Control Panel (Part 2)
STEP 4: Wiring basics
Wire size is denoted as 'gauge'. We use the 'American Wire Gauge' (or AWG) sizing in describing wire size in our instructions. The smaller the number, the bigger (not smaller) the wire is and the more current it can carry.
Three sizes of wire are used in our control panel:
- 10 gauge: Used for high power items like the heating elements. The elements draw up to 23-24 amps so large 10 wire gauge must be used.
- 14 gauge: Used for standard items that consume less than 15 amps such as pumps, lights, meters, etc.
- 22 gauge: Used for extremely low voltage/current devices such as the temperature sensors, shunt signal, DC power supplies.
All of the 10 and 14 gauge wire is type T90/THWN/THHN (Thermoplastic High Water-resistant Nylon-coated/Thermoplastic High Heat-resistant Nylon-coated) meant for wet or dry locations. It's typically used for pulling through conduit or in control panels such as ours. We used stranded wire (not solid core) as it is easier to work with.
A roll of 14 gauge T90 THWN/THHN nylon coated electrical wire:
For the 22 gauge low voltage/signal wiring we used various odds and ends we already had on hand.
The wire is small enough that either solid core or stranded may be used easily. Telephone station wire which is typically 24 gauge can easily be used here as it is very inexpensive and provides 4 individual conductors in a variery colours making hook-up easier. Divide the amount required by 4 when using 4-conductor wire such as this. Make sure it is rated to at least 300V.
4-conductor telephone station wire:
We use different coloured wire to identify the type of voltage or signal carried. We tried as much as possible to follow these standards:
- Black: HOT A line
- Red: HOT B line
- White: NEUTRAL line
- Green: GROUND
- Any other colour: DC or low voltage signals
When a signal is carried by two wires and polarity is important (such as in DC) we'd often include a small piece of black shrink wrap tubing on the end of one of the wires to remind us which end is negative. Hooking up polarized signals backwards is generally not a good thing.
All 4 SSR control wires are the same colour so using heat shrink tubing helps identify negative from positive.
Most of the components in the control panel use screw terminals. While bare wire could be used, it's more likely that single strands may break off and end up somewhere they shouldn't causing electrical shorts (also not a good thing). So we use compression spade and ring terminals that are crimped on to the wires to simplify wiring up the control panel.
Larger yellow 12-10 AWG ring terminals for 3/8" stud size are used for the 10 gauge wires. Blue 16-14 AWG #6 narrow spade terminals are used for the 14 gauge wires while Red 22-18 AWG #6 narrow spade terminals are used for the 22 gauge wires. Make sure to get the narrow size blue and red spades. The wider ones will not fit in the PIDs or timer.
Some locations (such as the XLR receptacle wires) are soldered on directly.
While ring terminals are more work to install (the entire screw must be removed) we use them for safety reasons with the high current devices. They ensure that the wire will remain in position even if the screw becomes loose by accident.
A cheap 3-in-1 wire cutting/stripping/crimping tool can be used but we recommend using a separate tool to crimp if you want to do it right. We recommend splitting the job over two tools as follows:
- A wire cutter/stripper to cut and strip the wire: Something like the Klein 11055 is simple and effective. Be careful to use the correct size notch when stripping to avoid cutting any of the strands which would effectively reduce the wire gauge. If you're all thumbs consider a self-adjusting wire stripper which does some of the work for you. The Irwin line of self-adjusting wire strippers works well.
- A double ratcheting terminal crimper to attach the terminal to the wire: These crimp in two spots at once which saves time and creates a better connection as they apply force continuously and evenly. They also save your hands from lots of pain.
Spiral wire wrap is used where bundles of wires pass from the back plate to the door. The spiral wrap prevents the wires from rubbing whenever the door is opened or closed and also prevents it from getting snagged on the various components.
They are used for more than just aesthetic purposes: They help keep wires away from controls, heat producing parts, and door hinges.
The trick to using tie mounts is not to be too stingy - use them liberally.
They are only a few dollars for a bag of 100. Use them every few inches and whenever there are twists and turns.