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Steve

External


Since: Jun 05, 2005
Posts: 14



(Msg. 1) Posted: Wed Mar 30, 2005 10:37 pm
Post subject: Inverter question
Archived from groups: rec>boats>electronics (more info?)
I would like to wire up the inverter on my boat to be very simple to
switch on and connect into the boats mains wiring. Ideally I want just
one switch. I am happy for this to be a big battery switch. I want the
plugs and other mains appliances (microwave, some lights etc) to just
work when I flick the switch. This is further complicated by the need to
not run other things - the battery charger is the only one that comes to
mind - from the inverter.

I am thinking about using a relay which will automatically disconnect
the inverter from the internal cct breaker and fuse panel if shore power
is connected. The same relay can also connect up the shore power only
circuits.

To do this seems simple... I use a 3 or 4 pole DT relay which is
energised by the shore power feed and will connect the feed to the fuse
panel input. When shore power is removed the relay will switch the
inverter output to the fuse panel input and disconnect the battery charger.

Does anyone see a problem with this? The only worry I had was that there
could be an issue with voltage spikes when the mains is unplugged and
some motor or coil gets connected to the inverter as its field collapses
(which may or may not be actually on). Presumably the inverter is
protected against such things cause by the DC power vanishing but having
the relay there means that the voltage switched on to the inverter when
the contacts eventually close could be quite high. Do inverters normally
have protection against such transients?

Alternatively, a 12VDC energised relay could be used that is on the same
switch as the inverter power. It would then disconnect the shore power
if the inverter is on. This has a couple of draw backs. 1) I need to run
the relay whenever the inverter is to be used (ok I know it is
insignificant but... well - you know!..) 2) I don't get an option for
automatic fail over if shore power fails. Which may be a good or bad
thing but at least it is an option. 3) the big spike could end up on the
shore power plug but I don't think will be any worse than when you
unplug the shore power by pulling the plug out.

Thanks in advance,

Steve

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Dennis Pogson

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Since: May 11, 2004
Posts: 18



(Msg. 2) Posted: Wed Mar 30, 2005 10:37 pm
Post subject: Re: Inverter question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
Steve wrote:
> I would like to wire up the inverter on my boat to be very simple to
> switch on and connect into the boats mains wiring. Ideally I want just
> one switch. I am happy for this to be a big battery switch. I want the
> plugs and other mains appliances (microwave, some lights etc) to just
> work when I flick the switch. This is further complicated by the need
> to not run other things - the battery charger is the only one that
> comes to mind - from the inverter.
>
> I am thinking about using a relay which will automatically disconnect
> the inverter from the internal cct breaker and fuse panel if shore
> power is connected. The same relay can also connect up the shore
> power only circuits.
>
> To do this seems simple... I use a 3 or 4 pole DT relay which is
> energised by the shore power feed and will connect the feed to the
> fuse panel input. When shore power is removed the relay will switch
> the inverter output to the fuse panel input and disconnect the
> battery charger.
>
> Does anyone see a problem with this? The only worry I had was that
> there could be an issue with voltage spikes when the mains is
> unplugged and
> some motor or coil gets connected to the inverter as its field
> collapses (which may or may not be actually on). Presumably the
> inverter is protected against such things cause by the DC power
> vanishing but having the relay there means that the voltage switched
> on to the inverter when the contacts eventually close could be quite
> high. Do inverters normally have protection against such transients?
>
> Alternatively, a 12VDC energised relay could be used that is on the
> same switch as the inverter power. It would then disconnect the shore
> power
> if the inverter is on. This has a couple of draw backs. 1) I need to
> run the relay whenever the inverter is to be used (ok I know it is
> insignificant but... well - you know!..) 2) I don't get an option for
> automatic fail over if shore power fails. Which may be a good or bad
> thing but at least it is an option. 3) the big spike could end up on
> the shore power plug but I don't think will be any worse than when you
> unplug the shore power by pulling the plug out.
>
> Thanks in advance,
>
> Steve

We have a 3-way switch (Off, Inverter,Shore Power) on our Beneteau 50. This
is the first switch we use on entering the boat. The battery charger is
wired to only operate when the switch is on Shore Power. Seems to work OK.

Dennis.


----
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Larry W4CSC1

External


Since: Apr 25, 2004
Posts: 110



(Msg. 3) Posted: Thu Mar 31, 2005 8:19 pm
Post subject: Re: Inverter question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
Steve <nospam.TakeThisOut@for.me> wrote in news:424BCD23.50909@for.me:

> You are kidding right? If not, what specific code are you referring to?
> I think my insurance says you need a electrician to certify it.
>

Unless you are in some third world country, your country will have an
ELECTRICAL CODE, like the NEC (National Electric Code) in the USA. All
electrical components must be NEC components.

