ELCI Breaker and Isolation Transformer Questions

[GrowleyMonster]

So I finally have some time to do some more work on the boat. The other day I installed a start relay and a push button start switch. No more scratching a wire on the battery post to start the Westerbeast. WOO-HOO! I burnt out several switches. I probably should have trued putting a big capacitor and a low R high wattage resistor in parallel, in series with the start switch, to control arcing. But I am liking what I ended up installing. Now, time to do some more work on the shore power. Shore power cable running in a window to a splitter feeding my battery charger and drop light is just too Redneck, even for me. I have a nice Charles isolation transformer mounted and temporarily connected to my official shore power inlet. I also have a Blue Sea 3116 ELCI breaker. I thought at first I was supposed to connect it between the shore power inlet and the primary of my transformer but I was advised differently. I was doing some research before hooking this up, partly because I wanted to make sure that the load hot was supposed to pass through the sense coil along with the load neutral, and partly because something just didn't seem right. Anyway I ran across a web page that says if I have an isolation transformer within 10 feet of my shore power inlet, I don't need an ELCI breaker at all.

So, any input on this?

My setup is pretty simple. 120v 30a shore power in. Transformer wired to give 120v out. No genset, yet. Blue Sea combination AC/DC breaker panel, connected to 12v, not yet connected to 120v, No load circuits hooked up yet. I have a source transfer switch, not installed. I have a possible gift of an elderly Onan 3.5kw diesel genset coming my way but I have to do some surgery to get it into its new home, so I am not in a rush to install it. I will probably give it at very least a good cleaning and painting , flush out the cooling system good, have a look at everything, and so it will probably be a year or so before it goes in, so it is not part of the picture at the moment. No fridge, no air conditioning, no household appliances. I need it only for occasional power tool use, and charging batteries. I have one charger charging two 8D's and I will add another charger and more batts up forward, when I install my 12V windlass. I have no dedicated start battery. I have a Perko OFF/A/BOTH/B battery switch so I can keep one topped up and ready to crank up the Westerbeast.

If I don't need the ELCI breaker to comply with ABYC recommendations then I am not going to put it in. Honestly, I don't see why I need it. Every single load will be fed from its breaker, which will be fed from the transformer secondary, ground isolated from the shore power ground. If I do need it, it would seem like I would need it between the transformer secondary and the load distribution panel. At least that's how I see it.

Now, if I DO need to install it between shore power inlet and transformer primary, what about the transformer primary ground connection? Do I connect it to neutral? Let it float?

Thanks in advance for any knowledgeable advice.

[goboatingnow]

Personally , RCBOs ( as they are known here ) are cheap. I’d put one in on the primary feed to the traffo , and then another in the secondly side. I agree keep everything onboard isolated from the shore system.

The advantage of secondary side residual current protection. ( ELCI is actually an incorrect term as the current may not be leaking to earth )

Having a secondary protection prevents the situation where a device goes “hot “ and it’s not obvious as there is no return circuit.

As I said for the money I’d have a residual device immediately after the shore inlet and then another on the secondary.

As for wiring , the transformer neutral , live and protective earth should just be connected out to the shore power system.

Note I couldn’t give a hoot about ABYC. In my view they are very late to the residual current protection space. Make yours the best not simply “ compliant “

[GrowleyMonster]

Originally Posted by goboatingnow

Personally , RCBOs ( as they are known here ) are cheap. I’d put one in on the primary feed to the traffo , and then another in the secondly side. I agree keep everything onboard isolated from the shore system.

The advantage of secondary side residual current protection. ( ELCI is actually an incorrect term as the current may not be leaking to earth )

Having a secondary protection prevents the situation where a device goes “hot “ and it’s not obvious as there is no return circuit.

As I said for the money I’d have a residual device immediately after the shore inlet and then another on the secondary.

As for wiring , the transformer neutral , live and protective earth should just be connected out to the shore power system.

Note I couldn’t give a hoot about ABYC. In my view they are very late to the residual current protection space. Make yours the best not simply “ compliant “

Thanks. I believe all my panel breakers are GFCI, actually. And my 120v receptacles will be GFCI protected, at any rate.

[smac999]

you can't leak ac into the water / shore / ground with a functioning iso transformer. which is the main reason for an ELCI, to stop electrocution of swimmers. so the elci becomes redundant with an isotransformer.

the elci before the isotransformer only helps if the wire between the ELCI and the transformer gets damaged / shorted etc. which is why they say if it's short run, less chance of damage, and less need for one. the elci before the transformer does nothing for any issues after the iso transformer. only before it. or the transformer itself failing

[CharlieJ]

OP: Your arrangement does not require an ELCI to be compliant with the ABYC Electrical Standard.

[goboatingnow]

Originally Posted by smac999

you can't leak ac into the water / shore / ground with a functioning iso transformer. which is the main reason for an ELCI, to stop electrocution of swimmers. so the elci becomes redundant with an isotransformer.

the elci before the isotransformer only helps if the wire between the ELCI and the transformer gets damaged / shorted etc. which is why they say if it's short run, less chance of damage, and less need for one. the elci before the transformer does nothing for any issues after the iso transformer. only before it. or the transformer itself failing

A residual current device on the output of a isolating transformer remains useful. Protective “ earth “ ( cause it’s not now an earth ) should be maintained and tied back to the neutral ant the secondary side of the transformer ( the common point )

A residual current trip is then wired into the secondary live and neutral on the load side of the common point .

This adds to the safety as any hot fault will trigger the residual device. Otherwise a hot fault can go undetected and cause issues where a person inadvertently bridges the circuit.

An isolation transformer whilst offering protection to swimmers is not primarily for that purpose. Firstly it comprehensively protects against impressed corrosion from unintended shore power currents

Secondly it adds a high degree of on board safety as there is no fault return path through “ earth “ or seawater for those onboard that may come in contact with a live feed.

Irrespective of standards. Given the cost of a good isolating transformer it’s adds virtually nothing to add a residual current trip to the incoming shore feed and the secondary live load feeds.

A waterproof small consumer box near the shore socket is easily installed in most boats and the secondary side residual unit can be mounted in the AC panel alongside the individual breakers in the normal manner.

[GordMay]

Another benefit is that, an isolation transformer will also limit [short circuit] fault currents, depending upon the xfmr’s internal impedance.

[GrowleyMonster]

Thanks for all the replies, everyone. I am going forward with just the iso transformer, and GFCI protection in the distribution panel and receptacles. Should be good.

[bauer965]

Note: ABYC Standards do require a ELCI (or RCD) if the Isolation Transformer is mounted more than 10 feet away from the shore power inlet.


Additional Note: you are not required to meet ABYC Standards (although many would come highly recommended, others may be situational, in any given instance).

[sailcrazy]

Following. Our Isolation Transformer is right at 10' from the shore power inlet-I'd never heard of either the requirement for the c/b, or the 10' consideration. And I do not have one on the lines from the xfmr to the AC Dist panel, either. Good info!

[CarinaPDX]

While you may not be required to install an ELCI (if less than 10' from power inlet) you are still required to have a Main Shore Power Disconnect circuit breaker that switches both conductors. If you already have one in place then you may wish to just leave it, but if not then the ELCI will perform that function as well.

Greg

[GrowleyMonster]

Originally Posted by bauer965

Note: ABYC Standards do require a ELCI (or RCD) if the Isolation Transformer is mounted more than 10 feet away from the shore power inlet.


Additional Note: you are not required to meet ABYC Standards (although many would come highly recommended, others may be situational, in any given instance).

Yeah I know I don't HAVE to be ABYC compliant, but I do try to give the nod to it when practical.