GESTRA NRG 26-21 Manual

1
Installation & Operating Instructions
818774-05
Level Electrode
NRG 26-21
GESTRA Steam Systems
NRG 26-21 EN
English

2
Contents
Page
Contents
Important notes
Usage for the intended purpose...............................................................................................................4
Function..................................................................................................................................................4
Safety note..............................................................................................................................................4
Directives and standards
VdTÜV Bulletin "Wasserstand 100" (= Water Level 100)..........................................................................5
ATEX (Atmosphère Explosible) .................................................................................................................5
UL/cUL (CSA) Approval ............................................................................................................................5
Note on the Declaration of Conformity / Declaration by the Manufacturer ..........................................5
Technical data
NRG 26-21..............................................................................................................................................6
Scope of supply ......................................................................................................................................7
Name plate/marking ...............................................................................................................................7
Installation
Dimensions NRG 26-21...........................................................................................................................8
Key .........................................................................................................................................................8
NRG 26-21..............................................................................................................................................9
Tools.......................................................................................................................................................9
Examples of installation
NRG 26-21............................................................................................................................................10
NRG 26-21............................................................................................................................................11
Key .......................................................................................................................................................11

3
Contents
Page
- continued -
Electrical connection
NRV 2-29 .............................................................................................................................................12
Key .......................................................................................................................................................12
Connection of level electrode ................................................................................................................13
NRV 2-29, connecting the terminal strip................................................................................................13
Wiring diagram .....................................................................................................................................13
Tools.....................................................................................................................................................13
Basic settings
Factory setting ......................................................................................................................................14
Establishing active measuring range (control range)..............................................................................14
Troubleshooting
Indication, diagnosis and remedy ..........................................................................................................18
Maintenance
Safety note............................................................................................................................................19
Cleaning the electrode rod ....................................................................................................................19
Removing and disposing of the level electrode
Removing and disposing of level electrode NRG 26-21..........................................................................19

4
Important notes
Usage for the intended purpose
The level electrode NRG 26-21 is used for continuous level monitoring in steam boilers and (pressu-
rized) hot-water installations or in condensate and feedwater tanks. In conjunction with the level switch
NRS 2-.. and the level controller NRR 2-.. the electrode can be used as water level controller with
MIN/MAX alarm.
The level electrode is designed for use in conjunction with the following level switches/controllers:
NRS 2-50, NRS 2-51, NRR 2-50, NRR 2-51, NRR 2-52 and NRR 2-53 or NRS 2-1, NRR 2-1, NRR 2-2
and NRT 2-1.
The electrode can be used in electrically conductive and non-conductive fluids.
Function
The level electrode and the electronic module NRV 2-29 work according to the capacitance measure-
ment principle and translate the level changes into a level-dependent current signal, with the length of
the electrode rod determining the measuring range.
The level electrode is installed inside steam boilers, vessels or in an external level pot. If the electrode
is installed inside the boiler or vessel, a protection tube provided on side ensures correct functioning.
(see section Examples of installation (page 10).
The level electrode can be installed together with one GESTRA level electrode for water level limiting or
for high-level alarm in a single protection tube or external level pot.
Safety note
Danger
When loosening the level electrode steam or hot water might escape!
This presents the risk of severe scalding all over the body!
It is therefore essential not to dismantle the electrode unless the boiler pressure is
verified to be 0 bar.
The level electrode becomes hot during operation.
Risk of severe burns to hands and arms.
Before carrying out installation and maintenance work make sure that the equipment is
cold.
Attention
The name plate specifies the technical features of the equipment. Do not commission or
operate any item of equipment that does not bear its specific name plate.
The equipment must only be installed, wired and commissioned by qualified and competent staff.
Retrofitting and maintenance work must only be performed by qualified staff who - through adequate
training - have achieved a recognised level of competence.

5
Directives and standards
VdTÜV Bulletin "Wasserstand 100" (= Water Level 100)
The level electrode NRG 26-21 in conjunction with the following level switches / controllers is type
approved according to VdTÜV Bulletin "Wasserstand (= Water Level) 100": NRS 2-50, NRS 2-51,
NRR 2-50, NRR 2-51, NRR 2-52 and NRR 2-53 or NRS 2-1, NRR 2-1, NRR 2-2 and NRT 2-1.
The VdTÜV Bulletin "Wasserstand (=Water Level) 100" specifies the requirements made on water level
control and limiting equipment for boilers.
ATEX (Atmosphère Explosible)
According to the European Directive 2014/34/EU the equipment must not be used in explosion risk
areas.
UL/cUL (CSA) Approval
The equipment meets the requirements of Directives: UL 508 and CSA C22.2 No. 14-13, Standards for
Industrial Control Equipment. File E243189.
Note on the Declaration of Conformity / Declaration by the Manufacturer
For details on the conformity of our equipment according to the European Directives see our Declaration
of Conformity or our Declaration of Manufacturer.
The current Declaration of Conformity and Declaration of Manufacturer are available in the Internet under
www.gestra.com documents
or can be requested from us.

