Switching a combi to "inverter only"

[blackrose]

One of my neighbours has a Vetus 3000w combi charger/inverter. Does anyone know if she can easily switch from shore power coming into the boat to an inverter only setting without her having to go outside to switch off the shore power at the bollard?

 

It seems pretty basic function to me. I had a quick look at it but I'm not familiar with combis as I have a separate charger and inverter. On my boat I have a rotary mains selector switch which allows me to easily switch from shore power to inverter, but I've spoken to a couple of neighbours with combis and apparently they have to go outside in the cold, rain, etc, to switch their shore power on/off. 

 

It seems odd to me. I realise with a combi you have other sophisticated features like being able to supplement shore power with extra mains from the inverter - that with my separate charger & inverter I can't do (not that I've ever needed to), but not being able to switch from shore to inverter from inside the boat can't be right can it?

Edited January 21, 2023 by blackrose

[nicknorman]

Not familiar with the Vetus, but generally with Combis you can’t easily stop it passing through the mains when mains is plugged in. You need to disconnect the incoming shore power. What you can usually do is set a max ac current input so that when the demand exceeds that, the inverter operates to supplement the limited shore power. 
 

I’m  not sure why you’d not want to use shore power but I suppose these days with the cost of shore power and the advent of free solar power, it does make sense.

Edited January 21, 2023 by nicknorman

[Kendorr]

I can only answer with mine.

 

When the inverter was installed, it goes through a 3 way switch, position 1 is for when I'm using shoreline, position 2 is off and position 3 is when I'm on inverter, so to turn the shoreline off, I've no need to unplug or go outside, just turn the switch.

 

 

[blackrose]

 

6 minutes ago, nicknorman said:

Not familiar with the Vetus, but generally with Combis you can’t easily stop it passing through the mains when mains is plugged in. You need to disconnect the incoming shore power. What you can usually do is set a max ac current input so that when the demand exceeds that, the inverter operates to supplement the limited shore power. 

 

Ok thanks. That does surprise me. I can't help thinking that Combi designers have overlooked the basics.

 

3 minutes ago, Kendorr said:

I can only answer with mine.

 

When the inverter was installed, it goes through a 3 way switch, position 1 is for when I'm using shoreline, position 2 is off and position 3 is when I'm on inverter, so to turn the shoreline off, I've no need to unplug or go outside, just turn the switch.

 

Thanks. Is yours a combi?

Edited January 21, 2023 by blackrose

[Kendorr]

4 minutes ago, blackrose said:

Thanks. Is yours a combi?

Mine is a 3kw Victron mini combi.

[nicknorman]

1 minute ago, blackrose said:

 

 

Ok thanks. That does surprise me. I can't help thinking that Combi designers have overlooked the basics.

well perhaps with the benefit of 2023 thinking, but if you’d asked anyone 5 years ago they would all have said that you’d be crazy not to use shore power if it was available. Certainly for us, with no solar, I have never wanted to disconnect the shore power to run on batteries when in the marina. I imagine the same sort of device, designed for houses with solar and capable of back-feeding the mains, have the ability to run from batteries when connected to mains.

 

Anyway, it would be easy to implement, just add a switch to the incoming mains feed.

[blackrose]

Ok cheers. 👍

[GUMPY]

Just turn off the breaker where the supply enters the boat. There is a breaker between the incoming plug and the Combi isn't there!

[cuthound]

15 minutes ago, Kendorr said:

I can only answer with mine.

 

When the inverter was installed, it goes through a 3 way switch, position 1 is for when I'm using shoreline, position 2 is off and position 3 is when I'm on inverter, so to turn the shoreline off, I've no need to unplug or go outside, just turn the switch.

 

 

 

Same with mine.

[GUMPY]

I just turn the MCB that feeds the Combi off, leaving the RCBO that feeds the Immersion/washing machine still on. Heavy loads then don't drain the batteries.

[nicknorman]

19 minutes ago, Loddon said:

Just turn off the breaker where the supply enters the boat. There is a breaker between the incoming plug and the Combi isn't there!

There doesn’t need to be. There isn’t one on our boat.

[GUMPY]

So does everyone rely on the shore post RCBO to protect the wiring before the combi or if no combi fitted the whole boat 😱

Not for me, you never know when the thing was last tested or if it has ever been tested or even if it still works.

