electric circuit 240v

[Richard Houlgate]

I have just purchased my first narrow boat. It's a 1999 Colecraft in good condition with a Heart Freedom Model 20 inverter.

 

I'm puzzled by the 240v electrics. When connected to shore power and with a 2kw electric fire on the battery voltage slowly goes down. Occasionally the 240v stops working for a few minutes. I would have thought the 240v circuit would have been independent of the batteries but according to the circuit diagram in the owners manual this is not the case, see attached.

 

I would have thought the circuit should be as in the second attachment.

 

Has the boat been wired correctly?

 

[nicknorman]

Firstly let’s be clear, there is a big difference in functionality and wiring between a Combi and an inverter. I think the Heart, though very old tech, is a Combi. So your second diagram is not relevant as it shows an inverter, not a Combi.

 

In the first diagram it is barking to have the changeover switch after the Combi. That means that the generator can’t charge the batteries. The changeover should be before the Combi, such that either shore power or generator power can be selected to feed the Combi and charge the batteries and pass through mains power to the sockets etc.

 

If your boat is really wired like that, that is a very strange (aka wrong) way of doing it. However it doesn’t explain your problem.

 

I am not familiar with the Heart but some Combis have a power support function. One can specify a maximum drain from the shore socket, to cater for a shore bollard with limited power capabilities. This shore power will be passed through to the sockets and, if the power demand exceeds the specified limit, will be supplemented by the inverter (and obviously draining the batteries as a consequence). Seems possible that this is what is happening for you - some power is coming from the shore bollard, some power is coming from the batteries via the inverter.

 

The remedy will be to read the manual and find out how to change the input current limit to 16A or whatever the bollard can deliver.

[BEngo]

The other apparent problem with the mains wiring is that the sockets are on a single radial circuit, and there are too many of them for a radial circuit. Depending on the actual size of the cable and the output of the generator, that radial circuit may also be too small for the possible load. The Normally the sockets are wired in a ring with 3 core arctic blue 2.5 sq mm.  To do this there should be a 3 core cable  from the lounge sockets to the protection device.

 

N

  

[nicknorman]

3 minutes ago, BEngo said:

The other apparent problem with the mains wiring is that the sockets are on a single radial circuit, and there are too many of them for a radial circuit. Depending on the actual size of the cable and the output of the generator, that radial circuit may also be too small for the possible load. The Normally the sockets are wired in a ring with 3 core arctic blue 2.5 sq mm.  To do this there should be a 3 core cable  from the lounge sockets to the protection device.

 

N

I disagree - it’s not a house! The maximum current that can be taken by any /all of the sockets is limited to 16A and that is catered for by 2.5 mm^2 

[Tracy D'arth]

29 minutes ago, BEngo said:

The other apparent problem with the mains wiring is that the sockets are on a single radial circuit, and there are too many of them for a radial circuit. Depending on the actual size of the cable and the output of the generator, that radial circuit may also be too small for the possible load. The Normally the sockets are wired in a ring with 3 core arctic blue 2.5 sq mm.  To do this there should be a 3 core cable  from the lounge sockets to the protection device.

 

N

  

The maximum current for a radial circuit on 2,5mm CSA cable is 20A.The bollard supply is only 16A therefor the circuit complies. Ring circuits are a UK convention for domestic wiring, not gospel.

[BEngo]

That is why I said it was dependent on the generator size; a 5 kVA generator or bigger would be able to overload the radial.   We also  do not know the size of the shore connection, either now or in the future.

 

N

[Alan de Enfield]

13 minutes ago, BEngo said:

That is why I said it was dependent on the generator size; a 5 kVA generator or bigger would be able to overload the radial.   We also  do not know the size of the shore connection, either now or in the future.

 

N

 

 

More and more marinas are offering 32 amp bollards, I'm guessing that the 'modern boat' with its full suite of domestic appliances is pushing the limits on the 16 amp ones.

[jonathanA]

17 minutes ago, BEngo said:

That is why I said it was dependent on the generator size; a 5 kVA generator or bigger would be able to overload the radial.   We also  do not know the size of the shore connection, either now or in the future.

 

N

nor do we know the rating of the MCB supplying the radial circuit.  That is actually the only number that is relevant.