6
NRG 26-21
Technical data
Level electrode
Service pressure
PN 40, 32 bar at 238 °C
Mechanical connection
Screwed G¾A, DIN ISO 228
Materials
Screw-in body: 1.4571, X6CrNiMoTi17-12-2
Electrode rod insulation: PTFE
Length of installation
at 238°C
373 477 583 688 794 899 1004 1110
Measuring range 300 400 500 600 700 800 900 1000
Length of installation
at 238°C
1214 1319 1423 1528 1636 2156
Measuring range 1100 1200 1300 1400 1500 2000
Weight
Approx. 1.8 kg (NRG 26-21 L=1000 mm)
Electronic module NRV 2-29
Supply voltage
12 V DC
Response sensitivity
Range 1: Water ≥0.5 µS/cm
Range 2: Water ≥20 µS/cm
Range 3: Fuel oil EL εr2,3
Output
≥ 0 – ≤ 7 V DC, level proportional
Adjustors
1 Code switch with 6 poles for setting the measuring range
Housing
PPO (Noryl®)
Electrical connection
1 Screw-type terminal strip with 3 poles, cable gland with integrated cable clamp M 16
Protection
IP 65 to EN 60529
Admissible ambient temperature
Max. 70 °C

7
TÜV.WR.09-317,11-320,12-425,-426,-427
Meßlänge / Range
H= mm
32 bar (464psi)
238°C (460°F)
T amb = 70°C (158 °F)
NRG 26-21
GESTRA AG D-28215 Bremen
Pmax
Tmax
PN 40 G 3/4 1.4571 IP 65
Betriebsanleitung beachten
See installation instructions
Voir instructions de montage
Scope of supply
NRG 26-21
1 Level electrode NRG 26-21
1 Joint ring 27 x 32, form D, DIN 7603, 2.4068, bright annealed
1 Installation manual
Name plate/marking
Equipment designation Safety note
Disposal note
CE Marking
Type approval no.
Manufac-
turer
Pressure rating, thread type,
material number, protection
Application
range
Fig. 1
Material number
Technical Data - continued -
TÜV · WR · XX-317, XX-320, XX-425, -426, -427
NRG 26-21 - continued -
Approvals:
TÜV certificate VdTÜV Bulletin "Water Level 100" Requirements made on water level limiting
& control equipment.
Type approval no. TÜV · WR · XX-317, XX-320, XX-425, XX-426, XX-427
(see name plate)
UL/cUL (CSA) Approval UL 508 and CSA C22.2 No. 14-13, Standards for Industrial Control Equipment.
File E243189.

8
Installation
Dimensions NRG 26-21
Fig. 2
NRG 26-21
Fig. 3
Ra 3.2
Ra 12.5
G¾ A, ISO 228
∅33
0.5
260
∅42
2
37
26
3
G¾ A, ISO 228
1Thermal insulation, provided on site,
d = 20 mm (outside of thermal insulation of
steam boiler)
2Joint ring 27 x 32 form D to DIN 7603,
made from 2.4068, bright annealed
Key
3Electrode thread
4Measuring range (mm) = xxx %
5Max. length of installation at 238 °C
1
45 ∅ 15

