Lochinvar MP2 - Manual (Page 15)

B OILER T ARGET D URING S ET P OINT
The boiler target temperature during a set point demand is
increased to at least the Set Point setting. This temperature
is maintained as long as the control has a set point demand.
S ET P OINT M ODE
SETP MODE 1 - Setpoint in Parallel
Whenever a set point demand is present, the boiler(s) is
operated to maintain the set point target. The primary pump
does not turn on, but may operate based on a Boiler
Demand or an External Input Signal, see Figure 24.
It is assumed that the Set Point pump will provide ade-
quate flow through the heat exchanger and the boiler.
SETP MODE 2 - Set Point in Parallel with Priority
Whenever a set point demand is present, the boiler(s) is
operated to maintain the set point target and the primary
pump (Prim P1) contact is opened.
It is assumed that the Set Point pump will provide ade-
quate flow through the heat exchanger and the boiler.
SETP MODE 3 - Primary Pump during Set Point
Whenever a set point demand is present, the primary pump
(Prim P1) is turned on and the boiler(s) is operated to main-
tain the set point target.
S ET P OINT P RIORITY O VERRIDE
The set point has a Priority Override while in SETP MODE
2. In order to prevent the building from cooling off too much
or the possibility of a potential freeze up during set point pri-
ority, the control limits the amount of time for set point prior-
ity. The length of Set Point priority is determined by the
Priority Override setting. Once the allowed time for priority
has elapsed, the control overrides the set point priority and
operates set point and heating simultaneously by turning on
the primary pump (Prim P1).
C ONDITIONAL S ET P OINT P RIORITY
If the boiler(s) supply temperature is maintained at or above
the required temperature during set point generation, this
indicates that the boiler(s) has enough capacity for set point
and possibly heating as well. As long as the boiler target
temperature is maintained and the heating and set point
targets are similar, set point and heating occur at the same
time.
SECTION G: EXTERNAL INPUT OPERATION
S ECTION G1: E XTERNAL I NPUT
E XTERNAL I NPUT
The control can accept an external DC signal in place of the
outdoor sensor. The control converts the DC signal into the
appropriate boiler target temperature between 50°F (10°C)
and 210°F (99°C) based on the External Input Signal and
Offset settings. To use the external input signal, the
External Input / Stand Alone DIP switch must be set to
External Input.
When operating in the external input mode, an external sig-
nal is required in order for the control to provide heat to the
heating system. An external signal is generated by apply-
ing a voltage between 0 V (dc) and 10 V (dc) across the Out
+ and Com - terminals (4 and 1) (FIG. 25). Once voltage is
applied, the External Input Signal pointer is displayed in the
LCD and the control closes the primary pump contact. The
control calculates a boiler target supply temperature based
on the external input signal and the settings made in the
control. The control then fires the boiler(s), if required, to
maintain the target supply temperature. If the external sig-
nal goes below the minimum voltage, the External Input
Signal pointer is turned off in the display. The boiler target
temperature is displayed as " - - - " to indicate that there is
no longer a call for heating. The primary pump and boiler
pumps operate as described in section C.
FIG. 24
Do Not Apply Power Do Not Apply Power
–
+
–
FIG. 25
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