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Installation Electrical
Condenser Water Flow Interlock
The Symbio800 shall accept an isolated contact closure input from a customer installed proof-
of-flow device such as a flow switch and customer provided pump starter auxiliary contact for
interlocking with condenser water flow. The input shall be filtered to allow momentary openings
and closings of the switch due to turbulent water flow, etc. This shall be accomplished with a 6
seconds filtering time. The sensing voltage for the condenser water flow switch is 115/240 VAC.
On a call for cooling after the restart inhibit timer has timed out, the Symbio800 shall energize the
condenser water pump relay and then check the condenser water flow switch and pump starter
interlock input for flow confirmation. Startup of the compressor will not be allowed until flow has
proven.
If flow is not initially established within 1200 seconds (20 minutes) of the condenser pump re-
lay energizing, an automatically resetting diagnostic "Condenser Water Flow Overdue" shall be
generated which terminates the prestart mode and de-energizes the condenser water pump relay
This diagnostic is automatically reset if flow is established at any later time.
Note: This diagnostic would never automatically reset if Symbio800 was in control of the con-
Chilled Water Reset (CWR)
The MP will reset the chilled water temperature setpoint based on either return water tempera-
ture, or outdoor air temperature. The Return Reset option is standard, Outdoor Reset is optional.
The following is selectable:
•
•
•
•
When the chiller is running, if any type of CWR is enabled, the MP will step the CWS toward the
desired CWS' (based on the below equations and setup parameters) at a rate of 1 degree F every
5 minutes until the Active CWS equals the desired CWS'. When the chiller is not running the CWS
will be fully reset immediately (within one minute). The chiller will then start at the Differential to
Start value above a fully reset CWS or CWS' for Outdoor, Return, and Constant Return Reset.
Equations for calculating CWR
Equation used to get Degrees of Reset:
Outdoor Air:
Degrees of Reset = Reset Ratio * (Start Reset - TOD)
Return Reset:
Degrees of Reset = Reset Ratio * (Start Reset - (TWE - TWL))
Constant Return:
Degrees of Reset = 100% * (Design Delta Temp - (TWE - TWL))
To obtain Active CWS from Degrees of Reset:
Active CWS = Degrees of Reset + Previous CWS
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denser pump through its condenser pump relay since it is commanded off at the time of
the diagnostic. It could however reset and allow normal chiller operation if the pump was
controlled from some external source.
RESET TYPE Setpoint.
This can be set to: NO CWR, OUTDOOR AIR TEMPERATURE RESET, RETURN WATER TEM-
PERATURE RESET, or CONSTANT RETURN WATER TEMPERATURE RESET. The MP shall not
permit more than one type of reset to be selected.
RESET RATIO Setpoints.
For outdoor air temp. reset, both positive and negative reset ratios will be allowed.
START RESET Setpoints.
MAXIMUM RESET Setpoints.
The maximum resets shall be with respect to the chilled water setpoint.
RTHD-SVX04K-EN
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