Installation and Operating Instructions for Blow Down Controller Type LRR 1-12

Transcription

1 LRR GENERAL PURPOSE & APPLICATION 1) Continuous monitoring of the conductivity of water within steam boilers, evaporators and similar plants with the added facility of temperature monitoring and compensation when relating conductivity to the measurement of Total Dissolved Solids (T.D.S.) in Parts Per Million (p.p.m.) The LRR 1-12 has been designed for use with electrode type LRG 16-4, LRG 16-8 as well as for the standard conductivity electrodes types ERL-16-1, LRG 17 and LRG 19 as the sensor. TDS Controller Type LRR1-12 2) Removal of sludge and precipitated solids from the bottom blow down. connection on steam boilers. The controller is designated LRR 1-12STDB when used with automatic total dissolved solids systems type T2, D2, L2 and H2 in conjunction with automatic intermittent bottom blow down. The controller is used in conjunction with RTK continuous blow down valve type MV5291 as the TDS control valve. The LRR 1-12 is easily configured to suit different TDS control system types as stated above. In the case of the LRG 16-8 a resistance thermometer has been built into the electrode to allow temperature measurement. When the LRR 1-12 is suitably configured through its menu it offers temperature compensation thus enabling accurate conductivity measurements against Total Dissolved Solids for variations of boiler pressure. With the build-in real time clock the controller LRR 1-12 is also designed for use in combination with the RTK intermittent bottom blow down valves type PV6291 with air or water actuation equipment for a timed bottom blowdown. The mode of operation for the system can be preset before dispatch if so desired but is easily configured through the menu as described in the commissioning procedures. The controller is designed to be installed in control panels; desks, cabinets or individual wall mounted GRP enclosures. The required panel cut-out for the instrument is 138mm x 68mm to DIN RTK Control Systems Ltd. Unit 25, Business Centre West, Avenue One, Letchworth Garden City, Herts. SG6 2HB. United Kingdom Tel: +44 (0) Fax: +44 (0) Website: info@rtk.co.uk

2 LRR INSTALLING THE LER Remove the mounting clips, ensure the panel gasket is in place. Insert the controller into the panel cut out from the front. Re-insert the clips and secure the controller by tightening the screws. (See also dimensional details) Note: Do not install the controller where it receives direct radiant heat from the boiler or pipework etc. WIRING Wiring should be in accordance with the relevant wiring regulations, standards and the LRR 1-12 wiring diagram. It is highly recommended that the controller be pre-wired down to a common dedicated terminal rail whether it is mounted in a control panel, desk, cabinet or wall mounted enclosure. In the case of the latter, special GRP wall mounted enclosures are available from RTK Control Systems Ltd which have a combined termination chamber and can be supplied on request. Note that four-core cable is required between the controller and the conductivity electrode even though the conductors are linked in pairs at the electrode. The two additional conductors form part of the signal voltage drop compensation along the cable. The cable should also have a collective screen around the four cores and carry a drain wire to facilitate the connection of the screen at the controller. (NB the screen should not be connected at any other point nor must it come in contact with plant earth). Experience has shown that the use of a continuous cable length between electrode and controller intermediate terminal rail gives a reliable installation which can be easily checked. With regard to the new combination electrode LRG 16-8 two separate cables to the electrode s terminal enclosure will be required, a four core and screen for the conductivity part of the electrode and a two core and screen for the PT1000 resistance thermometer. The recommended cable type for this application is Pirelli FP200 1mm², or alternatively Delta Enfield Firetuff is also suitable. Two cored with screen versions of the previously described cable will be required for the PT1000 input and 0/10v and 4/20ma output if used. As previously indicated it is not recommended that such cables be terminated directly to the controller plugs but via a locally mounted terminal rail within the mounting enclosure. In certain industrial applications it may be required to use armoured cable between the controller and electrodes as well as the network interface and 0/10v or 4/20ma output. In these circumstances multi-paired instrument cable is recommended. Single pair for 0/10v or 4/20ma output; two pair for the conductivity electrode; two pair for the network interface. In the case of the new combination electrode type LRG 16-8 a three pair is recommended thus allowing one cable to cover both functions. Each pair will be individually foil screened with drain wire and polyester tape wrapped, collectively screened and polyester tape wrapped, black P V.C. sheathed, single wire armoured and finally sheathed in blue P.V.C. This cable specification is generally to BS5308 Part 1 Type 2 and is available in three core sizes of which 0.5mm square is recommended up to 50 metres and 0.75mm square for distances up to 100 metres. Cores are made up of 7/0.2mm strands of annealed tinned copper for 0.5mm square, and 24/0.2mm strands for 0.75mm square cores. Advice should be sought for installation distances greater that this mentioned above.

