Installing ELCI Panel - Current Coil Question

[Scott T-Bird]

What is the purpose of twisting the hot and neutral wires as they pass thru the coil? It's odd that instruction diagrams do not show the wires twisted and do not mention anything about it in the written instructions (Blue Seas). But there is a tag on the coil that says that the wires should be twisted as they pass through the coil. Instructions focus on describing how the wires must be secured with a plastic wire tie to keep wires from moving within the coil. How many twists are enough? Is it important? I also used 12 AWG because I found no 14 AWG in black and white at the local WM. Does it make a difference?
Also, there is a current coil wired to the AC ammeter for only the hot lead to pass through. Does it matter where the current is measured? I intend to pass the lead thru the coil, which will be mounted to the panel, between the source (shore power) and ELCI connection. The coil hangs loose from the wires ... how securely does it need to be fixed to something solid? Or is it just important to secure the hot lead to the coil? Instructions just say that the hot lead should not move, but it seems odd that the coil is just hanging off the ammeter from the leads to the coil.

 

[LeslieTroyer]

The only thing I can think of is the twisting of wires makes it easier for the CT (current transformer - coil) to measure an imbalance between the incoming and outgoing current, by twisting the magnetic field so more of the CT is used.

 

[Chief RA]

Ask Maine Sail as this is his field. Chief

 

[walt]

A "shot" at your question..

The coil or toroid in the first part of your question measures the magnetic field inside the toroid. The hot wire and the neutral wire each generate a magnetic field and if the current in each wire is exactly equal and opposite, the magnetic fields cancel each other completely and there is no magnetic field for the toroid to measure. If the currents in the two wires are not equal, the magnetic fields do not cancel and the toried then measures some magnetic field and generates a signal to the electronics. The wires do NOT need to be twisted for this to work but there may be some secondary parasitic effect that is reduced by keeping the two wires close together. So.. I "think" that twisting is not a bad idea just to keep the wires close to each other as they pass through the toroid but its not at all critical how many twists per distance.

Also, if you look at the equations for magnetic field in a wire, the primary equation gives the magnetic field at at distance from the center of the wire. You need to dig deeper to find an equation that includes the diameter of the wire so I suspect (because it gets more complicated than I plan to dig into) that your using 12 gauge instead of 14 gauge likely only has a minor and secondary effect on the magnetic field generated by the wire inside the toroid. If the magnetic fields are about the same for the different wire gauges, then toroid measurement of the difference in current would also be the same. Anyhow.. I would guess that the ELCI trip current threshold is about the same for either 12 or 14 gauge..

 

[Maine Sail]

ELCI's have had some nuisance tripping issues and some have been caused by localized EMI interfering with the coil..

According to Carling Technologies twisting the wires before they are inserted into the coil helps minimize the effect of external noise causing issues with the coil measuring the wire balance and causing nuisance tripping. Simply twist the hot and neutral together then feed them through the coil and wire tie them at each end of the coil..

Unfortunately on boats we have a lot of sources that can cause EMI such as alternators, battery chargers, solar controllers, PWM light dimmers, VHF's, DC blower motors, air conditioners, generators, inverters, wiring etc. etc... I had a VHF tripping an early ELCI every time the mic was keyed.

Also remember that only the neutral and hot pass through the coil and any on-board neutral to Earth (green wire) bond will cause a trip as can incorrect dual service inlet wiring with common neutral busses.

 

[Scott T-Bird]

Thanks for explanation! I think I'm on the right track with my install.
Here's my panel inside the cabinet I made. The next step is to mount it on sidewall of the nav station.

The AC main ELCI and branch circuits are mounted side by side. The coil is fixed on the ELCI, shown with the yellow tag that indicates that the wires should be twisted. Hot and neutral leads are twisted as they pass thru the coil and secured with a tie per instructions. The hot post is actually very close to the coil so I had to loop the hot lead around to join with the neutral as they pass thru the coil. The hot lead connects to the post on the AC branch circuit, while the neutral lead connects to the neutral buss. The disc at the top is actually the coil for the AC ammeter.

When I am at the boat and have mounted the cabinet, I'll be ready to connect the hot lead from shore power. It will pass thru the AC ammeter loop. I'm not sure how I'm going to secure that donut ... it is loosely connected to the ammeter at the upper left with those 2 thin black wires. It seems odd to me that there is no instruction. I guess Blue Seas assumes that only those in the know will be doing the installation. (The black lead that I show is used just for illustration)
I haven't shrunk the crimp connectors yet if they look unfinished.

Those orange wires are provided for 24V backlight. I'm not sure what to do with them other than to simply clip them off. The red wires are positive for 12V backlight. I crimped them together to pass them thru the shield to the DC panel. I haven't decided if I want backlights to be permanently on with the main switch (connected to hot lead) or wired to a breaker so I can switch the meters on and off. Same with the water tank and fuel tank gauges. The Batt monitor is wired direct to Batt post, so is on all the time, unless I change the wiring.

 

[Maine Sail]

I usually tie back lighting to the cabin light circuit when breakers are in short supply... When you need cabin lights you'll also want backlighting. On boats with extra breakers backlighting gets its own breaker.

 

[LeslieTroyer]

Beautiful looking panel !! You should build a cover for the 120V section. A piece of flat lexan screwed to some wood standoffs would look good and be quick. (ABYC requirement IIRC)

 

[Scott T-Bird]

Beautiful looking panel !! You should build a cover for the 120V section. A piece of flat lexan screwed to some wood standoffs would look good and be quick. (ABYC requirement IIRC)

Thanks! Yes, the white board in the last picture separates DC section from AC section with small holes to pass the DC wiring thru for backlights. The back of the cabinet will have a lexan cover with passages for the AC wiring that comes into the cabinet. All will then be enclosed. The passages have to allow the wires to remain relatively stationary when the panel swings open on its hinges.

 

[Scott T-Bird]

I usually tie back lighting to the cabin light circuit when breakers are in short supply... When you need cabin lights you'll also want backlighting. On boats with extra breakers backlighting gets its own breaker.

Thanks, that makes sense. The backlights can be wired to the cabin lights. I think the gauges to a breaker switch. I have 16, with only 13 or 14 identified for specific use so far.

 

[Ward H]

Looking good Scott. Nice upgrade. Was down last Saturday and was looking over your mast. Looks like you are getting close.

 

[Ron20324]

...The backlights can be wired to the cabin lights. ....

I wired my panel lights, a nav fan, a nav ceiling red/white light to one breaker labeled "Nav Station". It is the lower, left, breaker. It is easy to come into the salon in the dark and find that breaker. Plus, it comes on as a red light overhead.

 

[Scott T-Bird]

I wired my panel lights, a nav fan, a nav ceiling red/white light to one breaker labeled "Nav Station". It is the lower, left, breaker. It is easy to come into the salon in the dark and find that breaker. Plus, it comes on as a red light overhead.

Logical! I like that location as well.

 

[jssailem]

Nice work Scott. I've starred your posting for my future refit.