Thumb rule for belt driven compressor - Power loss

We are comparing direct drive compressor system against Belt driven compressor system.

What is the thumb rule figure for loss due to belt driven system ( is it 2 to 3 %)

That is a reasonable percentage to use for belt drive compressors. You do need to find out if the compressor ratings include this loss, or if you need to correct for belt drive losses yourself.

I have incorporated belt drives in many installations on reciprocating compressors of varying sizes with little problems and have proved the transmission to be reasonably efficient and reliable. The correct selection for the Job being considered is paramount.
In general I have found the efficiencies to be in the rage between 95 to 98 % but this is hard to determine . The Input power can be determined fairly easily but the HP input to the driven device at best is estimated.
If you check out the Web or Google "Gates" Will give a back ground to this matter of belt drive efficiencies.

I know that it is difficult to determne the exact losses, but at the same time, we have to put in figures for the sake of consultants & I think Mr. John's Figures do match with What I knew. Many thanks

Dear Mr. John,

The client has atleast taken up the figures vey seriously & ofcourse he shall cross check with this own sources. But at the same , he said that the data furnished to him by all the concerned like consultants etc was worng on this score. We are now very much in the race to get this order, though it could be delayed for the time being. Your answer at the right time helped us a lot.