3 LRR LRR 1-12 CONNECTION DIAGRAM IN STD MODE (Continuous Auto TDS control )

4 LRR LRR 1-12 CONNECTION DIAGRAM IN STDB MODE (Continuous Auto TDS control and Intermittent Bottom Blowdown) Fused Spurs

5 LRR The controller operates with a switched mode power supply and can operate from an A.C. 50 to 60 Hertz supply from 100 Vac. up to 240 Vac. and offers two conductivity ranges of operation, PPM or µsiemens/cm. and PPM or µsiemens/cm. The conductivity range is accessed through the controller s menu and is described in the Calibration section of these instructions. The controller is equipped with its own mains fuse and rated at 1Amp Slow Blow. It is recommended that the electrical supply by the controller be externally protected by a 2 Amp fuse, or MCB. There must be two live supplies to the controller and these must be from the same phase. L1 is the supply from the burner circuit of the Boiler Control Panel and this powers the Controller, its display, the PM60 interface, the PT1000 resistance thermometer and 0/10v or 4/20ma output. L2 powers the actuator and must remain live after the burner is tripped manually or automatically on pressure to allow the motorised blow down valve to close. L2 is normally fed from the Boiler Control Panel s control circuit and should be the same phase as the supply to the burner circuit. This L2 supply should be protected by a separate 2-amp fuse. Complete isolation of the controller is therefore achieved when the boiler s main isolator is switched to the OFF position. Note. Caution must be taken however to allow possible closure of the blow down valve before final isolation of the boiler, not to do so, will result in the boiler losing excessive quantities of water. COMMISSIONING PROCEDURES Front Panel Push Buttons The LRR 1-12 has only four push buttons and is entirely menu driven. There is therefore absolutely no need to remove the back cover of the instrument to gain access and to do so could invalidate the instruments warranty. Calibration To enter calibration, press and hold the Menu button until the display shows SET-UP. After a couple of seconds the display will automatically move to the first item in the main menu and display SET-UP and on the line below the display will show SET PARAMETERS. Main Menu The main menu contains the following sub - menus 1) SET PARAMETERS 2) CALIBRATION 3) SET TEMP. COMP. 4) SET CLOCK 5) EXIT SET-UP By pressing either the UP arrow or the DOWN arrow button will enable scrolling through the main sub - menus.

6 LRR Having arrived at the particular sub - menu required pressing the P program button will take the controller into that sub - menu. Note. The P button is pressed to enter a parameter, to save and exit a parameter. Setting & Saving Parameters. 1) SET PARAMETERS In this first Sub - Menu are all the preset conditions necessary to fulfil the requirements associated with the particular type of blow down system. Once in a sub menu pressing the P button will allow you to scroll through and set accordingly as follows: a) OPERATIONAL MODE b) TEMP SENSOR c) 2 MINUTE DELAY d) ISOL. OUTPUTS i) and ii) e) DISPLAY f) OPERATING RANGE g) SET - POINT h) HIGH ALARM i) DURATION j) SET EVENT a) OPERATIONAL MODE When selected will also display one of the following displays on the second line SLH, STD or STDB. Using either the UP arrow or DOWN arrow buttons will permit scrolling of these three parameters. Choice of these functions is determined by the following criteria: SLH For high pressure blow down systems and or indirect blow down systems where the measuring electrode is used outside the boiler. STD For conventional blow down systems with the electrode into the boiler and providing both low and high T.D.S. alarms. STDB By far the most common application providing both continuous and intermittent bottom blow down facilities and a T.D.S. High Alarm. Lo Alarm is sacrificed in this application for driving the solenoid pilot valve of the intermittent bottom blow down valve. Select the one suitable for your application and then enter that choice by pressing the P button. b) TEMP. SENSOR When selected will show on the display as either being ENABLED or DISABLED. Using either the UP arrow button or the DOWN arrow button will allow toggling back and forth. Pressing the P button for whichever mode is required will enter that function.