I think we all expect it to be 16A but doesn't mean it is... 

[Richard Houlgate]

Many thanks for all your replies. 

 

My main concern is the wiring of the inverter, not the radial circuit. I'm assuming that the bollard can supply 16 amps so the maximum theoretical load is 16 x 240 = 3840 watts so I make sure that this is not exceeded.

 

Comments on Nicknorman's post

- What is the difference between an inverter and combi? Mr Google doesn't make this clear.

- I take the point about the location of the generator. This is a Transpower system, but I don't think we will be able to be away from the marina for more than a few days so won't be using it.

- I had expected the circuit to be as the picture.

 

So I'll take the following actions

 

Ask the marina what is the maximum amperage the bollard can deliver

Read the Heart manual. Of course this is on the boat and I'm 40 miles away; it will have to wait until we are next on the boat. But as the most we have loaded the circuit with is 2000 watts I'm not sure that this is the answer. Maybe best to bite the bullet and get a new inverter.

 

[Jen-in-Wellies]

8 minutes ago, Richard Houlgate said:

- What is the difference between an inverter and combi? Mr Google doesn't make this clear.

Mr Google ain't so bright.

An inverter takes power from a battery at low voltage DC and converts it in to 230V AC.

A combi combines an inverter and battery charger in to one box. When plugged in to a shore line, or mains generator, the battery charger  part will charge the batteries. Many combi units will automagically pass through the mains input to the mains output. When the mains input disappears, it will automagically turn on the inverter to substitute for this. As has been mentioned, some combi boxes will compensate for a limited shore power amperage by drawing extra power from the batteries to supply high power appliances on the boat. Not all do this.

Combi boxes are convenient, but have more parts to fail, any one of which will limit what can be done on the boat.

[Tony Brooks]

2 minutes ago, Richard Houlgate said:

What is the difference between an inverter and combi? Mr Google doesn't make this clear.

 

An inverter only changes 12/24V DC to 240V AC

 

A combi-unit contains an inverter PLUS a battery charger, so when the boat is supplied from a shoreline or generator, that supply can also be used to charge the batteries. Such units are usually far more sophisticated and allows a shoreline supply to pass through the inverter than the synchronises itself to the mains, so the inverter part augments an undersized shore supply. In general, such units do not use a change over switch because the external mains supply just feeds through them.

 

It is vital to read the manual, so you know how to set them up in such a way that if the mains fail the inverter does not supply inverted battery power to   the charger to charge the batteries - that way lies flat batteries.

[nicknorman]

1 minute ago, Jen-in-Wellies said:

Mr Google ain't so bright.

An inverter takes power from a battery at low voltage DC and converts it in to 230V AC.

A combi combines an inverter and battery charger in to one box. When plugged in to a shore line, or mains generator, the battery charger  part will charge the batteries. Many combi units will automagically pass through the mains input to the mains output. When the mains input disappears, it will automagically turn on the inverter to substitute for this.

Combi boxes are convenient, but have more parts to fail, any one of which will limit what can be done on the boat.

I’d agree but say that surely all Combis pass through mains input to the mains output.

[Jen-in-Wellies]

Just now, nicknorman said:

I’d agree but say that surely all Combis pass through mains input to the mains output.

Probably true, but if I'd said all, some one would have come up with an obscure combi that doesn't and since I don't know the full details of every one that has ever been on the market, some equivocation was called for!

[nicknorman]

24 minutes ago, Richard Houlgate said:

Many thanks for all your replies. 

 

My main concern is the wiring of the inverter, not the radial circuit. I'm assuming that the bollard can supply 16 amps so the maximum theoretical load is 16 x 240 = 3840 watts so I make sure that this is not exceeded.

 

Comments on Nicknorman's post

- What is the difference between an inverter and combi? Mr Google doesn't make this clear.

- I take the point about the location of the generator. This is a Transpower system, but I don't think we will be able to be away from the marina for more than a few days so won't be using it.

- I had expected the circuit to be as the picture.

 

So I'll take the following actions

 

Ask the marina what is the maximum amperage the bollard can deliver

Read the Heart manual. Of course this is on the boat and I'm 40 miles away; it will have to wait until we are next on the boat. But as the most we have loaded the circuit with is 2000 watts I'm not sure that this is the answer. Maybe best to bite the bullet and get a new inverter.

