levr LH-20S User manual

PORTABLE MOISTURE DETECTOR
LH-20S
(RESISTANCE ALARM SYSTEM)
USER MANUAL
levr
Ver. 2.6

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1.Moisture Measurements of Pre-Insulated Heating Pipelines with
the Resistance Alarm System
For the purpose of measurement, pre-insulated heating pipelines with resistance alarm
systems can be regarded as consisting of the following elements: carrier pipe, polyurethane
insulation, alarm loop, casing pipe. The alarm loop consists of the resistance wire (e.g.
NiCr8020), bare or with perforated insulation, and of the insulated copper wire. The
resistance of the resistance wire is given in Ω/m, and the resistance of the copper wire
(serving as the return wire for electrical measurement signals) is so low that its influence is
often omitted in measurements. The influence of the copper wire is further diminished by its
complete electrical insulation from other elements of the alarm system. Both wires are located
inside the polyurethane insulation between the carrier pipe and the casing pipe. In case of a
leakage from either pipe, moisture penetrates the insulation, changing its electrical resistance.
Resistance changes can be detected by periodic measurements of the resistance between the
resistance wire and the carrier pipe. The measured resistance value corresponds to the level of
moisture in the insulation. The resistance wire of the alarm loop is also used to locate the
leakage (moisture).
2.Representation of Measured Values
The LH-20S detector is designed to measure the resistance of polyurethane insulation and the
alarm loop. The resistance of the loop is used to automatically calculate the length of the
tested pipeline section. Insulation resistance, in turn, is used to determine the MH moisture
level or the C level of the short circuit between the alarm wire and the carrier pipe.
Relationships between insulation resistance and the MH and C levels are presented in table 1.
MH moisture level of
polyurethane insulation
C level of the short circuit between
the alarm wire and the carrier pipe
Insulation resistance range
1 1 100Ω÷500Ω
2 2 500Ω÷1,2kΩ
3 3 1,2kΩ÷5kΩ
4 4 5kΩ÷20kΩ
5 5 20kΩ÷65kΩ
6 6 65kΩ÷200kΩ
7 7 200kΩ÷300kΩ
8 8 300kΩ÷450kΩ
9 ---------------------------------------------- 450kΩ÷1MΩ
10 ---------------------------------------------- 1MΩ÷3MΩ
11 ---------------------------------------------- 3MΩ÷10MΩ
12 ---------------------------------------------- 10MΩ÷20MΩ
13 ---------------------------------------------- 20MΩ÷30MΩ
14 ---------------------------------------------- 30MΩ÷50MΩ
0 ---------------------------------------------- >50MΩ
table 1
In resistance alarm systems, the alarm loop length and the pipeline section length are
calculated along the length of the resistance wire. According to technical specifications, the
maximum length of the resistance alarm loop is 1000m. For loops of such length, the MH
moisture level should be equal to or higher than 12. Minimum polyurethane insulation
resistance for sections shorter than 1km can be calculated on the basis of the following
formula:

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R
min
R ═-------------
L/ L
max
R [MΩ] – minimum polyurethane insulation resistance value for a heating pipeline
with length of less than 1km
R
min
[MΩ] – manufacturer’s minimum polyurethane insulation resistance value in a
heating pipeline section with the length equal to L
max
= 1km
L [km] – length of the tested section (L ≤L
max
)
L
max
[km] – manufacturer’s maximum length of a pre-insulated heating pipeline
section with a resistance alarm system (L
max
= 1km)
Attempts to locate the leakage (moisture) in heating pipelines are generally undertaken when
the polyurethane insulation MH moisture level drops below 10.
Measurement and calculation results are displayed on the backlit alphanumeric LCD display.
The display has 2 lines, 16 characters each. The first line displays the following information:
•MH moisture level of polyurethane insulation,
•polyurethane insulation resistance [kΩ, MΩ],
or
•C level of the short circuit between the alarm and the carrier pipe,
•short circuit resistance [kΩ, MΩ].
The second line displays the following information:
•length the heating pipeline section [m],
•resistance of the alarm loop [Ω].
The device can also display text messages. The first line of the display displays text messages
which inform of possible problems with the measurement of polyurethane insulation
resistance:
•Brak kontaktu (No Contact) – poor quality of the connection between the carrier
pipe and the LH-20S detector.
•Zwarcie (Short Circuit) – metallic contact between the carrier pipe and the alarm
loop.
The second line of the display displays text messages which inform of possible problems with
the measurement of alarm loop resistance:
•Przerwana pętla (Open Loop) – there is a break in the alarm loop.
•HI – alarm loop resistance (length) measurement range exceeded.
Note that there is a logical connection between the type and location of displayed
measurement results and text messages.
The LH-20S device also alerts the user when its batteries are low. Since the device is powered
by two batteries, located one above the other, there are also two separate messages which may
be displayed:
 Górna bateria (Upper Battery) – replace the upper battery.
 Dolna bateria (Lower Battery) – replace the lower battery.
3.Measurements

