mains The Mains Electrical Thread

[Vaughan]

46 minutes ago, TheQ said:

 

If you follow the American system shown by BroadScot links (Projectzen), then Mains earth and DC Low are connected together.

 

They also suggest (can't remember the paragraph) that there is a risk of electric shock from an inverter installed in this way, in a boat.

49 minutes ago, TheQ said:

I would have liked to keep my Starter battery totally separate from the drive system, but as the Panda-Fischer is a quiet boxed unit, there is absolutely no provision for a separate alternator nor anywhere to fit one. it is a most peculiar omission by Panda -Fischer

Excuse me, I had forgotten that you mentioned your boat is electric powered. This opens a new can of worms! Are you talking of a pure electric drive, in which case you must be re-charging from the shore in some way, or is your boat diesel-electric, so that you have an engine driving a generator (in the literal sense of the word) which is charging batteries, to drive the propulsion motor?

In the latter case I can't see that keeping the starter battery of the diesel separate, is a problem. You would not need a 2nd alternator but you can separate the charge with a diode splitter, split-charge relay or preferably an electronic splitter called X SPLIT, also available from Peachment.

I don't know what installation you have so perhaps, tell us more?

 

[Bound2Please]

4 minutes ago, Vaughan said:

1 hour ago, TheQ said:

 

If you follow the American system shown by BroadScot links (Projectzen), then Mains earth and DC Low are connected together.

 

They also suggest (can't remember the paragraph) that there is a risk of electric shock from an inverter installed in this way, in a boat.

The neg on the batteries is a return not an earth so why the hell would you put a 24v ac earth onto a 12v dc return?

Charlie

 

[grendel]

one earth fault and your 12v system is at 240V yuk.

 

[Vaughan]

Sorry Charlie, I don't understand that one.

When I said "they also suggest" I meant what they say elsewhere in the article. I think we are at cross purposes.

[grendel]

I am also still trying to find out what the socket earth pin is connected to in the inverter (if anything). I can see myself pulling one apart at this rate just to see.

[Bound2Please]

1 hour ago, Vaughan said:

I agree that the panel shown in my last post appears to have a mechanical slide arrangement to effect the blocking of one circuit from another. A bit like the blocking of signals on a railway, if you like.

The blocking of signals on the railway on a mechanical frame is done with mechanical interlocking, a hybrid frame by a mixture of mechanical and electrical interlocking. A power box is done by just electrical interlocking. The principle as vaughan says is similar. Its what make the railway signaling system fail safe. UNLESS a circuit goes down to earth as to earth failures can give a wrong side failure.... So in certain circumstances earths are bad taboo.... But on a boat on 240v ac a dam must.... I cant stil;l get my head around the earthing of an inverter.

Charlie

[Vaughan]

Well I'm off to bed folks, to dream of electronic charge splitters.

Actually I hope it will be Olympic lady dressage riders, in their jodhpurs.

Talk to you tomorrow, no doubt!

[BroadScot]

Not to put a negative spin with positive thoughts, I haven't an earth ly what this thread will reveal tomorrow! All very interesting though.

Iain

[LondonRascal]

Thanks for the replies to the point I posed amount supplemented power from a generator if the mains fed supply from shore was unable to provide enough current. 

Not all Marina's have 32amp supplies which was why I wondered what one could do in such an example, basically not much - get a larger generator.

As to air conditioning, In my model I would certainly not be using any of the units built for marine applications.  They cost a fortune because they are relatively small, but also further require a raw water circuit to remove waste heat in the absence of a condenser so that means holes in the hull, pipes to scale up and filters to keep checking to ensure the system works.

Far easier to have a commercial split system where the outside condenser unit would effectively be housed in a custom moulded, louvered GRP enclosure on a reinforced 'swim platform'.  It would then chill coolant to be fed through the boat to cabin matrix units - or a central air handler where the chilled air is fed throughout the boat. In winter the system would reverse and provide heat using a heat pump, that that is one of the most efficient ways of getting heat energy from electrical energy verses other electrical powered heating systems.

Because the entire set up is not a specialist marine system any repairs or servicing can be carried out by any contractor used to commercial installations with easy to source off the shelf parts.

