See a Grown Man Cry - Corroded Prop !

[s/v Jedi]

Originally Posted by fstbttms

In any event, rapid-onset corrosion is not necessarily due to a poor anode bond. If you are truly concerned, have an electrician take a look. Could save your prop and/or the boat.

Agreed. With an electrical failure like that you can get up to 12 or even 24V DC which overpowers any size zinc anode.

cheers,
Nick.

[Randy]

Originally Posted by Dockhead

110 volts will kill you just as fast. And 220 volts (not 240); sometimes 230 volts (UK) is twice as efficient at moving energy over wires, half the amps for the same power, that much less likely to cause a fire, melt insulation, etc. I think overall it's safer.

I'm very happy our boat is 24 volts DC and 230 volts AC.

While both statements are true, the quality of the ground being the determinant of the amount of current flow. I can tell you from direct experience there's no comparison between a shot of 110 and 220 and I've got the scars to prove it.

[Stillraining]

I have been stung by 120 on several occasions...the few times Ive created sparks with 240 there is no comparison....I don't really sweat the next 120 bite...I'll let you experiment with the other..

[Randy]

I'm sorry for this diversion of the thread but my 220 shock was when I was installing a stove in a kitchen, laying on the floor I was reaching through the lower section to lift the connection pigtail out of the way of the stove sliding back when my right arm a couple inches above my wrist touched the 2 hot terminals and a couple inches away I touched the frame of the stove. Instantly as a reaction I jerked away but my right arm didn't move, a second later I consciously tried to lift my arm away and it still wouldn't move (the muscles in my right arm were apparently shorted out). Then I thought "well, I can't lay here like this all day", closed my eyes, totally focused and with the rest of my upper body pulled my arm out of there. My wrist was bleeding like a stuck pig and I was just worried about staining the new tile floor.

Truthfully I can't say it hurt more than 110 but there is no comparison between the experiences; 220 having totally disabled my arm and had I not shorted on the stove framework that 220 would have traveled into my torso and messing with my heart. I've heard of guys getting hit with 440 and blown off ladders.

So, be careful with your higher voltages guys!

[s/v Jedi]

120V vs 230V: in the 50's and 60's everyone switched to the 220-240V side except the USA and some poor countries and small islands.... and Japan. The reason that the US didn't switch is not that they didn't want to... they did, but the switch was deemed too costly because of all the 110V appliances owned by the population.

Japan went to 100V.

Now the interesting part; the number of lethal electrocutions (2009) in the different countries, per million people: USA (1.44), UK (0.68), Japan (0.27)

So, Japan (100V) is showing that a lower voltage is safer and they have less than half the deaths than the UK (230V). However, for some reason that I will try not to speculate on, in the USA (120V) they have more than double the deaths than in the UK. This proves that there is another factor at play which must be either the appliances in use or the people (I'm trying...)

A table with voltage per country is here: Electricity Around the World

ciao!
Nick.

[CarlF]

Have you considered that "lethal electrocutions" in the US are not always accidental?

Incredibly, the invention of the electric chair was a chapter in the "War of Currents" between two Americans - Edison and Westinghouse. Edison's company was all DC. Westinghouse used Tesla's AC power. One standard was going to win. Edison secretly paid for the construction of the first electric chair (using AC power) as part of a publicity campaign to show that AC power was more deadly than DC. When the chair was first tried on a prisoner, it didn't go well evidently because the voltage was too low. Westinghouse was reported to have said "They would have done better using an axe".

Hard to believe? Here's the Wikipedia listing:

War of Currents - Wikipedia, the free encyclopedia

And Nick, I hope this clears up any questions or concerns you might have had about us Americans and electrical safety.

Carl

[Dockhead]

Originally Posted by s/v Jedi

Now the interesting part; the number of lethal electrocutions (2009) in the different countries, per million people: USA (1.44), UK (0.68), Japan (0.27)

More electrocutions in the US probably indicates more do-it-yourselfers, less control. Japan would be the opposite.

But one thing those statistics show for sure -- it's not the voltage which is the main factor in safety.

[DotDun]

Originally Posted by s/v Jedi

120V vs 230V: in the 50's and 60's everyone switched to the 220-240V side except the USA and some poor countries and small islands.... and Japan. The reason that the US didn't switch is not that they didn't want to... they did, but the switch was deemed too costly because of all the 110V appliances owned by the population.

Japan went to 100V.

