■ Minimum pressure switch for CM2, CM3 and CT3B to 314 kW
■ Minimum pressure limiter for CT3U, CR3B and CT3B from 400 kW
■ Water level limiter in certain installation configurations, e.g. in attic
heating centres or where there is no static water column, install a
water level limiter instead of a minimum pressure limiter/switch.
Maximum pressure limiter
Required for every boiler in a system if the rated boiler heating output >
300 kW.
Minimum pressure limiter
For safe operation, a minimum operating pressure of 0.5 bar
(0.05 MPa) is essential. This can be ensured by using a minimum
pressure switch or limiter.
Safety valve
In accordance with EN 12828 for hot water heating systems with a
safety temperature of max. 110 °C and in accordance with their type
approval, these boilers must be equipped with a type-tested safety
valve. This must be designated in accordance with TRD 721 as fol-
lows:
■ "H" up to 3.0 bar (0.3 MPa) permissible set pressure and max.
2700 kW heating output
■ "D/G/H" for all other operating conditions
The connection line between the boiler and the safety valve may not
be fitted with shut-off devices. Pumps, fittings or restrictions must not
be present in this pipework.
Flash trap
For boilers above 300 kW, install a flash trap with discharge pipe and
drain line near the safety valve. The discharge pipe must lead out-
doors. Any extracted steam must not endanger anyone.
The discharge pipe on the safety valve should be constructed so as to
prevent the possibility of increases in pressure. Arrange the outlet point
of the drain line so that any water expelled by the safety valve can be
safely observed and drained off.
A flash trap may not be required, if each heat source is furnished with
an additional high limit safety cut-out and pressure limiter.
Safety accessories selection table for the Vitocrossal
This table indicates the safety accessories required for the boiler to EN
12828.
(x = required, – = not required)
Rated boiler heating output
≤ 300 kW
> 300 kW
Safety temperature
(High limit safety cut-out setting
*1
, STB as part of the standard delivery of the boiler control unit)
110 °C
110 °C
Temperature controller
Standard delivery of the boiler control unit
x
x
Boiler thermometer
Standard delivery of the boiler control unit
x
x
Pressure gauge
Pressure gauge (as separate accessory)
or
as part of the fitting assembly with accessories or the safety equipment block (only up to 142 kW)
x
x
Safety valve
A 3 bar (0.3 MPa) safety valve is part of the safety equipment block (applicable up to 142 kW)
x
x
Minimum pressure limiter
*2
As low water indicator
x
x
Maximum pressure limiter
–
x
Fitting assembly with accessories
(With pressure gauge, lockable shut-off valve, drain and two connectors for safety pressure limiters)
–
x
*3
Flash trap
–
x
*4
High limit safety cut-out
*5
(additional)
–
x
Safety pressure limiter
*5
(Additional) (maximum pressure limiter)
–
x
8.5 Fuels
Vitocrossal boilers are suitable for the combustion of natural gas, town
gas and LPG to EN 437 "Test gases, test pressures", or in accordance
with local regulations.
*1
In its delivered condition, the high limit safety cut-out (STB) of the Vitotronic is set to 110 °C and may need to be adjusted.
*2
For the Vitocrossal 200, 87 to 314 kW and the Vitocrossal 300, 87 to 142 kW, a minimum pressure switch can be used as a low water indicator
(accessories).
*3
Option; accessories to EN 12878 for the installation of the high limit safety cut-out.
*4
See Vitoset pricelist.
*5
EN 12828 specifies that a flash trap may not be required, if each heat source is furnished with an additional high limit safety cut-out and
pressure limiter. (Components are available as "flash trap replacement set" in Accessories.)
Design information
(cont.)
Gas condensing boilers
VIESMANN
23
5822 449 GB
8
