nicknorman
-
Posts
23,687 -
Joined
-
Last visited
-
Days Won
120
Content Type
Profiles
Forums
Events
Gallery
Blogs
Store
Posts posted by nicknorman
-
-
6 minutes ago, Arthur Marshall said:
There's no stopcock on mine, the outlet goes straight to the pump. I can see a modification coming...
I would suggest waiting until the tank is empty before cutting into the pipe. -
1 hour ago, Chris Watkeys said:
Thanks Nick - I might be able to access it from inside the cabin, will check when I get back to the boat.
On a separate note the plastic screw-on water filter attached to the pump (shurflo) had also cracked and fallen off but I'm pretty sure this wasn't the cause of all the water ending up in the cabin bilge (rather than an issue with the water tank which is my current theory), as I had turned off the power to the pump before leaving the boat for a couple of weeks.
The plastic filter is on the inlet to the pump, so if you didn’t turn off the water stopcock then when the filter cracked, all the water will come out of the tank.
For future reference, what I do on leaving the boat is to turn off the gate valve at the tank exit, then disconnect the pump inlet. I then run the pump (which sucks in air) and open the taps to push out as much water as possible. Because the lower you are in an unheated boat in winter the warmer it is (because the canal bottom never gets that cold) any water lying in the pipes at the bottom of the boat is unlikely to freeze badly and conversely things higher up eg shower hoses and valves are more prone to freezing. So I always disconnect the shower hose from the taps and drain it, push air through the shower valve etc.. -
Can you access the point where the pipe leaves the tank going to the pump? I would have thought that was a more likely source of leak. Could be wrong of course!
-
It’s worth mentioning that the top of the flue should be able to slide a bit in the deck collar as otherwise thermal expansion of the flue will put a big force on the top of the stove and maybe crack it. Also note in the envirograf instructions, no flame to be playing directly on to it. So you use glass stove rope to pack the bottom of the flue pipe / stove interface. The silicone goes on top of that to seal and look tidy.
-
1
-
-
It’s basically fire cement vs high temperature silicone. A lot of people use fire cement but IMO it only lasts a year then it cracks. It is terrible stuff!
I use high temperature silicone which lasts as new until for some reason you need to remove the flue. Ie probably 10 years. This stuff. https://www.ebay.co.uk/itm/251723362373
The only people who prefer fire cement are people who have never tried the envirograf silicone
-
5 minutes ago, Jen-in-Wellies said:
A cooking detector. I've found optical detectors to be less sensitive to carbonised bread than other types.
In house world you don't have a smoke detector in the kitchen, you have a heat detector. Trouble with narrowboats is that kitchen and living space tend to be one and the same.
-
1
-
-
8 minutes ago, MtB said:
This, and bits of other posts in this thread reflects the tendency of the amateur to assume gas work is all about the pipes and avoiding leaks. It isn't.
Fitting pipework without leaks is so easy it is taken as read that anyone attempting their own gas work will manage this successfully.
Almost all gas training focusses on everything except how to make pipe joints. Pipe sizing calculations, ventilation requirements, regulator sizing, appropriate pipework materials in the various situations, pipework fixing and bracketing, tightness testing, purging, working and static pressures, permissible lengths of flexible pipe, ventilation, flue performance, flame supervision, combustion analysis etc are all subjects taught in minute detail plus a lot more I haven't thought of composing this post. Few of these are even mentioned in the most basic (and slack) BSC rules.
You didn’t explicitly say it so I’m going to: many of the above topics are different within the confines of a narrow boat vs a house, which is why there is a separate ticket for marine lpg-
1
-
-
2 hours ago, blackrose said:
No I just repeated the procedure of switching to shore power on the rotary switch every time until it didn't trip. So I'd switch the rotary switch back to off or inverter reset the RCD in the shed and then turn the rotary switch back to shore power.
Ah OK thanks for the clarification. Back to plan A!
31 minutes ago, IanD said:As pointed out earlier, if you're connected to the grid (or even more than one AC source/generator connected together) you can't have any frequency difference, they must be locked together.
If there's a (small) amplitude difference then this changes the output power split between them (e.g. not 50:50 for two identical sources), if there's a (small) phase difference then you get a (possibly large) reactive current flowing between them, one leading and one lagging.
I've thought more about it and I think you are right. Put that on your mantlepiece!😱
-
2 minutes ago, IanD said:
There's very little that one hydro station connected to the grid can do though, the mains frequency error is controlled by the central grid control turning power generation/pumped storage up and down nationwide.
