Low-Loss Header - Viessmann VITODENS 100-W Installation And Service Instructions Manual

Boiler Connections
Installation Examples
Low-loss header (field supplied)

Low-Loss Header

–Type 80/50
Part No. 7134 230
(max. flow rate 17.6 GPM / 4 m
–Type 120/80
Part No. 7134 244
(max. flow rate 35.2 GPM / 8 m
Fig. 31
A low-loss header offers additional
benefits not provided by a pair of
closely spaced tees. Viessmann
strongly recommends and prefers the
use of a low-loss header over closely
spaced tees.
When used in conjunction with the
Vitodens 100-W boiler, the low-loss
header acts as hydraulic break,
decoupling boiler and system circuits
from each other (no sensor required).
It is recommended to use the low-loss
header in applications in which the
total system flow rate exceeds the
maximum (or minimum) boiler flow rate
or in cases where the system head and
flow rates are unknown.
For typical system flow rates, see the
table on page 28.
In addition, the low-loss header helps
eliminate air and debris from the
heating system.
See Fig. 33 and 34 for an illustration of
the principle of operation.
The low-loss header is available in the
following sizes. Select the size based
on the maximum system flow rate of
your application.
Model No. Max. system flow rate
Type 80/50 17.6 GPM / 4 m
Type 120/80 35.2 GPM / 8 m
36
(continued)
3
/h)
BS
3
/h)
TS
BY
BR
Fig. 32 Low-loss header design
(Type 80/50 or 120/80)
T1
V V
primary
T2
Fig. 33 Principle of Operation
3
/h
3
/h
AB Legend
AB Air Bleed
BR Boiler Return
SW
BS Boiler Supply
BY Bypass (with laminar flow)
SS
D Debris (or air if LLH is flipped)
DV Drain Valve
SR System Return
SS System Supply
TS Viessmann Temperature Sensor
SWSensor Well
SR
D
DV
Legend
T1 Boiler supply temperature
T2 Boiler return temperature
T3 System supply temperature
T4 System return temperature
V
V
V
T3
Q
Q
system
T4 V
bypass secondary
V
T1 > T3
T2 = T4
Q
T1 ± 176°F / 80°C
V
T4
When installing a low-loss header, the
system mixed supply temperature (T3)
must be calculated as follows:
T3=
(not used)
Boiler circuit flow rate
primary
Heating circuit flow rate
secondary
Bypass flow rate
bypass
Heat supplied by boiler
primary
Heat consumed by
secondary
< V
primary secondary
= Q
primary secondary
=V V
secondary primary+ bypass
IMPORTANT
T1 × V +T4 V
primary bypass
V
secondary