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3.1. Primary Measurements
Primary measurements provide the most detailed information regarding the tested sections of
a pre-insulated heating pipelines with a resistance alarm loop. Sometimes, particularly in
emergency cases, the information gathered from primary measurements suggest performing
secondary measurements to further identify the cause and location of the problem. Fig. 1
presents the connection diagram for primary measurements. Note that the wires of the alarm
loop should be connected together at one end of the tested pipeline section. The wires can be
connected together inside a terminal box, connector box etc.
Fig. 1. Primary measurements
After making the connections shown in fig. 1, press and hold the START button of the LH-
20S detector. The device will first display information about itself (type, serial no.) and then
the results of measurements and calculations. Example results are given below:
MH=0 90MΩ
1000m 5736Ω
The first line of the display displays the calculated value of the MH moisture level and the
measured polyurethane insulation resistance, while the second line displays the calculated
length of the pipeline section in meters and the measured alarm loop resistance in ohms.
Practical Advice
Primary measurements should be performed regularly during the installation of the alarm
system to ensure correctness of installation. Reasons for the importance of control
measurements are illustrated in fig. 2 depicting three pipeline sections which are to be joined
together. Measurement results of the MH moisture level and polyurethane insulation
resistance are presented for each section. Consider two cases:
Fig. 2.
CASE 1. The person assembling the pipeline measures the MH moisture level and
polyurethane insulation resistance.
Preliminary moisture measurements, performed individually for each section, suggest poor
condition of the alarm system. MH=0 results are not satisfactory if the polyurethane
insulation resistance of each section is only 50MΩ.The results of joining the sections together
resistance wire
copper wire
casing pipe
carrier
pipe
polyurethane
insulation
magnetic connector
LH
-
20S De
tector
DETECTOR
section 1
section
2
section
3
moisture
Polyurethane insulation
resistance
MH=0 R1=50MΩ
Polyurethane insulation
resistance
MH=0 R2=50MΩ
Polyurethane insulation
resistance
MH=0 R3=50MΩ

