Reply
 
Thread Tools Search this Thread Display Modes
 
Old 02-13-2014, 03:55 PM   #1
Veteran Member
 
City: Oregon
Vessel Model: 1979 42' Californian
Join Date: Oct 2013
Posts: 53
power voltage drops

I imagine that somehow this has been covered before... but here goes... I am not an electrician.. I understand enough to get by...

When I am hooked to 30amp120v shore, I can put a multi-meter on my power transfer switch connections and see 115vac. Start some item on the boat like a heater or microwave and it drops to 111vac. Start another thing and it drops to 108vac. plug in a lamp and it drops to 104... (all numbers are rough and vary but you get the idea). I can also plug in a device called a kill-a-watt and watch the same thing happen....

Testing also shows all AC outlets have an open ground.

When running the gennie, this problem does not occur. Even the open ground is gone.

At first I thought it was in the transfer switch, since this is the meeting point of the power sources... so got a new one and the problem still exists... double checked all my grounds.. everything is tight...

(side note: previous owner survey 3 years ago also showed an open ground... I thought it might be the electrical socket on the side of the boat, but he replaced that a few months ago.)

thought it might be the shore power cable, so brought over another one and the problem is still there...

I cannot put a load on the dockside plug in to see if the issue is there and if voltage drops at that point....

so what the heck do I do now?????

This boat has one piece of equipment that I am unfamiliar with and that is a 120/240 step up transformer or some such item.. I understand it was originally installed to run the 240vac oven, but that was removed and propane installed instead.. the transformer is still there and there is still some 240v lines up in the electrical box... the shore power runs through the transformer and up to the transfer switch... it has a ground that seems solid though...
tmiller1116 is offline   Reply With Quote
Old 02-13-2014, 04:32 PM   #2
Guru
 
rwidman's Avatar
 
City: North Charleston, SC
Join Date: Sep 2010
Posts: 4,871
An open ground is very dangerous.

My suggestion is to get a qualified marine electrician to go over your entire system ASAP. This is not a good time to try to learn marine electrical systems.

Any other information you get on a web forum is suspect, both from the qualifications of the poster and the fact that he or she may not understand what you are saying or you may not know enough to describe your problem exactly. A qualified person needs to be able to see touch and test your system.
rwidman is offline   Reply With Quote
Old 02-13-2014, 04:51 PM   #3
Guru
 
High Wire's Avatar
 
City: Cape May, NJ
Vessel Name: Irish Lady
Vessel Model: Monk 36
Join Date: Dec 2007
Posts: 4,966
From your description the voltage drop problem sounds like its on the dock side of the power cord. Theres lots of things that can cause it and the marina won't want you disassembling the the power post.
The missing ground could be a galvanic isolator on your boat (look for a small box with terminals on the boat side of the green wire inboard of the boats shore power connection) or a bad ground path between the boat end of the cable and the dock post. Easy to check with a volt meter at the boat end of the cord:
Hot to neutral should read ~120vac
Hot to ground should read ~120vac. If it reads zero volts, somewhere the ground connection is interrupted, maybe all the way back at the marina breaker panel.
Testing with a meter is the way to go. If your not sure of what you are doing, get a pro! Getting zapped on a damp dock can be fatal.
High Wire is offline   Reply With Quote
Old 02-13-2014, 09:12 PM   #4
Senior Member
 
Tonic's Avatar
 
City: Seattle, Salmon Bay
Vessel Name: Tonic
Vessel Model: 1987 Cheer Men Marine PT42
Join Date: Aug 2010
Posts: 184
Quote:
Originally Posted by tmiller1116 View Post

(side note: previous owner survey 3 years ago also showed an open ground... I thought it might be the electrical socket on the side of the boat, but he replaced that a few months ago.)
It sounds like the PO finally tried to fix the 3 year old survey's open ground (maybe for the sale?) but, whatever he did, didn't solve the problem.
Assuming the dock supply is grounded (see High Wire's post), my guess is that you have a bad connection (or other wire problem) somewhere between the boat socket and the transfer switch. A loose or poor connection on either the hot or neutral would give you those abnormal voltage drops. You could be arcing across a small gap somewhere on those conductors. Because you are not putting any load on the ground, a similar gap on the grounding conductor would just show up as no connection.

Be careful! If you haven't managed to trace it yet, you would probably be better off paying a pro to investigate before it bites you.
Tonic is offline   Reply With Quote
Old 02-14-2014, 05:09 AM   #5
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 22,553
Most docks have power drops , usually from heavy usage , like a hot day with dozens of air cond cycling on or cold days when everyone heats with marina electric.

First easy trouble shoot would be an 30-15 adapter to plug into the power pole and plug in 1 or two 120V heaters ,.
This will show weather the V drop is from the marina wiring .

OR you could simply grab a slip at a different marina , plug in and measure the voltage drops.

