air source heat pump

[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.