User Guide

35
VIII: OPERATING (continued)
Call for Heat Circulator Status
T-T
Input
ZR
Input
C1
Output
ZC
Output
off off off off
on off on off
on on on on
off on off on
TABLE 11: ZONE REQUEST, PARAMETER ZC_= ZR
TABLE 12: 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
ii. When ZC_ is set equal to Zone Request (ZR)
When there is no IWH the Cold Start Boiler
Control “ZC” output may be congured to
control a second heating zone. This is
particularly helpful when the home uses
only two heating zones. The boiler control
replaces the need for a two circulator zone
panel. When DHW Terminal Function
(dh_) is set to ZR the boiler control’s two
circulator outputs are used to control two
independent heating zones. Refer to Table
11. A “TT” input causes a call for heat and
energizes the System Circulator output to
service heating zone 1. A second zone’s
thermostat may be wired to the “ZR” input
to energize heating zone 2 circulator wired
to the “ZC” output. Both outputs function
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 12.