Socket & See DL 420 User manual

MULTIFUNCTION DIGITAL LOOP TESTER
Tests no-trip loop, PFC, socket, mains voltage & polarity
DL420
USER MANUAL 06/06

2
Caution
We strongly advise reading and understanding this guide
before the instrument is used. In particular note the safety
issues that follow:-
l Although fully protected up to 600V AC this tester is for
use on 230V AC circuits only.
l Always check the tester on a known correctly wired live
socket outlet before and after use.
l Before use - check your tester for any damage to
the plug, lead and cabinet.
BS EN
61010-1
DL 420
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If there is any aspect of your Socket & See tester you would like
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with any suggestions.
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We value YOUR opinion.
Important calibration/check box note
l Because of the Super Smart Loop Test System the test is
immune to sudden value changes (such as voltage spikes).
l As a result when changing calibration or check box loop
values the unit must be switched off between changes.

3
Operation overview
Your Socket & See tester has a special polarity test function.
It is a little known fact that a system can be reverse wired with Live (Phase) to
earth/neutral and earth/neutral to Live (Phase) The sockets will all work and
conventional loop testers will show and test that everything is correct despite
this very dangerous wiring condition.
Although extremely rare, this miswire condition can exist so if your test shows
this fault do not proceed - if in any doubt advise your customer to contact their
supply company immediately. (See test step 4)
overview
FUSE 100A
FUSE 100A
From Supply
Company Live (Phase)
to Meter
Neutral to Meter
To Main
Earthing
Terminal
Neutral to Meter
Live (Phase)
to Meter
To Main
Earthing
Terminal
From Supply
Company
Correct Polarity
REVERSE POLARITY
Typical Supply Service
Cut-Out Fuse
LIVE (Phase)
NEUTRAL
Typical Supply Service
Cut-Out Fuse
NEUTRAL
LIVE (Phase)
Solid Brass
Connecting
Block
Solid Brass
Connecting
Block

______________________________________________________________________________
4 Operation overview
Operation overview continued
The DL420 will test for No-trip loop, High current True Loop Impedance, No-trip
PFC (Prospective Fault Current), High current PFC using True Loop
Impedance, mains voltage (L-N, L-E and N-E) and correct socket wiring, In
addition to the incoming supply polarity check described on the previous page
Another unique feature of your DL 420 tester is high current 2-wire
measurement of TLI (True Loop Impedance). Regulations and guidance books
refer to loop impedance measurements but up until now loop testers measured
loop resistance which is different from loop impedance, particularly when
testing close to the main supply transformer.
This function is therefore recommended when testing for external earth fault
loop impedance (Ze) at distribution boards on non TT systems and similar
points on the supply side of any Switch/RCD gear and when testing the
Live/Neutral loop to determine prospective short circuit current.
It is the variation in power factor that makes the TLI measurement of your
DL420 so much more accurate than older loop testing techniques. (Because of
this there may well be variations in readings compared to ordinary loop testers
or the no trip function of this tester, particularly when the measurement is made
near to the main supply transformer).
The DL 420 also has a No-trip test mode that is guaranteed not to trip a 30mA
or higher rated RCD providing that the circuit is otherwise healthy.
No trip vs High current testing
Although the DL420 High current TLI measurement mode is inherently more
accurate than conventional techniques when measuring close to the main
supply transformer, the difference between resistance and true impedance
reduces the further away from the transformer the measurement is made.
This is why using the No-trip mode is suitable for measurement on final circuits
and similarly remote points. It should be noted however that whilst No – trip
testing at these locations will normally function at a similar high level of
accuracy, the low current measurement technique used is more likely to be
adversely affected by external factors such as contact resistance and circuit
noise. This can result in the occasional erroneous reading.
For this reason it is recommended that multiple measurements are made when
using the No-trip mode and any isolated odd results are ignored. When taking
multiple readings the tester or the supply should be powered off between
consecutive tests.
For safety reasons No-trip mode is recomended for all measurements made
on TT systems.

