Use and Care Manual

33
110637-01 - 5/20
RRO Installation & Service Manual
10 Operating (continued)
Table 10-7: 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
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 10-6: Zone Request, Parameter zc_= zr
ii. When ZC_ is set equal to Zone Request
(ZR)
When there is no IWH the Cold Start
Boiler Control “ZC” output may be
configured to control a second heating
zone. This is particularly helpful when
the home uses only two heating zones.
The Cold Start 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 10-6. 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, Step
2, Item 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 10-7.