Septic wiring - 3 - wiring

Previously: shopping

Back at the ranch, I put the subpanel on the post, and glued up the conduit. I plugged in my shop vac and taped it to one end of the conduit. 

At the other end of the conduit we had a spool of mason's twine tied to a plastic bag. The shop vac easily sucked the bag through, pulling the twine behind. This goes really fast. In fact it's so fast that the twine quickly cuts a groove in the edge of the conduit. Watch out for that.

Realize that I was sticking my hands in to a hot electrical panel at this point. No good way to avoid that, though.

We used the twine to pull a 1/4" nylon rope, which we then used to pull the aluminum feeder wire through. Hard work even with wire lube. Arms tired.

I bought a 30A double pole breaker for the main panel, but found the #2 wire wouldn't fit the breaker lugs - too big! You can buy special reducers that crimp on, but then you need a special crimper, too. I decided to upsize the breaker to one that could take #2 wire. I ended up with a 60A breaker. Sheesh. My project to power a 15A pump had turned in to a 60A project.

I did try to push a length of 12/3 + ground UG cable through the 3/4" conduit to the pump. With 3 elbows, it was very difficult. We even used wire lube, but that wasn't enough. We eventually gave up. When we pulled the wire out, the lube picked up grit from the ground. Yecchh. It turned out that 12/3+G was unnecessary, as the pump is 240V only, not 240V/120V, and so doesn't need a neutral conductor. 

I wired up the subpanel feeder and the receptacle on the subpanel post. Then I plugged in the shopvac there, and used it to suck pull strings in to the 3/4" conduits to the septic pump chamber. Electricity is so useful. This may be a violation of electrical regulations, as I was using circuits that hadn't been inspected yet. But maybe none of this is historical fact, but merely my opinion.

With the pull string, it was easy to get the wiring through. I left a pull string behind in each conduit, just in case I needed to pull something else in the future.

While wiring the septic alarm/control panel, I realized I needed another circuit. It wants its own 120V circuit, separate from the pump. It's not uncommon for pump circuits to trip. If they shared a breaker, the alarm wouldn't sound. Another reason the subpanel approach was a good choice!

To wire the control panel, you first have to drill holes in the bottom for the conduit. One for incoming power, one for outgoing pump power, one for the transducer.

I had 3/4" conduit, so I drilled a 3/4" hole with a spade bit. Those are meant for wood, and this was plastic. Spade bits were what I had already. They cut really slowly and made a big mess of plastic shavings on the ground. Sorry, ground.

Wrong size, though. 3/4" conduit needs a larger hole for its fittings. OK, try a 1" spade bit. Closer, but still not big enough. Some internet research, and I found that 3/4" conduit connects to 1 1/8" holes. I bought a 1 1/8" hole saw. The holes turned out nicely, but controlling it was hard - it was easy to pop through the plastic and hit the delicate internals. Maybe I should have removed them first? I also used a small grinder to enlarge the first hole to the proper size.

I sure wish they drilled the holes at the factory, or even provided knockouts.

It took me a couple iterations to get the wiring to the control panel right. There are 5 conductors coming in:

• hot to alarm
• neutral to alarm
• hot 1 to pump
• hot 2 to pump
• ground

I had 12/3+G cable (black, white, red, bare). I also knew I could pull conductors out of a cable as needed. White is usually neutral, but you can can use it for hot if you mark it with colored tape or paint. I wasn't sure what combination of options I liked, so I went to DIY Stackexchange. I ended up with separate conductors, arrange liked this:

• blue hot to alarm
• white neutral to alarm
• black hot 1 to pump
• red hot 2 to pump
• bare ground

I like this because everything gets it's own color. It's obvious what is what.

Here's the 6x6 post with the alarm/control panel on the left, and the subpanel on the right. You can see the flex conduit with the conductors in it, ready to go.

To get the conductors, I stripped the outer sheath off the 12/3+G cable. That was kinda hard, so for the run from the control panel to the pump, I just used 12/2+G, and put red electrical tape on both ends of the white conductor.

I bought the blue separately. It was the only stranded wire, and it was much easier to work with in this confined space. I wish I had used all stranded wire. A professional electrician can keep 500' spools of stranded #12 wire in the truck in a variety of colors, and pull off what they need. I have to measure ahead of time, add 10% just in case, and go on a shopping trip.

Here's the result. 

From left to right: alarm speaker, power in, power out to pump, transducer cable.

I worry so much about cutting wires too short, or about needing to put a new end on a wire in the future, or about wanting to rearrange things and needing a little slack. I try to cut everything as long as I can. Perhaps I should just cut to length, as it would make the wiring much neater. Thanks to conduit, replacing wire in the future is not very hard. *shrug*

Next: grounding