That is not about avoiding solder, it is based on two separate engineering concerns.If you're insured I would advise against solder.Insurers follow ABYC.... If you feel you absolutely must solder, because your crimp tool is low quality, crimp first then add some solder..
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First, while solder is electrically conductive, it is mechanically weak and brittle. The guidance just says that you should not mechanically rely solely on solder to keep to conductors mechanically connected. But, you shouldn't really leave any wire unsupported - just hanging on the connection - regardless of connection method. Wires should generally be secured so they to not rely on their connectors to mechanically keep them in place. Solder is no exception.
Second, if you connect a wire to a rigid conductor, there is a concentrated stress point where the wire tends to get flexed back and forth and weaken - that point where the flexible meets the rigid. When the wire is not properly secured, it will tend to weaken at that point, over time. This has nothing to do with solder. It is just that plain soldered connections tend not to have any other support to spread out some of that stress.
If the wire is secured, like with any wire organization device (conduit, wire clamps, zip ties, whatever) such that the wire is not hanging solely on the connection (solder or otherwise), then you satisfy these concerns. But, when you shrink wrap a soldered connection with adhesive-backed heat-shrink, this also satisfies the condition. This primarily addresses the second engineering concern, but "technically" addresses the first ... sort of.
Bottom line: ABYC or not, wires should be secured so that they are mostly supported by some mechanical wire-routing. This is usually some combination of clamps, conduits, zip ties, etc. The connection is just about conductivity. It should not be relied upon to support the wire or the thing attached to the wire. That is the point of 11.5.3.8. It is not a recommendation against solder.
The recomendation to crimp, then solder, is often-repeated but controversial. The problem is that, if you solder such that solder wicks into the wire strands past the crimped connector, then you have created that concentrated stress point that 11.5.3.8 specifically cautions against. The fact that there is a crimped connector downwind of that stress point is irrelevant to that concern. And, a proper crimped connection should already create a gas-tight connection.
But, this concentrated stress point exists where the wire meets a crimped connection, just like it does on a soldered connection. It just tends to be somewhat more distributed. Yet, I don't think ABYC has a mirrored statement similar to 11.5.3.8 which addresses this for crimped connections. But, the standards are very clear and consistent on the general importance of:
- wire support near terminals to prevent flexing at the connection
- strain relief provisions for cables entering equipment and panels
- general requirements that connections be mechanically secured independent of the terminal itself
Contrary to what a lot of people think, a properly soldered connection is not necessarily electrically superior to a properly crimped connection. And, improperly done, neither is adequate. The problem is that a crimped connection is easier to visually inspect. This is second reason industries prefer crimped connections.
None of this is a recommendation for or against soldered connections, though. Just that, if you solder, you need to do it properly and with due consideration - just like any method.