4, 6, 8 or 12 circuits: sizing a switch panel

Count the things you want to switch and you get a number: six, eight, twelve. That number is the second question.

The first one is how much current those things pull when they are all on at once, because that is the figure a panel is actually limited by — and it is not the figure most spec sheets lead with.

Two numbers, and the second one is the constraint

Here is the whole range, per channel and in total:

Read the last two number columns together. The TC-SW8 has eight channels rated 30A, 30A, 20A, 20A, 10A, 10A, 5A and 5A. Add them: 130A. The panel passes 60A.

Both numbers are true. The per-channel rating is the ceiling for one circuit. The total is the ceiling for the panel. You size each circuit against the first and your worst-case simultaneous load against the second.

Which produces the result that surprises people: the 8-way TC-SW8 and the 6-way TC-SW6 have the same 60A total. Two extra circuits do not buy you more current. They buy you somewhere to put it.

If you need more current rather than more switches, the step is the TC-SWT10 at 80A or the TC-SW12 at 100A. If you need more switches on the same budget of amps, TC-SW6 to TC-SW8 is the move.

Add up the worst night, not the shopping list

Work out what is on at the same time, on the night you bought the gear for. Something like: light bar on, driving lights on, work lights on at camp, fridge running, compressor going while you air back up.

Do it in amps. Watts divided by system voltage:

• A TC-Q90C driving light is 90W. At 12V that is 7.5A. A pair is 15A.
• At 24V the same pair is 7.5A. Same lamps, half the current, and this is the single biggest reason a 24V truck fits more onto one panel.

Add your list up, then add 20% because the build always grows. Compare that number against the actual ceiling column above, not against the count of switches.

Two things people leave out of the sum: the fridge, because it cycles rather than runs, and the compressor, because it is only on for ten minutes. Both draw while they are drawing. The panel does not average.

Electronic or relay: the clearest comparison we can show you

Most switching arguments are theoretical. This one is not, because we build the same panel both ways.

The TC-SW6 and the TC-SW6R are six-way panels with identical channel ratings — 2×30A, 2×20A, 2×10A — the same 60A total, the same IP65 sealing, the same -40°C to 105°C range. One difference: the TC-SW6 switches electronically, the TC-SW6R switches through relays.

The warranty is 5 years on the TC-SW6 and 3 years on the TC-SW6R.

That gap is the honest version of the argument. A relay is a mechanical contact that opens and closes under load. Contacts pit, contacts weld shut, and a relay that has started chattering will keep working long enough to convince you the problem is somewhere else. Solid-state switching has no contact to wear, which is why the TC-SW8 spec sheet leads with no relay clicking, no contact wear.

Relays still have their place — familiar, serviceable, cheaper to replace in the field. Choose one deliberately, though, not by accident.

Control type, and what each one costs you

Four ways to turn a circuit on across the range. They are not upgrades of each other; they trade different things.

Buttons — TC-SW8, TC-SW8B. The simplest thing that works, and the least to go wrong. 70 OEM icon options so the panel reads as a factory fitment. Both take the Bluetooth module as an option rather than as standard, so check what your panel was specified with before you plan on an app.

Touchscreen — TC-SWT10. A 5-inch 1920×1080 screen that dims itself off an ambient light sensor. It is also the only panel in the range specified with electronic-fuse switching on every channel, a per-channel working monitor with overcurrent protection, and LVCO low-voltage cut-off that protects the starting battery while you are parked up. If protection is what you are buying, that is the model, and the screen comes with it rather than the other way round.

Its sealing is quoted as two figures — control box IP67 / screen IP65 — because it is two enclosures. The box under the bonnet is sealed harder than the screen on your dash.

Wireless remote — TC-SW8W. Ships as two panels: the wired main panel for the dash plus a remote that works about 30m from the vehicle on 433MHz. It is rechargeable, and lasts anywhere from nine days to about five weeks a charge depending on how bright you keep its backlight. Useful when the switch you need is at the back of the truck and you are not.

Two things to weigh honestly. Its warranty is 2 years, not the 5 years the wired panels carry. And its wireless certifications — FCC ID and CE RED — are in progress rather than issued; they are available for volume orders, and until they exist we will not claim them.

App. Bluetooth, and it lives in the wired panel — the remote is a radio handset, not a Bluetooth device. Four things it does: backlight colour per switch, icon per switch from the same 70-icon set, mode per circuit (toggle, momentary, flashing or strobe), and grouping so one tap drives several circuits.

What the certification column tells you

The switch panel line holds CE, FCC, RoHS 2.0 and REACH, with certificate numbers published on the product pages — HTT2024121386E, F and R. A distributor can cross-check them against the scans.

Now look at our driving lights, work lights and light bars. Those fields are empty. Not because the products are untested, but because we hold no certificate on file for those lines yet, and a certification mark is a legal declaration rather than a marketing badge.

That is the more useful signal when you are comparing suppliers. A parameter table with gaps in it tells you the filled-in parts were not guessed either.

Picking one

• Under 40A, four circuits is enough — TC-SW4. A light bar, a pair of driving lights, a fridge, one spare.
• Under 60A, count your switches — TC-SW6 if six covers it, TC-SW8 if you want two more places to put the same current. TC-SW6R only if you specifically want relays.
• Under 80A and you want protection per channel — TC-SWT10.
• Over 80A, or twelve circuits — TC-SW12, with isolated positive and common ground wiring.
• You switch things from outside the vehicle — TC-SW8W, with the warranty and certification caveats above.

Leave one circuit spare. Every build grows, and adding a panel later costs more than the one you did not need on day one.

If you are not sure which side of a ceiling you land on, send the list — every circuit and what it draws — and we will tell you which panel covers it, or that none of ours does. The full range is here, with per-channel ratings on every model.