Common Point Sensor Insta llation
Lead/lag operation do es not require a common chil led water point sensor . Common point
sensors can be added to the 8-input option modu le, if desired. Refer to th e certified drawings f or
termination of sensor leads.
Note: If the common point sensor option is chosen on a chilled water system, both machines
should have their own 8-in put option module and c om m on point sensor instal led . Each
machine will use its ow n c om m on point sensor for control, when that machine is desi g-
nated as the l ead chiller. T he PIC cannot read the value of common poi nt sensors
installed on other machines in the chilled water system.
When installing chiller s in s er ie s, a common point sensor sho uld be used. If a common point
sensor is not used, the lea ving chilled water sens or of the upstream chiller m us t be moved into
the leaving chilled wa te r pipe of the downstream ch ill er.
If return chilled water c on trol is required on chill ers piped in series, the c om m on point return
chilled water sensor sh oul d be installed. If thi s sens or is no t installed, the retu r n c hil led water
sensor of the downstrea m chiller must be relocat ed to the return chille d wat er pipe of the
upstream machin e.
To properly control the common supply point temp er at ure sensor when chille rs are piped in
parallel, the wat er flow through t he shutdown chi llers must be isola ted so that no w ater by-pass
around the oper ating chiller occu rs. The common point sensor optio n must not be used if water
bypass around the oper at ing chiller is occurri ng.