Let's start off by saying that you don't need to fully understand the technical details of good wiring to follow good wiring practices.
The rail feeders of insulated 22 AWG solid copper are soldered to the side of the rail on average every 3 feet. Because of the transportation vibration these wires are subject to they must be striped with a nick free style striper. Use an Pro's Kit 8PK-371 Wire Stripper #10 to #22 AWG ($10) or equivalent. Rail feeders are typically red for the forward Rail A and black for the rear Rail B. We have had rail feeders nicked while being stripped with a stamped steel striper fail in just one outing.
The module bus run conductors are to be run uncut PowerPole connector to PowerPole connector. This eliminate addition of extra connections in a position where a connection failure could affect the entire layout.
The Red/Black solid copper 22 AWG Rail feeders are either:
1) soldered to stranded copper Red/Black 18 AWG wire which is in turn attached to the bus runs by using a ScotchlokTM 567 Tap Connectors. We make these up ahead of time for use on wiring days.
- or -
2) wrapped around and soldered directly to a stripped but uncut stranded bus wire.
It is important to the overall reliability of the layout in all cases that the the bus wires run uncut directly form PowerPole connector to PowerPole connector.
Soldering the 12 AWG bus wire into the PP contact is not recommended. During the soldering process solder can wick up the stranded wire removing flexibility which increases the stresses the contact in the housing. This can lead to a connection failure by forcing the contact into an abnormal position away from the mating contact. A ratchet style crimper is available in the club for crimping the PP contacts onto the 12 AWG bus wires. Some care needs to be taken not to deform the contact arm when using the crimper but it's easy to detect and overcome with a little training.
While our drawings show Red/Black 12 AWG zip cable we found inconsistent quality when buying it. Nearly all the recently built modules were built using 12 AWG black landscape cable sold in 100 ft coils from local home improvement centers.
DCC Analog and DCC AWG Resistance Data