Depending on load the accumulated error before the corrections catch up is routinely up to several tens of seconds, and is worst in periods of heavy power use in winter when it could be over a minute -- here's some data from one month in summer 2012, which was before much renewable energy was around so more rotational inertia than today... 😉
https://www.electric-clocks.co.uk/Technical/synchronouselect.html
I was thinking that as I typed. So I guess it must have been a nationwide thing assuming Scotland and Englandshire’s grids were connected back in the 1970s. But they did have the clock and he did talk about the cumulative time error.
-
1 hour ago, David Mack said:
This reminds me of a possibly apocryphal story told to me as a student by my then elderly electrical machines lecturer.
In the early days of municipal electricity supplies, a small town had its own generating station. But as demand had increased the supply was supplemented by a connection from the nearby city, with its much greater generating capacity. When the town's demand exceeded the local capacity, the town station operator would connect to the city supply. This required him to match the frequency and phase of the town station with that of the incoming supply. To to this there was a differencing meter on the wall of the control room, which had a large circular dial and a hand which rotated at a speed determined by the difference in frequency of the two supplies, and its position reflecting the phase difference. The operator had to adjust the town generating station until the hand on the meter was stationary at the 12 o'clock position, then he could close the connecting switch, and thereafter the town station would automatically lock to the frequency of the much larger city supply.
Unfortunately, in the style of dial instruments of the time, the differencing meter hand had a quite significant 'tail' on the opposite side of the central spindle, the operator was getting on in years and his eyesight wasn't as good as it had been, and the control room wasn't brightly lit. And so one one occasion he brought the hand to a stationary 6 o'clock position, then threw the switch. The resulting rapid acceleration of the town generator's rotor sent most of the turbine blades out through the turbine casing!
A friend of mine worked in one of the hydroelectric control rooms in the Scottish Highlands and gave me the tour. Turbine machines would be taken on and off line according to demand and it had exactly the phase meters that you describe. The other thing it had was a domestic mains clock - driven by a synchronous motor which was normal at the time. As the load varied the frequency would change slightly and they would compare the synchronous clock to real time. I think the allowed short term error was quite big (as in a few seconds) but of course the long term error had to be zero,51 minutes ago, IanD said:A non-apocryphal story -- because I was there when it happened! --
Of course you were there! After all you had just invented electricity and designed the research lab!1 hour ago, IanD said:Sorry Nick but I'm going to disagree here -- assuming all the waveforms are sinewaves and the load is resistive, all the voltages and currents are in phase with each other. If they weren't you'd just get reactive currents flowing from one to the other, for example between inverter and incoming mains, which just increases losses but does nothing to frequency since the mains is effectively immovable. It's definitely *not* about "pushing the phase", this is something you absolutely do not want in this application.
Nothing is zero impedance, either mains source or inverter output, so the currents flowing from each depend on the source impedance and the open-circuit voltages of each. If the load draws no current and both mains and inverter are the same (open-circuit) voltage no current will flow when you connect them together, but when you draw a load current it will split between the two according to their source impedances -- for example if the inverter impedance is double the mains it will only provide one third of the current, not half (or vice versa). To change this (e.g. more current from inverter to share equally) the inverter has to change the open-circuit voltage it generates, for example by increasing it slightly (Kirchoffs and Ohms Laws). It *doesn't* change or lull phase to do this, unless impedances are reactive -- which they probably will be, but that's a different kettle of fish...
This is why it's so difficult to get a system like this working, because the currents flowing depend not just on the voltages but also source and load impedances -- and these are also unlikely to be resistive (including shoreline and battery, when cabling is included) so phase shift comes into it too. The inverter has to continuously measure the magnitude and phase angle of the current it's providing as well as the magnitude of the incoming voltage, and change the amplitude and phase of the waveform it generates internally to provide the required amount of current -- usually while also trying to minimise reactive power (keeping output current in phase with output voltage) since this increases inverter losses.
So in one post you said same voltage, in another you said different voltage. Which post was wrong? -
1 hour ago, IanD said:
Exactly -- in this case "pushing harder" means trying to generate a slightly higher voltage than the other one, or pushing in more current. What it *isn't* doing is trying to push the phase forward (which *is* what you said...), this is what power-station generators do to try and push the grid frequency back up if it drops (by effectively adding reactive power), but good luck trying to do that with an inverter... 😉
Either way it all looks a bit like magic viewed from the outside, and even on the inside the control algorithms needed to make this work reliably are pretty complicated, especially with different grid (or even more so generator) and load conditions -- Victron seem to make it work pretty well, others not so much or don't even try.
