MoominPapa
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Posts posted by MoominPapa
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Strewth!
Question for 'experts'
You have a boat with an 16A inlet, you want to use this with:
1. An RCD protected shoreline
2. An inverter
3. A portable generator
Exactly where should any neutral-earth bonds for the inverter and generator be?
Inverter: Connect the neutral and earth terminals together (in case it's not done internally.) and then connect them direct to the hull earth point. Note that the earth bond cable should be different from the neutral cable which carries load. Just because you have a wire from your inverter neutral terminal to the changover switch (or fusebox) , it's not OK to do the earthing at the changeover switch terminal.
Generator: Similar situation. Connect neutral and earth at the generator and connect the earth conductor in the flex to those terminals. Again, don't use the neutral conductor in the flex for earthing, there should be seperate neutral and earth conductors and they should only be connected at the generator. The earth conductor in the flex should be connected to the earth pin on the blue inlet socket which should be connected to the hull.
HTH
MP.
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We were talking about connecting the neutral of an INVERTER to the hull not the neutral of the shore supply. I agree with you if it's the latter to which you are referring.
Yes, don't connect neutral and earth of a shore supply. Apart from anything else, you'll trip the RCD in the shore supply post.
This is one reason why inverter/shore changeover switches have to be double pole, switching both live and neutral. That way the earth-neutral bond gets removed when switching to shore supply.
I wish there was an easy way to include a sketch circuit diagram here - it would make explanations so much simpler. Anyway the main point remains: bond the neutral terminal of the inverter directly to the Hull earthing point.
MP.
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I wasn't arguing that Gibbo's expertise made him right about everything, but I would also apply that same rationale to your good self. The only reason I brought up that document again was because to me it appears very logical and thus far those who are against DC bonding seem unable to produce as robust an argument for their case.
I've read Gibbo's document, and in my opinion, it's correct and well argued. That's one more vote for Gibbo.
MP.
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The 240 volt energy out of an invertor is just as dangerous as a land line hook up. It really ought to be supplied via the boat RCD.
Agree completely to here.
If you earth the neutral conductor to the shell then you may short out the earth path and make the RCD unreliable.Disagree with this; I think the exact opposite is true.
Consider the following scenario. Boat supplied from inverter through RCD, human touches hull and live conductor simutaneously.
Firstly without the neutral to earth bond: If all is absolutely fine, nothing will happen: the hull will float to the 240v output of the invertor, but no significant current will flow since there's no circuit back from the hull to the neutral terminal on the invertor. The RCD will not trip. BUT, if there's already any connection from neutral to the hull, from any means (damp, cut insulation....), then the human will get a shock via the circuit invertor live -> human -> hull -> accidental neutral connection -> invertor neutral. The RCD will not trip. Before the live-touch, there will be no way to tell that the neutral to hull leak exists, everything will be working fine, such a fault could persist for years.
Now bond the neutral terminal on the invertor to the hull and try the same thought experiment: firstly there cannot be an accidental neutral to hull connection, it will trip the RCD because some neutral current will take the path via the hull and neutral terminal bond, bypassing the RCD and unbalancing it. Second, the live touch will also send some current live -> human -> hull -> bond -> neutral, unbalancing the RCD, which will again trip, before the current reaches a harmful level.
Even without an accidental neutral to hull connection, the bonded system is safer. Without a bond, a human touching the hull and live and neutral simultaneously will get a shock and not trip the RCD. With the bond, the RCD will trip, since some current will take the live -> human -> hull -> bond -> neutral route and unbalance the RCD.
To be clear, the Hull bond has to go to the neutral terminal of the inverter, the one that is connected to the RCD input. It should NOT go to the neutral output terminal of the RCD. In effect, this is the same as the electricity supplier does on land. The neutral terminal of the substation transformer is always very firmly earthed.
If you look at the IEE regulations you will see that only one point is earthed and all the other services bonded to that point. The earth can be provided by the electricity company or can be provided by the customer in the form of an earth electrode.That's true, for the in-building wiring. The difference on a boat with an inverter is that you have to worry about the equivalent of the substation. As I said substation neutral is always earthed, and inverter neutral should be also, for the same reason.
