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Arnot

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About Arnot

  • Birthday 14/04/1953

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  • Website URL
    http://www.narrow-boat-electrics.co.uk

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  • Gender
    Male
  • Location
    Stoke on Trent, Staffordshire, UK
  • Interests
    Narrow boat electrical systems, Audio engineering, Woodwork, Power Electronics design.
  • Occupation
    Narrow Boat Electrical Specialist
  • Boat Name
    Orianne
  • Boat Location
    Stone, Staffordshire

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  1. Hi Daniel, Hmmmm.... a steam master switch? Quite amazing considering the walk in fridge freezer, dish washer, aircon, mood lighting and jacuzzi :-) Seriously though, one reason for the longevity of your master switch is the use of a 24v system. For a given power loading this reduces the current by 50% and correspondingly the heat generated losses by 75% and its usually heat that kills master switches. Another, I suspect, is the lack of inverter. Even when switched off, when these are powered up they create a significant arc on connection. My take on master switches is to use the big metal jobbies, all the aesthetic appeal of a brick outhouse but I never remember changing one in 40 years of sorting boat electrics. For the OP, I would suggest the aforementioned metal jobbies, readily available from the swindlers especially given the 3.6kW inverter although the Mastervolt ones tend to be more gentle on connection surge. The shunt you refer to may be a master switch installed to use as an emergency link between batteries in case of unexpected failure. Not a bad idea on an offshore boat but not so relevant when you are unlikely to be stranded more than ten feet from the bank. I’ve seen these before but suspect that when needed, years of oxidisation on the internal contacts due to lack of use may mean they wouldn’t work. My suggestion to folk is to carry a spare jump lead to join battery banks in extremis. Arnot
  2. In my experience Leece Neville are the most reliable alternators on the market (with possibly one unusual and expensive exception) and I wouldn't bother carrying a spare. to back this up, I have one on my boat and don't carry a spare.... They can lose their magnetism occasionally but this isn't a problem to sort out quickly and without having to change any parts. Sometimes this even happens while they are in service. However It is possible to install a little circuit to give the alternator a nudge when you start the engine which prevents this remote possibility happening. Hope this helps... Arnot
  3. Ahh but protected from what? A boat without an earth that is isolated from an incoming supply is little different from a vehicle or any other largish conductive structure without any connected mains wiring attached to it. The incoming supply should be protected by an RCD and thus if there is any dangerous leakage current it will trip. If there isn't any RCD then connecting the hull to the incoming earth will actually increase the risk of electrocution. Any supply generated from within the electrical system of the boat should also be RCD protected and its PE would be bonded to the hull to ensure this worked. An interesting case. Actually I have an issue with the Victron isolation transformer in that it is not wired in accordance with the accepted norm as shown in post 15 and here. Instead the transformer case is connected to the outgoing PE and the incoming PE is unconnected internally. This is why they give that advice. I just think they don't wire their isolation transformers correctly. Possibly they do it because they use a toroidal transformer where it is difficult to connect to the core. A protective screen can be wound in, it just costs a bit more. Here is the internal wiring for the Victron unit.. IMHO the problem with this is that if, as is probably the most common and dangerous form of failure, the transformer windings overheat and short together, there is no path for the leakage to trip an RCD so only the overcurrent protection can prevent the incoming wiring burning out. This won't however prevent the transformer going into Chernobyl mode and even the thermal protection would be unlikely to act in time to save the day. So; that's why I don't install them... Regards Arnot
  4. I'm not sure I understand this... surely the whole idea of an isolation transformer is that it isolates. In effect the boat becomes an enclosed system, a sort of faraday cage. Any current flow has to be through this enclosed isolated system and would not interact with any external power source. There should be no need to provide any external earth given, as it should be, any outlet in the boat is protected by an RCD. Even if the boat system is used to supply power tools used on the hull or nearby, even if the boat is hooked up to a shore line at the same time, it still shouldn't need any conductive stakes or similar contrivances. All of this however presumes that it is a transformer that is used and that the PE has NOT been bridged or tampered with in any other way. I would be interested to know which if any manufacturer of isolation transformers requires PE bridging. I certainly would not recommend it and in fact would think it highly unwise. There is an argument for a galvanic isolator being bridged when a boat is lifted out and parked up but even this is both technically dubious and does not stack up in safety terms really. The galvanic isolator will increase the fault touch voltage but not significantly and given that the boat (if wired correctly) approximates to a domestic PME system in that the neutral and PE are bonded at source the PE impedance will be so low that the fault touch voltage will never get anywhere near a dangerous level under any foreseeable circumstances. My assessment is that having people mess with the wiring at all for such a fallacious justification only introduces a needless risk. Sorry if this is a bit obtuse but there isn't really a simple way of phrasing it and it needs to be said. Unfortunately there is quite a lot of misinformation