29
VII: OPERATING (continued)
Setpoint of 10°F. The Low Limit Differential
is the number of degrees the boiler temperature
must decrease below the Low Limit Setpoint
before the Warm Start Boiler Control takes
actions to warm the boiler. These actions include
starting the burner and stopping water flow
through the boiler. The Low Limit Differential is
adjustable between 10°F and 25°F.
e. Circulator Overrun Time (
OR_
)
Circulator Overrun Time (also called “circulator
off delay” or “circulator post purge”) continues
circulator operation after a call for heat has
ended, sending excess heat from the boiler into
the priority zone. Ensure system piping and zone
panel settings allow water flow to the priority
zone after the call for heat ends. The Circulator
Overrun Time has a factor setting of 0 minutes
and is field adjustable between 0 and 10 minutes.
f. Circulator Pre-Purge Time (
PP_
)
When the boiler is warm [boiler water
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 6.
The Warm Start Boiler Control Pre-purge Time is
factor set to 0 minutes.
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 6: 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 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 7A.
i. ZC and ZR Terminal Function (
ZC_
)
The boiler control allows configuration of the
ZC output functionality to help the V1 RO/FO
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
