Conference unifix::sailing

    When working into a big inductive load (like a constavolt or motor)
    the voltage and current are not in phase and this can cause strange
    readings on cheap power meters.   Power companies force their large
    customers to load balance in order to prevent this or they make
    the customer pay for the power factor angle with penalties.
    
    I don't know if it could make it run backwards (seems kind of extreme)
    but it surely won't help its accuracy any.   Why is an electric
    heater being protected like this?   It doesn't seem reasonable to
    me because generally these things are used only on sensitive gear
    like computers, etc..

    
    I'd have to agree that the phase angle delta is 180 deg out of sync
    with the power meter. It may be a faulty meter.. I would replace that
    first.
    
    I have to assume you have the boat owners permission to be mucking
    around with there equipment. I would hate to be the guy fooling around
    with my stuff if I caught him. 
    The power equip on the dock is the
    marinas responcibility, talk to the dock master. I know a lot of
    marinas don't have qualified personnel running them, two years ago I
    had my boat in such a place. The shore power consisted of a # 14 AWG
    3 wire romex running 500 feet down the dock to a open duplex recptical
    that feed six boats. If two boats tried to turn on a light it would pop
    the 15 Amp breaker on the dock. Real bright setup!
    
    Bottom line is if it don't affect your boat? Leave it alone.
    
    
                                      Walt
     

Watt meters run backward when they are connected backward- there are terminals
marked LINE and LOAD, when reversed they run backward. They also run backward
when some source of power on the load side is feeding back to the line, but
this can only happen with a generator - not simply phase shift from inductive
loads.

I once wired several dozen meters backward on an apartment house we were
building. The foreman insisted it would work oK, and my explanations why it
wouldnt were just theory- Of course I got paid well for going back and fixing
them all later. 

    There is one source of 110 VAC wending its way out the piers to
    a powere distribution center. There is a commercial metal power conduit
    assembly mounted at the power distribution center. On this assembly
    are mounted three watt meters. Below each watt meter is a 30 Amp
    female socket. Three boats are individually plugged into each of the
    three sockets. I have not checkd yet but the meters and sockets are
    identically wired. Consider them as A, B, C.  A and C work fine,
    showing power being used. B meter reads backwards. Take the feed
    going to boat B and plug it into socket C. Now Watt meter C runs
    backwards.
    
    A and C have small battery chargers and a small light to dispell
    cabin moisture. B has a Constavolt unit and an electric heater,
    probably 1500 watts on board.
    
    No one yet has suggested a way that one could wire the feed to boat
    B, that is, mix up the ground and neutral in such a way as to
    have the meter run backward.
    
    The only suggestion I have is that there is a phase shift from the
    heavy inductive load presented by the Constavolt unit...........
    
    Well, maybe we'll know something tomorrow.
    
    Don 

>    The only suggestion I have is that there is a phase shift from the
>    heavy inductive load presented by the Constavolt unit...........
    
I think this is the right answer. The meter is designed to measure energy
passing through the meter. With a heavily reactive load, there is a lot
of energy passing through the meter in BOTH directions (in different parts
of the cycle), with the NET energy going towards the load. Due to limitations
in the frequency response and linearity of the meter, this may cause the meter
to run backwards (slowly, I presume.)

If the meter is running backwards quickly, then there is probably another
power source going into the boat, possibly shorted to the secondary of the
constavolt??

--RS

    Ah, the plot thins........
    
    I just spoke to the owner of the marina. When he said "Constavolt",
    he really meant a battery charger! So, I'll be looking for something
    entirely different tomorrow afternoon. Will be interesting to find
    out what is actually happening. Maybe there are keel bolts popping!
    
    Don

    Don:
    
    	Be careful!   There is something very wrong there.   One thing
    that could be wrong (and it's extremely hazardous in a marine
    environment) is faulty grounding.   Bad ground coupled with some
    internal short on one of the three boats could leave one or more
    boats quite hot as well as making the power meters go nuts.
    
    	I think the marina should be involved and I think they should
    be involved with an electrician that knows something of the hazards.
    I wouldn't mess around unless I knew EXACTLY what was going on.

    yea verily, be carefull......
    
    I have been called in anumber of times to trouble shoot these kinds
    of problems. This is however the first time for a watt meter running
    backwards.
    
    ONe of the first things I will do is to check the internal wiring of
    the AC on the pier to make sure there is no miswire of grounds and
    returns. next step is to independantly check out the wiring of the
    cable from the pierr to the boat, that wires are  not crossed in it.
    By means of isolation of the components, and my own personal isolation,
    I'll find the fault.
    
    I've been zapped enough in the past as an engineer in radio stations,
    both land and marine, to avoid working in a dangerous environment.
    That will include carrying along the rubber floormat out of my car
    to stand or kneel on. I'm also fameous for working with one hand in my
    pocket!
    
    One of the factors I will consider will be to disconnect the other
    boats, to make sure I'm working with just one problem. The only
    real ground acceptable will be the cable ground wire. The battery
    chargers of today are isolated so there may be a ground fault here .
    
    Don

    Don:
    
    	I didn't know your background when I put my 'Be Careful' reply
    in here.   Sounds like you've got it under control.  I grew up on
    the yard of a CG cutter in the South Pacific on the edge of a typhoon.
    Had to go up the stick to wipe down the salt on our antenna insulators
    about 40 feet off the deck.
    
    	We had the whole boat jumpin' with our morse transmissions.
    You could read code right off the PPI on the bridge.

    Well, I wish I could tell you some neat stuff about troubleshooting
    this Saturday. I got down there just as the snow was setting in. The
    owner of the boat had brought along an electrician. They would not 
    allow the marina owner or myself on board. They worked for a couple
    of hours on something. Whatever it was, the meter now runs correctly.
    They would not tell what had happened.
    
