Install Instructions

29
VIII. OPERATION (continued)
7. Domestic Hot Water (DHW) Terminal Function (dh_)
The control allows conguration of the DHW
Circulator output functionality to help the Series 2
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 re 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 7.
b. When dh_ is set equal to Second Heating Zone
(tt2)
When there is no IWH the “DHW Circulator”
output may be congured to control a second
heating zone. This is particularly helpful when
the home uses only two heating zones. The
control replaces the need for a two circulator
zone panel. When DHW Terminal Function
(dh_) is set to “tt2" the control’s two circulator
outputs are used to control two independent
heating zones. Refer to Table 8. A “TT” input
causes a call for heat and energizes the “System
Circulator” output to service heating zone 1 and
a second zone's thermostat wired to the “DHW”
input causes a call for heat and energizes heating
zone 2 circulator wired to the "DHW Circulator"
output.
When there is a Second Heating Zone (call for
heat) the boiler is started and the DHW
Circulator terminal is energized. When Second
Heating Zone terminal is de-energized the call
for heat is ended and the DHW Circulator is
de-energized. A Second Heating Zone is detected
by sensing a voltage on the DHW terminal.
Table 7: 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
Table 8: DHW Terminal Function (dh_)
Selection = Second Heating Zone,
(Parameter dh_ = tt2)
Call for Heat Circulator Status
T-T
Input
DHW
Input
System
Circulator
Output
(Zone 1)
DHW
Circulator
Output
(Zone 2)
off off off off
on off on off
on on on on
off on off on