Well, they were talking about protecting the contacts of the switch that controls the coil, and how some methods of doing that decrease the speed of opening, which is bad for the relay contacts.

I'm not sure you will really see the inrush current with the shunt.  Too slow.

Buy really good relays...

On Nov 26, 2013, at 11:51 AM, John Cooper wrote:

Colyn--

Those Tyco links were excellent, thanks. Let's keep in mind, though, that Tyco was discussing the possible adverse effects of surge protection across the relay coils, not the contacts. Based upon the information in those articles I'm going to remove the small ZNRs I installed across my hydraulic relay coils to protect the landing gear switch contacts. Perhaps I'll replace them with those Snapjacks (Thanks for that link as well.) I plan to leave the large ZNRs in placed across the hydraulic relay contacts.

Those Tyco articles may be of special interest to Adam since his Bosch 0 332 002 156 hydraulic relays have the built-in diode protection across the coils. Also, the second article discussed how excessive inrush can cause relay failure.

FWIW, I ordered a 60A shunt which will (hopefully) allow me to measure the inrush current on the Oildyne pump motor. I'll report back if I learn anything.