Your question was about something home-made. If it ever caused a fire and
were "Not To Code", the insurance company would simply disallow the claim.

An example happened to a country church I used to fix the Hammond organ
for....

Instead of buying proper in-floor 115VAC recepticals, those round brass
floor outlets you see in a mall store all over which have flip-top covers
or screw covers to protect the sunken outlets noone can step on and break,
the church decided to save a few bucks by installing wall outlets in the
stage floor on either side of the pulpit and putting a metal outlet cover,
no protection at all, on them. This is NOT to CODE. They are WALL
outlets.

Well, someone stepped on one and cracked open the plastic outlet, but it
didn't immediately arc and catch the wooden stage on fire. That happened
some time between Sunday night service and Wednesday prayer service. Being
isolated way out in the country, noone saw it go up in flames. The
insurance company found out about the Not to Code wiring and disallowed the
claim for the fire.

Don't blame me....ask your insurance guy if you can put a home-made relay
in your AC line and be insured by his underwriters.....
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Larry W4CSC1

External


Since: Apr 25, 2004
Posts: 110



(Msg. 4) Posted: Thu Mar 31, 2005 8:21 pm
Post subject: Re: Inverter question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
Steve <nospam.RemoveThis@for.me> wrote in news:424BCD23.50909@for.me:

> 50A! I only have 20A wiring but then it is for 240V. Does that mean you
> don't think that the voltage spike will cause a problem to the inverter
> when the mains is unplugged?
>

Proper transfer equipment OPENS the circuit between the time it disconnects
from one AC source and connects to the other. There are no spikes. Break
before make it's called.

You'll notice a little dark period between when the AC line disconnects and
the genset connects when the transfer switch is thrown, automatic or
manual.
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Steve

External


Since: Jun 05, 2005
Posts: 14



(Msg. 5) Posted: Thu Mar 31, 2005 10:19 pm
Post subject: Re: Inverter question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
I did look at three way switches but could not get one with enough poles
to do everything I wanted. I would need 2 for the live and neutral, one
for the battery charger and then I would also have need something to
turn on the DC power to my inverter (probably an electronic battery
switch driven by another pole). I am guessing that you have something
very flash and expensive which I will wish I had spend money on in a few
years when my stuff is playing up.

Thanks for the reply.

Steve

Dennis Pogson wrote:
>
>
> We have a 3-way switch (Off, Inverter,Shore Power) on our Beneteau 50. This
> is the first switch we use on entering the boat. The battery charger is
> wired to only operate when the switch is on Shore Power. Seems to work OK.
>
> Dennis.
>
>
> ----
> Remove *nospam* to reply.
>
>
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Dennis Pogson

External


Since: May 11, 2004
Posts: 18



(Msg. 6) Posted: Thu Mar 31, 2005 10:19 pm
Post subject: Re: Inverter question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
Steve wrote:
> I did look at three way switches but could not get one with enough
> poles to do everything I wanted. I would need 2 for the live and
> neutral, one for the battery charger and then I would also have need
> something to turn on the DC power to my inverter (probably an
> electronic battery switch driven by another pole). I am guessing that
> you have something very flash and expensive which I will wish I had
> spend money on in a few years when my stuff is playing up.
>
> Thanks for the reply.
>
> Steve
>
Not really, it's a circular 3-way DC switch with a pointer/knob which turns
left, right, and straight up. AFAIR our +/- battery leads (massive) go
straight to the inverter via the main master switches (2,+/-), and there is
an on/off switch on the inverter itself. With the 3-way switch off, turning
on the inverter's on/off switch does nothing, with the 3-way switched to
shore power, the battery charger and all the 12-volt systems are activated,
but the inverter is still out of circuit. Only when the 3-way is switched to
inverter is it possible to activate the inverter and the 240-volt ring main
et al. The only remote switch we have is the gas solenoid in the cockpit gas
locker, actuated by a contact-breaker switch on the main saloon panel. It's
all manual, and all very simple.

Dennis.
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Steve

External


Since: Jun 05, 2005
Posts: 14



(Msg. 7) Posted: Fri Apr 01, 2005 8:40 pm
Post subject: Re: Inverter question [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
Larry W4CSC wrote:
>
> Proper transfer equipment OPENS the circuit between the time it disconnects
> from one AC source and connects to the other. There are no spikes. Break
> before make it's called.
>
> You'll notice a little dark period between when the AC line disconnects and
> the genset connects when the transfer switch is thrown, automatic or
> manual.
>
Surely a double throw relay does this as well in that it cannot connect
one (inverter say) unless the other (shore power) is disconnected.
Unless there is a much bigger delay than I am thinking (i.e. >20ms).
Even then I wonder what the delay would need to be to ensure no spike?
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