 

No the circuit definitely shouldn’t be as you’ve drawn with the biro edit. A Combi is wired with the shore and or generator power connected to its input. The output of the Combi then feeds the domestic circuit via consumer unit etc.

The only place for a changeover switch is to select between shore power and generator power. It is definitely not to select between inverter power and shore power - this is done automatically by the Combi and of course if the input to the Combi is not connected to shore power, the batteries won’t get charged.

 

I did have a quick look at the Heart manual last night, I suspect it doesn’t do power assistance (inverter supplementing the incoming shore power) but it does have a power limit function whereby if a set threshold of incoming shore power is exceeded, the charger function is shut down so as to reduce the shore power demand as much as possible.

 

You mentioned that the batteries were running down, but you didn’t say how quickly. Could it just be that with the charger part of the Combi shut down due to an input power limit of less than 2kw being set, the batteries are just slowly discharging due to other 12v loads on the boat (lights, pumps, fridge etc)? This seems the more likely scenario and just needs the input current limit setting on the Combi to be increased to 16A.

Edited October 31, 2023 by nicknorman

[Alan de Enfield]

29 minutes ago, Richard Houlgate said:

Ask the marina what is the maximum amperage the bollard can deliver

 

Not all marina bollards can supply 16 amps, due to 'age' or number of boats or only having a 'small supply' some marinas limit their bollards to (commonly) 10 amps, some are as low as 4 amps.

 

A combi (well my Victron does) allows you to 'dial in' to the combi what the maximum current available is so it does not trip the shore supply.

If you are then using appliances that exceed that level the combi will take the extra power from the battery (via the Inverter) to make up the difference.

 

Photo of my 'current limiting' knob on the Victron - as you can see, you can dial in anything between 0 and 16 amps.

 

 

 

 

 

Edited October 31, 2023 by Alan de Enfield

[IanD]

21 minutes ago, Jen-in-Wellies said:

Mr Google ain't so bright.

An inverter takes power from a battery at low voltage DC and converts it in to 230V AC.

A combi combines an inverter and battery charger in to one box. When plugged in to a shore line, or mains generator, the battery charger  part will charge the batteries. Many combi units will automagically pass through the mains input to the mains output. When the mains input disappears, it will automagically turn on the inverter to substitute for this. As has been mentioned, some combi boxes will compensate for a limited shore power amperage by drawing extra power from the batteries to supply high power appliances on the boat. Not all do this.

Combi boxes are convenient, but have more parts to fail, any one of which will limit what can be done on the boat.

 

Actually a combi has a lot fewer parts to fail than a separate inverter plus charger, so the chances of *a* failure happening are lower. But the consequences are worse if you lose both functions...

 

(similar power switches/drivers/controllers are needed for both a combi, an inverter, and a charger -- in the combi the same components provide both functions, but with a more complicated control algorithm)

43 minutes ago, Alan de Enfield said:

 

More and more marinas are offering 32 amp bollards, I'm guessing that the 'modern boat' with its full suite of domestic appliances is pushing the limits on the 16 amp ones.

 

Most "modern boats" have high-power combis like the Victron where if demand exceeds the bollard limit (e.g. 16A) the extra required power comes from the inverter and batteries, so long as they have enough charge -- which they usually will do, at least enough for several hours. It's very rare that sustained/average loads will exceed the 16A bollard limit, even allowing for electric cooking and other appliances.

 

But as you say more marinas are offering 32A bollards, and more boats -- mine included -- are built to be able to use them 🙂

[Richard Houlgate]

So having read all that:

 

I'm waiting for the marina to tell me the bollard supply amps

 

When next on the boat I'll read the manual, and make sure that the Heart combi limit is <= to that.

 

Many thanks to you all. 

[nicknorman]

Just now, IanD said:

 

Actually a combi has a lot fewer parts to fail than a separate inverter plus charger, so the chances of *a* failure happening are lower. But the consequences are worse if you lose both functions...

 

(similar power switches/drivers/controllers are needed for both a combi, an inverter, and a charger -- in the combi the same components provide both functions, but with a more complicated control algorithm)

This severity of failure thing is often bandied about but I don’t really agree with it. You need an inverter if you are not on shore power and you want (but don’t need) a charger when you are on shore power.

