jason121]

Samsung have buffer on there 210 litre tank its only 75litres. I thought for every 1kw for heat pump, 20litres is needed for buffer. I am right or wrong

 

[Earthstore]

I believe it depends on the size of the system, Ie if it is a large house with excellent insulation, then only a small buffer tank would be required,(as there is plenty of fluid in the wet system) but if it is a small house with poor insulation then a larger buffer tank would be reqd, heatpumps also work on return temperature, so this can effect the cycling effect.
As mentioned, it is all down to system design, not just buy one and connect it up.
I may stand corrected on all of this though.

 

[The Mud Mouse]

I have a 450 litre thermal store of which about half would be a buffer looking at the take-off point for the underfloor heating along with over 1km of UFH pipe so I would imagine I would be OK there. So the critical issue to me is what average COP am Ilikely to achieve with say a 12kW unit running 50˚C flow and 45˚C return temperature at a flow rate of about 2m3/hr over the winter months (unlikely to see any use May to September)??

 

[jason121]

download the panasonic heat pump soft ware

 

[Vegelen]

Wiklipedia: Air Source Heat Pumps

Air source heat pumps - Wikipedia, the free encyclopedia

"Efficiency Ratings" / "Risks & Precautions".

Air source heat pump efficiency is measured by the "Coefficient Of Performance".
In very mild weather, the COP of an ASHP can approach or exceed 4.
However, on a cold winters day, as ambient temperatures reduce more work is required to move the same amount of heat indoors.
Heat pump performance is limited by the Carnot cycle and approaches 1.0 as the outdoor-to-indoor temperature difference increases.
In cold weather ASHP's become progressively more inefficient consuming more electricity as ambient air temperatures reduce.
At this point you'd realistically want to turn your ASHP system off and turn on a secondary supplementary heating system like a gas condensing boiler to heat your home cheaply and effectively.
People conventionally install ASHP's in locations where natural gas mains dont exist.
If an inexpensive, economic, supplementary heating alternative doesn't exist, you are lumbered with significantly increased electricity bills over periods of sustained cold weather.
Those that dont get very high ASHP electricity bills have systems installed in extremely well insulated houses, with low heating requirements.

Daikin Altherma:

Daikin Altherma air-to-water heat pumps are currently amongst the most efficient on the market with average COPs between 3 and 5.

www.daikinac.com/content/residential/whole-house/daikin-altherma/#energy-efficiency

 

[MCS Renewables]

I have some comparison test results from the Swedish Energy Test Centre but have no idea how to attach the document to a forum.

If you have contributed to this thread you can email me and I will send you a copy.

Beware the Daikin high temperature unit as we are told it does NOT qualify for the RHI.

 

[richy3333]

Insulation seams to be the key before considering any heating system? I too haven't heard good things about this type of heating.

I had a customer that was convinced to go with a system by a renewables company, mainly because they would get financial help towards the cost. The house wasn't insulated and after finishing the work the renewable company accepted the house was also too large for the system and would never work properly!

Wish I'd seen the program Darkwood mentioned. Also looking forward to seeing the results from the EST

 

[solarsavings]

You can find the results of the EST heat pump trials here https://www.gov.uk/government/uploa...a_second_phase_est_heat_pump_field_trials.pdf

 

[Vegelen]

Additional Heat Pump Articles:

Energy & Climate Change Commitee:

Oral Evidence: Heat , Tuesday 12th November 2013.
Heat Pumps: Ground Source & ASHP's (Q89 - Q107).

http://data.parliament.uk/writtenevidence/WrittenEvidence.svc/EvidenceHtml/3570

Future Roll Of Heat Pumps In The Domestic Sector:

http://proceedings.eceee.org/papers...ceee.org/visabstrakt.php?event=1&doc=6-388-11

 

[jason121]

Heat pumps work very well if they are designed correctly and installed correctly.
Not all houses are suitable for heat pumps. Mine has been on since November on radiators that are oversized. Average temperature running central heating is 30 degree, jumps to 42 when weather is cold. Average temperature in house 22 all day and night. With my dual fuel discount my supplier owes me money. I'm on mains gas.

 

[marc8]

hi just been hooking up 2 x air to water unit working with thermal store on a barn conversion.

1st unit is main load with second unit as a slave. finished wiring last night 1st unit kicked in & ran whole system up without second unit cutting in.

speaking with the guy who supplied units they like to run lazy unlike a combi boiler you run hard.

they have 2 immersion back up's on cylinder aswell.

have 40loops of underfloor heating on system over 4 mainfolds.

looks good will get details & post