7 LRR c) 2 MINUTE DELAY Required if in SLH mode and also in applications where the conductivity electrode lies outside the boiler. In these applications temperature compensation is not used. Therefore to get accurate conductivity readings the system must be purged each time the system comes on, hence the requirement of the two-minute purge delay. This function is ENABLED or DISABLED exactly as described above. d) ISOL. OUTPUTS i). Representing Isolated Outputs are available in the following formats. When selected the display will show either of the following display. ISOL. OUTPUTS appears on the top line of the display while on the bottom line will be displayed 4-20mA v or alternatively 0-20mA v. Once again using either the UP or DOWN arrow bottoms will toggle the options too and fro. Select the one required by pressing the P button to enter and save that function. ISOL. OUTPUTS ii). Under this second heading of Isolated Outputs is a facility to allow rounding up of units. The display will now show on the bottom line either DIRECT or AS DISPLAY. This allows both output voltage and current to be outputted in a direct form following the T.D.S. output or round up to down as per the display back and forth. Pressing the P button once more on the preferred option will save and enter that feature. e) DISPLAY This function allows choice of DISPLAY rounding to the nearest 10 or 100 depending which range is selected. Toggling the UP or DOWN arrow button will allow choice of ranges between nnn0/nnn.0 or nn00.0/nn0.0. Press the P button to save and enter your choice. f) OPERATING RANGE Under this function the conductivity input sensitivity can be selected of which there are two ranges and are referred too as HIGH & LOW. As before toggling either the UP or DOWN arrow buttons will allow the operator to select the range most suitable. The ranges are as follows: - HIGH and LOW Having made the most suitable selection press the P button to save and enter. g) SET - POINT This is the function that allows the desired setting of the maximum level of T.D.S. (Total Dissolved Solids) p.p.m. (Parts Per Million) or if preference is in terms of conductivity µsiemens/cm. If there is any uncertainty as to what maximum level of Set Point should be chosen telephone advice is available from Invensys Flow Control (UK) Ltd. To adjust level of SET - POINT using the UP or DOWN arrow buttons will adjust the level respectively. Having adjusted the SET - POINT to the desired level press the P button to save and enter that value.

8 LRR h) HIGH ALARM This function allows the setting of a level of T.D.S. that if attained in normal operation and above the SET - POINT level will instigate a visual alarm and the operation of an internal relay whose volt free contacts can be used for driving further audible and visual alarm functions. Adjusting the level is again once more a function of the UP or DOWN arrow buttons which when pressed will adjust the level respectively. Once the correct level has been selected pressing the P button will save and enter that function. If Operational Mode = STD LOW ALARM This function which is only available in STD mode allows the setting of a LOW ALARM value and is set correspondingly lower that the SET - POINT as is HIGH ALARM above. Toggling the UP and DOWN arrow buttons will adjust the value accordingly. Once the value has been chosen press the P button to save and enter that value. If Operational Mode = SLH i) DURATION & CYCLE TIME These time functions are used for sampling and purging, necessary because the electrode is situated outside the boiler in the blow down discharge pipe work via an EF1 flange trapped between two other flanges. Because also temperature affects conductivity and also that it may not be practical to monitor temperature it is necessary to allow the system to purge before assessing thee conductivity of the boiler water and any consequential blowing down. If the T.D.S. is found to be above the SET - POINT limit during purging then the blow down valve will be maintained in the open position until the T.D.S. falls below the SET - POINT. If however after the purge cycle has run its course the actual T.D.S. value of the boiler water is below the SET-POINT then the blow down valve will be returned to its close position. In this situation however no blow down can take place and the associated pipe work starts to cool down and any remaining water in the pipe work and around the electrode also cools and also loses conductivity. The introduction of a second time function is also necessary to periodically cause the system to re-purge and this is referred too as the CYCLE TIME. DURATION 00 Min 10 sec through to 04 Min 00 sec To adjust the duration value press the UP arrow button and the value will scroll incrementally in ten second steps to a maximum of 4 minutes. Similarly pressing the DOWN arrow button will scroll the duration decrementally in 10 second steps to a minimum of 10 seconds. Stop pressing when the desired value is attained. Finally press the P button to save and enter and exit to next function.

