Air Source Heat Pump

[jackpreacher]

I just installed a 12kW ASHP today and am amazed at its performance. Photos and details to follow over this week.

Have any other P&C members got an ASHP?

[jackpreacher]

....naturally mine was secondhand, cheap and rejected by previous owner's wife on account of its aesthetics and noise.....

We think it's great

[Stock]

Com'on Jack don't keep us in suspense.................

[Muz]

Aye lad what is it? (In me best Yorkshire) does it do chips? Or can thee make bread from it?

[B4D2USA]

Jack, I have one out at the CPHQ studio apartment. When you say 12 KW, don't you mean 12,000 BTU? Or is that the way you folks on the other side rate electric heating devices? We have a "mini split" system that combines the heat pump to the air handler unit inside via a Freon line set. The unit is wired direct and the air handler/control head is connected via low voltage wiring. Mind you, it is only conditioning about 300 square feet of living space, but it will freeze you right out of the space if you set it too low in AC mode. It is quite capable of heating the space during the winter, although I have a propane direct-vent heater as backup should the electric fail or the air temp drops to sub zero. It can keep up with days where the temps are in the teens (Fahrenheit) but will cycle a lot more. It also frequently "burps" when very cold as the Freon needs to relieve built up pressure due to colder outside temps. This is a momentary cycle whereby the compressor clicks off and a large purging sound cycles through, then the system restarts and continues heating. All in all, we have been very happy with it's performance over the last several years and the electric required to run it has been quite economical.

[Wazza]

Cant afford luxuries like any form of heating that involves electrickery here ,the price of electricity is so high as to be frightening ,if 12kw is the motor size then .................................................. .................................................. .................................................. .................................................. ..................

[jackpreacher]

Sorry for the delay......!

No photos yet for many complicated reasons but I will take some of the finished installation on Monday. Basically my old LDV Pilot van had to be repaired and MOT'd [road worthiness test] in a short space of time as we were pulled off the M6 motorway by the traffic police as we headed to Scotland to pick up some stuff. They were doing a whole day or two of on-the-spot testing to catch illegal vehicles...you know the drill........anyway, 'Dobbin' [....ahem...my LDV], who looks a little rough to say the least, was inspected by some police mechanics who found only one fault - the front leaf spring to axle U-bolts were a little loose causing a creaking noise when the steering was pulled one way to its limit. They gave me 7 days to retest the van and get it passed its MOT or it would be prohibited from the road. So, there was no time to do anything in the way of recording the repairs or starting a thread [there aren't too many LDV Pilots left on the road these days anyway] - I just had to get down to it fix him. Last Saturday he had his MOT and failed on welding required in the engine bay......it took nearly 3 days of pretty solid work to fix him. The original fault found by the police took me 10 minutes to rectify BTW.
....in between doing this I managed to fit the ASHP and get it working.......I'll add a diagram of the bumbling circuit later this afternoon. I must say though that it is a noisy bit of kit.........bit like a small aircraft's prop noise...

Dobbin from behind.jpg
This is not Dobbin, though it is an LDV Pilot.
...add copious amount of rust ........

[jackpreacher]

The ASHP extracts heat from ambient air. The optimum outside temperature to do this is anything above 5℃ although the manufacturer states that the ASHP will operate at temperatures of -5℃. At these lower temperatures [or as Bert might say 'Warm' temperatures ] the efficiency of the unit drops to almost unity - as in it requires 1kW of electrical energy consumption to shift 1kW of extracted heat from the outside air. Have a look at this performance chart grabbed from the documentation that came with the ASHP:




At 5℃ the unit will extract 7.9kW of heat from the surrounding air.....HOWEVER....this requires 3.9kW of electrical energy to do this, therefore the performance is measured as a COP [coefficient of performance] number of 7.9/3.9 which is 2.02


At 15℃ the unit will extract 10kW of heat from the surrounding air but this still requires 3.9kW od electrical energy to do this, therefore the performance is COP is 10/4.9 which is just over 2.56


If you rely on electricity to heat up your DHW [domestic hot water] then it makes sense to have an ASHP solely to do this as it is always going to be cheaper to do this than immersion heaters which have a COP of almost 1, all the time. The only time when immersion heaters are as efficient as an ASHP for heating DHW is when the outside temperature is around - 5℃ as the COP of the ASHP approaches 1 at these temperatures.

[jackpreacher]

I installed the ASHP to supplement the heating, not replace it. As some of you may be aware I am in the middle of building a hydro-electric system using the fell supply water to generate up to 10kW of electricity, continuously. It makes sense to use this electricity to power an ASHP to multiply the power by the ratio of the COP.

In the diagram below the ASHP is bumbled straight into a 44kW plate heat exchanger that boosts the temperature of the central heating [CH] return water. This reduces the load on the Wood Pellet Boiler [..ahem....'Pele'.....] hence reducing the wood pellet consumption. At the moment the ASHP only operates during off-peak electricity tariff periods so the cost of the electricity is only £0.06 as opposed to £0.16 per kW.Hr

Heating Overview ASHP.jpg

[jackpreacher]

When you say 12 KW, don't you mean 12,000 BTU?

No, 12kW, or just under 41,000 btu!! Whether it actually shifts 12kW into the heating system waits to be seen............

It also frequently "burps" when very cold as the Freon needs to relieve built up pressure due to colder outside temps. This is a momentary cycle whereby the compressor clicks off and a large purging sound cycles through, then the system restarts and continues heating.

The equivalent on the ASHP is a defrost cycle where the heat extracted is pushed around the refrigerant coils if they get too cold.


I'd say the US is streets ahead of the UK with refrigerant based coolers and heaters - the cost of these units in the UK from new is astronomical - a brand new ASHP rated at 12kW is around £3500.00 [$5310.00] A bit daft considering the simplicity of the construction - a compressor, some copper tubing, a large coil and a fan. Ok, there's a bit more to it than that but certainly not £2000 worth.

[jackpreacher]

I paid about a quarter of the new price for a unit that is 3 years old.



Still, at 60dB, it's a noisy beastie........

[jackpreacher]

Aye lad what is it? (In me best Yorkshire) does it do chips? Or can thee make bread from it?

I would pay money not to be in a room with a Scotsman trying to do a Yorkshire accent!!!


It does a nice job of cooling yer legs when yer stand in front if it, so maybe it could make yer hot chips cold and soggy.....?

[B4D2USA]

Read it and weep Jack. These things are made in one of the Asia countries. Here is a 36,000 BTU unit. It is basically like mine, but mine is only 12,000 or 14,000 BTUs. They use Freon 410a (I think). You need a new fitting to adapt your refrigeration gauges and suction pump.

http://www.ebay.com/itm/36-000-Btu-K...item19d3610a71

[jackpreacher]

Those split units just blow hot or cold air..? I thinks so.
The unit I installed actually has a heat exchanger which puts the heat into a water circuit at a maximum of 55℃ which is more practical for the wet central heating system already installed. Still, US units are a lot cheaper..

[jackpreacher]

Read it and weep Jack. ..

...found this on the Navitron forum...

Extract from Navitron.jpg