So, I asked this on Facebook. It turned into quite the flamewar.
The majority of respondents were adamant that the resistor goes at the contact (hence EOLR= End Of Line Resistor).
- "It goes at the end, at the device. End of story. If you can't get it there, go find a new job."
- "End of the line, or EOL. In the panel is just lazy."
- "If you understand the theory as to why a resister is used, you'd get why it's placed at the contact."
- "For true supervision the resistor goes in the field."
Some respondents replied that the resistor goes in the panel.
- "Theoretically the end of the line is at the panel since electricity makes a loop right? At the device would be middle of the line"
- "Ok? Where is the end of line. The return voltage comes back on the negative. The negative ends at the panel. OR The cable goes out to the device and ends there. So which is End Of Line?"
- "If it's a N/O circuit it definitely goes at the EOL, if it's a N/C and it's not a critical circumstance that requires it be at the device it gets put I'm the panel. Perhaps that's not ideal to an engineer that sits in a desk and doesn't work on them day in and day out but that's the way the cookie crumbles.
- "On commercial jobs in field. Residential at panel except for fire devices and motion detectors or GB."
A few respondents mentioned that running a cable with four conductors instead of two allows the installer to leave the resistor in the panel while still ensuring proper supervision.
- "Most installers home run all their wires and they will use a 2 conductor wire. If you have a window bay with 4 windows, you have 4 wires at the panel. Most panel will give you 8 zones, so with large installs you have to bundle your wires. The EOL resistor is to detect shorts on a N/C circuit. You cannot monitor all 4 wires for shorts, so putting the EOLR out there won't do much. What's important is to put the EOLR on the negative side of the wire to detect ground faults, this is important because a ground fault can bypass the devices and no one will know until it's tested."
- "In NYC traditionally you run a 4-wire and put the resistor back in the box... but electrically still at the end of the line. Everywhere else, it should be at the end of the line... usually that means it's out at the device."
Now for my two cents: If the purpose of the resistor is supervision, the the argument for putting the resistor at the contact makes good sense to me. Many devices and most panels specify use of a resistor at the contact.In addition, the ESA says "Wiring should be done so that removing the device causes a trouble signal." That certainly implies a resistor at the contact to me.
That said, keeping the resistor in the can makes it more secure, and servicing is certainly easier.
Some respondents said they actually hide the resistor.
- "I run every door contact THROUGH the nearest glass break's box and leave a loop. This way, if I can't get it in the jam, I can put it in that box rather than at the panel."
- "Neither. Try to put them in a finished ceiling half way between contact and panel. The goal is to make nearly impossible to find."
All I can say to that is, I hope I never have to troubleshoot their jobs.