______________________________________________________________________________
Test lead configuration 5
Test lead configuration
Important
The DL 420 can be used with 2 different types of connecting lead. It is
important to understand and use the correct lead configuration for each test
mode or you may not obtain the correct results.
Lead options
1. Ref. IECP UKA The Kettle lead (IEC C13 to 13A plug) type connector
that is supplied with the tester.
2. Ref. ITLS 400 The 3-Pole fused test lead set which terminates in
fused prods/crocodile clips. This is supplied as a separate accessory to the
DL420 or complete with the DL420 Plus.
The lead is an integral part of the tester set-up and should accompany the
tester when being returned for re-calibration or service. Do not use any other
type of Kettle lead or fused test lead set as it would be likely to give incorrect
results.
Lead configuration for No-trip testing
This is the default mode that the DL 420 will start in when turned on. This mode
is most useful for testing either at socket outlets, luminaires, wiring terminals
etc. in installations where the circuit under test may be protected by an RCD.
In No-trip mode the tester can be used with the IECP UKA lead when testing at
13A socket outlets, or the ITLS 400 for testing at other points in the circuit.
When testing with the ITLS 400 in No-trip mode the 3 colour coded
prods/crocodile clips of the test lead should be connected to the corresponding
Live, Neutral and Earth terminals.
This mode can be re-selected at any time by pressing button 5 labeled No-trip

______________________________________________________________________________
6 Test lead configuration
Test lead configuration
Lead configuration for High Current 2-wire testing with TLI
feature
The TLI function is intended for use at distribution boards and similar points
where you are measuring on the supply side of any Switch/RCD gear.
The TLI measurement function is selected by pressing button 9 labeled
‘Ze/DB’. This function uses the maximum high current of the tester and
requires the use of the ITLS400 test lead set configured in 2-wire mode. Do
not use this function with the IECP UKA Kettle lead or the ITLS400 in 3 wire
mode.
To arrange the test leads in 2-wire mode pull the prod off of the end of the Blue
fuse holder and plug the exposed 4mm connector into the back of the Green
connector, reattach either the Blue prod or Green Crocodile clip to the Green
4mm plug as shown below. You will now have the Earth and Neutral leads
connected together ready for connection to the Earth conductor to be tested.

2.
Three LED’s
show socket
wiring status
3.
LCD (Liquid
Crystal Display)
display (default
L-N voltage
measurement)
1.
On/off button
5.
No-trip loop
select (default)
7.
No-trip PFC
(Prospective
Fault Current)
6.
Push to test
button
9.
High current
loop impedance
test
10.
High current
PFC test
8.
Voltage select
L-N (default)
L-E and N-E
Operation - a detailed view of the DL 420
Note numbers also indicate sequence of test.
7
overview
4.
Polarity test pad

A. Loop test function selected
B. PFC-PSC (prospective fault current - prospective short circuit
current selected)
C. Loop test mode selected - no trip (default) or Hi-I (high current)
D. HANDSFREE operation
E. Ohms symbol
F. Volts (AC)
G. Voltage measurement function L-N (default) L-E and N-E
H. Fault current
I. Wait - result calculation in progress
J. Tester has gone over operating temperature
K. Battery Condition ( =good)
L. Greater than (>) less than (<) indication
8
DL 420
Overview of the display
H
DCBA
E
F
G
H
J
L
K

Loop-PFC Testing 9
Loop-PFC testing
1. Power ON/OFF - Pressing and releasing this button turns the DL 420 on -
holding down for longer than two seconds turns the unit off (plus intelligent
Auto Power Off is incorporated).
2. When the DL 420 is first connected to a live socket it will automatically
test the socket wiring to establish that the circuit wires have been
connected to the correct terminals on the back of the socket. If all three
LED’s light GREEN and no sound is emitted the wiring status is correct and
you can proceed to the incoming supply polarity test (step 3).
A fault with the socket wiring will be indicated by an audible alternating
tone and the LED’s, at least one of which will be Red or Orange, will flash.
If a fault indication is given – DO NOT PROCEED -investigation and
remedial action is required before you can conduct a loop test.
If this happens placing your thumb on the Orange coloured polarity test
pad will now activate the ‘fault location’ function. With your thumb firmly on
the pad check the indication given by the LED’s against the chart on the
back cover to identify where the main problem lies. Note: The colour of the
LED’s may change when the pad is touched.
3. Incoming supply Polarity Test - this important test is discussed in full
on page three of this manual, please read.
To conduct the test with all three LED’s lit GREEN place your thumb on the
Orange coloured polarity test pad area. If the supply polarity is correct
there will be no change in indication and you can proceed to step 4. If the
supply polarity has been reversed the three LED’s will turn Red and flash.
If this happens stop testing and notify the supply company immediately.
4. Check that the mains voltage is in the correct range 207-253VAC.
Note: All tests are inhibited until the mains voltage appears in the display
5. NO-TRIP. Your tester defaults to no-trip loop testing when you first switch
on - button five re-selects no-trip loop test if you have selected other
functions.
6. TEST. A brief press of the test button will initiate the loop test and after a
few seconds the result will be displayed (Important: see notes on page 4).
The DL420 also has a HANDSFREE test function that is activated by
holding down the test button for 2 seconds. This is very useful for testing at
luminaires or similar connecting strips when your hands are occupied by
holding test probes.

