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Monday, March 23, 2009

Wiring Begins...

Not really wiring intended for "voltage", but wiring nonetheless. This is the wiring for the tank level sending units and RF ground plane. The tanks came with standard WEMA senders with a short pigtail wire with solder tinned bare ends. I extended these with 18/2 wire to the port side of the boat at two points, one for the fuel and one for the water tanks. Here they will intersect with whatever we choose to monitor the tank levels. About 100 feet of wire was needed to wire all eight tanks. Connected with crimped butt connectors sealed with heatshrink (I was tempted to solder, but I resisted OCD. This is good enough for ABYC standards). The tanks also came with ground strap terminals welded to the surface. A common practice (which we will try) is to use the tanks and their large metal surface area as a ground plane for the SSB/HF radio. This requires all the tanks to be tied together on the same RF ground circuit, but not necessarily part of the DC ground. So, wire was also run connecting the tank ground terminals also running to the port side of the boat, where the future radio will be located. While RF ground will carry little current, having a good connection is a must. But I have a spool of green coated 8 AWG wire that came with the boat that would never be used for a DC or AC circuit (wrong color), so I used that stuff. Better to go bigger gauge than smaller I guess, plus this was "free". Crimped battery terminals and covered the ends with heatshrink. Note, all runs must be "homed" in one direction. Can't wire things such that it creates a "ground loop". This can result in poor radio performance. Shoulda done this when I installed the tanks as I had to pull up the floorboards and battery box... again. Oh well. On tank monitoring... Though it is early, I have been keeping an eye out for options. As everything is going NMEA 2000 networked these days (this boat will have one), it would be nice to monitor tank levels via the network. Maretron makes a NMEA2000 tank level adaptor that can be calibrated for "odd size" non-rectangular tanks. And, analog gauges can still be used simultaneously. But the price of these are pretty steep at $200 each (so, $1600 to monitor eight tanks). I did notice at the last boat show that Blue Sea Systems has released an integrated battery and tank monitor system called the VSM 422 which can be used with standard resistive tank level senders. This model can support only three tanks, but, having spoke with their rep, I can report a new version coming that will monitor up to eight tanks. Street price on the Blue Seas VSM422 device is about $500.

1 comment:

Steve Roberts said...

Nice to see you using the Wema senders also; it felt good to replace the ancient swing-arm junk in my tanks with those! I'm using 3 of the Maretrons, but am really curious to see if that new Blue Sea unit will use the mystery port to pass the data onto N2K. Of course, the budget approach would just be a micro with a multichannel A/D input; it's a linear resistance change and with a bit of filtering (and even tank-shape lookup table) you could do just as well for a fraction of the cost (and lots more time!).

Cheers from Nomadness,