Jump to content

Three way switch


chevron

Featured Posts

In the day I run the mains electric via an inverter using the solar power. At night I switch back to shore power is there any need to disconnect the shore power lead before turning the three way switch between the different positions? Can I just leave the shoreline plugged in have been told leaving it in can cause arcing across contacts of switch when switching over. What do others do please.

 

 

Link to comment
Share on other sites

Depends entirely on the switch.

If it is a break before make switch rated to the correct current/voltage then no need to disconnect

unless you know that it is then its safer to disconnect the shore  power before you switch over to the inverter and reconnect after you have switched back. 

As always never switch/plug unplug when under load.

Edited by Loddon
Link to comment
Share on other sites

There are two conflicting issues at play, one is that repeated plugging and unplugging of the connector will eventually wear it out. The other is that having a permanent shore earth connection will maximise the chances of electrolytic / galvanic corrosion of the hull.

 

The latter issue is reduced by having a decent galvanic isolator or isolation transformer.

 

Since getting a new pair of connectors is pretty cheap compared to getting a new hull, I would favour unplugging when not in use. Especially if you don’t have a GI or an IT.

  • Greenie 1
Link to comment
Share on other sites

2 hours ago, Loddon said:

Depends entirely on the switch.

If it is a break before make switch rated to the correct current/voltage then no need to disconnect

 

This is a very good point. If the OP's switch happens to be make-before-break, then the two AC supplies will be momentarily connected and almost certainly out of phase with each other, leading to all manner of possible damage. 

 

I'm also wondering if by "three way switch" the OP means he has a three pole single throw switch.

Link to comment
Share on other sites

You should never be able  wear out a 16amp connector by plugging and unplugging it.

The industrial plug and socket has an average lifespan of more than 10 years. The allowed times of insertion is up to 100,000.

So that is 10,000 times a year over the average lifespan of a connector or 27 times a day every day of the year ;)

 

 

Link to comment
Share on other sites

37 minutes ago, Loddon said:

You should never be able  wear out a 16amp connector by plugging and unplugging it.

The industrial plug and socket has an average lifespan of more than 10 years. The allowed times of insertion is up to 100,000.

So that is 10,000 times a year over the average lifespan of a connector or 27 times a day every day of the year ;)

Unless it’s under load...

Link to comment
Share on other sites

1 hour ago, chevron said:

By underload the only thing drawing current is the mains fridge so I should turn that off at its socket switch first

surely easier to knock off the mcb/s on your mains, then nothing can be connected :) 

 

Rick

Link to comment
Share on other sites

If by Three Way Switch, you mean one that has three positions, ie. ON-OFF-ON, (like on my boat), then there is no need to disconnect the shore power as there is no possibility of the two sources meeting.

Link to comment
Share on other sites

16 minutes ago, dixi188 said:

If by Three Way Switch, you mean one that has three positions, ie. ON-OFF-ON, (like on my boat), then there is no need to disconnect the shore power as there is no possibility of the two sources meeting.

But the shore earth is still connected

Link to comment
Share on other sites

12 minutes ago, ditchcrawler said:

But the shore earth is still connected

Which matters not a jot if there is an IT or GI

The original question was about arcing not galvanic action..............

Link to comment
Share on other sites

What I was thinking was that by switching between shore connection to inverter or generator position with shore line connected would I cause any damage to the switch or worst current flow while switching over. I do have a galvanic isolator.

Link to comment
Share on other sites

6 minutes ago, chevron said:

What I was thinking was that by switching between shore connection to inverter or generator position with shore line connected would I cause any damage to the switch or worst current flow while switching over. I do have a galvanic isolator.

Mains switches are actually very good at switching  when under load. Much better than similar DC ones. The voltage and current drop to zero 100 times a second, which minimises the amount of arcing and the erosion of contacts. The risk in this case is if the switch makes one set of contacts before it breaks another, which could result in some combination of power source - inverter, shore line, or generator being momentarily connected together. As @Mike the Boilerman says, they are likely to be out of phase with each other and damage could result. Without knowing how the switch is constructed internally it isn't possible to say.

 

Jen

Link to comment
Share on other sites

42 minutes ago, Jen-in-Wellies said:

...damage could result.

99.9% sure that "damage" will be a big bang and loss of eyebrows!

 

Unless the two supplies are not only in sync but of identical peak voltage (and frequency) there is likely to be what the textbooks call "significant fault current"

 

And given the low probability of being in sync, same voltage, same frequency - if there wasn't a sharp "pop" when you did it the first time you are probably OK for the second...

Link to comment
Share on other sites

  • 3 months later...
On 18/07/2019 at 09:27, chevron said:

In the day I run the mains electric via an inverter using the solar power. At night I switch back to shore power is there any need to disconnect the shore power lead before turning the three way switch between the different positions? Can I just leave the shoreline plugged in have been told leaving it in can cause arcing across contacts of switch when switching over. What do others do please.

 

 

I have a similar question to Chevron's above regarding the equipment on our "new" to us boat.

 

We have moved into a marina after cruising all summer and now have the option of electrical hook up and like chevron I've considered disconnecting the hook up and using the solar during the day if the sun is out, hoping to reduce the electric bill. (probably wishful thinking over winter)

 

The boat has the following equipment fitted,

 

Mastervolt 2kw psw inverter

separate mastervolt charger

galvanic isolator

3.5kw travelpower

1.2kw solar.

1kw immersion (only on hook up or travelpower)

 

There is no change over switch, the boat seems to automatically decide which power supply to use depending on whether the hook up is connected or not. For instance when on hook up the charger automatically comes on and keeps the batteries at a steady 13.69v. (0.4 amp charge rate at the moment)

 

We are also pretty power hungry with a 240v fridge, tv, satellite box, freezer, washing machine and charging for laptop. tablets, phones. lighting is all led, + the usual pumps etc.

 

So, the questions,

 

 

On 18/07/2019 at 14:51, dccruiser said:

surely easier to knock off the mcb/s on your mains, then nothing can be connected :) 

 

Rick

1. What is best practice when disconnecting / reconnecting the shoreline? 

 

We have two 230v switch panels (will post a photo in a minute). I'm guessing one for shoreline and one for inverter ??? 

Would it be better to switch off / on there rather than plugging / unplugging the shoreline?

 

2. When on shore power should I switch the inverter off. It stays on according to the MICC panel?

 

3. Is it worth bothering with at all or just stay on hook up 24/7 and have a bigger leccy bill?

 

Photos of equipment to follow.

 

 

 

 

 

 

WIN_20191102_09_13_21_Pro.jpg

WIN_20191102_09_15_18_Pro.jpg

WIN_20191102_09_15_38_Pro.jpg

WIN_20191102_09_19_18_Pro.jpg

Edited by waterdog
edit to add photo's
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.