My guess your marina power is crap.
FF is offline   Reply With Quote
Old 02-14-2014, 05:46 AM   #6
Guru
 
City: Here
Join Date: Sep 2012
Posts: 2,940
The open ground probably goes away when you turn on the genny because the genny bonds neutral/ground automatically when its running.

If you do have an open ground onboard .... do not swim around this boat !
Get a pro in to check this, it could be lethal.
boatpoker is offline   Reply With Quote
Old 02-14-2014, 06:03 AM   #7
Guru
 
twistedtree's Avatar
 
City: Vermont
Join Date: Jan 2013
Posts: 10,094
You said the shore power runs "through" the transformer? If that's the case, it's also likely the source of the open ground. The secondary side of the transformer is isolated from the shore side, and you will need to re bond the ground and neutral. If this hasn't been done, it will appear to be an open ground, though it's actually a floating neutral.

Go find Charles Induistries and download the installation manual for one of their isolation transformers. They include a number of wiring diagrams showing different arrangements, including the correct way to set up the ground and the ground-neutral bond.

Normally on a shore power connection the ground-neutral bond is provided by the shore power. With an isolation transformer, the shore-side ground ties to an internal safety shield in the xformer. Then the ships ground connects to the xformer's case, and somewhere on the boat you re-establish the ground-neutral bond.

An isolation transformer is the ultimate in safety for shore power, so getting it wired up correctly is much better than taking it out.

Also check to be sure the transformer is rated for the full ships load. If not, it might be what's causing the voltage drop.

Once you have your ground sorted out, then you can track down the voltage drop.
__________________
MVTanglewood.com
twistedtree is offline   Reply With Quote
Old 02-14-2014, 07:44 AM   #8
Senior Member
 
Jbear's Avatar
 
City: Anacortes
Vessel Name: Adelante
Vessel Model: Shin Shing, Eagle 35'
Join Date: Oct 2013
Posts: 154
According to the NEC AC return and ground are bonded at the last disconnect which should be the shore power pedestal at the marina. On your boat, shore power ground and the ac return should not be connected together. When you turn off shore power and use the gen set ground and genset AC return should be bonded at the gen set.

I agree, get a marine electrician to help sort this out.

Jeff
Jbear is offline   Reply With Quote
Old 02-15-2014, 05:45 AM   #9
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 22,553
the gen set ground and genset AC return should be bonded at the gen set.

Same for another source , the inverter.
FF is offline   Reply With Quote
Old 02-15-2014, 08:18 AM   #10
Guru
 
rwidman's Avatar
 
City: North Charleston, SC
Join Date: Sep 2010
Posts: 4,871
Quote:
Originally Posted by FF View Post
the gen set ground and genset AC return should be bonded at the gen set.

Same for another source , the inverter.
When they are the power source, not when on shorepower.
rwidman is offline   Reply With Quote
Old 02-15-2014, 09:44 AM   #11
Senior Member
 
Jbear's Avatar
 
City: Anacortes
Vessel Name: Adelante
Vessel Model: Shin Shing, Eagle 35'
Join Date: Oct 2013
Posts: 154
FF and WesK,
Agreed. Someone said it earlier, something as important and potentially dangerous needs to be dealt with by a professional IF you do not posses the electrical knowledge yourself. On many issues following the advice on the forums on what/how to fix something is fine- this isn't one of those. Do a little web searching and you will find many horror stories of people that have died on the boat or in the water because of bad grounding, etc.

Just my opinion of course. ��
~Jeff
Jbear is offline   Reply With Quote
Old 02-25-2014, 10:17 AM   #12
Veteran Member
 
City: Oregon
Vessel Model: 1979 42' Californian
Join Date: Oct 2013
Posts: 53
partial update!

as for the voltage drop issues, we have found out the cause... and it is so simple we should have looked at it first. When the dock was built out however many years ago, they ran the electrical from the main service box to our end tie. The wire in question serves 5 slips.... it is 10 ga wire and runs almost 400 feet!!! Right now we are the only ones drawing any power from this line and if I start more than one item (be it heater, microwave, lamp, etc) that is all she wrote... fire off any more and it drops to almost useless levels.

SO, right now my options are to 1) live with it
2)move to a less desirable location with dual 30A outlets to tie into my 50A outlet and hope that spot has no similar issues
3) change marinas to one I know has true 50A service (newer) but not my preferred choice of locations.
4) go live on the hook....

sorry, Mama doesn't go for option 4 while we are still in the work force.