9 LRR CYCLE TIME The cycle timer is adjustable up to a maximum of 60 minutes in one-minute steps. Pressing the UP arrow button will increment the cycle time in one minute steps. Pressing the DOWN arrow button will decrement the cycle time in one minute steps. Once the value of the cycle time has been decided pressing the P button will save, enter and RETURN TO MAIN MENU. If Operational Mode = STDB DURATION The duration timer in STDB mode is for setting the time duration of the intermittent bottom blow down valve type MPA. This timer is adjustable in one second steps and is incremented by pressing the UP arrow button and correspondingly decremented by pressing the DOWN arrow button. Once the value of time has been entered pressing the P button will save, enter and exit to the next function. j) SET EVENT The display shows three fields DAY, EVENT & TIME. The flashing cursor indicates the field that is currently adjustable. When flashing in the DAY field the UP arrow button will increment the days of the week while on the other hand the pressing of the DOWN arrow button will decrement the days of the week. Pressing the P button at this stage assigns the Day and cursor passes to the EVENT field. The middle field is the EVENT field of which there are eight locations numbered 1-8. These can be incremented and decremented using the UP and DOWN arrow buttons respectively. Pressing the P button assigns that event number and passes to the next field where a time can be assigned to it. The cursor now flashes over the left hand character of the TIME field now indicating that a time is needed e.g. 12:30. The UP arrow button adjusts the hours incrementally, and the DOWN arrow button decrements the minutes. Pressing the P button now saves that time and passes the cursor back to the DAY field. Of course it may be that more than one intermittent bottom blow down is required in any one day so instead of incrementing the DAY field press the P button once more. This will take the cursor to the EVENT field again. Pressing the UP arrow button and incrementing the EVENT number before once more pressing the P button to move the cursor to the time field where another time can be entered. A maximum of eight events per day can be entered and when all events and times are entered in day one location which happens to be MONDAY (MON) a coping facility allows the remaining six days to be programmed as Monday. In the case of the boiler being shut down at the weekends it is still quicker to copy and edit for Saturday and Sunday than to enter individually. COPYING When all the data for Monday has been entered press the DOWN arrow button twice. This will take the program Menu through EXIT into COPY Mode. Now press the P button and this will now copy all Monday s Data to the remaining six days of the week. Pressing the M button (Menu) will take the program back to the beginning of the SET - UP SET PARAMETERS MENU. Press the DOWN arrow button Now!

10 LRR ) SET - UP CALIBRATION Firstly if the instrument has already been set up earlier and is requiring calibration only which will occur probably after a water sample is taken then the route is as follows. Press the Menu M button which will take the instrument into SET - UP & SET PARAMETERS and then press the UP button once. This will take the instrument into SET - UP & CALIBRATION. Now press the P button once. The instrument will now display CALIBRATION and also the current value of T.D.S. measured by the instrument. Now using the UP and DOWN arrow buttons adjust the T.D.S. value until it corresponds with the tested sample just obtained. Press the P button to save and enter. If a change of T.D.S. value was necessary; as the instrument saves away the new value, the display will show the message CALCULATING before returning to display SET UP & SET PARAMETERS. To exit CALIBRATION press either UP or DOWN but preferably DOWN as if offers the least number of button presses until it reaches SET - UP & EXIT SET UP. Now press the P button once and the display will now show EXIT SET UP &S SAVE SETTINGS. With one more and final press of the P button the display briefly show SET UP & SAVED and then returns the instrument back to normal operation. 3) SET TEMP. COMP. (Only if applicable when electrode LRG 1608 is used)) Before starting this exercise the boiler should be at or just below normal working level with water at or just below 100ºC. Press the P button once and observe display as it briefly shows the following message SET TEMP.COMP. & SET UP SAVED before displaying the current T.D.S. value and current temperature e.g ÙC with a bottom line display message TCF IN PROGRESS. Once the instrument is prepared as described above the boiler can be fired and as the boiler pressure starts to rise so will the temperature. The boiler should be raised to full steaming pressure e.g. 10 barg and where the temperature should have reached 184ºC. As the boiler settles at full working pressure and temperature the M button must be pressed and held until the display shows the message COMPENSATION SAVED for approximately 3 seconds before returning to SET - UP & SET PARAMETERS. N.B. CAUTION As described above temperature compensation follows conductivity calibration in a new boiler or newly refilled boiler, there is no need to run the temperature compensation again when correcting the T.D.S. value after routine sample testing. However during the temperature compensation routine it may be necessary as a result of thermal expansion to blow down the boiler if it reaches high water. As mentioned earlier preferred water level was suggested at normal or just below normal water with the above in mind. The feed water and feed check valves must remain closed and feed water pumps switched off throughout the whole of the temperature compensation routine.

