Product Overview

49
103859-12 - 8/19
MPO-IQ
Installation & Service Manual
Table 11B: Domestic Hot Water Demand,
(Parameter ZC_= DH)
outdoor air reset option card installed.
Call for Heat
Outdoor Air Reset Option
Card
P/N 102294-01
Circulator
Status
T- T
Input
ZR
Input
DHW
Input
Priority
time
Priority
Time
Expired?
C1
Output
ZC
Output
off -- off > 0 no off off
on -- off > 0 no on off
on -- on > 0 no off on
on -- on > 0 yes on on
on -- on = 0 no on on
off -- on = 0 no off on
Call for Heat Circulator Status
T- T
Input
ZR
Input
C1
Output
ZC
Output
off off off off
on off on off
on on on on
off on off on
Table 12: Zone Request, Parameter zc_= zr
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. When reset card is installed
pre-purge time may be adjusted down to zero (0)
minutes. Refer to Table 10.
6. Start Temperature (St_)
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.
7. 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 11A.
8. ZC and ZR Terminal Function
The boiler control allows configuration of the ZC
output functionality to help the MPO-IQ 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:
a. 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
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 11A: Domestic Hot Water Demand,
(Parameter ZC_= DH)
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 11A.
9 Operating (continued)