Use and Care Manual

30
TABLE 10: ExTERNAL LOW LIMIT,
PARAMETER ZC_= ELL
Call for Heat Circulator Status
T-T
Input
ZR
Input
C1
Output
ZC
Output
off off off on
on off on on
on on off off
off on off off
independently, "TT" input controls only the
System Circulator output and the "ZR" input
controls only the "ZC" output. Both inputs
cause a boiler call for heat.
The Warm Start Boiler Control with ZC_
set equal to Zone Request (ZR) energizes
the "ZC" terminal while the boiler is warm
as described earlier in this section (refer to
Paragraph A,2,f). The "ZR" input is a call
for heat that starts the boiler.
iii. External Low Limit, Parameter ZC = ELL
The Cold Start Boiler Control is capable of
functioning as a warm start control when
external limit control is installed that closes
a contact when boiler water temperature
falls below a setpoint. When an external
limit contact closes (boiler water is cold)
the boiler is started and the "ZC" and "C1"
output terminals are de-energized. When
the "ZR" terminal is de-energized (boiler
water temperature is above setpoint) the call
for heat is ended and the "C1" terminal is
released to operation and the "ZC" terminal
is energized. An External Low Limit
Request is detected by sensing a voltage on
the "ZR" terminal. The Warm Start Boiler
Control does not have the External Low
Limit Option. Refer to Table 10.