Multi Boiler Systems - Viessmann VITODENS 200-W Technical Manual

Design information

Multi boiler systems

We recommend the installation of a low loss header in multi boiler
systems. For this, order the low loss header that is available as an
accessory. See page 32 and the Viessmann pricelist.
Losses resulting from the use of third party low loss headers are exclu-
ded from our liability.
On-site safety equipment should comply with EN 12828.
As an alternative to the low loss header, a suitably sized plate heat
exchanger may be used to provide system separation. In that case,
the flow temperature sensor should be arranged on the secondary side
of the plate heat exchanger. See the following system example.
M
A
A Flow temperature sensor
Low loss header
Application
Design rules for system hydraulics:
■ When balancing the low loss header, adjust the flow rate on the
equipment side to approx. 10 to 30 % below the flow rate on the
system side (reducing the return temperature).
■ The low loss header should be sized for the max. flow rate which
may occur in the overall system.
The low loss header separates the heat source (boiler circuit) from the
downstream heating circuits.
Install a low loss header if the maximum flow rate in an individual sys-
tem design is greater than the values shown in the table below.
Boiler
Vitodens 200-W, 45 and 60 kW
Vitodens 200-W, 80 and 100 kW
Vitodens 200-W, 125 kW
Vitodens 200-W, 150 kW
We recommend installing a low loss header if the minimum flow rates
listed in the table below cannot be guaranteed.
Boiler
Vitodens 200-W, 45 and 60 kW
Vitodens 200-W, 80 and 100 kW
Vitodens 200-W, 125 and 150 kW
For installation schemes in conjunction with low loss headers, see the
relevant sample application in the "System examples" document.
VITODENS 200-W
(cont.)
M
Max. flow rate
l/h
3500
5700
7165
8600
Min. flow rate
l/h
450
1300
3600
Information on the plate heat exchanger
■ Provide air vent valves (for example quick-action air vent valves) on
the primary side (boiler side) and the secondary side (heating circuit
side) of the plate heat exchanger.
■ Flush existing heating systems thoroughly before fitting the plate
heat exchanger. The use of a sludge separator is recommended.
■ Fit the flow temperature sensor into the flow connector on the sec-
ondary side, as shown. Connection elbows with integral sensor well
are available as accessories.
■ Set the circulation pumps in the boiler connection sets to ΔP constant
and max. pump rate.
■ The connection of several plate heat exchangers is not recommen-
ded.
Sizing the plate heat exchanger:
■ The pressure drop in the plate heat exchanger must be lower than
the lowest pressure drop of connected heating circuits.
■ Fit a dirt trap on the secondary side of the plate heat exchanger.
■ When sizing, take the temperature differential of the plate heat
exchanger into account (max. flow temperature in a multi boiler sys-
tem with Vitodens 200-W: 76 °C)
Boiler circuit
The circulation pump in the Vitodens must be able to supply the
required water volume against the (mostly low) pressure drop of the
boiler circuit; the pressure drop of the low loss header is negligible.
Subject to the water volume circulating in the boiler circuit, the respec-
tive residual head may be determined for sizing the internal pipe diam-
eters using the pump diagram; alternatively the variable speed pump
can be adjusted accordingly.
Heating circuit
The heating circuit pumps to be installed on site must be able to deliver
the water volume in the heating circuits against their pressure drop,
and must be sized accordingly.
Principle of operation
T1 T3
V primary
V secondary
T2 T4
VIESMANN
4
45