EER + COP inverter figures

[Ybb]

Hi all, I'd like an explanation as to how the latest series of inverters seem to manage to double the efficiency of older a/c's. Previously an efficient machine ran with an eer or cop of up to 350%. ie. An input of 1kw for an output of 3.5kw. Recently I've seen several manufacturers claiming efficiencies up to 600%. An example is the Mitsubishi Heavy Industries MHI050705_RAC_SupDelux.pdf < can't post links sadly so that didn't work. The SRK25ZDXA-S claims to use 500w and put out 2.5kw for an eer of 5. Is this because of an increased volumetric efficiency and condensing capacity at 50% load? If so is it simply a case of fudging the figures because the eer would reduce as load did? It's hurting my head so I'd be glad if someone could shed light on what I suspect is pr spin.:)

[momo]

Take a comparison with the petrol car: we started with carburetors and manual adjust of ignition timing (1915ad +/-!) then vacuum + centrifugal advance then auto-chokes then ...+... A Haynes manual did wonders then:).

Now you have electronics controlling just about anything CO2 levels etc and ONLY the manufacturer's (expensive) authorized service stations can get to do anything even change the oil (I'm sure my current vehicle gets sluggish when it gets to service kilometers:eek:) Sorry I digress - back to the issue:
A/C are moving on: fixed capillaries... TXVs to EEVs, Sub-cooling of "liquid" line, variable speed condenser fans... Power speed, and phase control of 3 ph compressors (AC/DC; piston...scroll...) tightens the issue as does more careful pushing machines to the limits (sensors on discharge T) - at least they sometimes tells us what's wrong. (Problem then is interfacing with the owner and his/her interpretation of a number of flashes of this or that light :rolleyes: on domestic - at least on larger systems these are not so easy to find ;))
Perhaps we take a lesson: after six months code entered reset - good with delayed bill payment :D:D

Also how big and effective are you condenser evaporator units single/double/triple rows of pipes, slitted/flat/wavy fins... Each % improvement counts. As an installer: is the insulation on pipes adequate?

[Ybb]

Take a comparison with the petrol car: we started with carburetors and manual adjust of ignition timing

That's fair enough but the difference between the units with an eer of 3.5 and 6 is simply that they're running 410a and inverter compressors. I'm not comparing 1920's tech with 2007 just 2006 with 2007. It's one change which I find hard to justify the supposed efficiency increases.

In our local rating system 6 stars was the top of the scale and very few if any systems had that rating. Now a few new models suddenly claim nearly 11 stars under that same system. I fail to see how that increase can be justified by R410a and inverters alone. To me it seems the figures are being massaged for PR.

[The MG Pony]

look at the change of technology from 95 to now? It is how technology works, it jumps it dosn't walk.

You at this moment can take any old A/C and by rebuilding it using TXVs and PWM fan controls and a good programable thermistat increase its performance by magnitudes. Just scale it up for heat pumps!

[momo]

MG Pony - nice ideas !: I'm using some of them on a pet project modifying a 10 yr old Carrier dual split to provide physically separate heating and cooling sources...
Ybb - Reconsider what I said: It is is the sum of improvements, properly engineered. 2% here + 10% there +% +%...:) (Not price/cost engineered:p)
I'm trying to find an article I read on the topic of EER improvements...
Also consider part load improvements, when your switched compressor is short cycling because of inadequate matching with the heat load it is serving.

[Ybb]

look at the change of technology from 95 to now? It is how technology works, it jumps it dosn't walk.



As I said I'm not comparing 10 yo technology with todays. I'm looking at one model to the next in the same year. As an example the MHI SRK28HCA-S 2.5kw on 410a has an eer of 3.21. Compared with the 2.5kw SRK25ZDA-S on 410a which has claimed eer of 6.43. The only difference is the inverter.

If you want to use analogies that's the equivalent of Toyota bringing out a new model car that produces twice the horsepower for the same amount of fuel. Nothing that revolutionary has happened overnight in car design and it's why I question these claimed figures and would like an explanation.

[The MG Pony]

time scale is irrelivant, we are using it as an example!

Phase change systems are nothing like automobiles, there are alot of areas for A/Cs to improve with vehicles there is not much left.

We have detailed to you how they can do it. They can get big gains simply by reprogramming the thermistat, let alone improvments on the hard ware! Infact you answered your own question, they gained heavily by the inverter!

[Ybb]

time scale is irrelivant, we are using it as an example!


No it is relevant because historically changes of this order of magnitude don't happen overnight.



Phase change systems are nothing like automobiles, there are alot of areas for A/Cs to improve with vehicles there is not much left.


Inverter technology and the associated controls have been around for years. I don't want to argue over the progress of new technology I just want an explanation of the sudden doubling in efficiency on paper.



We have detailed to you how they can do it. They can get big gains simply by reprogramming the thermistat, let alone improvments on the hard ware! Infact you answered your own question, they gained heavily by the inverter!

No you haven't answered the question with numbers that justify the increase. I can speculate myself that the inverter is the difference which causes the 100% improvement in efficiency but that isn't a detailed answer. MHI claim the spectacular eer at 50% part load but as a conventional system cant run at part load it's not comparing apples with apples and hence why I think the figures are being tweaked for the sake of marketing. If it was run at full load it may return an eer of say 3.5 which is good but not way off the scale. It's for this reason I reckon it's spin because it's nice to think inverters spend their days idling along on 50% load but in reality on 40 degree days they're running flat chat and efficiencies will go out the window.

[The MG Pony]

Well get one rip it apart, then look at the other unit and do a comparitive analisys.

