chevron Posted July 18, 2019 Report Share Posted July 18, 2019 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 More sharing options...
MtB Posted July 18, 2019 Report Share Posted July 18, 2019 Simple answer is yes. This assumes the three way switch is rated to switch the voltage and current being used during switching. Link to comment Share on other sites More sharing options...
GUMPY Posted July 18, 2019 Report Share Posted July 18, 2019 (edited) 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 July 18, 2019 by Loddon Link to comment Share on other sites More sharing options...
nicknorman Posted July 18, 2019 Report Share Posted July 18, 2019 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. 1 Link to comment Share on other sites More sharing options...
Machpoint005 Posted July 18, 2019 Report Share Posted July 18, 2019 2 hours ago, nicknorman said: I would favour unplugging when not in use. That's what I always do. The lack of significant hull corrosion on a 20-year old boat, last time it was out of the water, suggests that the strategy works. Link to comment Share on other sites More sharing options...
MtB Posted July 18, 2019 Report Share Posted July 18, 2019 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 More sharing options...
GUMPY Posted July 18, 2019 Report Share Posted July 18, 2019 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 More sharing options...
chevron Posted July 18, 2019 Author Report Share Posted July 18, 2019 Looks like to be safe I still have to unplug the lead then Link to comment Share on other sites More sharing options...
WotEver Posted July 18, 2019 Report Share Posted July 18, 2019 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 More sharing options...
chevron Posted July 18, 2019 Author Report Share Posted July 18, 2019 By underload the only thing drawing current is the mains fridge so I should turn that off at its socket switch first Link to comment Share on other sites More sharing options...
WotEver Posted July 18, 2019 Report Share Posted July 18, 2019 1 minute 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 Yes you should Link to comment Share on other sites More sharing options...
GUMPY Posted July 18, 2019 Report Share Posted July 18, 2019 19 minutes ago, WotEver said: Unless it’s under load... See my first post on this subject! Link to comment Share on other sites More sharing options...
dccruiser Posted July 18, 2019 Report Share Posted July 18, 2019 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 More sharing options...
dixi188 Posted July 18, 2019 Report Share Posted July 18, 2019 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 More sharing options...
ditchcrawler Posted July 18, 2019 Report Share Posted July 18, 2019 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 More sharing options...
GUMPY Posted July 18, 2019 Report Share Posted July 18, 2019 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 More sharing options...
ditchcrawler Posted July 18, 2019 Report Share Posted July 18, 2019 1 minute ago, Loddon said: Which matters not a jot if there is an IT or GI The original question was about arcing not galvanic action.............. True, but did come into the conversation later on. Link to comment Share on other sites More sharing options...
GUMPY Posted July 18, 2019 Report Share Posted July 18, 2019 2 minutes ago, ditchcrawler said: True, but did come into the conversation later on. What colour are herrings these days ? Link to comment Share on other sites More sharing options...
ditchcrawler Posted July 18, 2019 Report Share Posted July 18, 2019 Just now, Loddon said: What colour are herrings these days ? Dyed or local? Link to comment Share on other sites More sharing options...
chevron Posted July 18, 2019 Author Report Share Posted July 18, 2019 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 More sharing options...
Jen-in-Wellies Posted July 18, 2019 Report Share Posted July 18, 2019 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 More sharing options...
1st ade Posted July 18, 2019 Report Share Posted July 18, 2019 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 More sharing options...
cuthound Posted July 19, 2019 Report Share Posted July 19, 2019 This^^^^ I have seen the results of 2 x 1000kVA being paralleled when out if sync and it wasn't pretty. Link to comment Share on other sites More sharing options...
ditchcrawler Posted July 19, 2019 Report Share Posted July 19, 2019 I have attempted to put 2 gennies on the line with bad sync and I was showing someone how to do it at the time, The breakers coming out were quite noisy Link to comment Share on other sites More sharing options...
waterdog Posted November 2, 2019 Report Share Posted November 2, 2019 (edited) 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. Edited November 2, 2019 by waterdog edit to add photo's Link to comment Share on other sites More sharing options...
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