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are not difficult to predict. The resulting resistance of polyurethane insulation for two sections
joined together will be equal to:
Rz M M MH
R R
R R
=
=
=
→
=
⋅
+⋅ +
1 2
1 2 5050 50 50
25 13[ ]
Ω
Ω
and after joining section 3:
Rc M M MH
Rz R
Rz R
=
=
≈
→
=
⋅
+⋅ +
3
32550 25 50
16 8 12[ ] ,
Ω
Ω
Person assembling the pipeline is not misled by the results, and does not try to correct the
joints between the three sections. If the same person performed the installation works, they
will regret not having performed enough control measurements of polyurethane insulation
resistance, as a result of which they allowed moisture to be locked in the joint(s) of the
installed sections.
CASE 2. The person assembling the pipeline measures only the MH moisture level of
polyurethane insulation.
Measurements for sections 1 and 2 of the pipeline suggest very good condition of the alarm
system (MH=0). After the two sections are joined together, however, their resulting MH
moisture level equals 13. Still, the situation is not yet critical. The situation becomes critical
after joining section 3, as a result of which the MH value drops to 12.
Three supposedly correct sections (MH=0) of the alarm system, after they are joined together,
barely meet the technical specifications regarding moisture levels (MH≥12).
An inexperienced person will be misled by the results and will look for faults in the joints
between the three sections.
3.2. Secondary Measurements when MH≤11 and when the ZWARCIE
(SHORT CIRCUIT) or C Messages are displayed
Example measurement results are given below:
MH=9 0,8MΩZwarcie C =7 0,2MΩ
1000m 5736Ω1000m 5736Ω1000m 5736Ω
Each of the problems discussed in this section needs to be located and removed. Choice of
action depends on the condition of the insulation of the copper alarm wire. If, as intended, the
copper wire is not connected electrically to the carrier pipe, either directly (short circuit) or by
the moisture between them, then the wire fault can be located using typical methods and
devices (e.g. the LP-10S fault locator). The condition of copper wire insulation can be tested
by performing a secondary measurement with the LH-20S device. Fig. 3 presents the
connection diagram for the secondary measurement. Note that the alarm loop should be open
at both ends of the tested pipeline section, and the blue wire of the LH-20S detector is not
involved in the measurement.
DETECTOR

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Fig. 3. Testing the insulation of the copper wire
Only the below measurement result confirms that the Teflon insulation of the copper wire is in
good condition.
MH=0 >99MΩ
Przerwana pętla
The Przerwana pętla (Open Loop) message results from the adopted measuring method
(without the blue wire) and is not significant in this case. If the measurement result is different
from the one above, locating the fault using standard methods is going to be difficult or even
impossible – particularly when the MH parameter has low values or when, instead of
measurement results of the resistance between the copper wire and the carrier pipe, the device
displays the Zwarcie (Short Circuit) message.
Practical Advice
The above observations strongly suggest the following conclusion: before attempting to
locate the leakage (moisture) or short circuit in the pre-insulated heating pipeline, always
test the insulation of the copper alarm wire.
A typical symptom of the negative influence of faulty copper wire insulation during attempts
to locate a leakage or short circuit are results which suggest that the fault occurs at exactly
the opposite end of the pipeline section. After heading to the indicated location and
performing a second attempt to locate the fault, the device, in turn, indicates that the fault
occurs at the exact same spot where the first measurement was made, and so on.
Accidental shorting of the copper wire with the carrier pipe or damaged insulation in the
moist location causes the wire to be no longer useful for measurements. The location of the
short circuit or moisture between the copper wire and the carrier pipe can only be determined
with the reflectometer.
Note, however, that the heating line consists of two identical pipelines: feed and return. It is
possible, therefore, to locate the moisture between the resistance and copper wires and the
carrier pipe by replacing the faulty copper wire with an undamaged wire from the twin alarm
system. If by doing so you manage to find the location of the resistance wire fault, then it is
highly probable that the indicated spot will also be the location of the damage (this does not
usually apply in case of a short circuit) in the insulation of the copper wire.
During attempts to locate the moisture, the damaged copper wire can be replaced with the
resistance wire from the second pipeline, as long as the second wire is not shorted with the
carrier pipe (MH=0; >99MΩ). In such cases, however, the method of calculating the location
of the leakage (moisture) is different. The length of thus formed alarm loop is twice as large as
the length specified in the technical documentation. (The length of the heating pipeline and
the alarm loop is calculated along the length of the resistance wire.)
Secondary measurements for the resistance wire of the alarm loop are performed in a similar
way but for different reasons. Connection diagram is presented in fig. 4.

