Heat pump / inverter DIY

housesitter

Just to go off on a random tangent if you don't mind.
Can you only get electrically powered ASHP's or are other power methods available for the systems?

Specifically I'm thinking of my Absorption Fridge I have for camping which is gas powered. No reason why the system wouldn't work in reverse. Certainly you can get gas powered fridges for the home if you look hard enough.

Gas power never really took off here. But if you consider the energy savings over gas boilers, I wonder if even more could be saved with the methods employed by the ASHP's but still burning gas to power them.

For my fridge, the excess heat from ignition is a problem. For the ASHP powered system, it would just be a further benefit for heating the house, maybe hot water.

mech_2

housesitter wrote: »

Just to go off on a random tangent if you don't mind.
Can you only get electrically powered ASHP's or are other power methods available for the systems?

Specifically I'm thinking of my Absorption Fridge I have for camping which is gas powered. No reason why the system wouldn't work in reverse. Certainly you can get gas powered fridges for the home if you look hard enough.

Gas power never really took off here. But if you consider the energy savings over gas boilers, I wonder if even more could be saved with the methods employed by the ASHP's but still burning gas to power them.

For my fridge, the excess heat from ignition is a problem. For the ASHP powered system, it would just be a further benefit for heating the house, maybe hot water.

Yeah I posted a link to such a thing in post #142 (http://www.robur.com/products/e3-systems/).

One advantage is that because the COP is lower, compared to an electric heat-pump they don't need such a large ground-source collector, nor do they have as much problem with frost with an air-source unit. They also seem to suffer less from a reduction in the COP at lower source temperatures.


Other types of gas-fired heat pump have been tried. This prototype I particularly liked because I'm a bit geeky and it's driven by a free-piston Stirling engine: http://www.globalcooling.com/documents/HermeticGasFiredResidentialHeatPump_000.pdf

stevehead

Cardew wrote: »

Stevehead,
I am trying to understand your system, and figures.

As I understand it you are stating that you have achieved the total heating of your 3 bedroomed, 3 storey house for the whole month of December with 304 kWh with 2 Mitsubishi srk20zgx ASHPs.

You reach that figure of 304 kWh by plugging in the two inside units via Maplin type power measuring units.

So each of those units is using approx 5 kWh per day.

Are you saying that your installer fed a mains supply power cable cable from each inside power unit to its outside compressor? That would be the only way the Maplins meter could measure the consumption of both units.

I am not up to date on the latest electrical regulations, but I would have thought that probably illegal and certain bad practice.

I think Rich has explained it well in his post; the external unit is powered via an outdoor isolator switch (you can see this in my vid clip) then cabled into the indoor unit alongside the coolant pipework.
The power for the outdoor compressor connects to terminals within the indoor unit.
It's the indoor unit that is connected to the 240v supply, and this is what I have plugged into a KWh monitor.
The 304KWh is the power consumption for both complete systems, not part thereof.

Cardew wrote: »

Last year just your heating with gas(not HW) in December cost £120.

Depending on what you paid per kWh that would be between 3,000kWh to 4,000kWh.

This December you have extended your house, albeit increased insulation, and this December has been much colder. Yet you have heated your house with 304kWh!!!

Something doesn't add up>

I have here in my hand just the front page from my gas bill for the period 4/12/07 to 4/3/08, which is not an estimate. It does NOT have the price per KWh, but it was a standard quarterly billing. The cost for those 3 months was £277.48 which I broke down to mean approx £90pcm.
I estimated that with the price increases it would have become £135pcm for all heating / hot water / cooking.

Current Gas Consumption is running at £3 - £4 per week DHW & Cooking (i-measure) so yes I do believe I would be paying £120pcm for gsh had I not changed a thing.

We did run the gsh for 1 night -needed a system check as the rads had all been drained down over the summer. The Entrance Hall was warm, which it isn't anymore using ashp. The unoccupied cellar where the boiler is located was also warm; obviously paying for that was a waste.
FYI The boiler is a Glow Worm Space Saver Mk 2.

stevehead

mech wrote: »

I think you're quoting a whole-system solar-to-electricity efficiency figure there, though I could be wrong.

Micro-CHP using ceramic fuel cells has also been tried, but I think they are currently too expensive to manufacture.

