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PORTABLE MOISTURE DETECTOR

LH-20S

(RESISTANCE ALARM SYSTEM)

USER MANUAL

levr

Ver. 2.6

LH-20S USER MANUAL

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.

moisture

level

polyurethane insulation

C level of the short circuit between
the alarm wire and the carrier pipe

Insulation resistance range

100

Ω÷

500

Ω

500

Ω÷

1,2k

Ω

1,2k

Ω÷

Ω

Ω÷

20k

Ω

20k

Ω÷

65k

Ω

65k

Ω÷

200k

Ω

200k

Ω÷

300k

Ω

300k

Ω÷

450k

Ω

----------------------------------------------

450k

Ω÷

Ω

----------------------------------------------

Ω÷

Ω

----------------------------------------------

Ω÷

10M

Ω

----------------------------------------------

10M

Ω÷

20M

Ω

----------------------------------------------

20M

Ω÷

30M

Ω

----------------------------------------------

30M

Ω÷

50M

Ω

----------------------------------------------

>50M

Ω

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:

LH-20S USER MANUAL

min

═

-------------

L / L

max

R [M

Ω

]

– minimum polyurethane insulation resistance value for a heating pipeline

with length of less than 1km

min

Ω

] – 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

≤

max

)

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 [k

Ω

, M

Ω

•

C level of the short circuit between the alarm and the carrier pipe,

•

short circuit resistance [k

Ω

, M

Ω

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 p

tla (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

LH-20S USER MANUAL

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 90M

Ω

1000m 5736

Ω

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 50M

Ω

. The results of joining the sections together

resistance wire

copper wire

casing pipe

carrier
pipe

polyurethane
insulation

magnetic connector

LH-20S Detector

section 1

section 2

section 3

moisture

Polyurethane insulation
resistance
MH=0 R1=50M

Ω

Polyurethane insulation
resistance
MH=0 R2=50M

Ω

Polyurethane insulation
resistance
MH=0 R3=50M

Ω

LH-20S USER MANUAL

are not difficult to predict. The resulting resistance of polyurethane insulation for two sections
joined together will be equal to:

R R

→

⋅

50 50

[

]

Ω

and after joining section 3:

Rz R

≈

→

⋅

25 50

16 8

[

]

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 0,8M

Ω

Zwarcie C =7 0,2M

Ω

1000m 5736

Ω

1000m 5736

Ω

1000m 5736

Ω

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.

LH-20S USER MANUAL

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 >99M

Ω

Przerwana p

tla

The Przerwana p

tla (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; >99M

Ω

). 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.

LH-20S USER MANUAL

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; >99M

Ω

) 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 p

tla (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 p

tla

(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÷4

Ω

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 >99M

Ω

2) MH=10 2,2M

Ω

3) MH=0

>99M

Ω

LH-20S USER MANUAL

Przerwana p

tla

Przerwana p

tla

4) MH=6 0,2M

Ω

5) MH=4

12k

Ω

│

highly unstable

653m

3745

Ω

←

│

measurement results

Under typical conditions, the above results should be interpreted as follows:

Result 1:

There is no moisture (MH=0; >99M

Ω

) 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.

LH-20S USER MANUAL

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 p

tla (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÷60

Ω

. Measurement results depend on the

length of the tested wire (0.036

Ω

/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÷3

Ω

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.

LH-20S USER MANUAL

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 (5.7

Ω

/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 p

tla (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; >99M

Ω

result 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 0

Ω

. 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.

LH-20S USER MANUAL

3.4.

Determining the reasons for the Brak kontaktu (No Contact) message

The Brak kontaktu (No Contact) message signals the lack or poor quality of the connection
between the LH-20S detector and the carrier pipe. When the above message is displayed, try
rubbing the magnetic connector along the carrier pipe. If this produces no results, check the
condition of the two black detector wires. To do so, connect the two wires together and start
the measurement. If the Brak kontaktu (No Contact) message appears, the wires are faulty
and should be repaired or replaced.

Often, the black wires are damaged because the magnetic connector was disconnected from
the carrier pipe by pulling on the wires.

LH-20S USER MANUAL

4. Technical Specifications:

Measurement results display

alphanumeric LCD display, 2x16 characters, backlit

Measurement ranges:

•

polyurethane insulation MH moisture level

1 ÷ 14 and 0

•

polyurethane insulation resistance

0,1k

Ω

÷ 99M

Ω

•

metallic short circuit of the alarm wire
with the carrier pipe

0 ÷ 100

Ω

•

C level of the short circuit of the alarm wire
with the carrier pipe

1 ÷ 8MH

•

short circuit resistance

0,1k

Ω

÷0,45M

Ω

•

alarm loop length

1 ÷ 2000m

•

alarm loop resistance

1 ÷ 12042

Ω

Measurement accuracy:

•

accuracy of the resistance measurement used in MH level determination

±5%

•

accuracy of the alarm loop resistance measurement

±0,2%

Text messages:

•

poor quality of the connection between the detector
and carrier pipe

Brak kontaktu (No Contact)

•

electric break in the alarm loop

Przerwana p

tla (Open Loop)

•

short circuit of the alarm wire with the carrier pipe

•

metallic contact between the detector wire
and the carrier pipe

Zwarcie (Short Circuit)

•

measurement range exceeded during alarm loop length measurement

---HI---

•

low batteries

Górna bateria (Upper Battery)

Dolna bateria (Lower Battery)

Power supply ............................................................................................... 2 x 6F22 (2 x 9V)

Working and storage temperature range .....................................................................5 ÷ 50

℃

Casing tightness class ....................................................................................................... IP65

Dimensions .......................................................................................................... 223x105x40

Weight with batteries ....................................................................................................... 450g

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