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TF1170-2 & TF1170-3 Smart Combination Relay
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The automatic trigger incorporated in the TF1170 self-switching combination relay is designed to switch two relays when certain voltages occur. The normal operating environment is a 12-volt DC circuit within a motor vehicle.
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TF1170 -2 20 amp Smart Combi
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TF1170-3 30 amp Smart Combi
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Application.
Typically it is used in an auxiliary towbar electrical circuit to switch the split-charging and fridge circuits on and off. It does not need any dedicated signal feed to the coils of its relays. When the voltage in the line from the battery reaches the appropriate level as the alternator begins to charge the battery, the trigger unit switches the relays on. When the alternator ceases to charge and the voltage drops, it switches the relays off.
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Accommodating different cars and different conditions.
In order to work effectively, the unit has to accommodate a number of variables. Some variables occur between one car and another and some occur within individual cars depending on circumstances. Therefore the trigger unit has, at the outset, to be preset very precisely to operate within that narrow window of conditions which can be identified as common to all or, at least, the great majority of cars in most circumstances.
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1. Variations between one car and another.
The performance of battery and alternator will vary between one car and another. Factors that affect performance
include good or poor battery condition, alternator condition and slipping alternator belts.
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2. Variations within each particular car.
The performance of the battery and alternator of any individual car will also be affected by circumstances. For
instance, not only do winter conditions make batteries and alternators work harder by virtue of the fact that heaters, wipers, lamps etc. are used more but in cold weather the voltage drop observed in a battery when even a fairly small load is applied to it is much greater than it would be in warm conditions. Other factors that affect performance and
battery condition include night driving, frequent short journeys and additional loads created by in-car accessories.
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3. Voltage drop under load.
One very important variable is the voltage drop that always occurs when a load is put on a battery (and the conse- quent rise in voltage when the load is removed). There is also some voltage drop across the length of supply cable.
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4. Accommodating normal voltage drops.
To succeed in doing its job in the context of all these variables the device has to be preset very precisely as des-
cribed above. The unit is also intelligent enough to deal with a number of other variables that would otherwise prevent
it working efficiently. It is also equipped with a time delay that allows it to ignore transitory voltage changes.
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Essential Fitting Notes:
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Eliminating variables which would prevent efficient operation In a device that depends for its operation on measuring voltage levels, it is obvious that installation should be carried out in such a way as to avoid accidental voltage drops.
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The following are important guidelines for installation.
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The first is to use a cable capable of carrying the currents involved. To carry sufficient current to run a fridge and a battery efficiently, through a cable which is typically five metres long, the cable should be at least 2.5 mm² . Thinner cable is likely to produce excessive voltage drops under heavy load conditions. (Finding other, thinner wires, such as the boot lamp wire, to feed the auxiliary circuits is potentially dangerous as these wires may overheat under load. It is unlikely that the trigger unit would operate under such circumstances, which could be just as well!) There is an argument that a thicker cable, up to 3 mm 2 should be used. The common standard in the industry is 2.5 mm² . The correct fuse rating is 15 amp, or 20 amp blade type. [Traditional glass fuses have different operating characteristics and we do not recommend them.] Fuse power source 15amp and use 2mm² cable (28's/030)
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The second is to make sure that all connections are well made. Amongst the most common problems encountered by fitters using these trigger units has been the problem of voltage drop caused by badly made connections. Loose battery nuts, and crimp terminals not made with the appropriate ratchet crimping tool are the worst culprits. In any event, poor connections can get hot or very hot under load conditions and may therefore become dangerous.
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One of the greatest safety features built into the trigger device and self-switching combination relay is that, under load in unsafe conditions as described above, they will switch off the current to the caravan.
