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I'm trying to figure out whether I need a PM OV protection kit in addition to the regulator or does that take place of the regulator? Thanks

The overvoltage protection kit is added into your electrical system and compliments the voltage regulator. These OV modules(https://bandc.com/product/pm-ov-filter- ... kit-14v-2/) can be used with PM alternators or wound field alternators. The primary benefit of the OV kit is that it sits in the background and constantly monitors the bus voltage. If the bus voltage rises above the set point the OV module automatically triggers a response to disconnect the alternator from the electrical system. This prevents a runaway alternator or bad voltage regulator from damaging sensitive avionics due to excessive voltage.

The OV modules are not expensive, easy to install, require no pilot interaction to operate, and offer another layer of protection for your plane. I think they are well worth the expense and effort to install.

Another option is to replace the existing (stock) voltage regulator with the new ACV-1 voltage regulator from B&C specialty (https://bandc.com/product/avc1-advanced ... lation-kit). This unit is super-high quality and includes an OV module as part of the regulator. They're about $250 but will last the lifetime of the plane, and will never burn up and leave you stranded somewhere away from home.

Jeff

I kinda figured that was the case. I spoke to B & C yesterday prior to placing a order. I need the regulator anyway and it sounded like the Bob Nuckell's unit was the only one that was really good for a PM alternator. It's not cheap but the other crow bar protection wasn't too bad. I was hoping that if you used that alternator then the other component was unnecessary and redundant. I bought the full Dynon HDX with AP. I've spent so much now that a few hundred dollars seems like chicken feed. Pat Murry

HI Jeff,

sonex1374 wrote:The overvoltage protection kit is added into your electrical system and compliments the voltage regulator. These OV modules(https://bandc.com/product/pm-ov-filter- ... kit-14v-2/) can be used with PM alternators or wound field alternators.

Ref. https://bandc.com/wp-content/uploads/20 ... 0_revI.pdf

So, is the switch connected to the Crowbar (ORG/YEL) a reset switch for the crowbar?

Thanks,

Wes

Wes,

The crowbar has two wires coming from the shrink-wrapped unit: a black wire (ground) and orange & yellow wire (positive). When the crowbar "activates" it will create a dead-short between the black wire and the orange/yellow wire. This will, of course, burn out the unit or wire in a second or two, but that's what the 2 amp circuit beaker is for - it pops instead of the OV module burning out.

The switch is the alternator on-off switch. In the on position it allows battery power to energize the coil and move the relay to connect the common terminal (which is connected to the bus) to the NO terminal, which is connected to the alternator output. If the switch is off, the bus is not connected to the voltage regulator output and the alternator is "off" (kinda, it's "isolated" from the bus, but not really off). This method works and is pretty simple to install. It has the added benefit of including a simple "alternator disconnected" light to show that state.

I've discussed this before, but another way to control the alternator is to break contact of one of the AC output lines before it reaches the voltage regulator. This approach has the advantage of stopping all alternator activity completely, as opposed to simply isolating the voltage regulator output from the bus. In an unusual voltage regulator failure scenario the VR can get so hot it literally melts down or catches fire, and breaking the AC output stops this. Either approach works, but the AC line approach can protect for that one fringe failure mode.

Jeff

Hey Jeff,

I understand. The switch I was referring to is the one shown just below the CROWBAR by the diode. Maybe that is their attempt to depict how the CROWBAR works. It was shown external to the CROWBAR so I assumed it was another manually activated switch.

Thanks,

Wes

I think that's just a "/" in the identification of the wire - "Orange / Yellow", and not actually a switch.

Duh ... :-)