[C38] FW: Re: Questions, questions

[Tom T.]

Hello sailors,

I have been reading the inverter posts with interest.  I have several
inverters and all of mine are of the modified sine wave type which are
cheaper but not as efficient as a true sine wave, especially starting an
inductive load such as a motor.

Inductive loads like motors usually require more current at start up but
the modified sine wave inverters require even more than the true sine wave
inverters, as much as 200% of the running load.  Purely resistive loads
like incandescent light bulbs are not effected by the less efficient
modified square wave outputs of the cheaper inverters but inductive loads
like motors are another story.

All of my inverters produce about 120v at the hot output side of the
receptacles.   The common side of the outlet should be zero output voltage
from the inverter in a perfect world but as Les pointed out, there are
usually small transient voltages on that leg in even the best inverters.

Grounding the inverter should reduce or eliminate these "ground loops" as
the old timers used to call them.  The transient voltages on the  common
cold side of the outlets of our inverters can also interfere with
electronic equipment on board reducing the sensitivity of our VHF radios as
well as making "white noise" on other radios, especially AM reception.

Getting back to the idea of using industrial rated 3-way light switches to
make a load transfer system may require more discussion.

A typical 2000 watt modified sine wave inverter will probably never require
over 28 momentary amps even on a momentary surge startup condition.  The
industrial rated 3-way switches I have been using are rated at 30 amps and
cost just under $13 at Lowe's and Home Depot.

I have personally used this load transfer switch technique on 3 boats and 5
homes over a 20 year period and I have yet to experience a single failure. 
The main solenoid switch on my home air conditioning is only 30 amps and
I'm sure it gets more abuse than we will ever give a similar rated switch
on a little 2000 watt inverter.

At one time, we had a portable second air conditioner on our Catalina 38
mounted on a bridge over the v-berth mounted between the two side
pin-rails.  I have pictures if anyone is interested.  That air conditioner
was a modified  8,500 BTU window unit with a water cooled condenser and
cooled by a 120v sea water pump mounted under the v-berth on the bulkhead
holding the water tank.

As an experiment, I powered the water cooled forward air conditioner with
my 2000 watt inverter system and the system did just fine.  I didn't leave
it running long because the load on my engine alternator was beyond its
capacity to keep my house batteries charged but it did instill confidence
in the load capacity of my inverter setup.  After that, the only thing I
used the inverter system for was for running my 120v refrigerator, the
microwave, and sometimes an electric saw or drill.  As a rule on inverters,
if you can start an inductive load, you can run it since the most demand is
in the first few seconds trying to get things going.

A 30 amp switch can carry a whole bunch of current, more than a 2000 watt
inverter will probably ever need.  If you use two switches, you can divide
the loads giving any high demand load its own switch for more safety or if
you use an inverter larger than 2000 watts.


Good luck,

Tom Troncalli
Recovering ex-owner of a Catalina 38



> [Original Message]
> From: Les <hlhowell at pacbell.net>
> To: Catalina 38 Listserve <listserve at catalina38.org>
> Date: 7/10/2010 5:51:00 AM
> Subject: Re: [C38] Questions, questions
>
> I noticed that the GFCI won't work on my inverter either.  It depends on
> whether your inverter is isolated or not, I think.  Generically the 12 v
> system on our boats as factory installed ( I think) was with negative
> tied to the shaft for boat ground.  When you run an inverter, the signal
> design puts the AC out as polarized differential, with no real ground,
> as there are considerable transients on the converter boards (unless you
> have one of the fancy true sine wave inverters with isolation).  That
> means that on one half cycle, one side of the outlet is tied to the AC +
> and the other to ground.  When the inverter flips, the signal is
> reversed on the AC receptacles, giving you the +60v on the opposite side
> of the receptacle and ground is also switched,  You can almost think of
> a 60v battery with a double throw switch where the output is the common,
> and the 60v is wired to one side, then the wires cross to the other side
> of the switch. Lets call the contacts a A, and b B with common being c
> C.
>
> 	+ wired to a and B
> 	- wired to A and b.
> 	when the switch is set to the A side, the C is + and c is -
> 	When the switch is flipped to the B side, the C is - and the c is +, so
> the full cycle on each across is from 60v one polarity to 60v the
> opposite polarity, giveing you 120v AC.
>
> 	If the inverter is not isolated, you can't make a GFCI outlet work
> because there is no real AC ground.  I don't know if this could be
> solved with a transformer or not.  If you could it would still be a heck
> of a big transformer to carry 15A safely.
>
> Regards,
> Les H
>
> On Fri, 2010-07-09 at 09:39 -0400, Charles B. Finn wrote:
> > Tom and Les,
> > Thanks!  I actually set out to employ Tom's version as he had told me 
> > about it a while back.  The problem I ran into that gave me pause has 
> > nothing to do with wiring.  Rather it is that recurring problem of 
> > memory!  The water heater and battery charger on my boat are wired into 
> > the two, separate circuits.  My inverter is capable of powering these, 
> > but of course my battery bank is not.  You would think I should notice 
> > the draw when I switch over, but the inverter has to be located within
3 
> > feet of the battery bank.  Second is people other than me routinely
turn 
> > the inverter on to charge cell phones, etc.
> > My official notice that something is wrong is when the inverter starts 
> > beeping to tell me voltage levels have dropped.
> > My choices then were to separately wire the water heater and battery 
> > charger, or separately run wires to the top outlet receptacle.  I am 
> > going with the later partially because the project is already underway 
> > and partially because it seems more of a "failsafe" setup.  The plan is 
> > one, two-wire from the inverter that runs up the port side to the cabin 
> > outlet, then to the one in the head (to charge my electric toothbrush 
> > which no civilized being can do without anymore), then to the vee berth 
> > outlets and then down the starboard side to the cabin outlet.  I don't 
> > plan to run a wire to the galley as the inverter is right there anyway.

