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ChillyWilley
13-12-2008, 06:43 AM
COP = Coefficient of Power

Am I correct?

Browsing through the forum, the subject of VRV systems has caught my attention. Never been exposed to such a system, I have been researching them. I am reading a report of Impact of the Variable Refrigerant Volume Air Conditioning Systems on Building Energy Efficiency. Energy Consumption is discussed, and COP is also a topic, but is not defined. A Google search of the acronym listed 35 possibilities, and Coefficient of Power seems the most logic answer.

Thanks!

Grizzly
13-12-2008, 07:20 AM
High Chilley Willey.

That's what we refer to on this side of the pond!
Grizzly

nike123
13-12-2008, 09:20 AM
COP = Coefficient of Power

Am I correct?

Browsing through the forum, the subject of VRV systems has caught my attention. Never been exposed to such a system, I have been researching them. I am reading a report of Impact of the Variable Refrigerant Volume Air Conditioning Systems on Building Energy Efficiency. Energy Consumption is discussed, and COP is also a topic, but is not defined. A Google search of the acronym listed 35 possibilities, and Coefficient of Power seems the most logic answer.

Thanks!

In fact, it is Coefficient Of Performance.

http://tinyurl.com/65g3zo

Argus
13-12-2008, 03:29 PM
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COP = Coefficient of Power

Am I correct?

Browsing through the forum, the subject of VRV systems has caught my attention. Never been exposed to such a system, I have been researching them. I am reading a report of Impact of the Variable Refrigerant Volume Air Conditioning Systems on Building Energy Efficiency. Energy Consumption is discussed, and COP is also a topic, but is not defined. A Google search of the acronym listed 35 possibilities, and Coefficient of Power seems the most logic answer.

Thanks!






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‘Coefficient of Power’ is an electrical expression that is becoming adopted to describe the efficiency of wind turbines. It has had other meanings in the electrical industry over the years as people search for adequate descriptors from time to time.
We’re not in that line of business.

‘Coefficient of Performance’ on the other hand, a has a strict meaning in the Carnot cycle, describing the efficiency of a refrigeration process in terms of heat transfer versus energy or power used.

There is also a secondary, commercial use of the term that is probably what the OP had in mind, especially as he refers to VRF systems.

In the field of Heat Pumps it is defined in the various national and international rating standards as a ratio of the heating capacity (the rated output) to the effective power input at a given rating temperature and condition. (Effective Power is the total of all the power absorbed by all parts of the machine, compressors, fans pumps, controls, the lot).

In commercially-made heat pumps and VRF you’ll see this in the specifications as ‘CoP’ followed by a number.
The cooling cycle is subject to the same calculation and is called the Energy Efficiency Ratio (EER).
Most standards allow the ratios to be refined by a correction to allow for energy associated with fluid and air transport, in other words, fans and pumps, where this is significant.

All the CoP and EER measurements are taken at 100% capacity, so that seasonal efficiencies are not taken into account.

You need to allow a little caution with CoP figures for VRF units as the manufacturers publish CoP and EER figures for the outdoor unit only. They have a tendency to omit the power absorbed by indoor units, so the systems appear more efficient than they actually are.


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ChillyWilley
13-12-2008, 03:46 PM
Argus,

Thank you for defining the differences between Coefficient of Performance, and Coefficient of Power.

Nike123,

Thank you for the formulas applied for calculating Coefficient of Performance.

Thermatech
13-12-2008, 04:12 PM
COP = Co-efficient of Performance.

Measure of the usefull energy a system can deliver compared to the energy that it consumes.

Calculated by dividing the energy output by the energy input.

The higher the COP figure the more efficient the system is deemed to be.

Due to the constant development & refinement & energy efficiency improvements of VRV & VRF systems over the last 10 years COP has improved from around aprox 2.8 on R22 systems up to arround 4.3 on R410a systems.

However due to the vast number of combinations of indoor unit & interconnecting pipe lenghts available on VRV & VRF systems it would be difficult to get Eurovent to test all available combinations.

However manufacturers do publish the electrical input data for all indoor units & also correction graphs for equivalent pipe lenghts & outdoor unit electical input.
So at the fixed standard condition you could calculate the overall COP for any VRV / VRF installation.

but

If you select heat recovery VRV / VRF system you would then need to consider the impact from heat recovered from any indoor units cooling to any indoor units heating.


How far do you go to calculate the actual COP of an infinately veriable system ?

Its all a bit more straight forward with split systems.
Just go to Eurovent web site & compare all the manufacturers equipment data as tested by Eurovent.

Argus
13-12-2008, 04:41 PM
How far do you go to calculate the actual COP of an infinately veriable system ?




It can be done.

The UK Government has an energy efficiency scheme that allows a tax break on certain eligible heat pump products, including VRF. (The Enhanced Capital Allowance scheme – ECA for short).

You can use their calculator tool to work it out.


http://www.eca.gov.uk/etl/default.htm

You can search eligible products by manufacturer and model, including the products of those VRF manufacturers who have submitted products for approval – this also includes VRF and there is an excel calculator that you can download with a selector page that you can build up a system with the outdoor unit and the selection of Indoor units of your choice. It will work out various combinations of VRF indoor units and display the CoP and EER plus whether it’s eligible for the tax break.

All the main VRF companies are represented.



Click ‘Find ETL Product.
Select ‘Heat Pumps – Split and Multi split, including VRF’ in the drop menu
Select your manufacturer.
Select the VRF sheet that you see ( If they don’t have one it will be absent).
Read the instructions for use - then do what it says.



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