No it definitely isn't trying to generate a slightly higher voltage, it is as I said all about pushing the phase. The phase doesn't actually change significantly of course. You nearly touched on it when you originally said "What it actually does is to try generate the same voltage* and phase as the incoming mains but also dump in-phase current into the load to generate power. "
* make your mind up, either the same voltage or, as you said later, a slightly higher voltage.
It is the dumping of in phase current as you say. But that is done not by increasing the peak voltage, but by adding the current slightly ahead of the phase - what I would call pushing the phase. It is of course "in phase" because the phase is the summation of the shore power and the inverter power, and with the low circuit resitances only the tiniest of phase differences is needed to radically alter the balance of currents.
-
1 hour ago, IanD said:
What Nick said isn't correct either -- if the "power assist" generated the same AC voltage but with a leading phase the current would be maximum near the zero-crossings (biggest voltage difference) and minimum near the peaks (smallest voltage difference). What it actually does is to try generate the same voltage and phase as the incoming mains but also dump in-phase current into the load to generate power.
But it won't close the relay which connects the inverter to the output until the waveform it's generating closely matches the input waveform (frequency, phase and amplitude).
Once this is done it continually monitors both voltage and current -- input and output current -- and dumps enough current in to stop the shoreline current exceeding the limit that is set. For example if the shoreline limit is set to 16A and the load demands 25A, the inverter will add 9A boost current (by discharging the batteries). If the load them drops to 16A or below the inverter will stop doing power assist.
This is just another way of saying what I said. The voltage and phase of both sources is the same when they are connected together (has to be, otherwise it doesn't make sense, in the same way that 2 batteries in parallel have to have the same voltage (local tiny resistive losses excepted), however if one source tries to "push" the phase ahead of the other source, this requires a lot of current to advance the phase of the whole system by a very small amount and the current from the other source will decrease. I don't know if you have ever played with parallelled 3 phase ac generator machines but it is the same idea. If you put more torque on one, the torque required on the other decreases (to maintain constant frequency) - and of course they are phase locked by the electromagnetics.
1 hour ago, Tacet said:As one of those people who don't understand, I'll risk a genuine question.
If the combi supply phase is advanced ahead of the shore power, is it not at a greater voltage at some particular instants? I.e as the voltage is rising from 0v. And, if you like, at a greater negative at others. i.e. falling from 0v.
The next question could be something about what the combi does when the shore power is rising from its lowest value but not yet yet reached 0v.
That's not quite what I said! I said "tries to advance" but since everything is connected in parallel, the actual phase of both sources must be the same. But one might be "pushing harder" and thus supplying more current.
Obviously one scenario is where the inverter is not contributing at all, and yet at the terminals there is still the 240vac 50Hz or whatever, but no current is flowing in/out of the inverter. And then the inverter can start "pushing" by adding current. The current only flows because the desired phase of the inverter circuitry is slightly ahead of that of the shore power. Ultimately it could push hard enough that the current from the shore falls to zero, even though there is of course still 240v or whatever at the shore bollard.
Another analogy is a tandem bicycle. Both sets of pedals are rotating at the same speed and same phase (instantaneous rotational position), but one person might be pushing harder and one less hard.
-
22 hours ago, blackrose said:
I think you're right Nick. I haven't actually changed the RCD yet, just tested the existing one a few more times without "live switching" and it's fine. I guess my manual changeover switch isn't actually designed for live switching. As a friend of mine just explained, there's only got to be a 30ms difference between when the L & N contacts connect and the RCD will sense the imbalance and trip, and that probably depends to some extent on the speed I manually rotate the switch.
In future I'll just switch the inverter off and change the switch to "generator" before starting the generator, wait 10 secs for the generator voltage to stabilise and then set the RCD to connect to the boat.
I've been thinking about this a bit more. So previously, you started the generator then turned the switch to shore power, the RCD tripped. Then you reset the RCD - several times - and eventually it worked and continued to do so. But of course after the first trip of the RCD, the changeover action of the switch is not relevant because it was already set to shore power (I presume?). This makes me think it is more likely to be a leak to earth somewhere between the RCD and the switch (cable, shore plug/socket, wiring to switch etc). What could be happening is that the current leaking through whatever the source of the leak is (damp leaf, spider, general damp gunge etc) to earth has a slight heating effect on whatever the source of the leak is, which dries it out a bit so that after a few moments of current flowing, it becomes too dry to conduct the 30mA required to trip the breaker.