surrounding the subject of protective earthing especially when it comes to boats and mobile applications albeit well meaning. A lot of this cloudy thinking and misinformation actually has sound foundations and dates from when RCD's were unusual on boats and the earthing systems in a lot of boatyards and boat builders were themselves unprotected by RCD's or RCBO's and provided by an untested spike in the ground. Of course now we have RCD's, PME earthing systems and regular inspection, test and certification of commercial installations so many of the historic precautions no longer have any relevance. So; here is my firm advice. If you have an isolation transformer or a galvanic isolator and have your boat lifted, don't mess with either of them. Attaching a spike or some such can be done but it won't improve the electrical safety apart from marginally and at the same time the introduced trip hazard will be greater so I wouldn't bother with that either. The whole idea behind the way installations are carried out now is to make them safe in normal usage regardless of any intervention. I hope (but somehow doubt) that this helps... Arnot Edited for smelling pistakes
  5. Hmm let me think about this... Being held in a stanglehold by a company who offers a better product at a lower price by investing.... Outrageous! Run by an individual who can take a decision without having to get it approved by a committee... Anarchy! And he makes money... Horrendous! Elon Musk once said of what he does that the way to make a small fortune out of it.... was to start with a large one. It would be ill mannered not to assist. Of course there is the state approved approach which is to motivate a bunch of spivs by throwing money at them and preventing any opposition. All fully regulated by a bunch of men from the Ministry. Arnot
  6. Sorry, I possibly didn't make myself clear here. In principle, current trips protect the wiring and/or equipment "downstream" of them not "upstream". It's not the shore power that is available that should be used as the marker for the transformer specification but the size of the input connector. It would obviously be impossible to use the power available for this because it would possibly change with the mooring and could not be anticipated. I am aware that there are some cheat leads out there with a 32A male leading to a 16A female. These should have some sort of current limit such as an RCBO in line but sadly rarely do. Presumably if you have a boat with a 32A inlet then someone at some stage installed this for a good reason. It may be that there was no good reason or that the reason has disappeared. If that's the case, after suitable examination and test, either a large transformer should be used or the inlet should be changed. Technically of course you are correct but another consideration is safety. Not just that of the person who installed it and (possibly) understood the risk but of all those who use the installation and work on it subsequently who are unaware of the risk taken on their behalf. If a smaller transformer is used, hidden in a cupboard or under a swim, someone at a later stage may want more current than the limiting protection device will pass, realising that the cable is good for it and not realising why the apparently undersized breaker was used, change it. In this case, the transformer will tend to generate a lot of heat and constantly trip the thermal protection but these are not designed for repetitive operation and will soon fail. I suppose that in the final analysis, if the job's worth doing, it's worth doing properly... Regards Arnot
  7. Actually I respectfully disagree... an Ah counting gauge is absolutely accurate (if that's what you meant). It's just that this won't give you any idea of how much of your available power you have used up. It knows how much power you have used with absolute precision, it just doesn't know how much you started with. It is true that the SOC indication on the popular Ah indicating instruments does not take into account the degradation of the battery and the inevitable loss of capacity. However, the Smartgauge doesn't know if the battery is on charge or being discharged. Ultimately, any SOC indication will have to be a finger in the wind. It has to make a lot of assumptions in one respect or another. I think that we need to be aware that there is no universal panacea for electrical power storage indication, all of them are just an indication not a calibrated measurement. My thoughts (and suggestions to my customers) are that for the technically challenged or those who just don't want to have to think about it, a Smartgauge is a good call. It will give an intuitive snapshot of the battery state that is good enough to base decisions on. I believe it was originally developed for use in active service military vehicles and I can speak from experience that peering at a miniscule gauge and doing mental calculations is not a good idea when someone is trying to kill you... The downside is that the information it provides is limited. On the other hand, if you are technically minded units such as the Victron BMV700 provide a lot more information, some of which cannot be gained or even inferred from a Smartgauge. One very useful part is to be able to accurately monitor the current flow to or from the battery. This in conjunction with the voltage can give very valuable insight into the condition of the charging system and battery condition. Another useful feature (from an engineers perspective) is the facility it has to store historical high and low points. This allows me as said engineer to gain valuable information about the battery and charging systems on a boat that I have never seen before or not seen for a long time and thus come to a faster and more accurate diagnosis of a problem. I guess the ideal is to have both. A BMV700 (or 702) somewhere near the engine or instrumentation and a Smartgauge easily seen in the cabin, probably somewhere near the galley. Does this help? Arnot