Fun subject this one isn't it.Oh yes!
Sorry it hijack your thread with more geekery, PB.
Cheers,
MP
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Well, Amy (Black Ibis on here) and I have finally taken the plunge.
Hopefully we'll see people when we go cruising....
Congrats. Looks like a nice boat. Hope to see you around when you make it to the flat, Eastern bits. Have you sorted a mooring?
Cheers,
MP.
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so, (whispers so as the electrical Furies don't come rushing in), is your understanding the same as mine that, in this (ideal) situation, there should be no 12V bonding to the hull?
And if there is a connection to the hull through the starter motor the domestic -ve should be kept separate and unbonded?
Rubber engine mounts mean this would be more common that might be supposed.
My marine electrical training leads me to believe that connecting electricity to the hull is, in general, a no-no. The exception being shore power, simply because it is already so connected (through its own earth).
Rather than as often stated (on this forum) the reverse.
In the situation you're describing, the engine, and therefore propshaft and prop are at the same potential as the battery negative, but the hull is floating somewhere between battery positive and battery negative, exactly where depending on the stray resistances between the boat wiring and the hull. You will therefore have a current between the prop shaft and the stern tube. This is Not Good.
One of the reasons for all this stuff is to ensure that every conducting part of the boat that's in the water is, as close as possible, at the same potential. That ensures that you don't get currents through the water and all the associated ionic chemistry and corrosion.
It's for the same reason that the hull is not used as the earth return. Even big lumps of steel have some resistance, so if you're pushing large currents through them, you'll get some potential difference, and some current will pass through the water surrounding the hull, rather than through the hull itself. A small proportion, to be sure, but a small proportion of the current flowing through a starter or inverter or alternator is enough to corrode the hull.
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Thanks for prompt replies. I have read Gibbo's post and I think that I understand? but I require further explanation - does bond mean fix, attach etc.or does it have a more technical meaning?
"Bond" means electrically bond, which means "connect together electrically with a secure, low resistance connection." Practically, it also implies some amount of mechanical strength, so that normal wear and knocks can't accidentally break the connection, and a connection with high current-carrying capacity which will withstand potentially large fault currents.
and does ground mean earth?on a boat, it means the hull. The hull of a boat should also be connected to the wider mass of the earth through the earth conductor of the hook-up lead when you are using shore power.
and given a negative earth 12v system (normal?) and a normal green and yellow earth 240v system do you just securely fix all the blacks and all the green and yellows to bare metal somewhere convienient.More or less. One conductor for each system is enough, and it has to be secure (protected from corrosion, locknuts or other locking devices.)
One other thing to check is that the neutral (blue wire) terminal of your inverter has to be connected to earth too. Some do this internaly, some don't. The inverter on Melaleuca doesn't, and the is high on my list of jobs to do,
No response to my Inverter question? perhaps there isn't one.It should have a fuse, in the positive wire, as close to the batteries as possible.
Cheers,
MP.
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Yes, they always have been. Linear regiulation would produce FAR too much waste heat. Even the internal ones (although they operate on a primitive "hysteretic" topology) are still switch mode. The field is either on or off. Never inbetween.
Thinking more, I should have known that it was possible. In the past I have owned several 70s era Fiats which had Magnetti Marelli alternators with external "vibrating contact" regulators. Electrical, rather than electronic, PWM!
MP.
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You can actrually get a very good idea of the maximum possible charge current from the PWM mark/space ratio.
Oh, I didn't know that alternator regulators are PWM. Makes sense, I suppose, to reduce power dissipation in the regulator. Do they have suitable circuit arrangements to allow the rotor inductance to smooth out the current waveform? If not I imagine the rotor will produce fairly high back-EMF as the current is chopped.
Is the whine you get from a heavily loaded alternator related to the regulator frequency? I had always assumed it was rotation speed x number of poles, but maybe not.......