MCB prior to transformer, MCB prior to combi, RCBO after combi. Possibly overkill but it's safe and things can be isolated when needed. 

Edited January 21, 2023 by Loddon

[nicknorman]

41 minutes ago, Loddon said:

So does everyone rely on the shore post RCBO to protect the wiring before the combi or if no combi fitted the whole boat 😱

Not for me, you never know when the thing was last tested or if it has ever been tested or even if it still works.

MCB prior to transformer, MCB prior to combi, RCBO after combi. Possibly overkill but it's safe and things can be isolated when needed. 

You need breaker(s) prior to any sockets etc. Since we only have one circuit after the Combi (mains ring which includes the immersion) and none prior (ie no shore power only circuit)  we just have one 16A RCBO after the Combi. It does mean we can’t use more than 16A at a time, whilst theoretically we could get up to about 26A (6kw) with 16A shore power and another 10A from the inverter, but we don’t really need that much and the wiring would have to be upgraded.

 

You can always spend money on “safety” if you wish, but sometimes adding a lot of unnecessary extra clobber can result in annoying failures. Before doing so one should determine exactly what risk one is trying to address. In the case of breakers before a Combi it would be to address a double fault of shore bollard breaker non-functional AND a wiring fault (short circuit) in the short run of cable between the breaker  and the Combi. About 2 metres of cables our case. Of course any fault in the cable between the bollard and the boat wouldn’t be covered. That cable is subject to flexing and chafing, being trodden on etc, whereas the short length of cable you are protecting is hopefully fixed and not subject to flexing, being trodden on etc. And you still have some “unprotected” cable between the shore socket and the breaker. So IMO, no point.

Edited January 21, 2023 by nicknorman

[GUMPY]

19 minutes ago, nicknorman said:

you still have some “unprotected” cable between the shore socket and the breaker. So IMO, no point.

Unless you want to run on inverter and still have shore power available for high current items as I do.

The cable from the socket to the first MCB is less than a foot  and is encased in flexible conduit 

It does help that 90% of the MCB/RCBO didn't cost me a penny.

Just for you to show its not that complex but covers all bases ....

230vAC NEW 2_0.pdf

Edited January 21, 2023 by Loddon

[nicknorman]

9 minutes ago, Loddon said:

Unless you want to run on inverter and still have shore power available for high current items as I do.

The cable from the socket to the first MCB is less than a foot  and is encased in flexible conduit 

It does help that 90% of the MCB/RCBO didn't cost me a penny.

Just for you to show its not that complex but covers all bases ....

230vAC NEW 2_0.pdf 19.29 kB · 3 downloads

Yes if you want to have a circuit that is only fed from shore power then of course it should have a breaker within the boat. But I’ve never really understood why one would want to do that. A Combi is very flexible as it will pass through mains power, supplement it with inverter power if necessary, or just invert if no shore power.

[GUMPY]

1 minute ago, nicknorman said:

Yes if you want to have a circuit that is only fed from shore power then of course it should have a breaker within the boat. But I’ve never really understood why one would want to do that. A Combi is very flexible as it will pass through mains power, supplement it with inverter power if necessary, or just invert if no shore power.

I fully understand how Combis work!

 

When the boat is mostly running on Solar/inverter as it is these days it allows the immersion and washing machine to be used without worrying about draining the batteries. Not all of us can afford or need new tech battery systems.

I have seen at least one person on here ask how this can be done.

[nicknorman]

1 hour ago, Loddon said:

I fully understand how Combis work!

 

When the boat is mostly running on Solar/inverter as it is these days it allows the immersion and washing machine to be used without worrying about draining the batteries. Not all of us can afford or need new tech battery systems.

I have seen at least one person on here ask how this can be done.

I'm reminded of those electricity tariffs that boast they are “100% renewable” when as we all know, it’s just electricity coming from the grid which is quite often mostly from fossil fuel or nuclear!

 

I don’t see how it can matter which bit of electricity from which source runs which bit of equipment!

[GUMPY]

1 minute ago, nicknorman said:

I'm reminded of those electricity tariffs that boast they are “100% renewable” when as we all know, it’s just electricity coming from the grid which is quite often mostly from fossil fuel or nuclear!

 

I don’t see how it can matter which bit of electricity from which source runs which bit of equipment!