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| Conditions that will not be accommodated. |
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| It is inevitable, however, that some cars will fall outside the defined operating window. In most cases, the poor condition of the battery or alternator or even the alternator belt will be to blame but it is possible that some cars may be "set up" differently even in prime condition. On such cars the trigger unit will not work properly. |
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| It is also inevitable that, even in cars where the system works well, there will be times when, due to the use of other accessories that subject the battery to heavy loads, the trigger unit will turn off. This should not be regarded as a failure since the device is effectively protecting the battery from further overload but owners should be appraised of the possibility and advised to monitor it. |
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| Technical Specifications |
| Nominal operating voltage |
12 volts dc |
| Maximum continuous current |
17.5 amps |
| Fuse rating (Blade type) |
15 amps (17.5 amps max) |
| Coil current |
.09 amps |
| Coil temperature |
90 Degree Celsius |
| Switch on voltage |
13.5 volts |
| Switch off voltage (no load) |
13.2 volts |
| Switch off voltage (Max load) |
12.7 volts |
| Relay switching capacity (TF1170) |
15 amps x 2 |
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| General Instruction, 12S installations (Caravan auxiliary circuits) |
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| 1. Drill a 13mm (9/16") hole in the floor of the boot adjacent to the socket mounting point on the towbar. (Take great care to ensure that you drill in a safe place where you will not damage wires, pipes, bodywork, etc.) Treat the edges of the hole with a rust inhibitor and line it with the grommet provided. |
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| 2. Wire the trailer socket, as shown in the table below and mount it on the towbar. Lead the 7-core cable into the boot through the hole you drilled. Make sure the cable is a snug fit in the grommet and that fumes will not be able to pass through them into the passenger compartment. |
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| 3. Route your power source cable(s) from the boot to the battery. Fit a fuse in line in the cable, close to the battery. Do not connect yet |
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| 4. Follow the instructions in the table below and connect together your 7-core cable and your relay. Note that post 1998 caravans use pins 4 and 2 differently from the way pre 1998 caravans did. If you wire according to these instructions, all caravans will be properly accommodated. |
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| 5. Connect your power cable(s) to the battery and insert the fuse(s) provided. Check that the fuse is of the value shown in table below |
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| 6. Use a suitable test board to test the circuits. The loads created by the test board must simulate the load created by a caravan fridge (red, Pin 6) and battery (yellow, pin 2 or green, pin 4). Make sure that the relay stays on under load. |
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| Wiring the 12S Socket & connecting to the vehicle: |
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| Socket pin number |
7-core cable colour |
to |
Relay pin |
Vehicle circuit |
| 1 |
Yellow |
to |
N/A |
Reversing light |
| 2 |
Blue |
to |
2 |
Switched live |
| 3 |
White |
to |
N/A |
Chassis earth |
| 4 |
Green |
to |
4 |
Permanent live |
| 5 |
Brown |
- |
N/A |
Spare |
| 6 |
Red |
to |
6 |
Switched live |
| 7 |
Black |
to |
N/A |
Chassis earth |
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Fuse rating: 15 amp (max 17.5amp)
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The feed cable from the battery must be heavy duty. We recommend TF15430D1, Double-insulated 27.5amp. This cable must be fused, as close to the battery (source) as practically possible: 15amp blade fuse (17.5 amp max) .
New large fridges (2003 onward)
Very large fridges may demand too much current fot these relays to handle. A larger relays and new 12S fitting kits to match will be available early in 2004. See our Newsletters section to keep in touch with developments. If in doubt, contact us.
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Unswitched output
Socket Pin 4 is fed by the green wire in the 12S 7-core and supplies the interior lights of the caravan; on new caravans this is automatically switched within the caravan when towing, to charge the caravan (auxiliary) battery. The switching is controlled by a relay in the fridge circuit. The fridge circuit is controlled by the self-switching combi. |
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Switched outputs
Pin 2 is fed by the blue wire in the 12S 7-core wire and is used to charge the caravan (auxiliary) battery except in new vans: see above, Pin 4. Pin 6 is fed by the red wire in the 12S 7-core and supplies the caravan fridge.
Please note that the two black relays on this device are designed to run at a temperature of around 90 degrees C. This is normal. When fitting the device, do not lodge it in a tight space or wrap it up. Allow some space around it where air can move. |
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| TF1170 Self-Switching Combination Relay |
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SYMPTOMS
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COMMENT/LOOK FOR
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| Relay feels hot: |
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This is normal. The relay coil operates at approx 90 degrees C. Mount where owner will not touch it and where there is space for some air circulation.
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| Relay will not switch on: |
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Poor battery condition.
Poor alternator performance.
Poor connections. Loose battery nuts and crimp terminals not made with the appropriate ratchet crimping tool are the most common culprits
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| Relay switches on but switches off again when load is applied: |
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Poor connections as above.
Feed cable too thin (Use 2.5 mm² or 3 mm² cable)
Overload: Current over 16 amps may cause excessive voltage drop. Check auxiliary battery, short circuits, etc. Check fuse in relay circuit.
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| Relay cycles on and off: |
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Poor connections as above.
Faulty battery causing abnormal voltage drop under load.
Lower value fuse in power line causing voltage drop as it heats up.
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| Relay takes time to switch off: |
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Caused by battery maintaining high voltage. Try draining battery slightly by applying load (switching on fan, brake lights, etc.) for a few seconds. Relay should switch off within approx 30 seconds of engine being switched off although some batteries can maintain unusually high voltage (above 13.2 volts unloaded) especially in warm weather.
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Check if there is any load on relay. Try another unit. |
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Phone for advice on 0161 273 5619. |
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All units are thoroughly tested. If you think a unit is faulty try another unit. It is extremely unlikely that you will find two in a row that are incorrectly calibrated.
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IF IN DOUBT PHONE FOR ADVICE ON 0161 430 1120
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