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Fig. 4. Testing the moisture level between the resistance wire and the carrier pipe and
detecting the short circuit
The primary reasons for performing this measurement will be explained later in Practical
Advice. At this point, it should simply be noted that the measurement for the resistance wire is
sometimes performed instinctively after detecting moisture between the copper wire and the
carrier pipe in order to confirm the detected condition for both wires. In most cases, also after
detecting moisture, the two results are compared. Although the comparison of the results is
unlikely to produce useful conclusions, it should be performed just in case.
It happens very seldom that attempts to locate moisture in a branched pipeline system can be
made directly after detecting the moisture. Even when the secondary measurement indicates
that the insulation of the copper wire is in good condition, it is possible that there are several
leakages, and proper actions need to be undertaken in order to locate them all. First, divide
the moisturized alarm loop into separate sections by disconnecting the connections in
terminal boxes (BS-AD; PPA) and everywhere else. Then, using the above-described
secondary measurement method (fig. 4), measure the moisture level in each section. When
moisture is detected in two or more sections, form alarm loops by connecting (e.g. in a
terminal box) the end of the “moist” wire (MH≤11) from one pipe with the end of the twin
“dry” wire (MH=0; >99MΩ) from the second pipe. Only after forming such substitute alarm
loops you can attempt to locate the leakages (moisture). Note that the length of the alarm loop
formed from two resistance wires located in separate pipes is twice as large as the length
specified in the technical documentation. Furthermore, if the pipeline system is branched, the
resistance wire in one branch may be extended with the copper wire in a separate branch. For
these reasons, substitute loops should be formed with the help of the connection diagram.
Sometimes, moisture appears simultaneously in two parallel (located in separate pipes)
sections of wires which are to be connected to form a substitute loop. In such cases, use an
additional copper wire lined outside the tested sections of the heating pipelines.
3.3. Secondary Measurements when the Przerwana pętla (Open Loop) or HI
messages are displayed or in case of Unstable Measurement Results
of the length and resistance of the alarm loop
Secondary measurements need to be performed when one of the situations mentioned in the
heading of this section occurs during primary measurements. When the Przerwana pętla
(Open Loop) message is displayed, check the detector wires of the LH-20S and all other
connections of the alarm loop (connection boxes, joints of the connectors welded to carrier
pipes). Detector wires (red and blue) are in good condition if, after shorting them together, the
second line of the detector display displays 0m and 0÷4Ω.
Presented below are some of the possible measurement results of the LH-20S detector which
signal that the alarm loop is open.
1) MH=0 >99MΩ 2) MH=10 2,2MΩ3) MH=0 >99MΩ
DETECTOR

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Przerwana pętla Przerwana pętla HI
4) MH=6 0,2MΩ 5) MH=4 12kΩ │highly unstable
HI 653m 3745Ω← │measurement results
Under typical conditions, the above results should be interpreted as follows:
Result 1:
There is no moisture (MH=0; >99MΩ) in the area of the break in the alarm loop between the
loop and the carrier pipe. It is impossible to establish the number of alarm loop faults. At least
one of the two wires of the alarm loop is faulty.
Result 2:
There is moisture (MH=10) in the area of the break in the alarm loop. It is impossible to
establish the number of alarm loop faults. At least one of the two wires of the alarm loop is
faulty. The reasons for the fault are external: the casing pipe may be damaged, allowing
external moisture (groundwater) to penetrate the insulation.
Result 3:
There is only one break in the alarm loop, caused by incorrect tightening of the sleeve
connecting the ends of the alarm loop inside the joint. It is impossible to determine which of
the two wires of the alarm loop is faulty.
Result 4:
It is impossible to determine the number of breaks in the alarm loop, although it is highly
probable that only one break exists. The ends of the broken wire of the alarm loop are
connected electrically by the moisture. The resistance of the connection is added to the
resistance of the wires and is high enough to exceed the alarm loop resistance (length)
measurement range. Simultaneous indication of moisture (MH=6) and displaying of the HI
message suggests that the fault is caused by external reasons: the casing pipe may be
damaged, allowing external moisture (groundwater) to penetrate the insulation.
Result 5:
There is only one break in the alarm loop. The ends of the broken wire of the alarm loop are
connected electrically by the moisture. Since the resistance of such connection has no fixed
value, results of the measurements of length and resistance of the alarm loop are highly
unstable. It is impossible to determine which of the two wires of the alarm loop is faulty. The
reasons for the fault are external: the casing pipe may be damaged, allowing external moisture
(groundwater) to penetrate the insulation.
The break(s) in the alarm loop can be located when the problem is correctly recognized and
after measurement conditions are properly prepared. The measurements should begin with a
test of the copper wire, which is most prone to sustain such type of damage. Fig. 5 presents
the connection diagram of the measurement circuit.

