Winterising

[ExSurveyor]

Hi Richard, 

I use ebac dehumidifiers as the restart after a power cut or timer switch off, had them five years now without a problem. 

Regards

Mark

[tjg1677]

Just to round off this thread when do folk generally start to De winterise and fill water talks etc again?

 

Trev

[dnks34]

This galvanic corrosion issue.

My shore system earth is not physically wired to any metal objects on my boat ie shaft, engine, tanks or anodes etc so I dont understand how these metal parts become at risk for galvanic corrosion on a GRP hull.

I have 1 magnesium anode on the rudder and at the last lift there was still some material left on it and it had been almost 5 years since the last lift.  I did put a new one on obviously. 

Is this not more of a concern for metal hulled boats or where everything inside is bonded? 

I have queried my floating system with an engineer in the past and he wasnt at all concerned about the way its wired up.  Ive got an RCD on my shore panel, my small inverter has its own RCD and then theres the trips on the actual shore supply post so we should be covered in electric shock terms without any earth bonding.........shouldnt we?!

[dnks34]

50 minutes ago, tjg1677 said:

Just to round off this thread when do folk generally start to De winterise and fill water talks etc again?

 

Trev

When it warms up a bit......hopefully by June or July we might get a few warm days and i can put the tubes away! 

[Viking23]

2 hours ago, dnks34 said:

When it warms up a bit......hopefully by June or July we might get a few warm days and i can put the tubes away! 

Don't store them too far away, as when September arrives, you'll be getting them out again lol.

Re galvanic corrosion, we have shore power on a grp hull, outboard engine in the water all year round etc and I fitted a galvanic isolator as we are now on permanent shore power for a de-humidifier. I wasn't bothered before when we got the occasional overnight hook up. When I measured the dc  voltage across the GI it was a surprising 150 mV not much, but this small voltage can create a current that can eat away at the anodes, to start with... This voltage is now blocked. However, if there is a small ac component on the earth, ( 2-4 volts ac) then the diodes go into conduct mode and this 150 mV will now conduct to earth creating galvanic corrision that you thought the GI would protect you from. 

When I add other items into the mains circuit, like the fridge, battery charger, or de-humidifier,  I always check both the DC voltage and the ac voltage if any. The 150 mV dc is generated from the connection of dissimilar metals, nothing to do with mains. I also do an occasional 9 volt battery test (small little 9 volt batteries as found in smoke alarms etc) on the GI to test the breakdown voltage, ( 2-4 volts dc, so you have to reverse polarity of battery to test other half of diodes) The test can show if the diodes in the GI are still functional. Info can be found on youtube on how to test them. 

I did not intend to link the aluminium body of the outboard to earth, but the negative of the battery is probably connected for the return from the electric start, or charging circuit, the propex warm air heater works on 12 volts, not sure if the negative of it's supply is wired to chassis or not, but the case of the propex is connected to a copper pipe that is also linked to the cooker, paloma water heater, and a three way gas fridge. For safety, the mains to the fridge is earthed to the chassis of the fridge, which also is connected to the copper gas pipe. We also have a 12 volt dc supply to the fridge, not sure if the fridge is connected to battery return or not. Then there is the battery charger, I think this might be insulated from it's mains earth, but not sure.  

As you can see, there are a lot of items that might affect the earth currents, I am an electronic engineer with test equipment to check earth continuity, and even I don't know what is connected to earth or not, intentional or otherwise, so this is why I fitted a galvanic isolator. One day I will start disconnecting things and check continuities, but caution, temporarily  disconnecting earths can be hazardous, if not potentially fatal. Only qualified people should be doing this. What I don't understand is that the BSS test does no more than look at plugs and sockets, mostly to check that the installation doesn't leave live accessible pins on plugs etc

A BSS test does not confirm the safety of a shore power installation, or how to check galvanic corrosion. The inspectors cannot test the earth leakage trips for current and speed of disconnect, they don't check earth continuity, and they can't check circuit breakers for current etc.

For the inspectors to do these tests, they would need to have specialist test equipment, regularly calibrated, and also trained on how to use it. As a consequence the cost of BSS test for boats with shore power would probably more than double.

Note... I have made reference to voltages of 2-4 volts ac or dc the reason for this, is that some galvanic isolators have two diodes in series but back to back,  reverse polarity to the other pair. Some fancy GI's incorpoate a couple of Leds back to back, that illuminate when the earth voltage gets above a certain voltage which indicates a fault.

However, to work, leds require a minimum voltage, and a pair of diodes in series conduct before the leds can glow, so the manufacturer puts 4 diodes in series on each side back to back, so if the voltage gets close to 4 volts ac, both leds will illuminate. If only one led illuminates, it means there is a dc component.

There are a few " homemade" galvanic isolators, some just incorporate a few diodes, or a bridge rectifier, the problem is, the galvanic isolator might have to pass a current greater than the shore power post can supply, often 50 amps, or more if you connect to a 32 amp socket, even worse, a current just less than the circuit breaker will trip, so it can supply this for a long time, so the diodes will heat up considerably, that's why you see huge heatsinks on GI's usually the case is the heat sink.

99.99% of the time, the diodes do not conduct, so the case of the GI should never feel warm. If it does, disconnect the mains and have it all checked out.

Some will say the shore power post should trip in the event of an earth leakage, it should do, if tested and maintained correctly, but if it's seen a few overloads, the contacts may have welded closed and it will never trip.