9
Installation
Note
One level electrode NRG 26-21 can be installed together with one GESTRA level elec-
trode, one level switch or transmitter in a single protection tube or an external level pot
(inside diameter DN80/DN100). Fig. 4 - 7. If the level limiting electrode is installed
inside the vessel, it must be at least 40 mm away from the upper vent hole.
For the approval of the boiler standpipe the relevant regulations must be considered.
Refer to pages 10 and 11 for typical installation examples.
The angle of inclination of the electrode must not exceed 45°, with the length of the
electrode being limited to 688 mm. Fig. 8
If installed outdoors the level electrode must be equipped with a GESTRA weather
protection cover.
The seating surfaces of the standpipe or the flange provided on the vessel must be
accurately machined, Fig. 3!
Do not bend electrode tip when mounting.
Do not subject electrode to physical shocks.
Use only the supplied joint ring.
Joint ring 27 x 32, form D, DIN 7603, 2.4068, bright annealed
Do not lag electrode body above the hexagonal section.
Do not insulate electrode thread with hemp or PTFE tape!
Do not apply conductive paste or grease to the electrode thread!
Observe the minimum withdrawal distance when installing the electrode!
Observe the specified tightening torque.
Do not cut the electrode rod.
Attention
NRG 26-21
1. Check seating surfaces. Fig. 3
2. Place supplied joint ring 2onto seating surface of the threaded standpipe or flange. Fig. 3
3. Apply a light smear of heat resistant silicone grease(e.g. WINIX®2150) to electrode thread 3.
4. Screw level electrode into threaded standpipe or flange and tighten with an open-end spanner
A. F. 41 mm. The torque required when cold is 160 Nm.
Tools
Open-end spanner A. F. 41, DIN 3110, ISO 3318
- continued -

10
Examples of installation
NRG 26-21
Fig. 4 Protection tube (provided on site) for
installation inside the boiler
Fig. 5 Protection tube (provided on site) for
installation inside the boiler
Fig. 6 Protection tube (provided on site) for installation
inside the boiler and in combination with other
GESTRA equipment
2
20
DN 50
G ¾
∅20
∅ 20
≤ 90°
c
9
6
7
8
0
a
e
f
DN 100
24.5 24,5
∅20
G ¾
∅ 20
≤ 90°
≤3000
1"
6
e
h
7
d
g
9
0
c
20
20
∅
20
≥ 10
DN 50
G ¾
∅ 20
≤3000
9
6
7
0
a
e
f
≤ 90°
≥14
Fig. 7 External level pot
DN 20
DN 20
Centre distance
≤ 20
G ¾
DN 20
≤20
6
0
9
e
h
8
8
190

11
Examples of installation
6Flange PN 40, DN 50, DIN EN 1092-01 (single electrode)
Flange PN 40, DN 100, DIN EN 1092-01 (combination of electrodes)
7For the approval of the boiler standpipe with connecting flange the relevant regulations must be
considered.
8Vent hole ∅ 20 mm
9High water (HW)
0Electrode tip
aProtection tube DN 80 (in France according to AFAQ ≥ DN 100)
bProtection tube DN 100
cDistance between electrode rod and protection tube ≥ 14 mm
dDistance between electrode tip (NRG 1..-50 or NRG 1...-51) ≥ 14 mm
(creepage distances and clearances)
eLow water LW
fReducer DIN 2616-2, K-88.9 x 3.2-42.4 x 2.6 W
fReducer DIN 2616-2, K-114.3 x 3.6-48.3 x 2.9 W
hLevel pot ≥ DN 80
Key
- continued -
DN 100
45°
max.688
8
Tube, e. g. 33.7 x 3.2 88
120
Fig. 8 Inclined installation
e. g. in steam boilers
6
NRG 26-21 - continued -

12
Electrical connection
Fig. 9 Electronic module NRV 2-29 integrated in terminal box
k
i
o
n
m
j
l
p
q
NRV 2-29
CEP
iScrew M4
jCover
kSeal
lTerminals
mCable gland M 16 (PG 9)
Key
nSealing plate
oTerminal box (electronic module NRV 2-29)
pCode switch
qWiring of terminals
≥ 0 V ≤ 7 V DC
Measuring voltage 12 V DC
Supply voltage for
NRV 2-29
1M3
Fig. 9

13
Electrical connection
Connection of level electrode
To connect the equipment use screened multi-core control cable with a min. conductor size 0.5 mm²,
e. g. LiYCY 4 x 0.5 mm², max. length 100 m.
A maximum of 3 switches / controllers NRS /NRR 2-5.. can be connected to one level electrode.
Connect the screen only once to the central earthing point (CEP) in the control cabinet. Wire terminal
strip in accordance with the wiring diagram. Fig. 9
NRV 2-29, connecting the terminal strip
1. Loosen screw i. Fig. 9
2. Detach terminal box (electronic module NRV 2-29) ofrom level electrode. Leave sealing plate n
on contact plate.
3. Remove cover jand seal k.
4. Unscrew cable gland m.
5. Pull cable through cable gland min terminal box oand wire terminals lin accordance with wiring
diagram Fig. 9.
6. Replace cover jand insert screw i.
7. Put terminal box oonto level electrode and fix it with screw i.
Wiring diagram
Please observe the instructions given in the installation & operating manual for the
level switches / controllers NRS 2-50, NRS 2-51, NRR 2-50, NRR 2-51, NRR 2-52 and
NRR 2-53 or NRS 2-1, NRR 2-1, NRR 2-2 and NRT 2-1!
Make sure that connecting cables leading to the level electrode are segregated and
run separately from power cables .
Attention
Tools
Screwdriver, size 1
Screwdriver, size 2.5, completely insulated according to DIN VDE 0680-1
5678
13
+12V
CEP
NRG 26-21
NRS 2-50, NRS 2-51
NRR 2-50, NRR 2-51
12 13 14 15
13
+12V
CEP
NRS 2-52, NRS 2-53
NRG 26-21
- continued -
Fig. 10 Fig. 11

