Sheilded, Unsheilded, or twisted wire for Pitot Heat?

[BalsaBat]

I was wondering what is "proper" pitot heat wire? It appears that 14 gauge is probably the minimum red/black power wire size for my length, with 22 guage for the white signal wire to EMS pin 9. Although some references advocate sheilding for nearly all applications, I didn't see mention of sheilded vs unsheilded from Dynon. It appears that 12 or 14 guage sheilded 2 conductor tefzel wire is nearly unavailable, although I have found it in "commercial" belden wire that I don't really want to use. In lieu of sheilding (or in addition to it), what about twisted pairs? In that case, should I twist the 22 gauge signal wire with the 14 guage??

I suppose part of the answer is in how the Dynon heated pitot controller operates. If it is a temperature regulating switching type power supply, it clearly COULD introduce some RFI, but I have no idea whether that's problematic.

So, did I miss something, or what have others found that works (or didn't) and what does Dynon say?

Thanks

 

[Rhino]

The controller already has wires on it for connecting to the pitot, and should be mounted close enough to the pitot to not require any additional wire. The white wire to the EMS only routes a ground signal, so you shouldn't need shielding. 14 or 16 gauge (such as M22759/16-14 or M22759/16-16 Tefzel) should be more than sufficient.

 

[BalsaBat]

Thanks Bob. Just to be clear, I was talking about the wires from my panel to the controller, not controller to pitot. But I take it from your experience that just straight runs of unsheilded appropriate guage M22759 is suitable?

 

[Rhino]

You can use shielded wire out of an abundance of caution if you want, but you shouldn't need it since you're just routing a ground signal. It's really up to you. The voltage is coming from the EMS, not from the pitot controller. The only time I'd seriously recommend shielded wire for that is if you're using it in a long bundle with other unshielded wires, particularly audio or strobe wiring. There really is almost no weight penalty with shielded wire if you want to be super careful.

 

[Rhino]

Aircraft Spruce has shielded M27500-14TG1T14 Tefzel wire for $3.37 per foot.

 

[jakej]

Thanks Bob. Just to be clear, I was talking about the wires from my panel to the controller, not controller to pitot. But I take it from your experience that just straight runs of unsheilded appropriate guage M22759 is suitable?

FWIW - I've never used "shielded wire" for Pitot heat power supply (16awg) & never had any issues (also in my composite IFR plane)