10 Loop-PFC Testing
Loop-PFC testing continued
When using HANDSFREE mode with the ITLS 400 test lead always
connect the Earth and Neutral poles before the Live, otherwise it will
indicate a polarity fault and inhibit further testing.
HANDSFREE testing in No-trip mode. The tester will automatically conduct
the socket wiring test upon connection to the Live supply. If all is well it will
immediately initiate a Loop test.
When the test is complete the result will be displayed for a few seconds
before the display reverts to showing the L-N voltage.
The Loop test result can be recalled by pressing the No-trip button.
7. NO TRIP PFC. Having carried out a No-trip Earth fault loop test - pressing
this button calculates the PFC (Prospective Fault Current) by dividing the
measured loop result into the measured L-N voltage.
8. VOLTAGE. The default voltage measurement is made between L-N. Using
this button you can override to measure L-E and as a final safety check
measure the N-E voltage present.
9. Ze/DB. This button selects the High Current True Loop Impedance mode.
Use only with the test lead set configured for 2-wire mode (see page 6)
Connect the test leads to the two conductors being tested. The supply
voltage (see step 8) will be displayed. A brief press of the test button will
conduct the Loop test and the result will be displayed almost immediately.
Note: In 2-wire mode the voltage displayed will be that measured across
the 2 conductors that the test leads are connected to. The display will show
this as L-N regardless of whether they are connected across L-N or L-E.
HANDSFREE testing in High current 2-wire mode. This function is
particularly useful for testing at distribution boards and is activated by
pressing the test button for two seconds.
The DL 420 will then automatically conduct a Loop test upon connection to
the live supply and display the result. The supply voltage can be recalled
by pressing the Voltage button.
10. PFC. Prospective fault current. Pushing this button divides the above TLI
(True Loop Impedance) result into the voltage measured between the two
points under test to give either the prospective short-circuit current (when
L-N is tested) or the prospective earth fault current (when L-E is tested).

11
Loop-PFC testing
Specifications
Wiring Test
Detects missing E or N (>15kΩ)
Detects L-E or L-N swap
Detects Live - Earth/Neutral reversal by use of Polarity Test Pad
Fault indicated by chart on front of instrument
Phase - Neutral voltage measurement ± 1% ± 1V
Phase - Earth voltage measurement ± 1% ±1V
Neutral - Earth voltage measurement ± 1% ± 1V
Loop Test
No trip mode 3 wire testing Phase - Neutral - Earth all connected
Test current <15mA at 253V AC
Range Accuracy
0.00 to 9.99Ω± 5% ± 5 digits
10.00 to 99.9Ω± 3% ± 3 digits
100.00 to 500Ω± 3% ± 3 digits
High current mode 2 wire testing Phase-Neutral or Phase-Earth connected using true
impedance measurement - auto test (hands free) is selectable.
Range Accuracy
0.00 to 9.99Ω± 3% ± 3 digits
PFC Measurement
10A - 19.9kA This is a calculated result using the loop test measurement but it will be
inherently more accurate than traditional methods as the test is of
impedance not solely resistance
Over Voltage Protection
440V AC No damage - complete recovery
Power
4 x AA batteries (not included)
Battery life (BS EN 61557) > 10,000 test (or shelf life of batteries installed)
Environmental
Operating Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00C to 400C
Storage Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -100C to 600C
Operating Humidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80% @ 31˚C to 50% @ 40˚C
Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157mm x 89mm x 39mm
Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400g

Above is the indication given when touching the touch pad
LED’s will flash to indicate fault condition NC=No Connection
Condition Wiring Supply LED Buzzer
Number Condition Terminal Display
N E L
Socket Wiring
1 Correct N E L Continuous
2 L-E reverse N L E Warble
3 L-N-E miswire E L N Warble
4 L-N reverse L E N Warble
5 L-N-E miswire L N E Warble
6 Faulty N / L-E miswire NC L N Warble
7 Faulty N / E miswire NC N L Warble
8 Faulty N NC E L Warble
9 Faulty N / L-E reverse NC L E Warble
10 Faulty E / L-N reverse L NC N Warble
11 Faulty E N NC L Warble
12 Faulty E / N miswire E NC L Warble
13 Faulty E / L-N miswire L NC E Warble
14 Faulty L / N-E miswire L N NC Warble
15 Faulty L / E miswire N L NC Warble
16 Faulty L / N-E miswire E L NC Warble
17 Faulty L / N miswire L E NC Warble
18 No Mains NC NC NC None
Socket & See Industrial
www.socketandsee.co.uk
Unit 4, Century Road, High Carr Business Park, Newcastle, Staffordshire, UK, ST5 7UG
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