Now the interesting part; the number of lethal electrocutions (2009) in the different countries, per million people: USA (1.44), UK (0.68), Japan (0.27)

So, Japan (100V) is showing that a lower voltage is safer and they have less than half the deaths than the UK (230V). However, for some reason that I will try not to speculate on, in the USA (120V) they have more than double the deaths than in the UK. This proves that there is another factor at play which must be either the appliances in use or the people (I'm trying...)

A table with voltage per country is here: Electricity Around the World

ciao!
Nick.

But look at the side benefit of 110v in the US. All those appliance cords help heat the house in the winter!!!

[Dockhead]

Well, I've been studying the isolation transformer versus GI issue which Nick is so passionate about.

Out of curiosity, Nick, how do you air condition your boat (which has about the same interior volume as ours, I think), on only 16A x 230V shore power?

We do not have air conditioning on our boat at the moment but plan to install it before moving to the Med next year. The most conservative installation I have come up with (Dometic Cruisair) seems to need about 4.5kW continuous, which would not work on a 16A power supply.

On the other hand, our home marina power supply is 16A and I get the impression that this is the usual shore power connection in Europe. Is this true? If so, how do you air condition?

[chala]

Originally Posted by Pete7

DH, couple of thoughts, it's difficult to tell from the photos but were is the shaft anode?
Pete

Autoprop have a “hub” anode. The first picture shows a new anode fitted to the prop it will be interesting to know how corroded was the original anode. I know "fstbttms" dislike the little nylon screws.

Originally Posted by mintyspilot

OK - dumb question of the day (because I do not know any better)
Why aren't props painted so that the metal is not in contact with the sea water. If the paint comes off, what about dipping them in epoxy resin or manufacturing them in a tough polyethylene coat over the metal body?
Surely it has been tried?
Just curious....

Not easy to do, Autoprop have moving blades.

Originally Posted by Dockhead

(any material removed would actually be replaced during the moment when the metal object becomes a cathode

Some time not all the time.

Originally Posted by Dockhead

Through-hulls can fail, hulls can fail, rigging can fail, engines can fail. At a certain level of reliability and with certain backup plans in case of failure, these risks may be acceptable.

Originally Posted by Dockhead

But I would not want to risk a blade disintegrating when I'm in the middle of a crash stop or difficult docking manuever.

Originally Posted by Dockhead

$2,000 isolation transformer.

Originally Posted by s/v Jedi

Keep in mind that a 7kW isolation transformer costs a lot while the 3.6kW models come out much much better (like at $700 or so for the Victron).
cheers,
Nick.

Originally Posted by Dockhead

I am hoping that I'll be able to polish the blades of my prop and keep going. If I have to replace it, it will devastate my boat budget. I reckon it costs about $10,000.

And two 3.6kW make 7.2kW and must cost less than $10 000. I am for double insulation but with air-conditioning units this is not achievable. So with shore supply, IT’s are the only good solution.

Originally Posted by DotDun

Nick,
No doubt that an isolation transformer is a better safety device than GI. One safety you failed to mention is the fault isolation breaker in the AC panel. My main breaker is 63a and trips at 30ma of fault, so from a safety standpoint, that is a fallback. (Note, it is not a GFI)
-Marc-

So yours installation can leak up to 30mA continuously.

[s/v Jedi]

Hi Dockhead,

We have one single CruisAir 18 kBTU stowaway unit. It's 240V and the brand new high efficiency model and takes less than half our 3.6kW shore capacity, but let's say it takes 7A or half of it. It cools the main salon plus the forward owners cabin. I could add a 8kBTU unit for the guest cabin but don't want to make guests too comfortable.

I use this single unit in a bloody hot Panama where you burn your feet when you step barefoot onto the dock. I have set it to 24 degrees Celcius.

I didn't know that there were bigger than 16A shore power connections in the EU. I think bigger means 3-phase 380V with the big red plugs but I've been gone for 7 years so things might have changed. I would not go over 16A connections on a boat. If you really need more, I would add a 2nd 16A just for the extra A/C units.

I cook on propane though so if you cook electric that will change the situation. I would go for 2 x 16A in that case.

cheers,
Nick.

[Dockhead]

Originally Posted by s/v Jedi

Hi Dockhead,

We have one single CruisAir 18 kBTU stowaway unit. It's 240V and the brand new high efficiency model and takes less than half our 3.6kW shore capacity, but let's say it takes 7A or half of it. It cools the main salon plus the forward owners cabin. I could add a 8kBTU unit for the guest cabin but don't want to make guests too comfortable.

I use this single unit in a bloody hot Panama where you burn your feet when you step barefoot onto the dock. I have set it to 24 degrees Celcius.

