Figure 35; Boiler - Weil-McLain 4 Series Manual

®
Series 4
U-Control operation and setup
Control is set for the proper water temperatures for the
system. Excessive water temperature can cause signifi cant
property damage in some applications.
includes circuits that require lower temperature water
(radiant slab circuits, for example) as well as higher
temperature circuits (DHW, fi nned 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 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 fi ring 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 (fi nned tube
baseboard, radiant fl oor, 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 fl ue 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 35 is a summary of the operating sequence for the U-Control.
2. The symbols shown appear in the display as the U-Control cycles the

boiler.

3. The wrench symbol appears when a scheduled maintenance date ar-
rives. This informs the homeowner to call the contractor for service.
4. The exclamation mark symbol appears when a problem has been
detected.
32
gas-fired water boiler — Boiler Manual
— You must ensure that the U-
— If the heating system

Figure 35

Check the boiler model listed on the power-up
screen. If it is not correct, turn off the boiler. See
Figure 115, page 102 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 — 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)
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 fi rst
Start circulators for this priority setup
Calculate target temp — If sensor temp is below
target temp, begin fi ring sequence
Blower to ignition speed for prepurge
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)
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
fl ame signal
Flame detected
Hold boiler at low fi re for 1 minute
Release boiler to modulation
NOTE: If fl ame 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 satisfi ed, go to postpurge
Flame detected
Release boiler to modulation immediately
NOTE: If fl ame 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 satisfi ed, go to postpurge
Demand satisfi ed (temperature reaches target
temperature or limit setting)
Gas valve off
Blower to ignition speed for postpurge
Return to standby after purge
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
Display turns RED due to error or limit event
Flashing display means lockout condition —
display toggles between three screens as in
Figure 124, page 117 .
Warm weather shutdown — the boiler will not
be allowed to fi re if the outside temperature is
greater than the WWSD setting.
Part number 550-100-400/0119
(also see Figure 36, page 33 )
— Start