Note from Trish: Last month, Mike began sharing his experiences rewiring his electrical system on Nelleke, his Moody 42 Pilothouse ketch. Though he hadn't gotten to the actual rewiring yet, he shared a lot of really useful information, and I have received many thumbs up from subscribers thanking Mike for his article. This month, we complete the saga of the Monkey's Breakfast.
Monkey’s Breakfast – a thorough mess, a mix up, an unplanned and unattractive mish-mash that has probably been stepped in.
We haven’t even begun the re-wiring yet and here I am still talking....
Oh well, only a couple more subjects. How about the colour of the wire? There is a marine standard for wire colour – red is DC hot or positive power, black is DC negative, green is ground, etc. There are even two and three colour wire codes for different types of circuits (starting, alternator, etc.). (See Table 2)
Table 2
If you are going to be a purist about it you will wind up buying many spools of wire for all the different gauges for each colour – big $$. The advantage of following the colour code is that you don’t have to trace a lead back to the source to find out what it is for – if it is green it is DC ground, etc. If you are like me though, and money is an object, then you will buy several spools of different grade wire of the same colour. I chose red, just to make it easier to see in dark places. This means that when I replace an existing wire, I have to run the complete circuit from beginning to end and back again, and I label it in several places along the way. A professional marine electrician reading this is probably cringing and making a note to call the insurance companies to suggest they cancel my boat insurance policy, but if you are confident in what you are doing and especially if you are replacing existing wires, I don’t see why you have to be anal about it. Just make sure that you do one circuit at a time and that you confirm that each one works before going on to the next.
If you are going to replace your panel there are a couple of things you should know. First, shop around. After eying my depleted bank account and nurturing my budding ulcer by shopping through marine supplier catalogues, ship chandleries and the internet, only to find that the type of panel I wanted was going to cost me between $500 to $1000 Cdn, we finally found a small company in Newfoundland, Terra Nova Marine, that built me a customized 15 breaker panel with a voltmeter and ammeter, a main breaker and a ground buss for $160 Cdn less than the cheapest comparable one that I could find commercially. I told them what each breaker was for, and the amperage and they engraved that information on the faceplate along with the name of the boat – all included in the price! Delivery was next day! They ship anywhere so if you’re looking for something like this, check out their website at www.tnm.nfld.net. Ask for Al.
After all this, the actual installation is easy.
First, TURN OFF THE POWER!!! Do it at the battery switch. Amazing the number of people that don’t do that! If you want to make especially sure, disconnect the positive lead from the battery. I prefer to leave the battery connected, at least until I have checked for stray voltage or ground faults, so you’re not done with the power yet!
Check with your voltmeter to ground that the circuit is dead. Don’t just try one spot. Test several, if not every circuit, on the panel to ground. If it is an old panel you may find some trickle voltage but fret not about that. What you want to avoid is an unpleasant surprise when you discover that one circuit that someone has wired direct to the battery. Who would do anything that stupid? Dunno, but I found two on Nelleke! Since we have both 24 and 12VDC appliances on board we have a converter to step the voltage down. This was one of the devices that I discovered was hardwired to the house bank, bypassing the battery switch.
Now, carefully label every connection coming from the existing panel. Masking tape will do. You just need to make sure that the hot side of the switch on the old panel is what you are putting on the hot side of the corresponding switch on the new panel. The ground leads are easy – just tie them all together with some string or tape until you are ready to fasten them to the grounding bus. They are all going to be joined together eventually anyway.
On Nelleke, the old panel was tucked away behind a cupboard door, so anytime that we wanted to switch something on or off meant that we had to open the door, shine a flashlight into the dark interior and flick the switch. I decided to put the new panel on the door itself. This gives me two advantages: first I have easy access to the switches, and second, if I need to work on the wiring, I don’t have to unscrew anything. I just open the door.
This is also a good opportunity to lengthen the connecting wires so you can bunch them together and route them neatly along the edge of the cupboard. This is where you make use of the new wire, the crimping tool and the heat shrink tubing we have spoken of. Bundling and neatly routing wire will pay future dividends in ease of access and making space in closed areas. Simple and cheap plastic cable wraps will do a great job for the bundling and cable clamps will control the routing.
One small point – never bundle alternating or modulated current with anything else. Why? Because of two basic principles of electromagnetism, namely: that when current flows through a conductor a magnetic field is generated around the conductor and that if the current changes as it does in a modulated or alternating circuit, the magnetic field expands or contracts. The second principle is that when a changing magnetic field cuts a conductor, a current is induced. What this gobbledegook means is that if you run an AC circuit in a bundle of DC cables the AC will likely induce a current in the DC so you will no longer have a clean DC circuit. Also, since you never get something for nothing, you will loose power in the AC circuit since it takes work to induce a current.
There are two possible solutions. The first is to shield the DC by running it through grounded conduit. This will protect the DC but could still allow a power loss if the nearby AC circuit induces a current in the conduit. The second and from my point of view preferable solution is to simply keep the two types of circuits apart. It doesn’t have to be far – the effect of electrical and magnetic force diminishes as the inverse square of the distance. That means that any force will affect something that is twice as far from it only a quarter as much, or three times as far only a ninth as much.
Don’t limit yourself to simply replacing the panel and the adjacent wiring. This would be a really great time to replace all of the wiring all the way to each appliance. If you are using a single colour of wire just remember to run one wire at a time. That way you won’t wire the wrong appliance to the switch.
Once you have done all this you can look at starting to turn things back on and check the circuits. If you experience is anything like mine, you will probably have discovered all sorts of fascinating things. Things like a major grounding cable that wasn’t even connected (kinda make you wonder what route the power had been taking all these years since you must have a ground to complete the circuit), fully wired switches that turn the power on to nothing, corroded connections, poorly soldered joints, wires simply taped together, fuses that I didn’t know were there but were hidden in the recesses of behind the cabin ceilings (would have been really frustrating if one of them had ever blown trying to find out why power wasn’t getting to appliance any more); and much, much more.
When you’re ready, the first thing you turn on is the battery power. Watch your ammeter. If there is a sudden large current drain with all of your panel switches off, you have obviously connected something up wrong and you need to trace out the short. Turn off the battery immediately and start to trace out circuits with your voltmeter.
If there are no problems here, turn on each switch individually and verify that the appliance works as intended. Again, when you first turn on the breaker if there is a short the breaker should blow. That would be your clue to get out the voltmeter again and start testing that circuit for shorts.
At the end, you will have a much better understanding of how your boat works and be in a much better position to diagnose and repair electrical faults that might pop up in the future. If you are like me, you will also discover that things that hadn’t worked in the past suddenly are working again; or that the SSB that previously has worked but generated a lot of static is suddenly very quiet and noise free.
You will have a safer, easier to use, DC power distribution panel that you will have the satisfaction of knowing that you installed yourself.
