Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 05-04-2010, 01:13   #91
Do… or do not
 
s/v Jedi's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 9,198
Quote:
Originally Posted by Dockhead View Post
So what I'll try to do is try to engineer an A/C system which will not overwhelm a 16 amp shore connection. That will be a better A/C in any case -- lighter, cheaper, taking up less space, besides being usable with any shore power connection (how stupid would that be, having an air conditioning system which you often can't use because there's not enough power for it). I notice that the 16,000 BTU Cruisair unit uses less power than the 12,000 BTU unit, and in fact only needs 5 amps full load, cooling. So at worst two of those should be plenty, and I will have 5 amps or so left over for other loads. At best maybe one 16,000 BTU unit plus a 7,000 BTU unit for the aft master cabin, which needs only 3 amps, which would leave 7 amps for other loads out of a 16 amp shore connection.
You are looking at the StowAway Turbo systems; for your main unit I would recommend this one instead: products - Dometic

You can choose between 18kBTU or 24kBTU. I have the smaller one. It uses just 5.4A @230V/50Hz which is very efficient plus it has a cupronickel condenser. But remember that the consumption of a pump must be added to that. I use a March pump and wouldn't know something better than that.
I re-used the simplest digital control that I already had from the old unit (SMX-II control).

The jet of cold air from these units is unbelievable. You actually have to hold on to something or it will blow you away ;-))

cheers,
Nick.
__________________

__________________
s/v Jedi is offline   Reply With Quote
Old 05-04-2010, 13:47   #92
Registered User

Join Date: Jun 2007
Location: SW Florida
Boat: FP Belize, 43' - Dot Dun
Posts: 3,432
Quote:
Originally Posted by chala View Post
So yours installation can leak up to 30mA continuously.
No leak, the GI diodes stop that. The 30ma means I won't die when the 1.2v GI diodes allow current to flow on the ground path. The 30ma is the fault isolation main breaker in the AC panel.
__________________

__________________
DotDun is offline   Reply With Quote
Old 10-04-2010, 18:48   #93
Registered User
 
SabreKai's Avatar

Join Date: Sep 2008
Location: Toronto, Canada on Lake Ontario
Boat: Roberts Offshore 38
Posts: 1,287
Images: 5
The 120v system on Sabre Dance consists of the shore power cable into its socket. From the socket it leads to a duplex recepticle. Period.

I am going to rebuild the entire thing, and based on this tread, an isolation transformer is included in the new system.

Sabre
__________________
SabreKai
SV Sabre Dance, Roberts Offshore 38
http://sabredancing.wordpress.com/
SabreKai is offline   Reply With Quote
Old 10-04-2010, 20:23   #94
Registered User
 
bill good's Avatar

Join Date: Oct 2006
Location: Brisbane Australia
Boat: sold
Posts: 721
Just skimmed thru but would also add I have seen this where there has been an insulated coupling has been installed in the prop shaft adding to the electrolysis sum. I like all metal parts bonded as it is too easy to make potential differences (batteries) with different metals in salt water. If that could be your trouble check with a voltmeter across the coupling for DC volts. If you can see volts then put a bond strap.
__________________
bill good is offline   Reply With Quote
Old 14-04-2010, 21:10   #95
Moderator
 
Boracay's Avatar

Cruisers Forum Supporter

Join Date: Feb 2004
Location: Pelican Bay, Great Sandy National Park
Boat: Steel Roberts Offshore 44
Posts: 5,175
Images: 18
Not the ususal suspect...

I had a brain snap when I saw a post about correct wiring for an automatic bilge pump.

So I dropped the red probe on my multimeter into the bilge water - result +0.04V. Switched bilge pump off - result 0.00V.

So my old bilge pump/switch combo has been churning electrons round my boat.

Short fix - lift the bilge pump up 4" so it doesn't sit in the bilge water. I'll use the manual pump to keep it under control.

Long fix - find how to wire a bilge pump properly, get a better pump switch, keep it higher in the boat, use a manually switched pump to empty the bilge?
__________________
Rust never sleeps
Boracay Blog.
Boracay is offline   Reply With Quote
Old 14-04-2010, 22:44   #96
Registered User
 
Stillraining's Avatar

Join Date: Oct 2008
Location: Puget Sound
Boat: Irwin 41 CC Ketch
Posts: 2,876
Quote:
Originally Posted by Boracay View Post
I had a brain snap when I saw a post about correct wiring for an automatic bilge pump.

So I dropped the red probe on my multimeter into the bilge water - result +0.04V. Switched bilge pump off - result 0.00V.

So my old bilge pump/switch combo has been churning electrons round my boat.

Short fix - lift the bilge pump up 4" so it doesn't sit in the bilge water. I'll use the manual pump to keep it under control.

Long fix - find how to wire a bilge pump properly, get a better pump switch, keep it higher in the boat, use a manually switched pump to empty the bilge?
This is a test I need to do as well......one question though....mine sits in a separate 10" x 18" by 6" deep well with no keel bolts or anything else but solid fiber glass...so what would any stray current hurt?
__________________
"Go simple, go large!".

Relationships are everything to me...everything else in life is just a tool to enhance them.
Stillraining is offline   Reply With Quote
Old 15-04-2010, 00:39   #97
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,751
Quote:
Originally Posted by Boracay View Post
I had a brain snap when I saw a post about correct wiring for an automatic bilge pump.

So I dropped the red probe on my multimeter into the bilge water - result +0.04V. Switched bilge pump off - result 0.00V.

So my old bilge pump/switch combo has been churning electrons round my boat.

Short fix - lift the bilge pump up 4" so it doesn't sit in the bilge water. I'll use the manual pump to keep it under control.