    Let me tell a war story of climbing masts.. a little different..
    
    As an 18 year old on a two week Navy Reserve cruise, we were given
    our first introduction to firing a 45 off the the stern of our
    destroyer escort. We were given little or no instructions. Just handed
    the 45 and told to pop away at a target off the stern.
    
    Well, my first time to handle a pistol. I pulled the trigger, up went
    the gun, pulled again in reaction, popped off 4 or 5 shots that way,
    with my arm elevated and pointing towards the rearmost radio mast. I
    proceeded to blow off one of the light fixtures on the mast. Guess who
    was delegated to climb that mast and effect repairs!!! A wild ride
    indeed!!
    
    I'm sure I picked up a nickname that cruise, but have convenitently
    forgotten it.
    Don

    I am a liveaboard in Annapolis. Just returned home after a 2 day trip
    and notice the shore power monitor is indicating an unsafe condition.
    Any suggestions on how to trouble shoot to determine what has changed
    or at least tell if the problem is on board or on the dock ?
    

    I would recommend a good book - one that I bought (from a mail-order
    book club) is "Your Boat's Electrical System" (I think). This is not an 
    area where trial and error is advised.
    
    Bill
    

    If it says unsafe and you don't know enough at this time to fix it, 
    
    o call an electrician and get it fixed
    o then buy the book and learn about it
    
    After all, the worst that could happen is you could be injured, killed,
    set fire to the boat and/or marina...

    Just a follow up on my note. I checked the voltage on board and noted 5
    volts between ground and neutral. The boat only indicates the unsafe
    condition when I'm pulling above 10 amps (water heater). Gave a call to
    the marina and they came down to check the power. They couldn't find a
    problem and said they thought it might be caused by another boat with,
    1 reverse wiring or 2 pulling a heavy load which would cause a
    unbalance. I think if it only stays in the 5 volt range the chances of
    injury is small. Also the boats are all separated with finger piers so
    that a person couldn't span between two ships.

    Since my last entry, my boat has moved to a new location.  The ground
    fault indicator started to tell me about a problem after I had an air
    conditioner installed.  I'm just getting the boat ready for the new
    season and guess what ? The problem is back and worst than ever.  When
    the compressor cuts in, the shore power drops from 120 volts to 80
    volts.  Where is the 40 volt difference going ?, you guessed it,
    between ground and neutral.  The main breaker pops when this happens. 
    Checked the wiring from shore power, right to the air conditioner. 
    Everything is correct.  I'm having the folks who installed the system
    come over for a look.  I'll post a note when the we find the problem,
    till then the air conditioner will stay off.
    

    It sounds as if you have a ground between the compressor side of the
    control which cycles the compressor on and off or a ground in the
    compressor motor windings.
    
    Jeff

    The story continues.  The air conditioning folks came out for a look
    see.  Seem the compressor bit the dirt at an early age, 3 to 4 months
    of operation over a 2 year period.  The system was warranted for 1
    year, so the cost of repair was quoted at $800 to $1000.  After talking
    with the manufactures Rep., he agreed to replace the unit at no cost
    with the exception of labor.  The compressor has been replaced as of
    this writing.  Now back to the same old thing.
    
    Shore power starts out at 122 volts,  the new compressor kicks in and
    the voltage drops to 90 volts for about a second.  During normal
    running the voltage is about 110 to 115 volts.  Checking the potential
    between the green and white, I have about 5 to 6 volts.  Just for fun I
    jumpered the green and white together and the voltage returned to 120
    volts. I removed the jumper.  The ground fault indicator shows an
    unsafe condition.
    
    The air conditioner folks will be back out today, stay tuned.
    

    You have a short from the white lead through a resistance to ground.
    That is your ground fault.  Find your partial short to ground and
    you have found your problem. 
    
    Jeff

    The search for the short to ground started yesterday.  By the book you
    are to disconnect the shore power and measure the resistance between
    the green and white. This proved to be unsuccessful since the variance
    between what is correct to not correct resistance may be a small
    percentage.  It would have been helpful to have a known benchmark
    recorded before the problem showed up.  The next approach is to apply
    power and start to disconnect componets, checking the ground fault
    indicator at each step.  As we disconnected the ground (green) at the
    air conditioner control box we noticed a slight spark. Checking the
    voltage between the ground terminal and the chain plate (reference
    Ground) we recorded 62 volts !  This should not be, I said to myself
    and the air conditioner folks.  Out went the control box, back to the
    shop.
    
    Although I don't derive great pleasure repairing the boat, it does
    provide a greater understanding of how the systems operate.  Once the
    problem is solved I will measure and record what the correct reading
    are so the next time, and I know there will be the next time, 
    Diagnosing the problem will be a little easier and less costly.
    
    Stay tuned
    

    After measuring the line voltage at the boat and following it back to
    the main distribution center at the dock head, the following voltage
    drops were recorded.
    
    Distribution center     125v
    Dock power breaker      119v
    Compressor              114v
    Return                  108v
    
    Measuring the ground to neutral showed the voltage drop from the wiring
    run from the distribution center to the boat's power input.  This drop
    is what caused the ground fault indication.  In other words, even
    though we showed a ground fault, the problem was not on the boat and
    therefore no chance of shock.
    
    Contracted an electrical engineer to review the dock power systems. His
    findings were:
    
    All wiring was 10 gauge.  This is adequate for most of the slips, but
    slips at the far ends of the docks should be upgraded to number 8.
    
    Breaker boxes are getting old and some show high levels of corrosion.
    
    A Temporary fix was to short the ground to neutral at the compressor,
    thus eliminating the voltage drop from central distribution to main
    input power.
    
    This is at a community marina where capitol improvements budgets were
    limited to plank replacements.  I expect the repairs will be slow in
    coming.