11 LRR The reason for this, of course, is to prevent any fresh feed water entering the boiler during this exercise which would affect the accuracy and integrity of the temperature compensation. It is also important to start the routine at or slightly below 100ºC because all the T.D.S. readings that the instrument takes at 5ºC intervals are normalised back to 100ÙC at the end of the exercise when the data associated with the new compensation curve is automatically saved away. 4) SET CLOCK Because the instrument has day and events programmed into it, it follows that the instrument needs a real time clock and is based on a 24 hour 7 day a week timer. It does not have a calendar function and therefore has no need to be Y2K compliant. The first press of the P button takes the instrument display to SET CLOCK and displays the current time on the bottom line e.g To adjust the clock to the correct time use the UP arrow button to increment the hours and the DOWN arrow button to decrement the minutes. When the correct time has been set press the P button to save, enter and exit to next function. The day of the week now needs setting and using either the UP or DOWN arrow button will allow scrolling back and forth through the days of the week. Stop on the current day of the week and then press the P button which will save, enter and return to the beginning of the SET - UP & SET PARAMETERS Menu. 5) EXIT SET - UP Now cycle through the whole of the SET-UP menu by pressing the UP arrow button Four Times. This will bring up the LRR 1-12 display message SET - UP & EXIT SET - UP. Press the P button once and the display will now read EXIT SET - UP and on the bottom line of the display will read SAVE SETTINGS. Toggling the UP and DOWN arrow buttons will cause the display to show RESTORE SETTINGS and then back to SAVE SETTINGS. One final press of the P button causes a brief display of the message SET - UP & SAVED. If the display was left in RESTORE SETTINGS when the P button is pressed the display briefly shows the message SETTINGS RESTORED and then the instrument returns to normal operation when if will display the conductivity the temperature the day and the time. e.g ºC MON 12:05 If the Temperature Compensation Feature is Disabled then the temperature reading will not appear in the display. N.B. Please note that any events that were changed in the SET EVENT (STDB mode only) have already been stored. Restoring calibration applies only to the other calibration details and to the calibration itself.

12 LRR The temperature compensation (if performed) has also already been stored. Also please note that all calibration data is stored on entry to the compensation routing and it is that data that will be restored if the RESTORE SETTINGS option is selected. The LRR 1-12 now returns to normal operation. BATTERY The lithium battery type CR2430 SLF Li-Mb us non rechargeable and is soldered in. Should a new battery required, the unit must be returned or a service visit requested. LED Indicators in STDB Mode HIGH - OPEN - Red for Conductivity above set point. Red flashing for conductivity high limit. Amber for bottom blow down valve open. CLOSE - Green for bottom blow down valve closed. LOW - Green for conductivity below set point. Automatic T.D.S. Control Systems T2, D2, L2, and H2 combined with Automatic Intermittent Bottom Blow Down using Controller LRR 1-12 STDB with Bottom Blow Down Network Interface. This network interface has been designed to prevent more than one boiler bottom blow down valve operating at the same time. This is in accordance with the revised Health & Safety Executive Guidance Note PM60, July The blow down interface is mounted on the rear panel of the LRR 1-12 and its six way plug and socket is located in the top left corner of the rear panel when viewing from the rear (See Diagram of Rear Panel). Six connections are terminated within the terminal socket and designated P1, four of which are for the interface and the remaining two for connection to a limit switch mounted on the blow down valve being driven by the unit. The interface is electrically isolated from the LRR 1-12 Pin assignment and connections are shown on the wiring diagram and as follows: Pin 1. Busy Lin As each LRR 1-12 signals to blow down, this line is pulled low for the duration of the blow down plus a further five minutes. No other LRR 1-12 in the network will be able to start a blow down cycle whilst this line is held low. The local limit switch to pins 5 & 6 from the blow down valve will also hold this line whilst it is still open thus preventing blow down of further boilers on the same network. The Busy Line of all other LRR 1-12 s on the network must be connected together.

