16
Circulator Pre-purge time has a factory
setting of 2 minutes and is field adjustable
between 2 and 20 minutes. When reset card
is installed, pre-purge time may be adjusted
down to zero (0) minutes. Refer to Table 8a.
8. PROGRAM ThE CONTROLS (continued)
5.
Start Temperature (
St_
)
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.
6.
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.
During Priority Time 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 8b.
Table 8a: Circulator Pre-purge Time example,
(
PP_
= 2 minutes)
Call for
Heat
Source
DHW
Terminal
Selection
Boiler
Temperature
Burner Status
TT = on
-
<140
Start with no delay
TT = on
-
>140
Start after 2 minute delay
DHW = on
tt2
<140
Start with no delay
DHW = on
tt2
>140
Start after 2 minute delay
DHW = on
dh
<140
Start with no delay
DHW = on
dh
>140
Start with no delay
7.
Domestic Hot Water (DHW) Terminal
Function (
dh_
)
The control allows configuration of the
DHW Circulator output functionality to help
the boiler integrate into each installation
more effectively. The DHW Circulator
output can be connected to a domestic hot
water circulator or a second heating zone
circulator. These applications are selected
as follows:
a. When
dh_
is set equal to Domestic Hot
Water Demand (
h
)
When there is an Indirect Water Heater
(IWH) the control provides “DHW” input
terminals for the IWH Aquastat and “DHW
Circulator” output terminals 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 DHW terminal. When the Priority
Time parameter is set to “
off
” the System
Circulator is not forced off for a DHW call
for heat. Refer to Table 8b.
Table 8b: DhW Terminal Function (
dh_
)
Selection = Domestic hot Water Demand,
(Parameter dh_ = dh)
Call for heat
Circulator Status
T-T
Input
DHW
Input
Priority
Time
(
Pt_
)
System
Circulator
Output
DHW
Circulator
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