MP.
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No, they are not allowed on new builds but for the following 'mad' reason - they have to be fitted by a 'competent' person if nothing else for 'common sense' reasons, generally defined as 'Corgi' registered. All to the good you might say BUT 'Corgi' registered fitters are not apparently allowed to fit non-room sealed appliances!! in any event not many are qualified to 'play' with LPG etc. This anomaly is a bit of a chestnut but what, I ask is the status of gas cookers? a non-room sealed device if there ever is one and one that is constantly being fitted/moved etc.
IF (big if) the boat regulations are the same as for domestic gas work, then the definition of "competent" is not formalised. It certainly doesn't imply CORGI. In theory, you can fit gas appliances yourself (for you own use, not for other people and for money) and if it conforms to the makers specs, works well, and doesn't blow you up or gas you then you are, by definition, competent. OTOH if it does blow you up, then you've broken the law, as well as being exploded.
More practically for DIY, if you can read, understand and follow the manufacturers installation manual and know how to do gas-tighness testing then there's really no magic. Since soldered joints in gas pipework are verboten by the BSS, you don't even need to be able to make those reliably. I'm not advocating that just anybody should be doing gas work willy-nilly, but just because your local Corgi won't do it doesn't mean it can't be done.
MP.
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Hi Snibble. At the risk of reopening old wounds, the K90 installation instructions say "We advise you to never set a charging rate which is more than about 2/3 of the alternator capacity. ie if you have a 55amp alternator, do not set the charging rate higher than approx 30amps. This is to compensate for the fact that Boat Engine alternators are usually very poorly cooled."
Don't shoot the messenger! That's just what it says!
I've had problems with "that toasty alternator smell" from my A127 when it's working hard. It's in an engine room and therefore should be well cooled, but on dismantling it, I found large amounts of fluff and crud blocking the airways. Hopefully with that cleared it will cool OK. Hobson's choice: cook the alternator in an engine compartment and keep it in an engineroom and have it collect hair, fluff and dust from the domestic activites aboard.
MP.
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But, everyone else, what are the relative merits of wheel vs. push/pull gear change?
I find it difficult to image how it would be possible to get enough force to change Melaleuca's Lister-Blackstone box with a wheel. It would have to be well geared down, in which case it would take even longer to engage emergency stop mode. (Oh look we're going backwards! Not because we're in reverse, just because we bounced off the target.) The alignment on the linkage is all wrong at the moment: when I've fettled it the forces should be easier.
The speed control is a wheel, and well geared down. It uses the Stanley drill technique to take the rotation through 90 degrees and the vertical shaft has a square-cut thread on the end on which runs a nut which is pinned to the engine speed control lever. The main thing I would like to change it to provide a positive stop at the idle end of the travel. At the moment it's too easy to repeatedly give the wheel another half-turn "down" to make sure its in tickover and then when you need to go it's an unknown number of rotations before anything happens.
MP.
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It's a Kestrel K90 made by Acorn Engineering. I'm not sure if they still make them. I wouldn't recommend one to you, as, IMHO, the're not very good!
Ah, OK. Does anybody know if it's possible to do the same thing on an Adverc? The 70A Lucas alternator fitted to the FR2 is driven by a belt which wraps around the flywheel, so the pulley ratio is very high - I'd guess 8:1 or 9:1 from memory and without measuring it. That means that the Adverc can wind the alternator up almost to maximum output even when the engine is at idle. This is good for charging, but I think it may be overloading the engine. The governor opens the fuel-racks quite wide and the exhaust tends to smoke. If I could find a way of limiting the current that the adverc demands, that may be more healthy for the engine.
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they don't need to be in cambridge itself and they have mentioned Wisbeach area. So, it looks as though Ely may have moorings?! Where shall I send them to look?
They could look at Bill Fen Marina, Ramsey, NE of Huntingdon. I don't know of there are available spaces ATM, but I've heard whispers of an extension, so there may be a chance for the future, even if there's nothing now.
