Centrif chiller pilot expansion valve

Can anyone shed some knowledge.

Between the condenser and evaporator is the expansion valve, but there is an additional line running between the condenser and the main expansion valve which has a small pilot expansion valve running directly into the bottom of the main expansion valve. What is the purpose of this?? does anyone have any literature on it's function.

Please see the image attached with the line highlighted. or view original document section "HSC Liquid Line" on page 44 of http://lit.daikinapplied.com/eprsup/...ts/7000002.pdf

Thanks!

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