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Fig. 5. Testing the copper wire for mechanical damage
As depicted in the figure, a magnetic connector is used to connect one end of the copper wire
with the carrier pipe. Red and blue detector wires are connected respectively to the second
end of the copper wire and the carrier pipe. A magnetic connector can be used for easier
connection with the pipe. After making the connections, start the measurements. If the
Przerwana pętla (Open Loop) or HI message appears in the second line of the display or if
measurement results are highly unstable, then the copper wire of the alarm loop is faulty. The
break in the loop can be located with a reflectometer. The copper wire is in good condition if
the measurement results are between 0÷11m and 0÷60Ω. Measurement results depend on the
length of the tested wire (0.036Ω/m) and on the resistance of the contacts between the
magnetic connectors and the carrier pipe.
Practical Advice
Connections for secondary measurements need to be made carefully to ensure that they do not
affect measurement results. Fig. 6 presents a method of testing the quality of the contact
between the magnetic connector and the carrier pipe.
Fig. 6. Testing the quality of the electric contact between the magnetic connector and the
carrier pipe
The quality of the contact is good if the device displays the following measurement results:
0m, 0÷3Ω.
The resistance wire should be tested regardless of the measurement results for the copper
wire. It is not uncommon for both wires to be faulty (broken). Appropriate connection diagram
is presented in fig. 7.
DETECTOR
DETECTOR

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Fig. 7. Testing the resistance wire for mechanical damage
In order to test the resistance wire, first connect the resistance wire to the carrier pipe at one
end of the alarm loop (e.g. in the connecting box or as shown in fig. 7). Then, connect the red
and blue detector wires respectively with the second end of the tested wire and with the
magnetic connector attached to the carrier pipe. Measurement results depend on the length of
the tested wire (5.7Ω/m) and on the resistance of the contact between the magnetic connectors
and the carrier pipe. If the connections are made correctly, then the detector simply displays
the length and resistance of the tested wire. If the Przerwana pętla (Open Loop) or HI
message appears or if measurement results are highly unstable, then the resistance wire of the
alarm loop is faulty. The displayed message and measurement results help to determine the
type of fault. (See example results and comments.) If a break in the alarm loop is detected,
then further actions depend on the structure of the heating pipeline system. If the pipeline has
no branches, locate the fault with the reflectometer. If the pipeline has branches, first isolate
the faulty section of the wire by disconnecting the connections of the alarm loop in all
terminal boxes. Then, the condition of each section should be tested almost in accordance
with the above-described method and fig. 7. The only difference is that, in the branches, the
resistance wire may be extended with the copper wire. In such case, connect the end of the
wire to the pipe.
In general, breaks in the isolated sections of the alarm loop wire should be located with a
reflectometer. Capacitive measurement method may be used to locate the break in the wire
only if there is no moisture in the area of the wire break (result 1).
Note: In each of the above-described secondary measurements, any information displayed in
the first line of the detector display is insignificant. The first line of the display may display
the MH=0; >99MΩresult if the black detector wires are connected together or the Brak
kontaktu (No Contact) message if the detector wires are not connected together.
When one of the wires of the alarm loop is connected to the carrier pipe, a substitute loop is
formed. In such cases, the pipe serves as a reference point, because there are no breaks in it
and because its resistance is almost equal to 0Ω. In making such substitute loops, it is crucial
to achieve minimal resistance values of the contact with magnetic connectors (figs. 5;7).
Sometimes, the difficulty in making connections is the distance between the end of the tested
wire and the access point to the carrier pipe to which the connector is to be connected. It is
easier to make the connections if you make substitute loops from wires located in two parallel
sections of the heating pipeline system. First, however, ensure that the wires used as
substitutes are not faulty. Connections between separate sections of the alarm loop should be
made with the use of terminal boxes. For non-faulty sections, length measurement values are
twice as high as specified in the technical documentation.
DETECTOR