Victron Inverter

[Bazza954]

Hi all,

I have just bought a victron inverter (multiplus 12v-3000va-120amp ) in the installation instructions it advises 2x 50mm square cables each, for positive and negative connection.

My present inverter has 70mm square cables running to it, can I add another cable sized at 40mm square to give slightly more area (110mm square ) or would it cause a problem as the cables would not be the same size as each other.

Would one cable take more load than the other ? or would this be ok ?

TIA for any replies.

 

Bazza

[Robbo]

1 minute ago, Bazza954 said:

Hi all,

I have just bought a victron inverter (multiplus 12v-3000va-120amp ) in the installation instructions it advises 2x 50mm square cables each, for positive and negative connection.

My present inverter has 70mm square cables running to it, can I add another cable sized at 40mm square to give slightly more area (110mm square ) or would it cause a problem as the cables would not be the same size as each other.

Would one cable take more load than the other ? or would this be ok ?

TIA for any replies.

 

Bazza

Why not add another 70mm2 cable?

[Bazza954]

5 minutes ago, Robbo said:

Why not add another 70mm2 cable?

Hi Robbo, I probably could add another 70mm2 cable, but being a tight arsed Yorkshireman I have some 40mm2 spare so wanted to use that. LOL.

I just checked on line and the 70mm2 has a rating of 485 amps which should be enough  shouldn't it  ??

 

 

Bazza

[Psycloud]

1 minute ago, Bazza954 said:

Hi Robbo, I probably could add another 70mm2 cable, but being a tight arsed Yorkshireman I have some 40mm2 spare so wanted to use that. LOL.

I just checked on line and the 70mm2 has a rating of 485 amps which should be enough  shouldn't it  ??

 

 

Bazza

Tight arses don't usually splash out on Victron

[Bazza954]

1 minute ago, Psycloud said:

Tight arses don't usually splash out on Victron

I'll let you guess at what inverter I am replacing

Bazza

[Robbo]

5 minutes ago, Bazza954 said:

Hi Robbo, I probably could add another 70mm2 cable, but being a tight arsed Yorkshireman I have some 40mm2 spare so wanted to use that. LOL.

I just checked on line and the 70mm2 has a rating of 485 amps which should be enough  shouldn't it  ??

 

 

Bazza

Amp rating on a cable is really meaning less unless you know the length of the cable run and voltage!   If your going anywhere near 3Kw and/or have a long cable run I would use a higher cable than 70mm2

[Bazza954]

2 minutes ago, Robbo said:

Amp rating on a cable is really meaning less unless you know the length of the cable run and voltage!   If your going anywhere near 3Kw and/or have a long cable run I would use a higher cable than 70mm2

Ah, didn't take the cable length into consideration, it's 2 mtrs long. (don't know how to work out volt drop etc. )

Oh well, just have to bite the bullet and buy some new cable

Don't suppose you know anywhere around Leeds that could supply ?

 

Bazza

[nicknorman]

Have you checked that 70mm cable actually fits the connections? It might be that they specify 2x50mm because 50mm is the max size that will fit.

70mm won't go on fire at 3kw but at 2 metres (4 meters round-trip presumably) you will get a fair bit of voltage drop at 3kw. Mind you, unless you intend to take 3kw from the inverter fairly often (and god save your batteries if you do!) then maybe it doesn't matter.

[Robbo]

2 minutes ago, nicknorman said:

Have you checked that 70mm cable actually fits the connections? It might be that they specify 2x50mm because 50mm is the max size that will fit.

70mm won't go on fire at 3kw but at 2 metres (4 meters round-trip presumably) you will get a fair bit of voltage drop at 3kw. Mind you, unless you intend to take 3kw from the inverter fairly often (and god save your batteries if you do!) then maybe it doesn't matter.

Could be running engine tho whilst running a 3kw device, batteries don't get hit but the cables still count!

[Bazza954]

2 minutes ago, nicknorman said:

Have you checked that 70mm cable actually fits the connections? It might be that they specify 2x50mm because 50mm is the max size that will fit.

70mm won't go on fire at 3kw but at 2 metres (4 meters round-trip presumably) you will get a fair bit of voltage drop at 3kw. Mind you, unless you intend to take 3kw from the inverter fairly often (and god save your batteries if you do!) then maybe it doesn't matter.

Hi Nick,

Yes 70mm will fit into the inverter, just checked.

I don't envisage using it at 3kw, max draw around 2100w (washing machine ).

Battery bank is 1050 Amp, 6 x 2v traction batteries.

 

Bazza

[Robbo]

3 minutes ago, Bazza954 said:

Hi Nick,

Yes 70mm will fit into the inverter, just checked.

I don't envisage using it at 3kw, max draw around 2100w (washing machine ).

Battery bank is 1050 Amp, 6 x 2v traction batteries.

 

Bazza

Does the inverter require both feeds to be populated?    I like doing it right, so I'm a little biased tho.

[Bazza954]

4 minutes ago, Robbo said:

Does the inverter require both feeds to be populated?    I like doing it right, so I'm a little biased tho.

Lost me there Robbo, can you explain ?

 

Bazza

 

[Robbo]

10 minutes ago, Bazza954 said:

Lost me there Robbo, can you explain ?