MoominPapa (Happy Bill Fen moorer, no other connection.)
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Chris - I agree, my alternator controller is a relatively simple, unsophisticated device. But it does have a charge current limiting pot. When you turn it, it does what it says on the tin. The max. charge voltage is set by a seperate pot.
What sort is it? Are they still available?
MP.
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I guess you will use a float valve in header tank to dictate pump demand?. If so fit a suitable solenoid to protect float valve electrical contacts, a favourite failure point.
The plan was to loose the header/day tank, and feed the engine injection pumps directly from the lift pump. I guess using a float valve and keeping the tank would be a possible alternative.
MP.
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My Lister FR2 has a day tank, filled by a rotary hand pump. Whilst this is all nice and trad, it has some disadvantages. The pump leaks, it's a pain to use and the only way to check the level in the tank is with a dipstick which is even more of a pain to use.
So, I'm wondering about solving the entire problem by ripping it out and replacing it with something like Clicky
The current arrangement down stream of the day tank is a fuel cock on the tank outlet, then to a filter/water separator, then a flexible pipe to the engine inlet. The engine has a second (wick type) filter. Injector overspill goes into the filter/water sep via a non-return valve.
Questions.
1) What pressure should the pump delivery be? The static head from the current day tank calculates to 1-2PSI. Facet make pumps which go that low, but commonly available ones are maybe 5-10PSI. Will it matter if I use one of those?
2) Apart from the injector overspill, there's currently no recirculation. The filter has two blanked-off spare ports, one marked as an inlet and one as an outlet. Can I use the outlet as a recirculate line back to the main tank, to avoid the need to bleed the pump and suction line from the tank?
3) Any BSS gotchas? I know that I need all metal pipes and connections, and no soldered joints.
4) The main diesel tank arrangment is odd: there's both a tank at the stern and one a bilge level. When both are full, the diesel level is about the same height as the engine injectors, when the tank is nearly empty, the lift pump will be lifting from almost base-plate level. Is that likely to cause any problems?
Thanks in advance for any suggestions or advice.
MP.
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Yes i found that at quite a few of the locks today, there's so much water coming over the gates that you don't need to open the paddles.
But with the vertical gate open your boat is sat in some fast moving water, tricky to untie and get back on board safely when single handed.
I really wouldn't fancy doing that single-handed. I've prefected a technique with rope for these locks, as on-board steerer, but it has been interesting getting in to the downstream landing to pick up the shore-crew on occasion. The boat gets flushed out of the lock like a cork from a bottle and it can be difficult not to shoot straight past!
Indeed, today's most difficult problem has been stopping. We've made good progress though!
Can't beat Chevetter, but Melalueca is moored for the night on the pontoon on the lake at Ferry Meadows, within easy reach of Stanground for out appointment tomorrow with Tina the lock-keeper.
MP.
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I bought my licence at Gayton and worked through the Northampton Arm yesterday 17 locks is plenty for me in one day,
so I spent the night on he Nene at the mooring before lock 1.
Not sure how far i'll go today as i'd like to try and watch the F1 this weekend, but when I do get to Lower Barnwell I will let you know how it looks
I couldn't believe how much rubbish was on the Northampton Arm, Lock 17 didn't look like it had been used for months!
Update from Melaleuca: we set off from Gayton at 10am this morning, and we're moored for the night just above Cogenhoe lock. We pulled some more crap out of lock 17, and got briefly stuck in lock 16 because of stuff jammed behind the gate. We were followed down the arm by another boat, so traffic is increasing.
Cheers,
MP.
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It's been fairly dry for a while now, and I don't want to risk waiting at Gayton only for the weather to turn again,
so i think i'll head onto the Nene and just hope that Lower Barnwell Lock is working when I get there.
Go for it! I just spoke to Roy Smith the inpector. Lower Barnwell lock is now passable, but you need to use a windlass to raise the guilotine: the electrics are still broken.
I'll be setting off from Blisworth early on Sunday.
MP.