I didn't know that there were bigger than 16A shore power connections in the EU. I think bigger means 3-phase 380V with the big red plugs but I've been gone for 7 years so things might have changed. I would not go over 16A connections on a boat. If you really need more, I would add a 2nd 16A just for the extra A/C units.

I cook on propane though so if you cook electric that will change the situation. I would go for 2 x 16A in that case.

cheers,
Nick.

I cook on propane. I guess the a/c system bid out by the PO must be overengineered, although if you are happy with your system set on 24 degrees (!) I may need something more engineered than yours. On the other hand, we have a balsa-cored hull with great insulating properties -- easy to heat and no condensation inside. Surely it won't take millions of BTU's to cool it.

Our marina has 16 and 32 amp single phase service, and our shore power connection is engineered for 32 amps. But my slip has 16 amps and we have been perfectly happy with it despite our 2.2kW consuming washer/dryer and other odds and ends. We have never managed to trip the breaker.

If we can design the A/C system to work happily on a 16 amp connection this will have great benefits. As we wander around the Med next year, we won't have to worry about shore power connections. The Victron Quattro which I will fit this year will automatically control the charger current to prevent overloading the shore power connection (one of its many virtues).

One question, however. The minimum size generator fitted to Moody 54's is the 6.5kW Kohler, which is what we have. Most of them had the 11kW generators. Why in the world would you need 6.5kW (or more) of generator capacity in a world with 16A shore power?

[s/v Jedi]

You think 24 degrees is too hot when it's 35 outside? We find that the reduction in humidity is more important than the temperature. If we walk into the boat it's freezing cold compared to outside. I guess some years in the tropics changes things... most visitors think it's too cold on our boat and even visitors from Holland put on a sweater sometimes. When we don't do any work inside, we even put it up to 25 sometimes and use a fan or two.

On gensets: we have a 6kW Northern Lights. Your genset needs to have much more capacity than the shore power connection if you don't want to run it continuously. When we run it at anchor or underway, we start:
- battery charger which will pull full load (1.6kW) because batteries are low. On shorepower it is just on float with hardly any draw.
- the watermaker (1.8kW), something we normally don't use when docked.
- the A/C (1.7kW) to get the moisture out of the boat and cool it down after a hot day.

That adds up to 5.1kW right away. This means there isn't enough power for the water heater, but it is plumbed into the coolant loop of the genset so hot water is "free" (further improving the efficiency of the genset). We have 900W for stuff like computers etc. If we start the coffeemaker, the charger limits output to not overload the genset. We do not need the power assist other than coping with start-up surges.

When we do laundry, we add that to the load without switching off anything. Remember that a washer like yours will only use 2.2kW when heating the water or in the dry cycle. When it does, it will just limit the charger output.

Edit: our washer uses hot water from the water heater instead of heating cold water. I think it's the USA way of doing it.

cheers,
Nick.

[s/v Jedi]

What I forgot to add: when you buy the Quattro, make sure you get the Digital Multi Control with the digital display and rotary knob. Also, get the (cheap) adapter to connect the data-bus (VEnet) to your PC. You need it to make sense out of programming the system.

You can program a fixed value for maximum current drawn from the genset. Mine is at 25A for the 240V genset. It also allows you to program the maximum current drawn from shore power and the rotary knob on the remote panel allows you to adjust that down to any smaller value. I use that sometimes to force it into power assist when my solar panels generate a lot while the batteries are full. Pull two ethernet cables from the Quattro to the nav station: one for the remote panel and the other for the computer-converter. You can connect both to the Quattro.

Also, I recently made a change that is very convenient. I added two AC multimeters from Blue Sea systems. One measures at genset output and the other shore power input between isolation transformer and Quattro. These meters show Volts, Amps, Hertz and Watts. I can see the shore power readings even when I am currently running the genset. I normally have it on Watts. The frequency reading allows you to check the genset (rpm's).

ciao!
Nick.

[Dockhead]

Thanks! That's great information; I really appreciate it.

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.

The previous owner had planned to install total 41,000 BTU capacity in three units -- looks like massive overkill to me. I agree with you -- getting the humidity down is more important than temperature, and it is definitely not a requirement for me that the system be capable of keeping the boat at 18 degrees 24 hours a day.

I'll install the Quattro in the way you suggest (thanks for the installation details), which will give me great control over alternating current loads and allow me to use battery power momentarily for inrush loads.

And I'll install the Victron isolation transformer (16 amp one), which will solve isolation problem and also stabilize voltage.

I like it.