 

Off shore power you don’t need a charger (can charge with the engine) and you’ve lucked out on having mains just as you would have done if you had an inverter that had failed.

 

On shore power but no Combi - you can still charge with the engine and you have ac power from the mains (might possibly need to connect Combi output wires to Combi input to get the pass-through but that is not too taxing).

 

Set against that questionable “severity of failure” is the massive convenience of the Combi automatically switching between sources of power, and the ability to use power support (combined shore and inverter power).

 

We use the latter a lot when cruising with the tumble drier on (2kw) setting the Combi current limit to 4A with the Travelpower on. Thus the travelpower gives about 1kw and the inverter gives about 1 kw effectively fed from the alternator. Travelpower and alternator belts are thus not excessively loaded when we reduce to idle passing moored boats.

 

 

2 minutes ago, Richard Houlgate said:

So having read all that:

 

I'm waiting for the marina to tell me the bollard supply amps

 

When next on the boat I'll read the manual, and make sure that the Heart combi limit is <= to that.

 

Many thanks to you all. 

Probably it is 16A but you should be able to tell by looking at the breaker on the bollard, normally the rating of the breaker will be visible.

[IanD]

1 minute ago, nicknorman said:

This severity of failure thing is often bandied about but I don’t really agree with it. You need an inverter if you are not on shore power and you want (but don’t need) a charger when you are on shore power.

 

Off shore power you don’t need a charger (can charge with the engine) and you’ve lucked out on having mains just as you would have done if you had an inverter that had failed.

 

On shore power but no Combi - you can still charge with the engine and you have ac power from the mains (might possibly need to connect Combi output wires to Combi input to get the pass-through but that is not too taxing).

 

Set against that questionable “severity of failure” is the massive convenience of the Combi automatically switching between sources of power, and the ability to use power support (combined shore and inverter power).

 

We use the latter a lot when cruising with the tumble drier on (2kw) setting the Combi current limit to 4A with the Travelpower on. Thus the travelpower gives about 1kw and the inverter gives about 1 kw effectively fed from the alternator. Travelpower and alternator belts are thus not excessively loaded when we reduce to idle passing moored boats.

 

 

Probably it is 16A but you should be able to tell by looking at the breaker on the bollard, normally the rating of the breaker will be visible.

I agree -- there's far too much FUD bandied around about combis, usually by people who don't understand what's inside them (and inverters and chargers).

 

Seamless switching and power assist are big advantages, but of course not ones appreciated by boaters who don't have them... 😉

[Alan de Enfield]

34 minutes ago, nicknorman said:

This severity of failure thing is often bandied about but I don’t really agree with it. You need an inverter if you are not on shore power and you want (but don’t need) a charger when you are on shore power.

 

But (as happened to me) when the Charger part of the combi breaks down, and you send the 'blue box' away for repair you lose both your Charger and inverter. You can still use the engine to charge the batteries but have now lost all 230v AC when cruising (No freezer, no microwave, and no toaster) you can use a gas hob-hob for the kettle and grill (if you have gas installed) but boogered re the freezer and microwave.

 

That is why I would never again have a combi.

[IanD]

21 minutes ago, Alan de Enfield said:

 

But (as happened to me) when the Charger part of the combi breaks down, and you send the 'blue box' away for repair you lose both your Charger and inverter. You can still use the engine to charge the batteries but have now lost all 230v AC when cruising (No freezer, no microwave, and no toaster) you can use a gas hob-hob for the kettle and grill (if you have gas installed) but boogered re the freezer and microwave.

 

That is why I would never again have a combi.

And how is that any different to if your inverter broke down? No AC in either case, unless you're plugged into shoreline.

 

In case you didn't read what I posted, the actual electronics inside an inverter a charger and a combi are pretty much the same, a power bridge plus transformer plus control circuits, and so you'd expect the failure rates to be similar. The only "extra bits" for a combi are a couple of relays to switch between inputs -- but then inverters and chargers each usually have such isolation relays anyway to meet regulations.

