Safety Devices; Fire Extinguishing Water Tank; Expansion; The Boiler System With 3-Way Mixing Valve - Viessmann Vitoflex 300-UF Series Installation And Operating Instructions Manual

Mechanical

Safety Devices

1. Install the pressure relief valve, discharge pipe, air
vent and pressure gauge as illustrated in section piping
and installation of safety devices.
A 30 or 60 psi pressure relief valve is supplied with
the boiler (standard equipment).
The UF 1250, 30 psi will have 2 PRVs.
2. Install a discharge pipe on the pressure relief valve.
The end of the pipe must not be threaded. The pressure
relief discharge pipe should extend to a floor drain and
end approximately 6 in. (150 mm) above the drain.
IMPORTANT
DO NOT install a shut-off valve in the discharge pipe.
DO NOT reduce the discharge pipe diameter.
DO NOT pipe the discharge to outdoors!
IMPORTANT
Install an approved factory supplied pressure relief valve.
Air vent(s) in the system supply must be installed to
purge the air from the system. To ensure the boiler can
be purged of all air, ensure supply / return water lines do
not contain restrictive piping where air could be trapped.
WARNING
Do not install an isolation valve between the boiler and
the pressure relief valve. The discharge pipe for the
pressure relief valve must be oriented to prevent scalding
of attendants. Pipe the pressure relief valve discharge
pipe close to floor drain. Never pipe the discharge pipe
to the outdoors.
IMPORTANT
This boiler does not require a flow switch.
A low water cut-off may be required by local codes.
If the boiler is installed above radiation level, a low water
cut-off device of approved type must be installed in all
instances. Do not install an isolation valve between boiler
and low water cut-off.

Fire extinguishing water tank

The self-activating extinguishing device must be installed
next to the boiler feed system. Refer to section fire
extinguishing systems for the assembly.
The fire suppression is performed by means of an
extinguishing valve, which is not dependent on an electric
current. A float-type switch monitors the water level and
should be electrically connected (see field wiring diagram).
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Vitoflex 300-UF Installation & Operating

Expansion

With closed expansion, the supply pressure to the
expansion tank should be equal to the max. amount
of the system pressure plus 3 psi (0.2 bar).

The boiler system with 3-way mixing valve

To reliably prevent boiler corrosion through condensation
of the flue gases, the boiler return temperature must
never be below 149°F (65°C).
The stepless control of the Vitoflex 300-UF Grate Firing
System output requires a constant flow through the boiler
of the water to be heated. The boiler circuit, the boiler
pump and boiler-mixing valve must therefore be installed
according to section piping and installation of safety
devices.
The boiler circuit should be designed that the temperature
difference between the boiler supply and the boiler return
temperature is equal to or less than 27°F (15°C).
The activation of the boiler pump and boiler mixing valve
is integrated in the custom control panel.

Drain inspection port

UF 390 - 720
G
UF 950 - 1250
Legend
A 3 in. x 5 in. Nipple
B 3 in. x 3 in. x 1b in.
Reducing Tee
C 3 in. Plug
D 1b in. x 2 in. Nipple
E 1b in. Ball Valve
F 1b in. Cap
G 1b in. x 5 in. Nipple