[TheQ]

9 hours ago, Bound2Please said:

 

"They also suggest (can't remember the paragraph) that there is a risk of electric shock from an inverter installed in this way, in a boat.

The neg on the batteries is a return not an earth so why the hell would you put a 24v ac earth onto a 12v dc return?

Charlie"

Actually on many boats 12DC negative IS an earth , because 12DV is connected to the Engine Block / Starter motor, which is connected to a sacrificial Anode attached to the hull in the water, That gives you earth on the Negative DC line.

 I'm not saying that is the best way of finding earth,  just that some authorities such as the USA one shown demand that all negative DC and AC earths are bonded together.

This Is not uncommon on land based systems, I have worked on many equipments , where Negative DC of 5V ,12V, 24V or more, is bonded to the same earth as ACV. I've also suffered from the odd shock when it failed as well..

[TheQ]

Vaughan,

My Motor boat has a 10KW 3 phase electric motor, this comes from a Box of tricks that converts the 48VDC of the battery pack , into 3 phase AC, the dashboard just has a simple "throttle" lever (a potentiometer) and a battery level left meter on it.

You can use full power just from the batteries, however every time you do that you are eating into the number of battery recharge cycles you have left.

So if I'm not just trickling across from my mooring to the sailing club, I'll start the generator, then as you use more power you can hear the genny loading up, it takes power more from the genny than the batteries at that point.

The Genny cannot drive the Motor without the batteries, there are quite severe warnings about that in the genny manual.

As a help to keep the batteries charged there are also solar panels on the roof of the boat, and if I've just done the trip across the river only, then the panels can replace the power used.

[TheQ]

Oh two points I missed,

  Even if a sacrificial anode is not fitted to the boat, many boats have a route to Earth on Negative DC through the engine , propshaft , prop.

Also this blog, http://worcesternb.blogspot.co.uk/ has a detailed system similar to that installed on my boat and is what Inspired me to go for the system I have. I have been in contact with Mr Osborne and must get round to sending a few pics of the installation, when I get some decent ones. I'll put them on here too...

[TheQ]

LondonRascal, I have actually fitted a similar system to your description, like this https://www.amazon.co.uk/Mitsubishi-2-5kW-Conditioner-System-SRK25ZMP-S/dp/B01BKWDK7G/ref=pd_sim_sbs_107_4?ie=UTF8&psc=1&refRID=804PEZ40Z3R8T4YPV0C0

It went on Our Mobile home, and  has been very successful. It came precharged with gas, and plugs into a normal mains Socket.

It was a simple job to do, you do have to be careful making the pipe runs and gas connections as the copper tubing is very soft.

 There is a club member that has such a system with the exterior unit sat on the rear roof of his boat, however he did bring the boat back from the south of france where the need for such a system was somewhat more than here..

 Reading the thread  on "unexpected visitors" would make me worry about having the exterior unit on the swim platform.

 Right, thats enough of me catching up with the thread, time for others to stick their oar in

[Viking23]

13 hours ago, TheQ said:

Right now you mention battery charges here's a problem I do have to sort.

The panda - fisher generator charges a stack of 24, 2v traction batteries. What it doesn't have is a 12v charging circuit for its own car type starter battery.

What would be the best way of charging this battery when not on shore power,

note I do have a small solar trickle charger.

Hi, what you don't want to do is tap off a section of the 2 volt batteries, it will discharge some, and when the whole stack is charged they will have uneven charging and some may even gas excessively.

However, I have a solution for you, quite simple, resonably priced too.

Send a Cheque made payable to ****  

 

No this forum is not about that lol,

Buy an inverter 48 Volts DC to 240 volts ac yes they are available, cheap too, google 48 Volt inverter, then take a mains battery charger of your choice.

You have the advantage that you can have a few main sockets for charging mobile phones etc.  

Simple, but what's the snag? left on for any great length of time might discharge your main batteries, but if you are only charging when the generator is running then fine. 

Also if one day your starter battery is low, then you can run the inverter, and charge the starter battery, start the gen, then you are up and running.

Could this be too simple? best things usually are lol

Richard

[TheQ]

I will be buying an inverter as shown somewhere back in this monster I seem to have started, but going from 48V to 230V to 12V is electrically very wasteful with a lot of losses.

