air source heat pump

[Lc_shi]

air source heat pump has more advantages: easy installation \maintenance\low operation cost etc. but it can't work well in winter.Is there other way out to improve it except for adding electricity heating? any ideas? thanks

[Deejey]

air source heat pump has more advantages: easy installation \maintenance\low operation cost etc. but it can't work well in winter.Is there other way out to improve it except for adding electricity heating? any ideas? thanks

Air source heat pumps can work well down to as low as around 4.4C or 40F. When outdoor temperatures fall below 40ºF, some units have electric heater elements that kick in to provide indoor heating. This is why air-source heat pumps aren't always very efficient for heating in areas with cold winters.

Geothermal heat pumps are similar to ordinary heat pumps, but use the ground instead of outside air to provide heating, air conditioning and, in most cases, hot water. Because they use the earth's natural heat, they are among the most efficient and comfortable heating and cooling technologies currently available. They use loess energy the conventional heat pumps and are much quieter

[Abe]

air source heat pump has more advantages: easy installation \maintenance\low operation cost etc. but it can't work well in winter.Is there other way out to improve it except for adding electricity heating? any ideas? thanks

Is it possible to show some diagrams, or pictures Ic Shi.........
on air source heat pump and how it works
Thx

[frank]

Air source heat pumps can work well down to as low as around 4.4C or 40F.

The current range of Daikin R410a inverter heat pumps will work perfectly well with ambients at -15C and without the help of electric heaters

[smileypete]

The current range of Daikin R410a inverter heat pumps will work perfectly well with ambients at -15C and without the help of electric heaters

Really? Do you know what sort of capacity drop and efficiency they have at freezing temperatures and below? Also the length of the defrost cycle could be useful to know.

There is technical info on the Daikin site, but it's not available to mere mortals...

For countries with a mild climate and relatively high average winter temperature like the UK, I wonder if pumping water through a ground loop and over the 'condenser' coil in the outdoor unit would help.

The ground loop pump would only be used when necessary together with disabling the fan.

When the temperature is mild it could be recharged by running the fan and circulating water, so it's warmed by the air. This way it would become a thermal 'flywheel'

The ground loop could even be a pond or large water tank instead of a loop underground. The circulating water could be normal condensate from the outdoor unit.

cheers,
Pete.

[Peter_1]

The current range of Daikin R410a inverter heat pumps will work perfectly well with ambients at -15C and without the help of electric heaters

Thermodynamically seen, it will of course work but the overall COP?? Should it reach 1 at that time. I doubt it very much.

In the last company I worked together as a freelancer, we installed a Mitsubishi Electric VRF in the offices. In the place I sat, there was a ductable unit but due to the heavy workload at that moment (winter, outside temperatures less above freezing point) the ducts were partially installed an no grills. The ducts hanged out the ceiling temporarily.
This was also the reason why I felt very good what the outdoor unit was doing. It went almost every 45' in defrost and a defrost cycle lasted more than 5'. While defrosting, the fan ran at a very low speed but out of the duct, there was a very cold air coming out it.
The temperature in the office dropped by this.
It then took some minutes again before the unit went into his heating mode.
And it took again several minutes before the coil warmed enough to start the fan. This whole cycle from start of a defrost/cooling of the room/ waiting for heating/ reheating the coil lasted at least 15'. The temperature in the room had dropped also in the meantime.
So it took at least 20' before it reached the previous temperature and +/- 30' later, a new defrost started again.

Even Mitsubishi Belgium came with their fabulous software but everything was normal.

They were serious thinking about installing water heated coils (with gas) in the ducts.

Another strange technique: Mitsubishi also has a water cooled version of their R2 system - can't remember the type right now - the complete heat regain system.
All the outdoor units are connected on the waterside together and the main water lines goes to an outside drycooler.
Well, they don't use the hot water from the 'too-hot' coils to heat the 'too-cold' coils.
They don't use the benefit of lowering HP when it's outside cold.
The units keeps running at the same HP, whatever water temperature they can reach.
They don't use the benefit from free cooling when available.


And for those who read my posts in the past, they know that I
have very much faith in geothermal heatpumps, especially the DX ones. You can reach in some occasions COP's from 5 even 6.
BESC5240 and I did together once a theoretical approach of it - while eating our sandwiches at noon- and we even reached COP's more than 7? Do you remember this?

Geothermal heatpumps are the only heatpumps that can perform the best under all conditions.
Why?
Compared to air cooled systems, when do you need the heat inside the building the most? When it's very cold outside and heat is then almost outside not available anymore. But, it's still available deep in the ground at a very stable temperature.

Same picture in summer: when suffers a compressor the most to reject his heat? When it's outside at his highest point. But again, we can use the cold soil to condens at very low stable temperatures.

So it benefits in winter and in summer. The only disadvantage is the price and the price for the drilling.

We even started with the construction for a vertical drill with an auger to drill holes of 5 inches and +/- 75 feet deep.
Auger is almost finished, special drill head with possibility to use pressurized water in the center of the auger is finished but...time, time, time.

[frank]

i,ve got to agree Peter, the COP measurements are taken and published but I don't know at what operating conditions.

I was just quoting the published data from the latest R410A equipment. Having installed a lot of these systems I am quite impressed with their performance and quietness.

Here's a link to the Daikin site where you can read all the relevant advertisements for the current Daikin kit http://www.daikin.co.uk/default.jsp

[Peter_1]

Do once the test for yourself and re-calculate some values.
In the technical manual, you can find the heating capacities at varying outside conditions, also -5°C as far as I remember.
If you then look for the power at these econditions, you will find a much lower COP.
But, you then haven't even taken in account the negative impact of the whole defrosting cycle which takes a long time and drops the COP even more. (or do we wall this the EER like the Americans do?)