It would be interesting to consider if there is any correlation between the propensity to trip, and the relative humidity of the air. And also whether there is any correlation between propensity to trip and whatever else is plugged in (battery chargers and any other ac consumers in the boat). If you can identify that it only trips when x device is plugged in, there is your problem. Of course the tripping might well not be down to just one thing, there might be several sources of slight leakage which add up to the 30mA required to trip the RCD.
-
1
-
-
4 minutes ago, blackrose said:
But I can only see two live and two neutral wires? There may be 3 of each but access is difficult without actually disconnecting wires.
I asked that question on the forum a few years ago and everyone seemed to think it was fine as long as it was breaking the connections before making them. I accept what you're saying now but when I asked the question previously I got a different answer.
To some extent it depends on the nature of what is being supplied. If it is a resistive load eg a heater or kettle, then a phase jump is not an issue. But if it has a transformer or motor it’s another matter. People don’t understand how ac works, for example if you ask people how a Combi Inverter supplements incoming shore power in “power assist” mode, they will tell you that, well, I guess it supplies the ac at a slightly higher voltage than the shore power or something…. Which is of course total BS! The inverter will supplement the shore power by supplying at the same voltage but trying to advance the phase of its supply vs the shore supply’s phase. Phase is king when it comes to ac systems!Anyway, let us know the outcome of starting the genny with the ac selector switch already set to that way and inverter already off. It will prove or disprove the point.
1 minute ago, MoominPapa said:If the neutral-earth bond in the inverter is active when you're using the generator, then that's most likely the source of your trips. There's an alternative route for neutral current from the boat neutral to the generator neutral which doesn't pass through the RCD. It goes neutral->boat bond->earth cable->generator bond->generator neutral.
MP.
Not if it is a double pole break before make, which apparently it is. The Inverter neutral is not connected to anything when the switch is set to shore power. And assuming the NE bond is the inverter side of the switch, which it must be otherwise the RCD would be tripping all the time.-
1
-
-
Switching near-instantly from an ac source at a certain phase, to a different ac source at a random and different phase, is quite a brutal thing to do. Although I can’t immediately see why it would trip the RCD, I would suggest the following test: switch off the inverter first, then changeover the switch, then start the generator. This eliminates the transient “shock” of a near instantaneous major phase change.
If that trips the breaker then there is an earth leakage fault but if it doesn’t, then I think the issue is the inadvisability of nearly instantly changing to a supply of different phase.
As background, a Combi inverter charger can instantly switch between say shore power and, when shore power is unplugged, inverter power. But the inverter circuitry has been “tracking” the phase and frequency of the shore power so that when it suddenly needs to supply power the phase and frequency are matched for a seamless transition.
The same applies in reverse (shore power suddenly plugged in, inverter no longer needed) - there is a few seconds delay before the switchover happens whilst the inverter adjusts its frequency and phase to match the shore power, again resulting in a seamless transition.
-
2
-
-
1 hour ago, blackrose said:
I thought the shunt counted elections going in and out? I guess it can't count both ways at the same time.
It doesn't really matter, I don't really need to know that badly, I just wondered why the MPPT gave that info but the battery monitor didn't. It just seemed odd. Anyway, no problem, I'm not installing more kit to find out.
I can't count both ways at the same time because the electrons aren't going both ways at the same time! Electrons coming from the solar will split, some will go into the battery and some will not go near the battery, instead being diverted to run the boat services (fridge etc). You can't expect the battery or the battery shunt to know about electrons that don't visit it!
The MPPT gives the value because all the electrons generated by the MPPT leave the MPPT, and that is all it knows about. It doesn't care where they go. Similarly you could have a monitor to count all the electrons coming from the engine alternator, one for the electrons coming from the generator/battery charger etc etc. But as you say, it is probably not worth the hassle!
-
1
-
-
3 minutes ago, cheesegas said:
The heater in a washing machine is either on or off - filling with hot water might reduce the time the element is on for, but it'll still draw its rated power. If that's too much for the inverter it'll still trip.