> > I probably should run a remote shutoff switch for the inverter (it has 
> > this option) to the chart table.  Total cost is about $40.00.  One
thing 
> > I should note is that GFI's won't work on the inverter circuit.
> > 
> > Tom,
> > I actually am adopting your home charging solution!  Home Depot wants 
> > $300 for a switch that does not do half of what your solution does. 
Thanks!
> > 
> > Chuck Finn
> > Mighty Quinn #114
> > Great Lakes
> > 
> > On 7/8/2010 4:33 PM, T. Troncalli wrote:
> > > Hello Charles,
> > >
> > > I'm behind in reading my emails but if I'm not too late, there is an
> > > alternative to having a dual wiring system on your boat to
accommodate an
> > > inverter.
> > >
> > > I ran the receptacles from three outlet boxes to a double pole
switch.  The
> > > common terminal on the double pole switch ran to the three
receptacles and
> > > one of the switchable terminals ran to my 120v service and the other
to the
> > > inverter.  With this system those outlets would deliver either shore
power
> > > or inverter power depending on how the double pole switch was set.
> > >
> > > I had one outlet box in the corner of the quarter berth above the
mattress
> > > and below the electrical panel.  With that outlet, I could run things
on the
> > > nav station like TV's, phone chargers, etc.
> > >
> > > I had another outlet just forward of the sink drain valve door on the
side
> > > of the end of the aft table seat just to starboard of my house
batteries.
> > > This outlet was fairly central to things in the cabin and with an
extension
> > > cord I could reach anywhere in the boat.
> > >
> > > The third outlet on this system was in my sail locker which ran my
120v
> > > refrigerator when underway as well as giving me a source of 120 volts
in the
> > > cockpit if the sail locker was open.
> > >
> > > A good double pole industrial grade switch is cheap but you can also
use an
> > > industrial rated 3-way light switch found at any hardware store like
Lowe's
> > > or Home Depot.   The nice thing about using a 3-way switch is you can
use a
> > > plastic residential switch enclosure making installation very cheap
and
> > > easy.
> > >
> > > If you want, you can even make two or three transfer switch circuits
> > > allowing more dual voltage outlets as well as allowing more current
from an
> > > inverter or genset without exceeding the amperage limits of your
switch.
> > >
> > > I've have also used this system to run my whole house when we had
power
> > > outages.  I had 10 transfer switches.
> > >
> > > One other nice thing about using multiple switches to transfer the
loads to
> > > an inverter or genset is that this system stages the transfer so the
> > > inverter or genset can adjust to the increased loads as the loads are
> > > switched.  When I tried to use a large single 40 amp motor contactor
relay
> > > to power my house it would stall my generator with the same loads that
> > > worked fine using multiple double pole switches to accomplish the same
> > > transfer.
> > >
> > > I wrote an article about wiring generators using multiple double pole
> > > switches back in the Y2K daze when everyone thought the sky was
falling.  MY
> > > article was cloned and plagiarized all over the world and no telling
how
> > > many people used this technique.  Every now and then I still run
across a
> > > clone of my original article, usually including spelling errors and
all.
> > >
> > > Good luck,
> > >
> > > Tom Troncalli
> > > Recovering ex-Catalina 38 owner
> > >
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: listserve-bounces at catalina38.org
> > > [mailto:listserve-bounces at catalina38.org] On Behalf Of Charles B. Finn
> > > Sent: Thursday, July 08, 2010 10:41 AM
> > > To: Catalina 38 Listserve
> > > Subject: [C38] Questions, questions
> > >
> > > I finally am going to do the right thing and set up separate wiring
for my
> > > 2500 watt inverter.  My plan is to split the existing outlets so the
top
> > > receptacle is for the inverter circuit and the lower is shore power. 
I will
> > > do this simply by running separate wires to the outlets and removing
the
> > > jumper to separate upper outlets.  But I have two questions.
> > >
> > > 1.  What type of wire was used on the AC side of our boats?  Are they
> > > stranded wire?  What gauge?
> > > 2.  I would like to use the common ground that is already wired in,
which
> > > will save running a third wire.  I don't think this is a problem, but
sure
> > > would like to hear if it is!
> > >
> > > On another topic, the forward in my transmission went away three
weeks ago
> > > just before I had to leave for two weeks of business in California.
> > > This meant I had to pay folks to remove it and repair it....
something I
> > > hate to do!   But, I will shortly be able to report on shop times and
> > > costs for a repair like this!  I also have researched parts costs and
even
> > > found additional manuals on our transmissions, which I will shortly
> > > be posting to our website.   But for now, I can report that the HBW-5
> > > (50) is another part of our boat (like the heat exchanger) that is at
the
> > > outer design limit for our powertrain.....  We should expect to see an
> > > increasing number of failures and it is forward gear that wears out.
> > >
> > > Happy Sailing!
> > > Chuck Finn
> > > Mighty Quinn #114
> > > Great Lakes
> > >
> > > _______________________________________________
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> > >
> > >
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> > >    
> > 
> > 
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