  8. There are a few things to consider... 1) The power rating of the transformer should not be less than the power rating for the incoming connector. So; as in the majority of cases the inlet is 16A, 16 x 230 = 3680W or as near as you can get. Any smaller and it could get unintentionally overloaded and in addition will tend to be less efficient. 2) You need to consider how much power you will use for extended periods when attached to a shore line. For those who use incoming power for heating the water, ironing, kettle boiling and other such loads then an air cooled unit would probably be best. So why? Well, the transformers in sealed cases (IP 67) whilst being good at surviving being located in a damp and cold environment such as on a swim, because of the encapsulation tend to lack cooling ability and overheat. Remember this sort of casing was intended for site work tools and these don't stress the transformer for long, are located where they can be easily seen (that's why they are yellow) and the loads they serve tend to be intermittent. Conversely, the air cooled units (IP23 metal case) whilst handling higher extended loads better because of their cooling ability are prone to damage from damp. These really need to be located inside the cabin in a cupboard or some such warm and dry location. 3) It is important to have some sort of thermal overload cut off switch located inside the windings of the transformer and it is very sensible to be able to replace this if it fails (as they sometimes do). If the transformer starts to overheat, the heat is generated deep inside the windings (or at least the temperature rise is greatest) and if there is no thermal protection then the overheating fast becomes very dangerous. 4) Transformers usually generate some mains hum at 50Hz and this can become annoying if it has been located under a bed or near where you are likely to be enjoying peace and quiet. Also, since they operate on the basis of a cyclical magnetic field, any magnetic conductive item in the vicinity may well vibrate as well. So; it's best to locate them somewhere where they are not likely to be surrounded by clutter. 5) For the purposes of fault finding and diagnosis it is a good idea for them to be installed with male/female BS4343 ( blue three pin) connectors on the inlet and outlet arranged to that they can be temporarily bypassed. 6) As previously mentioned, they can and usually do generate a bit of heat if under load so it is essential that they are located in a space that has some ventilation and not tucked up in spare bedding, wet weather gear, towels, upholstery etc. etc. So it's not as simple as it seems but then electrickery never was... Hope this helps Arnot
  9. Just as a matter of interest, if you are (interested) that is... Have a search for Vanadium Redox Flow Battery. Now this is the future! I guess what Elon Musk has done with the Powerwall battery isn't all that radical, especially if you are a boat owner or an "off gridder". But, and it's a massive BUT, he has my absolute admiration and respect for not only making it happen but doing it without a lot of government market support and at what is quite a reasonable price for the technology and quality. I don't notice the corporate world queuing up to introduce new technology to the general benefit of the human race. Unless they can get a commercial stranglehold on it or keep to the ephemeral benefit products, they are noticeable by their absence. Rantette over.... :-) Arnot
  10. Correct, the non electrical savvy can't really check a GI, it requires some good instrumentation and understanding of how they work. However, there are some that have a test facility built in. My thoughts however are that an isolating transformer is a more reliable and safer option if you can afford the extra. If it was my boat, I'd have one but there's no real application in a 72' skip (working boat). An isolation transformer is not a simple replacement for a GI and despite being a bit biased here, I really do suggest it is a professional installation job. A GI just interrupts the earth bond, an isolation transformer interrupts the entire mains inlet and has to be installed carefully to avoid problems. Hope this helps... Arnot
  11. Another possibility given the comment about it seeming to flatten the battery is that the field windings have internally short circuited to the casing of the motor. The symptoms of this are much as you describe in terms of the power drain and lack of drive. This probably won't explain the one direction thing though... The way to find out is to dismantle the motor and test the insulation of the field coils. The good news is that this is usually easy to sort out given the skill and equipment. It doesn't involve hard to get parts, just some paint, cotton tape and varnish. It is however one of those old fashioned skills that seem to be dying out, it's probably best to find an old fashioned auto electrician to have a look at it. Hope this helps Arnot
  12. Welcome and I hope it all works well for you. It's a lovely life on a boat but it is a paradigm shift and a sharp learning curve... I will offer my advice, based on my experience and I'm sure you will have lots more, some contradictory. But - it's all well meant and constructive. Windows - I have only done this a couple of times and it's not a nice job. The neoprene seals tend to be proprietary and can be a problem to get unless you know who made the windows. What I did discover was that the seals tend not to deteriorate too much despite the appearance and I had some success by cleaning them in a warm weak bleach and detergent solution followed with some thinners to remove historic over painting. Getting the frames out is a pane, they will probably have been fixed in place with sealant and then screwd tight, even when you get the screws out the frame will still be stuck fast. It's best to try to remove the screws with an impact screwdriver, at least to loosen them. If you do break one or round it off, use a cobalt drill (carefully)to get it out, a normal drill will not fare well on stainless. My way of removing the frames was to arm myself with a range of slim wooden wedges and one of those old bone handled table knives a bit like a pallet knife, suitably sharpened. Then I slid it between the frame and the hull and cut away at the sealant. Slowly, with care, it