*sigh*
tmiller1116 is offline   Reply With Quote
Old 02-25-2014, 01:31 PM   #13
Guru
 
rwidman's Avatar
 
City: North Charleston, SC
Join Date: Sep 2010
Posts: 4,871
Option #5 is to request that the marina take care of the problem. I assume you are paying for shorepower so the marina should be supplying effective shorepower.
rwidman is offline   Reply With Quote
Old 02-25-2014, 07:50 PM   #14
Guru
 
psneeld's Avatar
 
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,155
or set yourself up for "cruising"...while tied to the dock...enough batteries and inverters and you can live like everything is normal with the shore power just supplying minimal power for a battery charger. Add solar or wind or both and run a genny a bit if need be (offset the fuel burned by the genny by bashing the marina for letting you plug into a hazardous situation and ask for a price reduction). Most gennies need more running time anyhow...(also ask for a price reduction on genny parts till they fix their dock).
psneeld is online now   Reply With Quote
Old 02-26-2014, 06:04 AM   #15
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 22,553
The simplest and perhaps cheapest solution that will work every place that has rotten power is ,

Automatic Load Shedding.
FF is offline   Reply With Quote
Old 03-02-2014, 03:04 PM   #16
Member
 
salmonchanted's Avatar
 
City: Kenai Peninsula and Poulsbo
Vessel Name: Scotch Knight
Vessel Model: Knight and Carver
Join Date: May 2013
Posts: 11
Neutral to Ground Connection by Mike Holt for EC&M magazine

For clarification on this topic I encourage all to visit Mike Holts web posting. Important clarification can be gleaned of the sole point for neutral bonding at the Service Disconnecting Means [250.24(B)], and separately derived systems in 250.30(A)(1)] in accordance with 250.142 (The isolation Xfmr discussed above).
"Separately Derived Systems – The neutral-to-case bond for a separately derived system shall not be made at more than one location because doing so results in a parallel path for neutral return current".
This is important stuff and definitly the way to go for isolating your onboard electrical system.

Important generator neutral bonding and isolation from shore power neutral is addressed also here.
Generator – If the grounded (neutral) conductor in a transfer switch is not opened, then the grounded (neutral) from the generator will be solidly connected to the utility’s service grounded (neutral) conductor. Under this condition, the generator is not a separately derived system, and a neutral-to-case bond shall not be made at the generator or at the generator disconnect [250.20(D) FPN 1].

If a neutral-to-case bond is made at both the generator and generator disconnect, then objectionable neutral current will flow through metal raceways and grounding and bonding


The reading can be a bit dry, for those not active participants of the electrical industry please do seek professional guidance relating to this most important safety issue.

To FF, we do use an auto loadshed program predicated on the 27 and 81uf elements to initiate 86 feeder lock-out starting with everyone elses feeders and ending with our own!! yuck-yuck
__________________
Bruce and Carol, Avatar; Salmon Bay Lake cabin Tongass Nat Forrest, North Prince of Whales Is.
salmonchanted is offline   Reply With Quote
Old 03-02-2014, 03:41 PM   #17
Guru
 
caltexflanc's Avatar
 
City: North Carolina for now
Join Date: Aug 2011
Posts: 6,348
Most Iso transformers can be tapped and switched to boost voltage. One thing that was attractive and that I was very grateful for on my boat was the PO's installation of Charles Iso Boost transformers. Not an economy solution, but made things very easy, a no brainer vs a manual system which has to be actively monitored and managed.

Marine: Isolation and Boosting Transformers

Charles now also makes an add on auto boost unit for standard 50A transformers.
Marine: Smartboost AC Transformer Booster
__________________
George

"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"
caltexflanc is offline   Reply With Quote
Old 03-02-2014, 04:55 PM   #18
Senior Member
 
bluebyu's Avatar
 
City: Northern Chesapeake
Vessel Model: Carver 440, 6CTA8.3's
Join Date: Oct 2007
Posts: 424
Boosting a low voltage caused by the voltage drop of the long run will yield lower amps.
bluebyu is offline   Reply With Quote
Old 03-02-2014, 06:41 PM   #19
Guru
 
caltexflanc's Avatar
 
City: North Carolina for now
Join Date: Aug 2011
Posts: 6,348
Quote:
Originally Posted by bluebyu View Post
Boosting a low voltage caused by the voltage drop of the long run will yield lower amps.
Well of course it does. Many motors and compressors and various other items are quite sensitive to volts. As far as amps, you have to manage loads accordingly. Low voltage is much more damaging than not having enough amps to go around.
__________________
George

"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"
caltexflanc is offline   Reply With Quote
Old 03-02-2014, 06:46 PM   #20
Guru
 
twistedtree's Avatar
 
City: Vermont
Join Date: Jan 2013
Posts: 10,094
Quote:
Originally Posted by bluebyu View Post
Boosting a low voltage caused by the voltage drop of the long run will yield lower amps.
True, but at reduced voltage most loads will draw more current, so one way or another you need to deal with lower available power when the voltage is reduced. A boost transformer just handles the situation with a device built for the purpose rather than stressing everyhing else.
__________________
MVTanglewood.com
twistedtree is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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


» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 08:56 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012