Advice... when connecting to shore power, do a quick test using the button on the post before use, but check that the power is actually disconnected to the boat.

Sound complex easy for electrical and electronic engineers to understand, but some still think that the GI's are a black art, another way of getting your money into the manufacturers of GI's bank account, I hope my explaination helps to explain the need for them, but only if tested regularly for leakage and continuity. 

If a breaker trips on the post or boat unexpectedly when using a GI then it is wise to test the GI in case the GI has passed a huge fault current and may have gone open circuit, thus affecting your safety earth. Otherwise some people test them at the start of the season, maybe more.

 

 

[Vaughan]

4 hours ago, Viking23 said:

The 150 mV dc is generated from the connection of dissimilar metals, nothing to do with mains.

I think this is the main answer to dnks34's question, although the rest of the answer is excellent!

Electrolytic action will take place between certain metals in any sort of impure water, especially if it is "brackish". Don't think that the Broads are fresh water, in this case.

The boat should have an anode on the rudder and best, on the prop shaft or propellor boss. Ideally there should be an earth strap between the engine and the inboard bearing, as most flexible couplings will not pass current.

If an anode looks worn at all, it is finished and needs replacing.

 

[ExSurveyor]

I have an electrical safety test carried out around the same time as the BSS. 

I choose to do this as water and electrickery are not good bedfellows and the boat has a built in generator that runs when the engine runs. 

Once a year I use a plug in fault detector in each outlet. 

Two weeks time is booked for the big clean,  depending on the weather outlook the water will remain filled but I leave the heaters and dehumidifier in place until at least Easter. 

I will also put the little Brush ( Broom ) back in the water ready for the grandchildren's Easter visit. 

The new season is within touching distance 

 

[Jim]

On 03/03/2017 at 11:55 PM, tjg1677 said:

Just to round off this thread when do folk generally start to De winterise and fill water talks etc again?

 

Trev

Around now is the time we normally do. Water should be back on at Ferry and the tanks need more than a good flush through plus tons of sterilising tabs to get rid of the "eggy pong".  We never drink from the taps and rely on fresh water for tea, coffee etc so no real risk there.

[dnks34]

Eggy pong....are they stainless tanks?  Ours is stainless and even though we do put some tablets in each year we have never yet had to investigate an Eggy pong.

For the price you pay to moor at the Ferry Marina the water should be kept available at the berth all year! I know they say its turned off to prevent burst pipes but our basic little boatyard on the southside keeps the water on all year round without a fuss....at less than 1/2 the price!!! 

[tjg1677]

8 hours ago, Jim said:

Around now is the time we normally do. Water should be back on at Ferry and the tanks need more than a good flush through plus tons of sterilising tabs to get rid of the "eggy pong".  We never drink from the taps and rely on fresh water for tea, coffee etc so no real risk there.

Yes  Jim, the water is back on at FM. Will check the tanks for odour but have to confess I have not come across the eggy pong syndrome before in 25 years of boat ownership, can you give us more details please as it sounds like some sort of a chemical reaction, be intrigued to hear more. Thanks

Trev 

[Jim]

Thanks Trev!  I haven't been to the marina since late January.  I did start a thread in the tecchie area re this problem last year and got some good suggestions for a fix.  The issue only arose after the workshop fixed a water leak on board and it seems the tank vents have either been blocked off or bypassed since the repair.  I have asked the marina to investigate but as the boat is winterised, I doubt they have been able to do much.

As I posted in the other thread, since the repair, when filling the tanks water overflows from the filler cap and no longer the vents.  I'm pretty sure this is related to the rotten egg smell. I should emphasise that we never have nor will drink the tank water, even when boiled. Washing up and showers is all it gets used for.  

[BroadAmbition]

I've heard of this before now - crews not drinking water straight from the tank onboard. To put another view on it, every two years we thoroughly sterilise 'B.A's two s/steel tanks, pressure tank, pipes etc. (They are due to be done again now) We never leave much water in the tanks when tucking her up in her home berth preferring to fill up when we are next onboard. 'B.A' as most know is used all year round, the longest period she is left is no more than 6 or 8 weeks and that is unusual.  We drink / use the Fresh Water straight from the onboard tanks and have done so for the last 10 years. Never experienced an eggy pong smell, no crew member ever had an upset tum either - well they might have done but not due to the water onboard that I'm aware of.   During 'Lads Week' we use the water straight from the Hireboats tanks too - again,  never been an issue.  I can't even claim it is down to the strong Yorkshire constitution either as crews are from far and wide 

Griff

[Jim]

Hi Griff,

I suppose we both got in the habit of not drinking from the tanks once we bought her in 2004.  When we hired, we would drink the water but then it was also filtered. There was an old filter on our boat but we could never get the top to unscrew to fit a new cartridge and it is long gone after the cold winter of 2010.  The marina lost power and it got so cold on board that the whole unit exploded!  I was gonna get rid of it anyway so that solved the problem .

Our tanks are newish Aquaflow units fitted in 2009 and the calorifier was new in 2012. Some of the original pipe work is very old though. I'm going to follow the suggestion in the tech thread and dose the system with loads of sterilising fluid and leave in contact with all the surfaces, rinse out and repeat.  I am certain that once the tank venting issue is resolved, the problem should go away    

 

[Jim]

These are the tanks we have fitted

http://www.sheridanmarine.com/product/aquaflow-water-tanks