 

Let's (for example) put the average failure rate of a unit (any type) at once every five years. With a combi, you lose both inverter and charger every five years. With separate units you lose the inverter every five years, and independently lose the charger every five years, so on average you get a failure every 2.5 years (twice as often as a combi) but only use one function or the other. The availability of AC is the same as with a combi, but your repair costs are doubled. And it's cheaper to buy a combi than separate inverter and charger of similar power, because you're not paying for all the duplicated components.

 

Separate units don't look like a bargain to me... 😉

Edited October 31, 2023 by IanD

[jonathanA]

I think like many things in life and boating its not black and white and there is no right or wrong answer.   its a long time since I did MTBF and availability calculations, but it isn't going to be a simple as two units therefore twice as likely to fail as one (combined) unit - far more complex than that, as some components in the combi will be permanently in use whereas the separate units components will only be use for part of the time and so on..  so that 5 yrs use for the combi might be equivalent to say 7.5 years use for the standalone charger and say 10 years use for the standalone inverter (made up figures who knows  ?).  

 

I suspect for many of us, we inherited what we have with the boat - I did - mine came with an inverter and no charger. As we were marina based the logical thing to do was buy and fit a charger.   Now we are not marina based and are 'off grid' if one or the other fails I might consider whether a combi would be better as any 'shoreline' power is now derived from my permanently installed shoreside diesel generator and the combi auto switchover would be a benefit (which it wasn't in the marina).  Power assist is currently of no interest and as I only have a modest bank of LA batteries, it would be pretty limited anyway.  However if I changed to Lithiums that could change things...  

 

I think it comes down to personal circumstances, personal preferences and maybe how much you want to pay... 

 

 

 

[IanD]

31 minutes ago, jonathanA said:

I think like many things in life and boating its not black and white and there is no right or wrong answer.   its a long time since I did MTBF and availability calculations, but it isn't going to be a simple as two units therefore twice as likely to fail as one (combined) unit - far more complex than that, as some components in the combi will be permanently in use whereas the separate units components will only be use for part of the time and so on..  so that 5 yrs use for the combi might be equivalent to say 7.5 years use for the standalone charger and say 10 years use for the standalone inverter (made up figures who knows  ?).  

 

I suspect for many of us, we inherited what we have with the boat - I did - mine came with an inverter and no charger. As we were marina based the logical thing to do was buy and fit a charger.   Now we are not marina based and are 'off grid' if one or the other fails I might consider whether a combi would be better as any 'shoreline' power is now derived from my permanently installed shoreside diesel generator and the combi auto switchover would be a benefit (which it wasn't in the marina).  Power assist is currently of no interest and as I only have a modest bank of LA batteries, it would be pretty limited anyway.  However if I changed to Lithiums that could change things...  

 

I think it comes down to personal circumstances, personal preferences and maybe how much you want to pay... 

 

 

Indeed -- if you want to pay more and have more frequent problems, get two separate units... 😉

 

(I do work with MTBF calculations regularly, and though the assumption of equal use/lifetime was simplified the conclusion still stands -- two separate units with pretty much double the hardware and component count will be less reliable than one combi, other things being equal...)

 

There will always be some things on a boat that you don't have backup for if they go wrong -- engine and gearbox on a diesel boat, for example -- because you can't get rid of all single points of failure, any more than you can in a house, unless you have two of everything. And it's true that the more stuff you have the more things can go wrong, though the only way to really get round this is to get rid of everything modern that might fail and go back to horses, fires and paraffin lamps... 😉

[nicknorman]

19 minutes ago, IanD said:

 

Indeed -- if you want to pay more and have more frequent problems, get two separate units... 😉

 

(I do work with MTBF calculations regularly, and though the assumption of equal use/lifetime was simplified the conclusion still stands -- two separate units with pretty much double the hardware and component count will be less reliable than one combi, other things being equal...)

 

There will always be some things on a boat that you don't have backup for if they go wrong -- engine and gearbox on a diesel boat, for example -- because you can't get rid of all single points of failure, any more than you can in a house, unless you have two of everything. And it's true that the more stuff you have the more things can go wrong, though the only way to really get round this is to get rid of everything modern that might fail and go back to horses, fires and paraffin lamps... 😉

Horse might get lame. Then what would you do?

[IanD]

1 minute ago, nicknorman said:

Horse might get lame. Then what would you do?

Shoot it and eat it, then bowhaul? 😉