My background is electronic maintenance and calibration, not design, because it should be a simple task to design a 48V to 15V dropping circuit followed by a charge controller. Integral to that would be a circuit to stop overdrawing of current from the 48V battery, and an "if all else fails button" to use more than you should, as you really do need to  the generator started.  

[Viking23]

17 minutes ago, TheQ said:

I will be buying an inverter as shown somewhere back in this monster I seem to have started, but going from 48V to 230V to 12V is electrically very wasteful with a lot of losses.

My background is electronic maintenance and calibration, not design, because it should be a simple task to design a 48V to 15V dropping circuit followed by a charge controller. Integral to that would be a circuit to stop overdrawing of current from the 48V battery, and an "if all else fails button" to use more than you should, as you really do need to  the generator started.  

Yes you could do a switch mode power supply, that would be at best 80% efficient, you might find one already done, if you used just a straight forward voltage regulator arrangement then that would be at best 25% efficient, as the 75% will be given off in heat, and you would need to make provision for that dissipation.

Using my suggestion, you have the option of having 240 volts on board, hair curlers, charger for your electric tooth brush and mobile phone, and a battery charger with say a tripple charge rate, that will maintain your main starter battery in tip top condition, and you still have a battery charger you can use elsewhere.

You might find that if you use the right inverter and the right charger, you could be 75-80% efficient, but they would need matching, as choosing an inverter too big for the job, would use power even when no power was taken from the inverter.

Some would say using fuel to charge batteries is not that efficient then converting to mechanical energy. Have you done the sums? I guess 50%

Far more efficient to drive the prop direct. But I know this is not the point.

So does efficiency matter that much compared to buying something off the shelf well proven, work first time out of the box, and can be running in a few hours? 

Solution available now ! 

[Vaughan]

Morning all! I won't tell you what I have been dreaming about  but I did wake up and do some thinking. As one does.

In Crown Blue Line we built 2 boats for  America, called Royal Classique, for hire on the Hudson River in New York State. I was involved in their layout and went over there to commission the first boat for hire.

They had an ONAN diesel generator, a large AC aircon unit and a Peachment AC panel, as described yesterday. Built to US regs, they had to have every fitting in the boat bonded together, even the galley sink and of course, all the hull skin fittings. The basic boat was the standard Crown build so there was no need for an inverter. It did have a marine VHF though. On a hire boat!

I have realised that provided the AC earth is bonded to the rest of all the bonding then there will be an efficient passage out of the boat. But what about a GRP boat built on the Broads?

There is no bonding to skin fittings and the propshaft is not bonded to the engine on a hydraulic drive, unless someone has fitted a bonding strap. All domestic pipework is plastic these days. So a good earth out to the water is not so likely. I have not met this problem since although the newer Crown boats have a lot of plug points in their cabins, they are only live when plugged into the bank.

Sacrificial anodes  might be on a boss behind the propellor, bolted to the rudder, or the skeg of the keel. This does not necessary mean they are bonded. Bow thrusters also have their own anode (or should do!).

So maybe a dedicated anode, screwed to the hull with a cable bonded to the earth of the AC circuit? I wonder if modern Broads boats with powerful inverters are built like this? Perhaps someone knows?

 

[Viking23]

I thought about my efficiency comment above..

"Some would say using fuel to charge batteries is not that efficient then converting to mechanical energy. Have you done the sums? I guess 50%"

 

So here are my thoughts a electrical generator, power is in Hp via the shaft to electrical energy out in Kw some say they can be 90%  so efficiency 0.9

Battery charging, power in to power out is around 85 % efficient so 0.85 

Electric motors are most efficient at over 75% of their rated power and are said to be upto 90% efficient or 0.9 but rapidly drops to 50% efficienct  0.5 at 20 % power out. Some moters are multiwound and automatically switch to help maintan efficiency, so let's assume average efficiency of 80% or 0.8

To arrive at the overall efficiency multiply together, 0.9 x 0.85 x 0.8 = approx 0.6  or around 60% efficient, so not far off from my best guess.

At lower revs, where the efficiency of the drive motor is much much less then the overall efficiency will be a lot lower than 50%.

