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Part number 550-100-400/0119
46
The Gas-fi red water boilerFeaturing Flexibility
Ultra Models -299/310 and -399
The advanced blower design and air inlet silencer on Ultra boilers
result in very quiet operation.
Air enters the boiler enclosure through the air intake adapter (18),
fl ows through the enclosure, enters the air inlet silencer (5), then
enters the venturi (6). The blower pulls air and gas through the
venturi and pushes the mixture into the burner.
The automatic gas valve (4a) senses the vacuum in the venturi caused
by fl owing air, and allows gas to fl ow when power is applied. The
manual gas valve (4b) allows shutting off the gas supply for servic-
ing or shutdown.
The horn-shaped air inlet silencer signifi cantly reduces fan noise,
providing exceptionally quiet operation.
When air fl ows through the venturi, it creates a vacuum. This vacuum
pulls gas from the gas valve. So gas will only fl ow if air is fl owing. The
gas/air mixture enters the blower before passing on to the burner.
This sensor monitors boiler outlet water temperature. The control
module adjusts boiler fi ring rate so the outlet temperature is correct,
based on boiler outlet and system supply temperatures.
This sensor monitors return water temperature. The control module
reduces or increases boiler input, depending on how close the return
water temperature is to the outlet water temperature.
The electronic display is used to confi gure boiler settings and moni-
tor boiler operation.
The buttons allow changing display mode, entering setting values,
and resetting after lockout.
Made with high-grade stainless steel construction, the burner uses
pre-mixed air and gas. The burner and control provide modulat-
ing fi ring.
U-Control
The U-Control
odule responds to signals from the room ther-
mostats, DHW aquastats (when used), boiler sensors (boiler return,
boiler supply, system return, system supply, fl ue temperature, and
outdoor temperature, if used). The control module automatically
adjusts blower speed (and gas fl ow rate) to match boiler output to
space heating and/or DHW heating demand.
The Ultra control panel is mounted to a hinged sub panel, allow-
ing the panel to be swung forward and down for easy access to the
electrical connections.
Knockouts are provided in the jacket top panel, allowing conduit
entry directly behind the control panel or near the wall.
Connect the boiler internal condensate trap line to the heat ex-
changer here (parts supplied with boiler, but fi eld installed).
The condensate trap PVC fi ttings are fi eld-installed, connected to
the condensate trap line as shown in this manual.
The front door is sealed to the boiler assembly around its entire
perimeter.
Two (2) screws secure the door in place.
The burner fl ame is ignited by applying a high voltage to the igni-
tion electrode. This causes a spark (from electrode to ground). After
ignition, the electrode measures fl ame signal.
The quartz glass window provides a view of the burner surface
and fl ame.
This dual sensor monitors the fl ue gas exit temperature. The control
module will shut down the boiler if fl ue gas temperature gets too hot.
This protects the fl ue pipe and the heat exchanger from overheating.
®
Series 4
gas-fired water boiler — Boiler Manual
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