Computer tech can skyrocket one day to the next let alone a month, unles you get an engineer to tell you exactly what the dif is I'm afriad we wont be able to explain exactly other then explaining how they can do it!

And yes they will be doing some spin, they'll messure in some isolated set of peramiters, and published the best and most faverable resualts.

[Ybb]

And yes they will be doing some spin, they'll messure in some isolated set of peramiters, and published the best and most faverable resualts.

That's my hope. That an engineer reading this can explain how they set up the tests to double the results overnight.

[The MG Pony]

Seting up the ideal situation won't net them performance, it will just highlight them, the unit has to be capable in the first place.

To get real world performance is much much harder to do. As how they set the test up, it is just an ideal situation for that design, nothing sneaky or special.

[Electrocoolman]

Hi guys,
I must admit a COP of 6+ does seem incredible, but would agree with you that the technological advances are the probable reason for the increases in COP.

I believe SANYO have a small 2.5kW unit with a COP of 5. (AIRE 75)

Certainly R410a has a big part to play in the increase and allowed smaller compressors to be used...these in turn require less power to drive them.
Also dont forget that Inverter technology has moved on from a few years ago.....we now have better semiconductors (power FETS)...much more efficient ...we also have DC (digital or direct commutation) motors using powerful magnets....so a lot lower motor losses when compared to the AC inductive motor.
I also believe that the Sanyo unit manages to defrost the unit differently and more efficiently when in heat pump mode.

So the advances in lots of different areas and better control technology all adds up bit by bit.

[Ybb]

Hi guys,
I must admit a COP of 6+ does seem incredible, but would agree with you that the technological advances are the probable reason for the increases in COP.

I believe SANYO have a small 2.5kW unit with a COP of 5. (AIRE 75)

Certainly R410a has a big part to play in the increase and allowed smaller compressors to be used...these in turn require less power to drive them.

That's what I question. Both the examples I quoted were on R410a so the only difference is the inverter and slightly different electronics modulating to the load. Theoretically the driven load should be the same given they run the same refrigerant.



Also dont forget that Inverter technology has moved on from a few years ago.....we now have better semiconductors (power FETS)...much more efficient ...we also have DC (digital or direct commutation) motors using powerful magnets....so a lot lower motor losses when compared to the AC inductive motor.
I also believe that the Sanyo unit manages to defrost the unit differently and more efficiently when in heat pump mode.

So the advances in lots of different areas and better control technology all adds up bit by bit.

Thanks for the input. I accept that it's going to be more efficient due to to progression of technology. What I find hard to stomach is the doubling of figures from the non inverter equivalent on the same gas. I'd imagine inverters by their nature have losses in converting AC to drive using DC which to an extent offset the efficiency gains in the motor design. If that's the case it makes the instant doubling of efficency all the more incredible.

As I understand it and I don't work with these everyday, I mainly do commercial / industrial refrigeration. The benefit of inverters is they have the DC torque (and motor efficiencies) to modulate speed under load which a standard AC compressor couldn't do. The fan speed control etc is nothing new so the only difference is compressor modulation alongside fan speed control based on room load. Very little difference to justify the figures doubling overnight.

I might contact the star rating people to see if they have anyone who can explain the jump and where the "50% part load" comes into the equation. I'm sure that has a lot to do with it.

[Peter_1]

I haven't read this thread completely but COP figures going over 5 are thermodynamically seen impossible for an air/air heatpump.
You can add as much as electronics you want, you just can't change nature laws, even how hard the electronics tries.

[wkd]

I agree with Peter1 are you looking at EER in the literature and mistaking it for ESEER.The ES is European Seasonal Energy Efficiency Ration which takes into account part load conditions where using an inverter is much more efficient.It is tested by running at 100% load and then measuring EER and dropping the condenser inlet condition and load in increments of say for example 75-50-25% load.Its now very common in chillers to see EEr of say 2.8 and ESEER of 4.1+.This is measured at the following conditions and obtaining EER for each point.
100% at 35 C ambient (A)
75% at 30 C ambient (B)
50% at 25 C ambient (C)
25% at 20C ambient (D)
For chillers the above EER's are then weighted according to a yearly model based on a tested building load cycle in seville somewhere.Basically over one typical the unit runs at:
100% for 3%
75 % for 33%
50% for 41%
25 % for 23%
So ESEER = (A x 0.03)+(B x 0.33)+ ( C x 0.41)+(D x0.23).
This is how its done for chillers according to Eurovent.

[Ybb]

I agree with Peter1 are you looking at EER in the literature and mistaking it for ESEER.The ES is European Seasonal Energy Efficiency Ration which takes into account part load conditions where using an inverter is much more efficient.

Thanks wkd for the explanation.

The documentation that started my quest is hXXp://XXX.mhi.net.au/CommercePortal/download/MHI050705_RAC_SupDelux.pdf (You'll need to replace the X's in that url if you want to follow the link.)
It specifically refers to EER and COP. I suspect that they are using the ESEER means of testing and passing it off as EER without clarification. The mention of 50% part load was what made me suspicious that it was spin due to testing methodology.

[Peter_1]

Certainly R410a has a big part to play in the increase and allowed smaller compressors to be used...these in turn require less power to drive them.

R410a has a higher specific heat which makes that smaller pistons in the compressor can be used , that's true but this necessarely doesn't say that these use less power to drive them.
The needed power for a given capacity (or the COP) doesn't change that much in the range an airco is working in.

R410a compressors gives the same or even worse COP factors then those with R410 at EN conditions. Do once the test with a compressor software and compare both once