 

Bazza

 

It may require both the feeds to be cabled up?  Ie. each feed has a individual fuse reflecting the cable size of 50mm2.   Try to put 3kw load on it may blow the fuse as it expecting the load to be shared between both cables?    My Victron is a older model and I've not seen a dual feed one.

Edited August 31, 2017 by Robbo

[Bazza954]

9 minutes ago, Robbo said:

It may require both the feeds to be cabled up?  Ie. each feed has a individual fuse reflecting the cable size of 50mm2.   Try to put 3kw load on it may blow the fuse as it expecting the load to be shared between both cables?    My Victron is a older model and I've not seen a dual feed one.

Hi Robbo,

Installation instructions recommend 1 x 400amp fuse.

Picture of connections in unit.

 

[Robbo]

5 minutes ago, Bazza954 said:

Hi Robbo,

Installation instructions recommend 1 x 400amp fuse.

Picture of connections in unit.

Picture says it all really so can be ran from one cable.

[Bazza954]

10 minutes ago, Robbo said:

Picture says it all really so can be ran from one cable.

Cheers.

[nicknorman]

Just so you know, there is a bit of an issue with using two cables for + and two for -. There should be a fuse near the battery to protect the cable under fault condition. If the fuse is selected to protect the combined current carrying capability of the pair of cables, what happens if one cable becomes disconnected for some reason? The inverter still works, but now you have a relatively thin remaining cable protected by a fuse that is much bigger than the cable's rating. So to do it properly, you really should have an appropriate fuse for each of the + cables.

[Bazza954]

20 minutes ago, nicknorman said:

Just so you know, there is a bit of an issue with using two cables for + and two for -. There should be a fuse near the battery to protect the cable under fault condition. If the fuse is selected to protect the combined current carrying capability of the pair of cables, what happens if one cable becomes disconnected for some reason? The inverter still works, but now you have a relatively thin remaining cable protected by a fuse that is much bigger than the cable's rating. So to do it properly, you really should have an appropriate fuse for each of the + cables.

That's a good point Nick, no reference to that in the instructions !!

cheers

Bazza

 

[nicknorman]

1 minute ago, Bazza954 said:

That's a good point Nick, no reference to that in the instructions !!

cheers

Bazza

 

No, I know, it's been mentioned here before! I suppose it depends on your degree of risk averseness and how lucky you feel! Having one fuse almost certainly won't result in a problem. It depends on whether "almost certainly" is good enough for you!

[Bazza954]

Ok, I have managed to source some 95mm2 cable, so will be using that instead of 2 cables or the 70mm2 cable, hence 1 fuse. This should avoid the 1 fuse 2 cable scenario .I think there maybe more questions later regarding the earthing of the unit, just reading through the destructions, to check.

bazza

[cuthound]

1 hour ago, nicknorman said:

No, I know, it's been mentioned here before! I suppose it depends on your degree of risk averseness and how lucky you feel! Having one fuse almost certainly won't result in a problem. It depends on whether "almost certainly" is good enough for you!

Paralleling large cables is fairly comments in high power critical power applications, simply because they don't make cables big enough to carry the current. 

The largest I have paralleled is 5 x 630 mm sq (autowrong suggest "sq" should read squirrels ), and these were never individually fused.  I accept your point that there is a very, very small chance of one or more parallel cables becoming disconnected, but in 42 years, never saw this happen,  even when connected to generators,  which can and do vibrate a bit.

The OP has found the best solution (a single cable large enough to cope with the current and volt drop criteria), but personally I wouldn't worry about using parallel cables as long as they were properly crimped and tightened.

[Robbo]

23 minutes ago, cuthound said:

Paralleling large cables is fairly comments in high power critical power applications, simply because they don't make cables big enough to carry the current. 

The largest I have paralleled is 5 x 630 mm sq (autowrong suggest "sq" should read squirrels ), and these were never individually fused.  I accept your point that there is a very, very small chance of one or more parallel cables becoming disconnected, but in 42 years, never saw this happen,  even when connected to generators,  which can and do vibrate a bit.

The OP has found the best solution (a single cable large enough to cope with the current and volt drop criteria), but personally I wouldn't worry about using parallel cables as long as they were properly crimped and tightened.

Also if a cable did short out say against the hull, a 400amp fuse will quickly blow before 50mm2 cable would heat up and melt, etc.

[WotEver]

7 hours ago, Bazza954 said:

I think there maybe more questions later regarding the earthing of the unit, just reading through the destructions, to check.

It's a Victron. New users always query the earthing arrangements because the manual is so badly written. 

[Bazza954]

17 hours ago, WotEver said:

It's a Victron. New users always query the earthing arrangements because the manual is so badly written. 

The manual wasn't too hard to follow, (after reading half a dozen times  )

It's in and working, nowt went bang, so presuming I've got it right.

I've set it up using the dip switches to suit my type of batteries amongst other settings.

The earthing arrangement seemed quite straight forward, 3 core cable in and out and 1 cable from earth point on casing to boat hull.

Instruction from manual below, I have an IT fitted with an RCD after, so I think it meets the requirements.

If anyone thinks I've missed owt, feel free to advise.

Bazza

 

[WotEver]

3 minutes ago, Bazza954 said:

and 1 cable from earth point on casing to boat hull.

That's the bit that catches folk out. Assuming that you have an Earth bond from CU to hull the extra wire from the casing isn't required.