The Encroaching Wiring Rat’s Nest

Article By : Bill Schweber

Even a simple wiring project can eventually become a rat’s nest of hard-to-trace and debug, poorly routed and dressed, arrangement over time, if you are not careful.

Back in the day when I did hands-on hardware design and debug, I soon learned the importance of clean, documented, consistent, “connectorized” cabling between the various subassemblies. Debugging is hard enough that you don’t need to add to the frustration with the inefficiency of trying to figure out which cable connects to where, carrying which power or signal, and the physical paths between sensors, supplies, loads, PC boards, and displays.

After wasting too much time during debug sessions due to sloppy cable “management,” with unlabeled or improperly labeled runs, “mid-air” splices wrapped with electrical tape or heat-shrink tubing, and marginal documentation, I came in after hours, carefully re-did the cabling run-by-run with consistent and reliable interconnects and connectors, labeled everything consistently, and documented it all. Due to my diligence, careful step-by-step efforts, and a large amount of luck, everything still worked when I was done. The next day, when the others on the team arrived and saw what I had done, I was a “hero” – but I could have just as easily have been in the doghouse, so to speak, if things didn’t work.

After that, I vowed I’d never allow a rat’s nest in any of my professional or personal projects. But talk is cheap and easy, and I recently found out that the path to a rat’s nest of wiring can be a long and incremental one. You don’t start out planning to create this spaghettis-like mix; instead, it just sort-of happens a little bit at a time. The steps from one stage to the next may be small and no big deal, but when you step back and look at the big picture, it’s not pretty.

How do I know this? A few years back, a friend asked me to help install an Ecobee smart thermostat, Figure 1. We ran into some problems due to issues with the instructions but eventually figured it out. The rat’s nest “rating” of the wiring was low since there were only a few wires.

Ecobee3 Lite

Figure 1 This Ecobee smart thermostat requires just a few wires but can be the start of a real wiring mess. (Image source: Ecobee, Inc)

A year later, my friend wanted to add one for another zone, and again asked for help. This round went more quickly, since I had carefully documented the wiring of the first effort and had noted the misleading instructions from the vendor (not necessarily their fault, since the many heating systems in use have their own idiosyncrasies). Now, the rat’s nest “rating” had doubled, and while I did label the wires, it was becoming a soup of inconsistent colors, connectors, interconnects, and more. But hey, it was working and we were done, and I figured I’d clean it all up at the mythical, mystical time called “later.”

Fast forward to a few weeks ago, two years after that first installation, and – surprise, surprise – that friend decided to add yet another smart thermostat on the third and final zone of the house. Since it was the same make and model, the installation went fairly quickly. The good news is that all three zones were now working with identical hardware on each loop including AC transformer, relay, and thermostat. The bad news is that when I stepped back and looked at the big picture, it was a mess, Figure 2.

Rat Nest Wiring

Figure 2 After retrofitting thee Ecobee units, this is what the basement wiring looked like – not something of which to be proud. (Image source: author)

While I wasn’t worried about basic reliability since the wires are not subject to any physical abuse, it looked like some total amateur had rigged things together and hoped it all worked. If any maintenance or upgrade is needed, what I left behind – even with my detailed documentation including wire colors and connection points clearly called out – will frustrate me or the next person dealing with it.

There’s some irony here. Among the many publications I read regularly is the always informative and interesting Cabling Installation & Maintenance which deals with everything related to copper and fiber interconnects including standards (did you know there is an ANSI standard for cable labeling?), tools, techniques, technologies, and test. They also post a regular series where installation professionals share photos of the rat’s-nests they have encountered in the course of their works, such as Figure 3.

Rat Nest Wiring 2

Figure 3 One of the many commercial “rat’s nest” installation photos published by Cabling Installation & Maintenance (Source: Cabling Installation & Maintenance)

You think “who would do such a sloppy job? What were they thinking?” followed by “I would never do it that way.” But the reality is that I, too, did do it that way, admittedly on a smaller, three-zone, low-voltage, non-data-network DC-loop installation. The lesson is that this sort of stuff happens, and coming back “later” to clean it up is often wishful thinking.

Of course, not all installations are a rat’s nest. Several years ago, I was treated to a behind-the-scenes tour at CBS production headquarters in New York City. Over the 50+ years they had installed countless copper cables with some bundles as thick as your arm, and over the last decades they have pulled any of these out and replaced them with fiber cables where possible. When my host described this before we started the tour, I expected the world's largest wiring mess. Instead, it was absolute neatness everywhere. Every cable was in place, and every individual cable and its connections panel was labeled and tied down neatly.

As for me, I have resolved that as soon as the weather warms and that heating system is on seasonal break, I will spend a day and redo it all, but neatly. I’ve already scoped out the needed multiple-position barrier strip I need (Figure 4) and a multi-position fuse holder for the 3AG fuses (Figure 5), and I will re-do the three thermostat loops neatly, consistently using crimped spade lugs and slip-on connectors, with visible labels for each run and at each transition, plus a comprehensive documentation package. It’s a matter of personal pride and professional integrity.

dual-row terminal block

Figure 4 This the 12-position, dual-row terminal block I plan to use, with four terminals allocated to each thermostat loop. (Image source: You-Do-It Electronics)

3AG fuse holder

Figure 5 Even the fuses will be nicely connected, via this four-position 3AG fuse holder with slip-on quick-connect terminals; the unneeded fourth position can be for a spare fuse. (Image source: You-Do-It Electronics)

Have you ever had to work on someone else’s rat’s nest? Have you ever created your own, either in one sitting or incrementally over the course of a project? Did you go back and clean it up?

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