Pitot Heat Wiring and AWG

[Karetaker]

Howdy everyone. I have a blade type heated pitot with 2 new cartridge heaters installed. Both are 14v heaters; one is 100W and the other is 70W. Each have two conductors that have no ID marks on them, about 12" long. AWG seems to be about 18 to 20. ( Thin in my opinion.)

Do I connect each + and each - together and run 2 wires to cockpit or do I run all 4 individually? Opinion on local ground? AWG for run back to cockpit? I planned on 12 or 14 AWG.

Thanks for the insight.

[GeoffP]

FWIW, when I installed my Dynon heated pitot I ran 14G down the wing for both power & earth. I don't have local grounds in my wings, rather I've run specific grounds back. Technically I probably could have got away with thinner gauge wire, but I wanted to play it safe.

Double check the manual you have to see their recommended wiring connection. You might need to wire the two elements separately depending how it all functions.

[Karetaker]

My blade type pitot was an eBay purchase with no documentation. It was beat up and did not heat. Now it has new heaters as described above but I am not sure how to wire them. There must be others with these type heaters on their RVs. Any more opinions on local grounds and "home run" grounds? I like the idea of running grounds home but not to keen on the added weight.

[Desert Rat]

Basic electrical theory would seem to indicate that you should wire them in series for a 28v system and parallel for a 14v system.

figure out your max amp draw and length of the wire run and size your wire accordingly. it will likely be 14g.

I just pre-wired my wing before closing it up, so I'm nowhere near flying, but I chose to run a wire for both + & - rather than have a local ground potentially goofing up anything else I might eventually stick out there.

[rocketman1988]

If you know that the heaters are 100W and 70W, running at a system voltage of, say, 13.6V, then they will draw 7.3A and 5.1A respectively.

18AWG is good for 10A with a 35 degree rise, so separately, it would be adequate. If you run them in parallel, 14AWG would be a good choice.

[Karetaker]

Thanks. Twisted pair or shielded?

[rocketman1988]

I used neither; just a 14 AWG for power and a 14 AWG for ground...

[Karetaker]

Copy. Thank you all!

[AlpineYoda]

For what it is worth, the Garmin G3X manual lists different AWG for the length of the wire run.

For dual 14v heater circuits, Garmin says to use a minimum of
14AWG up to 12 feet
12AWG for 13-20 feet
10AWG for 21-30 feet

So, 14 AWG is probably good, depending on where you mount the pitot tube, but remember that service loops in the wiring, routing through the fuselage, etc adds some distance.

[Desert Rat]

Garmin likely got that wire run guidance from ac43.13. Theres a chart that allows you to calculate the min wire gauge for pretty much any length voltage and current.

Just google ac43.13 wire gauge chart.