GRT Avionics

Hi folks,

I am about to finish up a couple of wiring details and was scratching my head. The OAT probe is going in the right wing of an RV 8, near an access panel. I had originally planned to ground it locally and run the wire to the EIS. I noted in re-reading the literature, that they suggest twisting the wires and running them together. How far should I carry this twisted pair? All the way to the EIS and then pull the ground down or just behind the panel. Is this crucial? It is going to be a little bit of a challenge to run the second wire.

I had originally left the EFIS warning light off. I recent problem with a local guy not noticing that his CHT's were topping 525 (and no idiot light) led me to reconsider the idea. I understand that the warning light needs power and that the unit will send its end to ground to complete the circuit.

Should I use power from the battery bus or from the switched main power? I have a single AHRS and dual screens. Which screen should I bring the warning lamp from, the lower MFD or the upper with the artificial horizon, etc?

Thanks,

Michael Wynn
RV 8 Finishing
San Ramon, CA

Twisted pair is best. Attach the ground wire to your single point ground buss. It will probably work okay grounded locally in the wing, especially until some time passes and lap joints start having some resistance build up. Then it would be a nightmare to trouble shoot.

I wired the warning light to the EIS, not one of the EFIS units. My logic was that my EFIS units are not on at engine start, but my EIS is. The red light is on until I have electric current from the alternator and oil pressure. If the light stays on after engine start I check the oil pressure on the EIS display, and if the alternator field switch is on. I took power for the light off the EIS circuit breaker. Another good function for the light off the EIS is the timer function. Mine comes on every 30 minutes to remind me to switch tanks.

Frankly I find it hard to believe someone could miss an EFIS blinking red if the CHT limits were exceeded.

I have my CHT limits set at 430 F in the EFIS, and 440 F in the EIS. So if the EFIS blinks red, I need to do something. If the red light (EIS) comes on I really need to something. IMHO 500 is way too high.

I'm at LVK if you want a first hand look at an RV10 with HX, HS, EIS.