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VRV Combination Ratio or Connection Ratio?Helpful Member! 

tomVDV (Mechanical) (OP)
17 Feb 11 6:23
HI
If any one can help me I want to know what is the Combination Ratio or the Connection ratio in VRV & VRF system?
Thanks
cdxx139 (Mechanical)
17 Feb 11 16:32
Ive done a couple of these systems and I dont understand the question.

Are you asking how many evaporator units can fit on a condenser system?  Mitsubishi allows up to 130% capacity.

knowledge is power

Helpful Member!  Drazen (Mechanical)
17 Feb 11 17:43
Different manufacturers have slightly different terms, but that is about the mentioned principle.

Your outdoor unit has nominal and maximal rating, while indoor units have something like maximum  capacity they can have under certain conditions.

Sum of indoor units maximum ratings divided to outdoor unit maximum rating gives your connection ratio.

You have to remember that it does not mean you can reach sum of indoor maximums, it is only allowed conneciting. Maximum is defined by outdoor maximum.

This reflects reality of coincident loads. If you calculate coincident maximal load for system in your calculations, and maximums for all romms, difference will be large the larger number of rooms and the more different orientation.

What does this all means? It means you can save money by specifying outdoor unit on maximum coincident load, not on sum of indoor maximums, taking care that connection ratio is not exceeded.
marcoh (Mechanical)
23 Feb 11 7:04
in chilled water systems it is called diversity
AnotherEllis (Mechanical)
25 Feb 11 9:56
This is the biggest fight I have had on VRV/VRF systems. A design zoned to take advantage of diversity can get well in excess of 130% FC:CU ratio.

Daikin and Sanyo understand this. LG does not. It is maddening.

www.ellisconsultingengineers.com

lavish410 (Mechanical)
25 Feb 11 12:02
It is the ratio of nominal capacity of all indoor units to nominal of outdoor unit.

Like daikin, now LG has also launched new version with 130% combination and solution for AHU/FAHU connectivity...

Cheers!!!
mtss (Mechanical)
10 Mar 11 17:59
130% is the usual maximum connection ratio for most systems. Some of them allow up to 200 % ratio (Daikin, Mitsubishi) only you have to work with a manufacturer's rep. They can submit your application to the manufacturer's engineering department. For all applications exceeding 130% ratio, the o.k. is given on individual project basis.  
AnotherEllis (Mechanical)
10 Mar 11 23:21
Not with LG. The Koreans are a nervous bunch.

www.ellisconsultingengineers.com

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