Long fix - find how to wire a bilge pump properly, get a better pump switch, keep it higher in the boat, use a manually switched pump to empty the bilge?
I'll do the same. You were measuring potential between what -- bilge water and your grounding/bonding system? How would that work? Where was the black probe?
__________________
Dockhead is online now   Reply With Quote
Old 15-04-2010, 02:06   #98
Moderator
 
Boracay's Avatar

Cruisers Forum Supporter

Join Date: Feb 2004
Location: Pelican Bay, Great Sandy National Park
Boat: Steel Roberts Offshore 44
Posts: 5,175
Images: 18
Black probe...

Being a steel boat I just put the black probe on random bits of steel. Engine, engine mounts, hull.

It came as a bit of a surprise as I did put a fair bit of epoxy resin into the bilge and I thought I had a fairly thick coating.

The real test would be to put the black probe (maybe with an extension) on the propeller shaft, and to turn the bilge pump on and off.

As it went on and off with the switch that's electrolysis, not galvanic corrosion.
__________________
Rust never sleeps
Boracay Blog.
Boracay is offline   Reply With Quote
Old 15-04-2010, 03:14   #99
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,751
Quote:
Originally Posted by Boracay View Post
Being a steel boat I just put the black probe on random bits of steel. Engine, engine mounts, hull.

It came as a bit of a surprise as I did put a fair bit of epoxy resin into the bilge and I thought I had a fairly thick coating.

The real test would be to put the black probe (maybe with an extension) on the propeller shaft, and to turn the bilge pump on and off.

As it went on and off with the switch that's electrolysis, not galvanic corrosion.
But you need something to measure potential against. If the black probe is connected to your bonding system (or your shaft, etc.), wouldn't the potential be zero? Even if it's eating your boat up?
__________________
Dockhead is online now   Reply With Quote
Old 16-04-2010, 00:14   #100
Registered User
 
Stillraining's Avatar

Join Date: Oct 2008
Location: Puget Sound
Boat: Irwin 41 CC Ketch
Posts: 2,876
Im confused.
__________________
"Go simple, go large!".

Relationships are everything to me...everything else in life is just a tool to enhance them.
Stillraining is offline   Reply With Quote
Old 16-04-2010, 04:54   #101
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,751
Quote:
Originally Posted by Stillraining View Post
Im confused.
OK, look. The voltmeter reads electrical potential, right? Between two conductors?

So if you stick the red probe in the bilge water, then the black probe has to be stuck somewhere else, right?

So where would you expect the current to be flowing to, if you've got a problem?

To the shore power ground, maybe?

To your bonding system?

To the ocean?

To the negative side of your DC power system?

That's the question. I don't have too good expertise in electrickery, so apologize if it is a stupid question.
__________________
Dockhead is online now   Reply With Quote
Old 17-04-2010, 02:28   #102
Moderator
 
Boracay's Avatar

Cruisers Forum Supporter

Join Date: Feb 2004
Location: Pelican Bay, Great Sandy National Park
Boat: Steel Roberts Offshore 44
Posts: 5,175
Images: 18
Yesterday upon a stair...

I really have no idea how it works, or doesn't.

I found a voltage difference switchable by the bilge pump switch, hopefully I've removed it, and I'll continue to upgrade my system to totally eliminate it as the opportunity occurs (things break!).

Possibly you're looking at it the wrong way, assuming that boats are either insulators or conductors. From my very limited experience of one steel boat it seems to work more as a bunch of resistors of varying values. I would suspect that fibreglass, particularly older fibreglass, may be similar.

From a practical point of view I want to prevent electrical corrosion of my propeller, my hull, other below the waterline components and non essential loss of my anodes. I don't care how it happens. I just want it to happen.
__________________
Rust never sleeps
Boracay Blog.
Boracay is offline   Reply With Quote
Old 17-04-2010, 06:58   #103
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,583
Images: 240
Quote:
Originally Posted by Dockhead View Post
OK, look. The voltmeter reads electrical potential, right? Between two conductors?
So if you stick the red probe in the bilge water, then the black probe has to be stuck somewhere else, right? ...
See The Galvanic Series and Corrosion

And http://www.fluke.com/Application_Not...r/B0269b_u.pdf

"... Sign of corrosion potential assumes that the "COMMON" or negative (Black) terminal of the voltmeter is connected to the reference electrode and the "VOLTS-OHMS", or positive (Red) terminal is connected to the metal to be measured. The reference electrode must be immersed in the same body of electrolyte as the metal being measured, preferably in close proximity ..."
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 17-04-2010, 09:07   #104
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,751
Quote:
Originally Posted by GordMay View Post
See The Galvanic Series and Corrosion

And http://www.fluke.com/Application_Not...r/B0269b_u.pdf

"... Sign of corrosion potential assumes that the "COMMON" or negative (Black) terminal of the voltmeter is connected to the reference electrode and the "VOLTS-OHMS", or positive (Red) terminal is connected to the metal to be measured. The reference electrode must be immersed in the same body of electrolyte as the metal being measured, preferably in close proximity ..."
Now we're getting somewhere. Thanks for the info and leads. So that would be equally valid for a potential galvanic corrosion problem, as for an electrolytic corrosion problem like current leakage from a bilge pump?
__________________

__________________
Dockhead is online now   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
Free Corroded Zipper Double-Wide Auxiliary Equipment & Dinghy 6 26-11-2015 05:11
Vari-prop vs. Max-prop winds aloft Product or Service Reviews & Evaluations 21 30-07-2008 11:22
Corroded mast step kismet424 Deck hardware: Rigging, Sails & Hoisting 6 19-04-2008 02:49
Home Grown DC Genset ssullivan Electrical: Batteries, Generators & Solar 31 18-09-2007 13:28
It's ON Old Man ! ssullivan Liveaboard's Forum 27 08-12-2005 10:56



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 02:33.


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.