started to move and when this happened I inserted a wedge to keep the "pull" on. Eventually they did come out but it took time. Ammeter/voltmeter - I would recommend the Victron BMV 700, I have used these for years, installed countless numbers of them and they give you all the information you could desire and more. Better yet, they can be used for an audible warning and retain a history of the limits which can be invaluable in diagnosing problems. Any voltmeter needs to be wired directly to the battery (with appropriate fusing) to give an accurate reading, tagging onto internal wiring will not give readings that can be relied on. Installing the BMV 700 is quite easy and the cat5 lead used to connect the display to the shunt can easily be extended if required and won't compromise the accuracy. Gas Locker - these are traditionally rusty but it's best not to let it get out of control. Cleaning it out is just hard and dirty work. My suggestion would be to clean the worst off and then treat it with Owatrol CIP. This is an anti corrosive paint intended for use on rusty and pitted steelwork. As long as you make sure the surface is good and dry it will seep into the porosity and give you a sound substrate for any paint you use as a top coat if you want to. My experience is that hammerite doesn't work so well in the long term on damp pitted steel but on my boat, difficult areas that I painted with CIP six years ago are still sound. On the matter of ballast, I wouldn't rush into this until you have moved in and got settled as long as the trim isn't atrocious. Then, try to collect steel, it's density is far greater than concrete or cement. Kitchen and Bathroom Fans - yes I have done this, no it's not difficult and yes it is effective. I tend to use a low noise 80mm ball bearing fan made by Papst. Difficult to get hold of but usually available on fleabay. Get the lowest noise ones you can, the cheapies sound like a mosquito on steroids. Hope this helps... Arnot
  13. I take your point about lead calcium batteries and agree. However in practice unless well maintained (when they do very good service) sealed wet batteries do have their issues. The problem is that the electrolyte can't be checked apart from the little magic eye thing on the top. And this is difficult to see on a lot of boats where the batteries are tucked in the side if the engine well under the deck. So; often if there is a problem with the charging, the first indication comes with a bill for new batteries as well. And, as you mention, they do tend to prefer a slightly higher voltage to achieve full charge. No I'm not basing my advice on batteries of yore but it's also true that I'm not basing it on calcium batteries. Maybe I'm unusual in this respect but a lot of boats I work on have traction cells and semi traction blocks which are both lead antimony. Actually a lot of my experience in batteries is on very modern cells. In fact there is one type that gives significant improvements in CCA that hasn't even hit the market yet as far as I know. Ever seen a 24Ah battery with a 1200A output? Regards Arnot
  14. Unfortunately we still don't seem to know how far away from the battery this fridge is or what thickness the cable is so any comment on this must be guesswork. However, the symptoms do seem to point to problems in the supply side. Just a couple of ideas based on my experiences with fussy fridges... One is to check the fuse for the fridge. Sometimes with age and damp, the connections at the ends of the fuse increase their resistance. This is difficult to check without good instrumentation, knowledge and experience but the good news is that it is easy and cheap to eliminate as a possibility. Just change the fuse... Of course it's not so easy if you have circuit breakers, these are popular but can cause problems such as this. Another is a bit more obscure. I note the use of a solar controller and suspect it is a PWM type. In a few instances I have seen these slowly reduce the electrolyte levels in the battery to a point where the capacity falls significantly. Have you checked your battery levels? If they are very low, this will cause the voltage to sag prematurely and cause the problem you report. If this has occurred then consider replacing the controller with something like the Victron blue power mppt unit. I have cured this problem by fitting this unit three times and at the same time got a useful increase in the solar panel charge rate. Hope this helps... Arnot
  15. It was indeed the norm. But, things have changed since then, RCD's have become more reliable and a whole lot cheaper. And - we have a generation of boaters who expect to be able to plug a toaster in, and why not? The concept of earthing the hull is to ensure that an RCD operates at the earliest possible moment, ideally before the fault voltage or current becomes high enough to initiate combustion or death. If the hull were to be insulated from the mains electrical system, then if a short circuit between the "live" conductor and the hull would not necessarily trip the RCD and prevent the hull from becoming live. Of course, at sea this is a redundant concept but when moored and connected to shore power, if someone were to board or disembark a faulty boat and accidentally touch both the hull and any shore connected metallic device at the same time, they would get a sharp belt. In the case of bigger ships, they can generate sufficient power to be self sufficient and so rarely if ever connect to shore power. But - in the case of smaller craft, pleasure craft and particularly narrow boats, a connection to shore power is commonplace. The risks are somewhat mitigated by using a correctly configured isolation transformer but even then, the extra safety provided by bonding the neutral to the hull as an earth point is significant, whereas the cost of the bit of wire, a terminal and a bolt is not. The real downside of course is that if the mains supply to the boat is problematic and no isolation transformer is used, it can lead to hull erosion and pitting. Oh and BTW, I'm no "expert", I'm old enough to remember Blaster Bates... Hi Tim! Regards Arnot
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