Boiler Circuit And Shunt Pumps; Safety Equipment To Din En 12828; System Examples - Viessmann KOB PYROTEC Technical Manual

Grate combustion 390 to 1250 kw, fully automatic wood boiler, for the combustion of woodchips, pellets, shavings and mixed wood
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Design information
(cont.)
Connect all heat consumers or heating circuits to the boiler flow and
return connectors. Never make any connections to the safety flow or
to other connections.
We recommend you install shut-off valves into the heating flow and
return lines, so that the entire water content will not have to be drained,
should work be required on the boiler or heating circuits.

Boiler circuit and shunt pumps

In order to reliably prevent boiler corrosion caused by flue gas con-
densation, the boiler return temperature must never be below 65 °C.
The boiler has variable output control. This requires a constant boiler
flow rate of the water to be heated. The boiler circuit with boiler pump
and boiler mixer should therefore be installed in accordance with the
design recommendations.

Safety equipment to DIN EN 12828

Installation of the safety equipment of the heating system should be
carried out by the authorised heating installer.
EN 12828 applies to the design of DHW heating systems with safety
temperatures up to max. 110 ºC.
This standard contains safety requirements laid down for boilers and
boiler systems.
■ Sealed expansion vessel.
■ A safety valve at the highest point of the boiler or a pipe connected
to the boiler. The pipework between the boiler and the safety valve
must not be able to be shut off. Pumps, fittings or restrictions must
not be present in this pipework. The blow-off line should be con-
structed so as to prevent the possibility of increases in pressure. Any
expelled heating water must be able to be drained off safely. Arrange
the outlet of the blow-off line so that any water expelled from the
safety valve can be safely observed and drained off.

System examples

General information
■ In order to reliably prevent boiler corrosion caused by flue gas con-
densation, the boiler return temperature must never be below 65 °C.
A boiler circuit pump with boiler mixer should be provided in accord-
ance with the system scheme.
■ The sizing of the boiler circuit should be carried out in such a way
that the temperature differential between the flow and return is 15
°C or smaller.
PYROTEC
Easy installation
For safety temperatures up to 110 ºC, the boiler requires no inter-
mediate flow piece for the connection of safety equipment.
All connections required for the various pieces of equipment, e.g. for
water level or pressure limiters, are provided on the boiler.
The sizing of the boiler circuit should be carried out in such a way that
the temperature differential between the flow and return is 15 °C or
smaller. The control of the boiler pump and boiler control valve is inte-
grated in the control unit supplied.
■ A low water indicator is not required, except in attic heating centres
(water level limiter available as an accessory).
■ Thermometer and pressure gauge.
■ Integrating heat consumers
■ The expansion vessel must be connected to the boiler without shut-
off devices via the boiler flow.
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