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Just to clarify here, Lower Barnwell had its welding finished and was operational. However it promptly suffered an electrical problem and broke down again. Apparently this is EON's problem and they are fixing it now.
Thanks, Chevetter. Please continue to keep us all informed.
How are river flows looking, at the moment?
Cheers,
MP.
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What about the poor Moomins? Has any one seen them?
We fought rain, snow, hail, etc, etc and made it to Blisworth by Thursday mid-afternoon. I didn't know about Barnwell lock at that point, but decided anyway to take a break. I talked to Andy Hall, the inspector for the upper Nene, who confirmed that it was open and off SSA, but still quite high, and likely to go straight up again with any significant rain. Since significant rain has not been exactly unknown recently, I decided that I didn't want to fight marginal stream conditions and marginal weather for my very first Nene trip, with the added risk of getting stuck half-way down.
Given the announcement about Barnwell, that looks like a good move. (What were the EA doing between the 20th when it was supposed to reopen and the 28th when they anounced it's still closed?)
So, Melaleuca is moored towpath side at Blisworth opposite Blisworth Tunnel Boats, That feels to me like a safe location, talking to locals seemed to confirm that, and there were at least two other private boats left unattended at the same place. Anyone who passes, please take a look and make sure it's all OK.
If Barnwell opens when EA says it might, and the weather is good this week, we may be moving again by next weekend. If we miss that, it may be towards the end of the month before we can get the people together again and time off. I'm hoping I can stretch my 14 days towpath mooring in that case.
I'll try and write up a trip report and some photos soon. (PB, WW should have something in her work email-box.) We passed "Keeping up..." going the other way in the middle of Stoke Bruerne flight
MP - who really should have had a nice meal of pine-needles and hibernated 'till spring finally arrives........
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Did you forge through the blizzard to and through Apsley on Monday? was i on the water point?
We forged through the blizard from Winkwell to the top of Marsworth on Monday, with a stop at Berkhamstead Waitrose. Compared to Sunday it was a quiet day. Sunday's highlights include several wind-related groundings catching a bow fender on a lock gate, and fishing no.2 daughter out of a lock. This will be a journey to remember!
I'm sure I remember passing Bristol and Argo, but where and when, I don'r recall, sorry.
We're now North of Leighton Buzzard and well placed to do the long Milton Keynes pound tomorrow. The Nene is off strong-stream, so we may just get there.
Posting photos by radio is being difficult, I'll do it when we get home.
When we stopped for the day the sun came out, so i appologise for any inconvienience .another Simon.
I should have padlocked you to the piling as we passed!
Cheers.
Simon.
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How much are High Line charging? Only asked coz i aint used them yet. last fill up was at Harefield back in October so im expecting a bit of an increase since then.
To be honest, I don't know. I wouldn't expect a very low price, since they don't have a passing trade to compete for.
BTW have a really good, safe trip and if you get the chance some pics of the journey would be great.Thanks, I'll get some pics, probably of NB Melaleuca forging on through a blizzard!
We're working over the easter weekend so probably wont get to see you but hope to meet up maybe on the system sometime in the futureI'm sure our paths will cross again.
Cheers
SImon.
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Travelling
in New to Boating?
Posted
Very good advice. We just brought our new boat home along some of the same route and had to take a break for a week whilst the Nene flow went down. The weather is improving now, which will help. Bad weather can slow you down a lot, as can short daylight hours. Don't forget that you will need to book passage times 24 hours in advance at Stanground and Salter's Lode, which will cost you time since you'll have to be conservative to be sure of making the booked time. Salter's Lode passage times depend on the tides and can, in extremis, involve a long wait. It's probably best to talk to the Lock-keeper sooner rather than later to get advice.
Don't assume you can do heroic amounts - two or three long days are OK, but not ten in a row.
Enjoy the trip, and the new boat.
MoominPapa.
P.S. I assume the weather is OK now. I'm currently holed up in California, but I'll be back at the end of the week to claim my newly-machined pump casing from Baldock!