14
Basic settings
Factory setting
The code switch ris set at our factory so that the max. measuring range for water (conductivity
≥ 20 μS/cm) is activated. The max. measuring range is the range between the lower and the upper end
of the measuring range. Fig. 11
The level electrode features the following factory set default values:
Measuring range up to 350 mm: Code switch rposition 4, 5 ON, 1, 2, 3, 6 OFF
Measuring range 350 mm up to 750 mm: Code switch rposition 4 ON, 1, 2, 3, 5, 6 OFF
Measuring range 750 mm up to 1500 mm: Code switch rposition 3 ON, 1, 2, 4, 5, 6 OFF
Measuring range 1500 mm up to 2500 mm: Code switch rposition 2 ON, 1, 3, 4, 5, 6 OFF
XSelected (active) measuring range [mm]
4Measuring range (mm) = xxx % see Fig. 2
sLower end of measuring range, adjustable
tUpper end of measuring range, adjustable
uDiagram for water, conductivity ≥20 µS/cm
vDiagram for water, conductivity ≥0.5 µS/cm
wDiagram for fuel oil EL, dielectric constant εr2.3
Lower measuring point
Attention
If Xis clearly below 4change the code switch settings according to the diagrams u,
vwfor the fluid to be measured.
Establishing active measuring range (control range)
Within the measuring range of the electrode you can establish the active measuring range. Use code
switch rFig. 9 to establish the length of the active measuring range.
Fig. 12
ON
123456
r
26 37
t
s
X
4

15
Basic settings
Establishing active measuring range (control range)
Ascertain the type of fluid that will be measured. Determine the active measuring range (control range)
in mm. Refer to diagrams u, vor vfor the required code switch settings for water and fuel oil EL.
Example: Max. measuring range at 25°C: 1500 mm, selected active measuring range: 1000 mm, toggle
switch 3 of the code switch must be set to ON, all other toggle switches to OFF.
If a fluid other than water or fuel oil EL is to be measured, the position of the code switches must be
determined by measuring the voltage. For this purpose apply supply voltage to the connected level
switch / level controller.
1. Unscrew screw iland remove cover j.
2. Fill vessel to required maximum level and connect a voltmeter between terminals "1" (+) and "M"
(–). Before starting the measurement set all toggle switches of the code switch to OFF.
3. Now operate each individual switch in turn: only switch 1 to ON, only 2 to ON, only 3 to ON, only 4
to ON, only 4 + 5 to ON and only 4 + 5 + 6 to ON. As soon as with one of the switch positions the
value measured by the voltmeter exceeds 7 V, stop operating switches, and select the preceding
switch position.
4. After having set the code switch, place cover jonto the terminal box oand fasten with screw i.
2 ON3 ON
4 ON
7
6
5
4
3
2
1
0200 400 600 800 1000 1200 1400 1600 1800 2000
0
4+5 ON
Code switch
Example
AA A
A
BBBB
Selected (active) measuring range [mm]
Output voltage UM[V] DC
A= completely submerged B= completely exposed
Fig. 13
uDiagram for water, conductivity ≥ 20 μS/cm
- continued -
- continued -

16
Basic settings
Establishing active measuring range (control range)
7
6
5
4
3
2
1
0200 400 600 800 1000 1200 1400 1600 1800 2000
0
4 ON4+5 ON
4+5+6 ON
Code switch
AA
A
B
B
B
Selected (active) measuring range [mm]
Output voltage UM[V] DC
A= completely submerged B= completely exposed
7
6
5
4
3
2
1
0200 400 600 800 1000 1200 1400 1600 1800 2000
0
2 ON3 ON
4 ON
4+5 ON
Code switch
AAA
A
BB B B
Selected (active) measuring range [mm]
Output voltage UM[V] DC
A= completely submerged B= completely exposed
Fig. 14
v
Fig. 15
w
Diagram for water, conductivity ≥ 0.5 μS/cm
Diagram for fuel oil EL, dielectric constant εr 2.3
- continued -
- continued -

