Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 10-08-2010, 12:24   #16
Registered User

Join Date: Jun 2007
Location: SW Florida
Boat: FP Belize, 43' - Dot Dun
Posts: 3,432
Quote:
Originally Posted by Microship View Post
I think the ELCI is a great idea, and indeed would have saved your electronics during that event. But would not an isolation transformer have done so as well? Since I had to get the latter anyway, I decided the ELCI would be redundant (or at least pretty sure!).
Even though I installed an ELCI in front of my isolation transformer, I don't disagree with you, in this usage the positive attributes of the ELCI is small.

I'm going one step further. I'm installing MOVs & gas tubes between the primary IT windings and boat ground. My thought process is if a high voltage, like a lightning strike, comes in on the shore power, the MOVs/gas tubes will bleed it off to boat ground. If my thinking is correct, this will save the common mode on the boat from surging. Also, since MOVs normally blow short, the ELCI will blow at the same time both saving the IT and letting me know the MOVs are blown (as it won't reset until I change/remove the MOVs).

My concern is the 'leakage' the MOVs allow. They appear to leak about 175ua at 120vac. So in my case (240vac) I'll have 350ua (.35ma) of current flow on my zincs. I don't think that'll cause a problem (I'll measure the current again after I get them installed).
__________________

__________________
DotDun is offline   Reply With Quote
Old 10-08-2010, 12:39   #17
Registered User
 
Microship's Avatar

Join Date: Dec 2005
Location: living aboard in Friday Harbor, WA
Boat: Vic Franck Delta 50
Posts: 699
Images: 7
Hmmm, that's an interesting thought. I like the ionizing tube idea, but given the scope of lightning, I would say the MOVs are not going to be useful (and, as you've noted, will introduce leakage). But the gas would do no harm, and possibly help when things get feisty.

Of course, in an actual strike, all bets are off.

Steve
__________________

__________________
M/V Datawake
Nomadic Research Labs
Microship is offline   Reply With Quote
Old 10-08-2010, 12:56   #18
Registered User

Join Date: Jun 2007
Location: SW Florida
Boat: FP Belize, 43' - Dot Dun
Posts: 3,432
MOVs & Gas Tubes

I'm looking at these:

MOVs
http://www.littelfuse.com/data/en/Da...ltraMOV25S.pdf

Gas Tubes
http://www.littelfuse.com/data/en/Da...CG3_Series.pdf


The specs on the MOVs are impressive....but yeah, I don't like the leakage.

The good news is this stuff is cheap, so no harm in playing with it.
__________________
DotDun is offline   Reply With Quote
Old 13-08-2010, 16:04   #19
Registered User

Join Date: Dec 2007
Posts: 8
I've been doing some thinking about your ELCI dilemma. If you only have one 30A inlet then I'm not sure it would be such a big deal.. having one after the transformer may be of more use for protection. If, however, you have 2 30A inlets or any 220V inlets then having one to protect the transformer in the event of a lifted neutral may be a good thing.

S/V Green Flash has 2 30A inlets, one for the added A/C units (a necessity here in the sub-tropics) and one for everything else. An ELCI will be installed on the house line to start since everything connected to the ground of the cable is on that leg.

The next thing will be to convert the useless twistlock A/C plugs to the new design. The twistlocks my claim to be rated for 30A, but we eat at least one a year here. The contact area is just too small for a salt air environment, especially when we're pushing 20+ amps 24/7 during our 6 months of summer.

If you ever make it to the Keys, I'll cover the sundowners in exchange for a tour of your boat!

Chris
S/V Green Flash
Marathon, FL
__________________
Captain Dad is offline   Reply With Quote
Old 13-08-2010, 16:45   #20
Registered User

Join Date: Jun 2007
Location: SW Florida
Boat: FP Belize, 43' - Dot Dun
Posts: 3,432
Quote:
Originally Posted by Captain Dad View Post
I've been doing some thinking about your ELCI dilemma. If you only have one 30A inlet then I'm not sure it would be such a big deal.. having one after the transformer may be of more use for protection. If, however, you have 2 30A inlets or any 220V inlets then having one to protect the transformer in the event of a lifted neutral may be a good thing.
Neutral isn't a problem if the primary on the IT is 220v. It doesn't use neutral at all. In my case, my IT is fed with 30A 220v (on a 50A 220v cord) to the primary and puts out 50A 120v on the secondary.

The ELCI on the primary protects the IT in the case of a fault to it's internal static shield. It serves no protection on the secondary side of the IT. In my case, I'm adding MOVs & Gas tubes from the primary side L1/L2 to boat ground in an attempt to drain any surge that comes my way. With the ELCI there, it'll tell me when the MOVs/GTs short out and need replaced. Other than that, ELCIs on the primary side of an IT don't make much sense.
__________________
DotDun is offline   Reply With Quote
Old 19-08-2010, 16:54   #21
Registered User

Join Date: Jun 2007
Location: SW Florida
Boat: FP Belize, 43' - Dot Dun
Posts: 3,432
Quote:
Originally Posted by Microship View Post
Hmmm, that's an interesting thought. I like the ionizing tube idea, but given the scope of lightning, I would say the MOVs are not going to be useful (and, as you've noted, will introduce leakage). But the gas would do no harm, and possibly help when things get feisty.

Of course, in an actual strike, all bets are off.

Steve
As a followup, a good read on using Gas Tubes combined with MOVs is at:
http://www.littelfuse.com/data/en/Ap...otes/EC640.pdf

My installation is 240vac on the primary of the IT (50A 125/250 shorepower). When I placed the MOVs from L1 to boat ground and L2 to boat ground the leakage from the MOVs went to effectively zero. Using 240vac I have the luxury of the MOV leakage being directed to the other hot side vs. ground, hence my zincs shouldn't see anything. Regardless, the MOV leakage under 200ua is far less than the leakage I saw with my old galvanic isolator.

I agree on the direct strike, all bets are off, I just trying to protect from the surge coming in on the shorepower (bleed it off to the boat ground plates).
__________________

__________________
DotDun is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Victron Isolation Transformer Voltage Increase Ultimarv Electrical: Batteries, Generators & Solar 5 06-09-2010 10:42
Isolation Transformer and SSB Sailabel Marine Electronics 3 02-04-2010 17:30
Westinghouse Transformer Stolen Kiss Electrical: Batteries, Generators & Solar 5 30-12-2009 09:23
Frequency transformer? Jeannius Electrical: Batteries, Generators & Solar 3 09-09-2008 15:58
Isolation transformer Pa La O La Construction, Maintenance & Refit 11 12-08-2008 14:14



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 12:39.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.