68
Low Temperature Heat Exchanger (LTHX) Margin Vs
Capacity Control Signal
The microprocessor will control the generator
concentrations to maintain the selected Low Temperature
Heat Exchanger (LTHX) service setting setpoint. The Low
Temperature Heat Exchanger (LTHX) margin setpoint is
located in the service settings field startup group menu.
The standard set point is 15°F which is the solution margin
at nominal design conditions. As the evaporator load
decreases and the capacity control signal decreases, the
margin will increase to a maximum of 30°F at minimum
generator flow as illustrated in Figure 18. Between 15% and
minimum solution pump speed, the Low Temperature Heat
Exchanger (LTHX) margin increases to 30°F. The following
chart illustrates this activity. The generator flow is
controlled by changing the Low Temperature Generator
(LTG) pump speed as evaporator load decreases.
Figure 18
Plus 15°F
Service Setting: Low
Temperature Heat
Exchanger (LTHX)
(15°F)
Minimum Flow
(Minimum LTSP
AFD speed)
Capacity flow control signal
Maximum Flow
(Maximum LTSP
AFD speed)
Note:
When the energy input is greater than 90% and if the
margin begins to widen (lack of heat input to concentrator)
the UCP may slowdown the drives in an effort to maintain
Low Temperature Heat Exchanger (LTHX) margin setpoint.
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