Circuit breakers

[carl_nank]

I have a D100 & D10. One wants a 3A CB & the other a 2A CB.
I have an (Instrument) SCB on my RV7A panel and I want to know if it is kosher to use that SCB for both dynons. I was thinking 5A, (2A plus 3A).

Right now my avionics panel has only Dynon. Nav Comm is on its own SCB.

 

[josok]

It's not right to add CB values together. CB's are there to protect your wiring, including wiring inside equipmet. If you uses 5 A instead of 2 A, the result is that if there is a short circuit somewhere that there will be 5 - 2 = 3 square = 9 times more energy will be dissapated. You might (or not) see some smoke. Maybe it's possible to hang both instruments off a 2 or 3 A circuit breaker, if you are cramped for space. The power consumption of both instruments would allow that i guess. The Dynon folks should give their blessing though.

Regards,

Jos Okhuijsen

 

[dynonsupport]

As Jos says, CB's are for wires, not for the instruments.

As long as you run wires to everything after the CB that are sized for 5A, you should be fine, but you can't split two 2A wires and be safe.

 

[carl_nank]

Thank you for your replies. Just to clarify, my mistake is use of too high amps for wire size. (2A and 3A wires does not mean you can add this together and put in a 5A CB. I appreciate you straightening me out.

I would like to use the instrument SCB to turn on both Dynons. This seems to not be possible.

Are most users installing 2 SCB's or are they using 2 Circuit breakers? I notice it is OK to allow the Dynons to power up without waiting for the engine start, but that is not what I am used to.  Maybe I am overthinking this.

I appreciate your guidance.

Carl Nank
Dynon panel

 

[meljordan]

Carl,

I have over 750 hours on my Dynon units and they are just wired to the master switch. Having them on when the engine is started works fine and does not hurt them. In fact, you really need to have the engine monitor on so you can verify oil pressure, fuel pressure and other values just before and after engine start.

Best Regards,
Mel Jordan

 

[carl_nank]

Hi Mel,

Thanks for your reply. I really appreciate your guy's help. What you said makes sense.

I beleive what you are saying, is to use two circuit breakers, per the manual, one for each Dynon, and physically attached to the buss bar so when the master switch is turned on, both Dynon's come up immediatly. Forget about the instrument SCB.

I believe I sometimes overthink things!

Again, I appreciate your help.

Carl Nank