Specifications
Part number 550-100-090/0809
g a s -f i r e d w a t e r b o i l e r — Boiler Manual
28
U-Control operation and setup
Temperature settings — You must ensure that the U-
Control is set for the proper water temperatures for the
system. Excessive water temperature can cause significant
property damage in some applications.
Multi-temperature systems — If the heating system
includes circuits that require lower temperature water
(radiant slab circuits, for example) as well as higher
temperature circuits (DHW, finned tube baseboard, etc.),
it is recommended to protect low-temperature circuits
with limit controls that are wired to a U-Control external
limit circuit. Failure to provide regulation can result in
substantial property damage.
U-Control sequence of operationFigure 33
Display Control action (also see Figure 34, page 29)
POWER
UP
Check the boiler model listed on the power-up •
screen. If it is not correct, turn off the boiler. See
Figure 102, page 86 to change setting.
When power is turned on, the screen lists sen-•
sors that are detected. If any sensor is not listed,
make sure it is connected correctly. Turn off
power and restart.
Standby
Standby — no calls for heat•
Toggles through no dots, 1 dot, 2 dots, then •
3 dots while in standby (wrench symbol will
show instead if maintenance is needed)
Blower on
Call for heat detected•
Display on with BLUE light (space heating) or •
PURPLE light (DHW)
Start min/max on timers if more than one system •
is calling — highest priority starts first
Start circulators for this priority setup•
Calculate target temp — If sensor temp is below •
target temp, begin firing sequence
Blower to ignition speed for prepurge•
Multiple boilers/heat sources only• — Start
additional-heat timer — type 1 boiler starts
immediately; type 2 activates other heat source
immediately, but doesn’t start unless the timer
times out; type 3 (LEAD boiler) starts immedi-
ately and sends 0–10 VDC signal to others after
timer times out; type 4 receives signal from
LEAD boiler and starts immediately (and starts
timer for the next boiler, if programmed)
Ignition on
After prepurge times out, begin ignition cycle•
Activate gas valve and ignition spark•
Continue ignition spark for ignition period•
Turn off spark and use electrode to check for •
flame signal
Space
heating
Flame detected•
Hold boiler at low fire for 1 minute•
Release boiler to modulation•
NOTE: If flame is not detected, the gas valve •
is turned off, blower turns on (postpurge), and
control starts cycle again. After 5 failures, the
control waits 60 minutes, then tries again.
If priority timer times out, switch to next priority •
and start priority timer
If demand satisfied, go to postpurge•
DHW
heating
Flame detected•
Release boiler to modulation immediately•
NOTE: If flame is not detected, the gas valve •
is turned off, blower turns on (postpurge), and
control starts cycle again. After 5 failures, the
control waits 60 minutes, then tries again.
If priority timer times out, switch to next priority •
and start priority timer
If demand satisfied, go to postpurge•
Blower on
Demand satisfied (temperature reaches target •
temperature or limit setting)
Gas valve off•
Blower to ignition speed for postpurge•
Return to standby after purge•
Maintenance
Display turns RED, toggling between graphic •
screen and maintenance screen (occurs when
maintenance schedule timer times out)
Will show during standby only•
Boiler operates as normal•
Error/fault
Display turns RED due to error or limit event•
Flashing display means lockout condition — •
display toggles between three screens as in
Figure 111, page 101.
WWSD
Warm weather shutdown — the boiler will not •
be allowed to fire if the outside temperature is
greater than the WWSD setting.
U-Control overview
The U-Control is fully programmable to meet system requirements, allow-
ing supply water regulation for up to three different systems.
U-Control features include:
Blower speed modulation to control the Ultra boiler’s firing rate.
Advanced PID response to anticipate system needs based on response
to heat input.
Graphic and robust text display for ease of operation monitoring and
troubleshooting.
Preset operating parameters for typical heating systems (finned tube
baseboard, radiant floor, DHW, and others), including target tempera-
tures, reset curves and circulator assignments.
Control of up to three circulators (boiler circulator plus two others),
assignable for each of the three possible inputs.
Programmable priority assignments for the heat inputs.
Integral outdoor reset option, with reset curves matched to the system
type selected.
Multiple boiler/heat source sequencing or modulation.
Built-in 0–10 VDC signal generator to allow parallel modulation of
multiple boilers; also capable of accepting 0–10 VDC input.
Dual sensors for boiler outlet temperature and flue temperature, pro-
viding redundant protection.
Integral low water protection (by monitoring boiler heat exchanger
temperature).
Boiler is shipped with an outdoor sensor and strap-on system supply
and return sensors.
Sequence of operation
1. Figure 33 is a summary of the operating sequence for the U-Control.
The symbols shown appear in the display as the U-Control cycles the 2.
boiler.
The wrench symbol appears when a scheduled maintenance date arrives. 3.
This informs the homeowner to call the contractor for service.
The exclamation mark symbol appears when a problem has been 4.
detected.