Switch between solar panels and controller?

[dor]

I've just bought one of these to fit as a panel isolator between the panel and controller:

https://www.ebay.co.uk/itm/Removable-Knob-Car-Marine-Boat-Battery-Isolator-Cut-Off-Kill-Switch-12V-24V-600A/253800990407?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20160323102634%26meid%3D64bc7c52a8504bb9ada5d60ed0949255%26pid%3D100623%26rk%3D1%26rkt%3D6%26sd%3D173464219375%26itm%3D253800990407&_trksid=p2047675.c100623.m-1

 

The voltage may go higher, but there still appears to be plenty of insulation and the high current rating should mean it should be beefy enough to handle 30 or 40 volts.

 

 

[Gareth E]

8 hours ago, dor said:

I've just bought one of these to fit as a panel isolator between the panel and controller:

https://www.ebay.co.uk/itm/Removable-Knob-Car-Marine-Boat-Battery-Isolator-Cut-Off-Kill-Switch-12V-24V-600A/253800990407?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20160323102634%26meid%3D64bc7c52a8504bb9ada5d60ed0949255%26pid%3D100623%26rk%3D1%26rkt%3D6%26sd%3D173464219375%26itm%3D253800990407&_trksid=p2047675.c100623.m-1

 

The voltage may go higher, but there still appears to be plenty of insulation and the high current rating should mean it should be beefy enough to handle 30 or 40 volts.

 

 

I've wondered about that, the connection between high amp rating and high volts. The inline isolators I've been looking at, which would be the easiest and neatest solution for me are available in different specifications, up to 150 amps. A pretty massive load. Having said that there's only mention that they are 12 or 24 volts. Does high current rating automatically correspond to high volt rating? 

[Chewbacka]

2 hours ago, Gareth E said:

I've wondered about that, the connection between high amp rating and high volts. The inline isolators I've been looking at, which would be the easiest and neatest solution for me are available in different specifications, up to 150 amps. A pretty massive load. Having said that there's only mention that they are 12 or 24 volts. Does high current rating automatically correspond to high volt rating? 

Nope.  High current rating means big contact area and high contact clamping to keep current density and contact resistance low.  High voltage rating is related to contact separation and insulation.  Too small a contact gap and any arc created when opening the switch especially under load will take some time to quench, resulting in contact burn.  This is why a switch has a much lower D.C. voltage rating than AC.

[Richard10002]

20 minutes ago, Chewbacka said:

Nope.  High current rating means big contact area and high contact clamping to keep current density and contact resistance low.  High voltage rating is related to contact separation and insulation.  Too small a contact gap and any arc created when opening the switch especially under load will take some time to quench, resulting in contact burn.  This is why a switch has a much lower D.C. voltage rating than AC.

Agreed..... exactly what I became aware of.

 

The 200A version of this has a voltage rating of 48V, the same as the 50A version that I have. All to do with the switch, and nothing to do with current carrying capability.

 

https://www.12voltplanet.co.uk/waterproof-switchable-surface-mounted-circuit-breakers.html

[WotEver]

2 hours ago, Chewbacka said:

Nope.  High current rating means big contact area and high contact clamping to keep current density and contact resistance low.  High voltage rating is related to contact separation and insulation.  Too small a contact gap and any arc created when opening the switch especially under load will take some time to quench, resulting in contact burn.  This is why a switch has a much lower D.C. voltage rating than AC.

And with fuses the distance between the ‘terminals’ matters for the same reason - no point the fuse wire blowing if an arc continues across the ends. 

[Gareth E]

2 hours ago, WotEver said:

And with fuses the distance between the ‘terminals’ matters for the same reason - no point the fuse wire blowing if an arc continues across the ends. 

Interesting to read all this. Does this suggest that the standard cheap inline midi fuses holders are OK for a very high voltage, given that there's around 5mm between the contacts in the holder when the fuse is removed?

[cuthound]

54 minutes ago, Gareth E said:

Interesting to read all this. Does this suggest that the standard cheap inline midi fuses holders are OK for a very high voltage, given that there's around 5mm between the contacts in the holder when the fuse is removed?

 

Short answer is no

 

Depends what you mean by very high voltage.

 

The definition used in the IET wiring regulations EN BS 7671 is:

 

 

Voltages 600 V and below are referred to as “low voltage,” voltages from 600 V-69 kV are referred to as “medium voltage,” voltages from 69 kV-230 kVare referred to as “high voltage” and voltages 230 kV-1,100 kV are referred to as “extra high voltage,” with 1,100 kV also referred to as “ultra high voltage.”

 

From 11,000 volts upwards circuit breakers are used, rather than fuses, which with filled with insulating oil, SF6 gas, or having a vacuum between the contacts to prevent arcing.

 

However with dc voltages used on boats etc, anything less than 75 volts is considered to be extra low voltage.

 

 

 

Edited September 8, 2018 by cuthound
Missing worm

[WotEver]

54 minutes ago, Gareth E said:

Interesting to read all this. Does this suggest that the standard cheap inline midi fuses holders are OK for a very high voltage, given that there's around 5mm between the contacts in the holder when the fuse is removed?

It’s not the distance between the holder contacts, it’s the internal design of the fuse that fits the holder. 

 

The chances are that it’d be fine, but the spec states it’s unsuitable.