 

Its very simple on the boat:

Electricity from shore bollard 60p a unit

Electricity from solar already paid for. 

so I try and use as little shore power as possible.

 

As for grid electric when there is a lot if wind as there was last week my electric unit price decreases and can go negative at night so they pay me to use electricity. 

 

[nicknorman]

2 minutes ago, Loddon said:

 

Its very simple on the boat:

Electricity from shore bollard 60p a unit

Electricity from solar already paid for. 

so I try and use as little shore power as possible.

 

As for grid electric when there is a lot if wind as there was last week my electric unit price decreases and can go negative at night so they pay me to use electricity. 

 

60p!!!??? Still 22p at our marina. As I said earlier, with current on-grid energy prices and relatively cheap solar, I can see the point. But 5 years ago, or even 2 years ago, I could’t see the point.

[arbutus]

If it's a Venus Combi-Gamma Inverter-Battery charger, then the installation and operations manual can be downloaded by going to https://vetus.com/service-support/search-by-product/?_categories=technical-documentation&_productgroups=power-on-board and then clicking on the box "Operation manual and installation instructions Combi-Gamma"

 

It has some good diagrams of operation modes and also functions of the front panel.

 

It seems that it can be changed to "Inverter priority support". 

 

Worth a read if this is the unit on the boat

[blackrose]

14 hours ago, nicknorman said:

 

I don’t see how it can matter which bit of electricity from which source runs which bit of equipment!

 

Shore power now costs me 80p/kWh while the power generated from my recently installed solar panels is still recouping the cost of the installation. I expect to break even in about 3 years so as far as I'm concerned it very much matters to me which bit of electricity from which source runs my equipment.

14 hours ago, nicknorman said:

60p!!!??? Still 22p at our marina. 

 

I would get ready for a steep increase very soon.

[nicknorman]

3 hours ago, blackrose said:

 

Shore power now costs me 80p/kWh while the power generated from my recently installed solar panels is still recouping the cost of the installation. I expect to break even in about 3 years so as far as I'm concerned it very much matters to me which bit of electricity from which source runs my equipment.

 

I would get ready for a steep increase very soon.

My point is that you need x amount of electrical energy to run your boat. Some of that energy comes from solar, some comes from shore. Of course you want to be able to control how much energy comes from the solar and how much from the shore. But once you have determined that, it doesn’t matter which bit of equipment on the boat uses the energy from which source.

 

As to commercial electricity rates, at the gliding club we are still on sub-20p a unit and we are just moving on to a new annual contract with a different company that was set up about a year ago, even cheaper I think. Thanks to the foresight of the Hangar Manager. So commercial rates are very dependant on what long term deals you have negotiated, rather than the instantaneous market price of power.

[MtB]

On 21/01/2023 at 21:38, nicknorman said:

I'm reminded of those electricity tariffs that boast they are “100% renewable” when as we all know, it’s just electricity coming from the grid which is quite often mostly from fossil fuel or nuclear!

 

I don’t see how it can matter which bit of electricity from which source runs which bit of equipment!

 

Electric supplier bod on the radio the other day explained this when challenged over his company's "100% Renewable" claim. 

 

He said for every mWh of leccy they sell, they buy a mWh from a wind farm or solar farm so ALL their leccy must be renewable. Okaayyyy....

 

The flaw in this reasoning is timing. At 6pm on a calm, dark winter's evening I reckon they WILL be sucking on the nuclear or gas plants to feed their customers. 

 

 

[rusty69]

3 minutes ago, MtB said:

The flaw in this reasoning is timing. At 6pm on a calm, dark winter's evening I reckon they WILL be sucking on the nuclear or gas plants to feed their customers. 

 

Or the French or Dutch. Not that I recommend sucking on one of those after dark.

[David Mack]

52 minutes ago, MtB said:

 

Electric supplier bod on the radio the other day explained this when challenged over his company's "100% Renewable" claim. 

 

He said for every mWh of leccy they sell, they buy a mWh from a wind farm or solar farm so ALL their leccy must be renewable. Okaayyyy....

 

The flaw in this reasoning is timing. At 6pm on a calm, dark winter's evening I reckon they WILL be sucking on the nuclear or gas plants to feed their customers. 

 

 

And if your electricity really was 100% renewable there would have been no need for the supplier to put up the prices when gas prices increased.