You're thinking about it the wrong way around. The house is basically heated from the waste heat from generating the electricity. Therefore efficiency isn't really crucial as long as it's quiet, reliable and cheap to manufacture. Though obviously the more electricity from the unit the better, especially if you don't have an export meter.

They use all of the heat from the boiler, not the excess heat. Flue losses would be the same as for a modern boiler, so the house is heated at ~90% efficiency, but you get some of your electricity from the same heat rather than having to burn fuel in a power station somewhere and supply it to homes at 40-50% efficiency.

Aaah I get it now... the other way around.
So (and I still adhere to the 25% max for Stirlings) you blast the hot side of the Stirling with your burner to spin a genny, and use the waste heat (75%) to heat your water via a condensing exchanger and voila! efficient power & heat.

paceinternet

stevehead, in your post #154 I'm not sure you have the wiring explained correctly.
Normally, the mains power is supplied to the outdoor unit. An isolator may be outside in th supply line for maintenance purposes.
Each indoor unit run by the outdoor unit is then cabled and fed it's supply from the outdoor unit.
To record the kwh used by each "system", you would need to monitor the feed to the outdoor unit.

stevehead

Cardew wrote: »

Further to my post above you state that:

However the technical spec from the link you gave (and quoted at me!) gives the input power for each unit as up to 1.27kW (1,270 watts each)

Also if I understand the tech spec correctly, at maximum input of 1,270 watts the maximum output is 4,600 watts(under ISO conditions 7C/20C etc) so that is rather less than a COP of 5.45 - is it not 3.62??

The INPUT Wattage is variable from 0.09 - 1.27KW, it doesn't run at 1.27KW unless it's within it's startup cycle or Turbo overdrive. It's rated at 440w INPUT to give 2400W OUTPUT. (=5.45)
During November, when I first quoted my usage stats, I was running on it's 'LOW' setting when it does only pull 320 - 340W then cycles off to a couple of watts... I'm on Low/Med now.

I can't really be getting any further into the symantics of the way these specs are derrived as I'm an enthused and fairly bright end-user not a tech expert. I'll just do my best to report my findings and back it up with a reasonable understanding of the way these things work. Other than that - I'll go by the Tech Manual where it clearly states COP=5.45

stevehead

paceinternet wrote: »

stevehead, in your post #154 I'm not sure you have the wiring explained correctly.
Normally, the mains power is supplied to the outdoor unit. An isolator may be outside in th supply line for maintenance purposes.
Each indoor unit run by the outdoor unit is then cabled and fed it's supply from the outdoor unit.
To record the kwh used by each "system", you would need to monitor the feed to the outdoor unit.

Same difference though Pacey... I'm monitoring the mains to the whole system. I didn't actually connect the mains but I do know where it comes from and what it runs.

paceinternet

well this is what you said:
"It's the indoor unit that is connected to the 240v supply, and this is what I have plugged into a KWh monitor."

Presumably you meant "outdoor unit" ?

Cardew

stevehead wrote: »

I think Rich has explained it well in his post; the external unit is powered via an outdoor isolator switch (you can see this in my vid clip) then cabled into the indoor unit alongside the coolant pipework.
The power for the outdoor compressor connects to terminals within the indoor unit.
It's the indoor unit that is connected to the 240v supply, and this is what I have plugged into a KWh monitor.
The 304KWh is the power consumption for both complete systems, not part thereof.

Stevehead,

Richard said your outside units were connected to a 13 amp socket and that was where the Maplin monitor was connected.

You have either explained things badly or you don't understand electrical wiring.

I totally agree that your installer should have wired it as you state above, but in that case the Maplin monitors will not be registering the power taken by the outside units.

Your Maplin monitors that each measured 152kWh(to keep it simple) for December are just monitoring the power the inside unit takes from the 13 amp socket to which it is connected.

It is not(or should not) be monitoring the power taken by the outside unit.

How do you explain that the maximum power shown on the Maplins Monitor is 360watts when your unit input is 1,237watts?

Cardew

stevehead wrote: »

I can't really be getting any further into the symantics of the way these specs are derrived as I'm an enthused and fairly bright end-user not a tech expert. I'll just do my best to report my findings and back it up with a reasonable understanding of the way these things work. Other than that - I'll go by the Tech Manual where it clearly states COP=5.45

Our point is your posts are totally misleading to people reading this as well as utube etc..