17
A= completely submerged B= completely exposed
Commissioning procedure
When adjusting the measuring range when the system is cold, the adjusted measuring
points will shift with rising temperature as a result of the longitudinal expansion of the
electrode rod. Correct the settings accordingly.
Note
Please check that the level electrode is wired in accordance with the wiring diagram (Fig. 10, 11) and
switch on supply voltage of the connected level switch / controller.
Applying supply voltage
The supply voltage can be measured between terminals "3" and "M" in the terminal box o. The
voltage should be 12 V DC. If this voltage is not present, check the connected level switch / level
controller.
The level-proportional voltage UM can be measured between terminals "1" (+) and "M" (–).
Raise level in vessel to the highest point (completely submerged) of the selected (active) measuring
range (e. g. 1000 mm) and measure the voltage.
Compare the value measured with the value of the corresponding chart (in diagram uUM for 1000 mm
is 4.6 V). The following values must be obtained in any case:
Level electrode completely exposed: UM ≥ 0 V, level electrode completely submerged: UM ≤ 7 V DC
If the electrode is submerged and you measure UM = 0 V or UM > 7 V DC, replace the level electrode.
Checking measuring voltages
Checking measuring range
Before commissioning the level electrode make sure that the active measuring range (= control range)
agrees with the service conditions of your installation.

18
Attention
Before carrying out the fault diagnosis please check:
Supply voltage:
Is the level electrode supplied with the voltage specified on the name plate?
Wiring:
Is the wiring in accordance with the wiring diagram?
Troubleshooting
Indication, diagnosis and remedy
Malfunctions
Equipment does not work accurately
Error Remedy
The level electrode was installed without a protection
tube. The protection tube is required because it serves
as reference electrode.
Install a protection tube.
The vent hole in the protection tube does not exist,
is obstructed or flooded. Check protection tube and, if necessary, provide vent hole.
The isolating valves of the external level pot (optional)
are closed. Open isolating valve.
The desired lower measuring point is outside the
measuring range of the level electrode.
The level electrode is too short.
Install a sufficiently long level electrode.
The adjustment of the measuring range is wrong. Correct code switch hsettings.
See Basic Settings
The electrode rod is covered with dirt deposits. Remove level electrode and clean the electrode tip with a
wet cloth.
The level electrode is submerged and
UM = 0 V or > 7 V DC. Replace level electrode.
Equipment fails to work
Error Remedy
Power failure. Switch on supply voltage. Check all electrical connections.
The earth connection to the vessel is interrupted.
Clean seating surfaces and screw in the level electrode
together with the joint ring 27 x 32, form D, DIN 7603
(made from 2.4068), bright annealed. Do not insulate the
electrode with hemp or PTFE tape!

19
If faults occur that are not listed above or cannot be corrected, please contact our service centre or
authorized agency in your country.
Maintenance
Cleaning the electrode rod
The equipment may only be installed and removed by qualified personnel. Observe note in chapter
"Installation" on page 9.
Before cleaning the electrode rod decommission and remove the level electrode.
Clean the electrode rod with a wet cloth.
Safety note
Danger
When loosening the level electrode steam or hot water might escape!
This presents the risk of severe scalding all over the body!
It is therefore essential not to dismantle the electrode unless the boiler pressure is
verified to be 0 bar.
The level electrode becomes hot during operation.
Risk of severe burns to hands and arms.
Before carrying out installation and maintenance work make sure that the equipment
is cold.
The equipment must only be installed, wired and commissioned by qualified and competent staff.
Retrofitting and maintenance work must only be performed by qualified staff who - through adequate
training - have achieved a recognised level of competence.
Removing and disposing of the level electrode
Removing and disposing of level electrode NRG 26-21
1. Switch off supply voltage.
2. Unscrew screw eand remove cover =.
3. Disconnect the connecting wires from the terminals band pull wires out of the cable gland.
4. Before removing the equipment make sure that it is neither hot nor under pressure.
For the disposal of the equipment observe the pertinent legal regulations concerning waste disposal.

20
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818774-05/07-2017cm (808388-11)· GESTRA AG · Bremen · Printed in Germany
GESTRA AG
Münchener Straße 77
28215 Bremen
Germany
Telefon [phone]
Telefax [phone]
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