I disagree. If you select a 40C wash and fill with water at 45C, the heater will never kick in.-
1
-
-
1 hour ago, SandyD said:
Hi, we are thinking of getting an automatic washer for the boat, we already have a little twin tub machine that has served very well this year but it takes up a lot of room in the bathroom, so we would like to get one that can be plumbed in rather than being filled and emptied in the shower.
Ideally we would like one that would fit in the bottom of a cupboard (52cm wide, 45cm deep) and run off our 1600w victron inverter (yes I understand that some machines don't like inverters and that mine may be underpowered). A few have been mentioned on this forum and I have searched them out on the internet but I can't find one for sale, can anyone reccomend anywhere to look for a new one?
Thanks
Unforunately I think the two compact makes Candy and Zanussi are no longer made, and like you I am struggling to find an alternative.
-
10 hours ago, Gybe Ho said:
I am buying too many alkaline AA batteries to keep electric candles and Christmas lights running.
After some Amazon research I was all set to order NiMH rechargeables until I found a review warning their nominal 1.2 volt technology means electric candles run a little dull, even with freshly recharged NiMH AAs, compared to regular 1.5v alkalines.
This led me onto the niche sector of AA batteries, namely 1.5v lithium rechargeables. None of the big names do lithium AAs, what is the reason?
Does any forum member happily coexist with 1.5v rechargable lithium AAs onboard?
There is no such thing as a 1.5v rechargeable lithium cell, the chemistry can’t do it. The 1.5v AA batteries have 3.6v Li cells and boost/buck/bms circuit to convert between the cell voltage and the 1.5v output and give the usual protections. Probably the major manufacturers think this is too difficult and unreliable.
As to whether safe, you are into the area of exploding lithium polymer cells. Probably ok if the electronics hold up and you use the purpose designed charger, but I would want to charge them outside the boat.-
1
-
-
37 minutes ago, Phoenix_V said:
which mats did you use?
Can’t remember exactly, but it was something along the lines of thishttps://www.amazon.co.uk/heating-foil-130Watt-underfloor-laminate/dp/B07DL1Y79M
-
2
-
-
17 minutes ago, magnetman said:
Google search suggests it may work at 0.5C or more. Maybe 1C. So perhaps more of an option for smaller batteries. Pulling 550A would need some serious wiring but on a 100Ah battery 100A would be doable.
it would be easier and less Ah-consuming to place heating mats under the battery, like wot I did. Plus a bit of insulation so the heating doesn’t disappear downwards.-
1
-
-
Yes it’s funny how seeing a windlass left on the spindle of a raised paddle makes one cringe! I did notice the volockie removed it when the presenter walked away to talk to the other person.
-
22 minutes ago, blackrose said:
Does anyone know whether you can see when the heater is activated on Fogstar drift batteries?
Battery temp is around 4.2C this morning and the solar panels are just kicking in with a 0.1A charge, but when I look in the Battery protect history on the Fogstar app there is no low temp charging or discharging shown.
Does the temperature have to go a bit lower before the heaters activate and would I see the discharge on the Fogstar app? I guess I wouldn't see that on my battery monitor as it doesn't go through the shunt.
It's supposed to be 0C outside so is the higher 4C battery temp coming from the internal chemical reactions or is it because the batteries are sitting just above the swim? It's supposed to be getting down to -3C tonight and -5 tomorrow night so it will be interesting to see what happens.
I think the heater is only enabled at 0C. In any case, it doesn’t use current from the battery, it only uses charging current coming eg from the solar. So you would for example see a few amps charge from the solar controller or shunt, but no charge current on the BMS. It diverts any available charge current to the heaters, until the battery is a few degrees above zero.The battery is warmer than outside due to the canal water. Even when the surface of the canal is zero, the steel hull which is fairly heat-conductive, can transfer some heat up from the water at the bottom of the hull which will be warmer, plus some heat transferred from the living quarters.
-
12 minutes ago, Arthur Marshall said:
As far as I recall, there's no restriction at all on the wide itself or there wasn't last time I was there.
Well, there is the usual 14 days. But no short term restrictions.
-
1
-
Inline RCD tripping
in Boat Equipment
Posted
There are some in line RCD devices that need power to stay on. You say “non-latching in-line RCD” which implies it’s not one of those, but I struggle to see how an RCD can trip when there is no current flowing through it. You do mention starting the genny and then setting the RCD. Can you set the RCD to on and THEN start the genny? If not I suggest that the inline RCD needs power to remain set to on. In which case not surprising that it trips off again when power is removed (generator turned off).