To be fair, where these motor generator overall efficiences come from is in the diesel engine. On a direct drive, a big engine is required, and power has to range from tick over to full power, whereas a motor gen set the diesel engine is smaller, tends to run at constant revs for a shorter time and is more efficient.

Which is more environmentally friendly?  the down side for the electric set up is having to replace those batteries, same with electric transport, When battery efficiency improves with weight reduction and battery life, we will see more of these.

 

 

[TheQ]

Someone , Grendal? asked where the earth pin is connected to on an inverter, well, wading through dozens of Circuit diagrams and pages of information generally it seems the answer is.... nothing. Also the 240V is spread equally across the 2 pins so it is 240V relative to each output pin.

I've been wading round many UK web sites (because the yanks do all sorts of strange things on their systems.)

The conclusion I've found on UK Narrow boats WITH INVERTERS and generators,  is that when running an inverter onboard you do not have an earth. This requires that your Shore power / inverter switch, switches Live, Neutral AND earth

SO the alternatives are,

1, Onboard Earth, as Vaughan says, bonded to it's own sacrificial Anode.

2, OnBoard Earth, as the Yanks do, bonding AC earth and DC Low, together to a sacrificial anode.

3, No Onboard Earth, But if I choose that, then I would ensure ALL onboard electric equipment is double insulated. though the narrowboaters seem not to go for double insulated.

 My preference is for 1.

 

[JennyMorgan]

By the cringe, is it all worth the bother? Keep it simple, no hair straighteners and a Seagull outboard slung on the transom, plus a sail or two, needless to say. It does strike me that the industry is making a rod for its own back with all these electrical gubbins.

[Vaughan]

I have been waiting for you to enter this debate, Peter. You have not let me down!

[TheQ]

Vicking 23. 

Yes, my system would be less efficient, except for:

My electric motor is direct drive, so no Gearbox losses,

A diesel has a gearbox for which you need to take the losses off for that.

A diesel is less efficent when warming up (like my generator),  at low revs it's less efficient as well.

Some of my power comes from solar,

 So short trips from my mooring to the sailing club (or anywhere else) use no outside power source, where as the diesel would be very cold and inefficient for trips like that.

If I've done a long trip and used power from the batteries, the generator will be warm and stay at high revs  (more efficient)

[JennyMorgan]

2 minutes ago, Vaughan said:

I have been waiting for you to enter this debate, Peter. You have not let me down!

You can count on me!

I have read the thread with interest and a degree of amazement. I visit craft that have the very latest in electrical gadgetry. Seems to me that not only are the owners tethering themselves to a 'leccy' bollard they are also tethering themselves to a yard. The more that is crammed aboard then the more that is likely to go wrong, plain and simple.

[TheQ]

25 minutes ago, JennyMorgan said:

By the cringe, is it all worth the bother? Keep it simple, no hair straighteners and a Seagull outboard slung on the transom, plus a sail or two, needless to say. It does strike me that the industry is making a rod for its own back with all these electrical gubbins.

Sadly SWMBO is not interested in sailing, (or hair straighteners) and taking all my venerable relatives out on trips in a sailing boat, is not an answer when they can barely get to the boat in the first place. Although it is the answer I'd prefer.

I am an electronics Technician / engineer, so electronics to me is no more difficult than pulling bits of string during Horning regatta week.

 These pages and pages of discussion almost all depend on one (EARTH) point that even the UK authorities seem not to have made a recommendation on.

Oh Vaughan, I've had a look at the Only X-splt I could find, It appears to be made by Driftgate 2000 ltd who's directors seem to have resigned in 2015!!

 SO if i go that route I'll probably uses something like. http://foundry4x4.co.uk/index.php?route=product/product&product_id=173

[Bound2Please]

28 minutes ago, JennyMorgan said:

You can count on me!

I have read the thread with interest and a degree of amazement. I visit craft that have the very latest in electrical gadgetry. Seems to me that not only are the owners tethering themselves to a 'leccy' bollard they are also tethering themselves to a yard. The more that is crammed aboard then the more that is likely to go wrong, plain and simple.

We have no 240v ac on Bound 2 Please but still charge phones etc via USB outputs from our 12v dc domestic batteries. No earths to worry about there.

Charlie