User Guide

34
VIII: OPERATING (continued)
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 9: CIRCULATOR PRE-PURGE TIME EXAMPLE,
PARAMETER PP_= 2 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 reect 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 eld 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 eld
adjustable between “On” and “Off” Refer to
Table 10.
i. ZC and ZR Terminal Function (ZC_)
The boiler control allows conguration of the ZC
output functionality to help the AP-U 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 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 “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.
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: DOMESTIC HOT WATER DEMAND,
(PARAMETER ZC_= DH)