Use and Care Manual

32
110637-01 - 5/20
RRO Installation & Service Manual
10 Operating (continued)
temperature higher than 140°F (adjustable
using Start Temperature parameter)] and
there is a thermostat call for heat, the
system circulator is started and boiler
firing is delayed pre-purge minutes. If the
temperature drops below 140°F or there is
a DHW Call for Heat the boiler is started
without delay. Additionally, the boiler is
started without delay if the thermostat call
for heat is initiated when the boiler water
temperature is less than 140°F. This feature
helps save energy by satisfying home
heating needs with residual boiler heat
rather than cycling the boiler. The Circulator
Pre-purge time has a factory setting of 2
minutes and is field adjustable between 2
and 20 minutes. Refer to Table 10-4.
The Warm Start Boiler Control Pre-purge
Time is factor set to 0 minutes.
g. Start Temperature (t_)
The amount of “Heat available” is
calculated by taking the difference between
measured boiler water temperature and
the Start Temperature setting. Useful
“Heat Available” is dependent on the type
of heating emitter installed in the home.
Heat emitters require a certain minimum
temperature to operate effectively. Our
default settings reflect cast iron radiators.
Fan Coils may require a start temperature
setting of 180°F or 160°F before providing
heat to the home. The Start Temperature
has a factory setting of 140°F and is field
adjustable between 140°F and 180°F.
h. Priority Time (Pt_)
When the Priority Time parameter is set to
“on” and Domestic Hot Water (DHW) call
for heat is “on” the DHW demand will take
“Priority” over home heating demand and
the system circulator will be forced “off”.
Priority Time ends and the system circulator
is released to service home heating
demand when Domestic Hot Water call for
heat is over. When Priority Time parameter
is set to “Off” the DHW call for heat does not
force “off” the system circulator. The Priority
Time has a factory setting of “On” and is
field adjustable between “On” and “Off”
Refer to Table 10-5.
i. "ZC" and "ZR" Terminal Function (ZC_)
The boiler control allows configuration
of the "ZC" output functionality to help
the RRO integrate into each installation
more effectively. The "ZC" output can
be connected to a domestic hot water
circulator or a second heating zone
circulator or be used to enable pumps in a
warm start application. These applications
are selected as follows:
i. When ZC_ is set equal to Domestic Hot
Water Demand (dh)
When there is an Indirect Water Heater
(IWH) the boiler control provides a “ZR”
input terminal for the IWH Aquastat
and “ZC” output terminal for the DHW
Circulator. When there is a DHW call for
heat, the System Circulator is “forced
off”, the DHW Circulator terminal is
energized and the circulator pre-purge
time delay control logic is bypassed
to allow the boiler to fire without delay.
When DHW demand ends the System
Circulator “force off” is removed, the
circulator can respond normally, and
the DHW Circulator is de-energized.
The DHW call for heat is detected by a
voltage on to the "ZR" terminal. When a
Priority Time parameter is set to “off” the
System Circulator is not forced off for a
DHW call for heat. Refer to Table 10-5.
Call for Heat Circulator Status
T- T
Input
ZR
Input
Priority
Time
(Pt_)
System
Circulator
Output
DHW
Circulator
ZC Output
on off
On
on off
on on
On
off on
off on
On
off on
on off
OFF
on off
on on
OFF
on on
off on
OFF
off on
Table 10-5: Domestic Hot Water Demand,
(Parameter ZC_= DH)
Call for
Heat
ZC and ZR
Terminal
Function
(ZC_)
Boiler
Temp.
Boiler Status,
(B1 Output)
TT= on -- < 140 Start with no delay
TT = on -- >140 Start after 2 minute delay
ZR = on
ZC_ = ZR
<140 Start with no delay
ZR = on
ZC_ = ZR
>140 Start after 2 minute delay
ZR = on
ZC_ = DH
<140 Start with no delay
ZR = on
ZC_ = DH
>140 Start with no delay
Table 10-4: Circulator Pre-Purge Time Example,
Parameter PP_= 2 Minutes