13 LRR Pin 2. Sense Line This must be connected to the sense line of all other LRR 1-12 s on the network. On the last unit in the network link wire is taken from Pin 2 (Sense Line) to Pin 1 (Busy Line). Note: Only one LRR 1-12 must contain this link and that unit must be located at the end of the cable. The Sense Line is checked by each LRR 1-12 to establish network integrity before any blow down sequence is commenced, Pin 3. 0 Volt Reference Line This must be connected to the 0 Volt reference line of all other on the network. On the last unit in the network a link wire is taken from Pin 3 (0 Volt reference) to Pin 4. Pins 5 & 6: Limit Switch These are connected to normally closed contacts (i.e. open during blow down) of the limit switch attached to the blow down valve. If no limit switch is fitted to the valve then these two pins require linking together. If the LRR 1-12 is used alone the connector plug (Designated P1 on the rear panel) must be linked accordingly 1 & 2, 3& 4, 5 & 6. Operation Before any LRR 1-12 commences blow down, it first checks the sense line. If this line is already low, the unit will wait until it is released before it starts blow down. The Amber LED indicating blow down valve open will flash to indicate that the unit is waiting to start blow down. Having detected that the sense line is free, the LRR 1-12 holds the busy line low and then tests the sense line. If this remained high, the network must be broken and the unit displays NETWORK FAULT in the message area. As the blow down time is reached and no blow down is initiated. The Green LED indicating blow down valve open will flash. If however, the sense line was pulled low, the LRR 1-12 momentarily releases the busy line and confirms the sense line is released. If this is not the case, it is assumed that another LRR 1-12 is attempting blow down and the unit reverts to monitoring the sense line. If no other LRR 1-12 is detected, the busy line is again pulled low and held low for a further five minutes after the blow down valve has closed. Once five minutes has elapsed any fault shown as NETWORK FAULT which is rectified will enable that valves blow down cycle to commence immediately. The Green LED which was flashing will remain on until blow down sequence is completed. If the external limit switch on the local blow down valve is not closed after this five minute period, the LRR 1-12 holds the busy line low to prevent any other blow downs and the message LIMIT SWITCH FAULT appears in the display area.

14 LRR Note: Should one or more of the network links on the Busy Line Pin 1, 0 Volt reference line Pin 3 Sense Line Pin 2 be broken NETWORK FAULT condition will be displayed in the message area. WIRING DIAGRAM FOR NETWORK INTERFACE ON SYSTEM INTERFACE (Multi boiler installation) FRONT PANEL - PANEL MOUNTED LER TYPE LRR 1-12

15 LRR REAR PANEL - PANEL MOUNTED LER TYPE LRR 1-12 DIMENSIONS - PANEL MOUNTED LER TYPE LRR 1-12

16 LRR TROUBLE SHOOTING On occasion, the LRR 1-12 TDS controller may lock itself in calibration mode after attempting to re-calibrate the unit with a freshly taken TDS sample. When this occurs the controller is usually not at fault and rather the reason for the locking is generally due to one of the following reasons: The electrode tip has deposits on it increasing control circuit resistance, giving the impression of an open circuit situation to the LRR1-12 controller. As deposits may continue to build up over a period of time on the electrode tip, this phenomenon will increase the resistance in the electrode circuit. Even if sample TDS readings may be consistent for a period, every re-calibration of the LRR1-2 unit will effect a small drift away from recommended Factory settings in order to compensate for this gradually increasing resistance due to the furring up of the electrode tip. This compensation is finite and will eventually approach a limiting value. When it does, the LRR1-12 controller appears to lock in the Calibration Mode. The solution: Remove the electrode and clean the tip with some emery cloth. The key to avoiding this is in the correct conditioning/treatment of the boiler feed water. A controller behaving in this manner is an indication that the feed water conditioning may not be correct. An internal inspection of the boiler is advisable to investigate it s condition. An open circuit or very high resistance exists between the conductivity probe and the LR1-12. Check for continuity in the wiring between the probe & controller. Also check continuity between electrode tip and electrode connector terminal. Very low conductivity levels due to fresh and/or cold water in the boiler. The solution: Take boiler up to temperature and pressure before calibrating unit. It may also be necessary to build-up the TDS in the boiler to achieve this. A function test can be carried out on the controller as follows: Disconnect the electrode from the back of the controller. Wire link terminals 1 & 2 and wire link terminals 3 & 4. Connect a resistor between 2 & 3 of a value between 18 and 100 ohms (18 ohms = simulated 0 ppm). e.g. A 50 ohm resistor will simulate a TDS reading of around 3000 ppm. (A test block with the 18 ohm resistor is provided with the LRR 1-12 unit). If the LRR1-12 calibrates, then the unit is operating correctly.