Hydraulic connection
Hydraulic resistance
∆
T-measurement
∆
p-measurement
16
Hydraulic resistance
The hydraulic resistance depends on
the flow rate through the boiler and the
boiler type. In the graph the resistance
for a specific flow rate can be found.
The R40 is able to control a speed
controlled pump via a 0-10VDC signal.
It makes the flow rate modulate in pa-
rallel with the burner load. The mini-
mum flow rate, to which the pump is
allowed to modulate with the burner
load, is 30% of the nominal flow rate
through the boiler.
The flow rate through the boiler can
also be checked by calculation. This
can be done with a
∆
T as well as a
∆
p
measurement.
R4
0/1
00-
150
R4
0/6
5-8
5
∆
T-measurement
Check the temperature difference over
the boiler (
∆
T flow-return) when the
boiler is running on 100% load. The
nominal
∆
T is 20K and must be at least
between 15K and 25K for secure boiler
operation. An indication of the actual
flow rate can be found with the follow-
ing calculation (see table below for
nominal data):
∆
p-measurement
Check the pressure difference over
the boiler (
∆
p flow-return) when the
boiler pump is running (burner on is
not required). The nominal
∆
p for
each boiler type can be found in the
table below, actual
∆
p must be within:
0.35*
Δ
p
nom
≤
∆
p
≤
1.75*
∆
p
nom.
An indi-
cation of the actual flow rate can be
found with the following calculation
(see table below for nominal data):
Water flow data
R40/65
R40/85
R40/100
R40/120
R40/150
Nominal flow rate
m
3
/h
2.6
3.4
4.0
4.8
5.6
∆
T at nominal flow rate
K
20
∆
p at nominal flow rate kPa
16
29
15
22
34
q
actual
= (
∆
T
nominal
/
∆
T
measured
) * q
nominal
q
actual
=
√
(
∆
p
measured
/
∆
p
nominal
) * q
nominal
