genset vs. inverter
So the new boat needs a complete electrical system overhaul. No small
matter, and I would like to get it right. I have talked to several
people, including some of you offline, regarding many aspects of the
system, but the biggest brain bender for me right now is: do I install a
genset or no?
My (perceived) problems/issues/concerns.
Pro genset:
Aaahhhh, power to spare!
Want to run the A/C while at anchor? Sure, fire it up.
While on the trip down from Sault Ste Marie we had an alternator die, so
my son ran up to the auto parts store and bought an automotive battery
charger. Plugged her into the 120v system and the starter battery. Then
whenever we had 120v (genset or shore power) the starter batter was
charging. So in that case the genset was used as a backup system.
Pro inverter:
Power? What do you need the extra power FOR?
A/C at anchor? Ventilation and fans should do fine.
Sssshhh, do you hear that? Ahhhh no genny noise.
HEY! I just gained some space and lost some weight! Woohoo!
Did my wallet just get lighter? Man those gensets are expensive.
So my original thought was a genset for HVAC, emergency and whatever
else may need it. But when at anchor and not using a huge draw such as
HVAC then run off of the inverter.
Two boat owners in my area, both professionals in the boating industry
have opposite setups.
One has NO genset and a huge battery bank with a properly sized
alternator.
The other has a genset that runs ALL THE TIME. Literally. He gets on the
boat, disconnects shore power and fires up the genny. If he is underway,
the genset is running.
They both love their setups and recommend them.
For those of you who have worked with me on this in private, please feel
free to jump in, its good for the archive! :-)
On Dreamer, we have both a genset and inverter along with a large battery
bank. We also have both 12 VDC and 230 VAC air conditioning/refrigeration
so we can run the A/C with the genset off if we choose to do so, when at
anchor or when running. We run the genset a couple times per day when at
anchor to charge batteries, make water, do laundry, heat water, etc.
Wouldn't do it any differently if doing it over except for a bit larger
genset. Ours is an 8 KW Northern Lights and we would probably put in a 10
or 12 KW.
Good luck,
Bob Lowe
www.MV-Dreamer.com
www.CruisingAndMaintainingYourBoat.com
So the new boat needs a complete electrical system overhaul. No small
matter, and I would like to get it right. I have talked to several
people, including some of you offline, regarding many aspects of the
system, but the biggest brain bender for me right now is: do I install a
genset or no?
I don't have an inverter right now so I rely on the genset which runs
whenever I'm away from the dock. After a year and 900 hours on the genset,
i will be installing an inverter and dedicated battery bank so that I cut
down on the nr of hours at least in winter, from late oct thru early may,
when we don't need A/C and enjoy the silence :-)
The rest of the year, even with good ventilation, it's just too hot and
humid down here so no genset isn't an option.
pascal
miami, fl
1970 hatteras 53 MY
----- Original Message -----
From: "Paul H.P. Christen" p.christen@comcast.net
To: trawlers-and-trawlering@lists.samurai.com
Sent: Wednesday, September 29, 2004 8:49 AM
Subject: T&T: genset vs. inverter
So the new boat needs a complete electrical system overhaul. No small
matter, and I would like to get it right. I have talked to several
people, including some of you offline, regarding many aspects of the
system, but the biggest brain bender for me right now is: do I install a
genset or no?
My (perceived) problems/issues/concerns
.<><>><><><><>
3rd (or 2.5) alternative.
Inverter + small DC generator
-al-
Paul,
Maybe I'm spoiled but I want (and have) both. I believe to have a complete
system takes both.
Unlike Bob Lowe though I favor a smaller gen-set. We have a 4 KW and while
I'll admit there are probably times that we would use a larger one, we have
learned to get by.
Another thing I like about a small gen is that it is not that noisy. We have
actually been rafted with folks that did not realize our genset was running.
Also smaller units are easier to start and making sure that it will start is
key to our overall "plan".
I think I look at electrical systems a bit different from most. To me each
"appliance" stands on it own.
Example- Refrigerator. We use a "household" model, 120 volt only. It has its
own inverter and battery bank. It is wired so as to run off the 120 v A/C
system while on shore power or genset OR off 4 dedicated golf carts and a
600 watt inverter otherwise.
Same with computer. Stereo system. TV. Cabin fans. All 120v A/C only with
"their" inverters. These do however draw their power from the "house bank",
2 8Ds which also supply the normal 12v stuff. Cabin and nav. lights, helm
electronics, fresh water and bilge pumps, etc.
We run the genset very little but I'd still not be without it. Its cranked
up to make coffee most mornings as well as to run the microwave
occasionally. We like coffeemaker coffee vs. perked even though we could
perk it on the propane stove without the genset.
If the fridge batteries get low, they are only charged by a 3 stage charger,
not from main engine alternator; the genset runs for a couple of hours
recharging them.
My philosophy, flawed as it probably is, is this. The genset is our
"lifeline". It has its own cranking battery. It does nothing else and I
watch it carefully because its the anchor to the lifeline. If we go
brain-dead at anchor and let all the batteries go dead, including engine
cranking, which can be switched into the house bank so without proper
switching it could be depleted by the house load, we can start the genset
and using the two on-board chargers recharge all the batteries. Actually
three chargers if you include the Sears portable I always carry. I also
carry a "jumper" cable long enough to combine the dedicated fridge batteries
with the house batteries with the start battery. Court of last resort being
connect them all together and hope to start the main.
Does this make any sense to anybody else?
Bill
My philosophy, flawed as it probably is, is this. The genset is our
"lifeline". It has its own cranking battery. It does nothing else and
I
watch it carefully because its the anchor to the lifeline. If we go
brain-dead at anchor and let all the batteries go dead, including
engine
cranking, which can be switched into the house bank so without proper
switching it could be depleted by the house load, we can start the
genset
and using the two on-board chargers recharge all the batteries.
Actually
three chargers if you include the Sears portable I always carry. I
also
carry a "jumper" cable long enough to combine the dedicated fridge
batteries
with the house batteries with the start battery. Court of last resort
being
connect them all together and hope to start the main.
[PaulC says:]
that was my line of thinking as well. If all else fails, power up the
genny!
Paul, I'll contribute my two cents worth. Maximum flexibility, as you can
presume, is afforded by having both. I can think of plenty of scenarios
where the presence of a genset would be very useful; among others, such as
when something has drained your batteries and you're anchored out. In fact,
the amount of time you expect to be away from shorepower and anchored out or
cruising bares directly on the type of electrical system you need. I'm sure
you've heard the conventional wisdom about running the genset in the morning
to brew coffee, heat the hot water heater, do the dishes and put a decent
charge in the housebank. Then run off the inverter for most of the day,
until evening when you might crank up the genset again to help prepare
dinner, reheat the hot water heater, run the stove and/or over and top off
the housebank. That routine still makes sense in many ways.
Now, if you were underway cruising, a high-output alternator and multi-stage
voltage regulator are the way to keep both engine-starting and housebank
batteries topped off and keep the hot water heater hot. So you need to do
some forecasting regarding how you will use your boat, to best determine
what sort of electrical system(s) you need. I have both an Onan genset and
a sizeable housebank and inverter, and use them both regularly. That
affords maximum flexibility. But then, they were both aboard the boat when
we bought it. Size up your cruising plans realistically, and if you see
yourself cruising more than anchoring or docking, you may get away without a
genset. If you see yourself anchored out for long stretches, you'll
probably want the gennie.
Bob Peterson
47' Lien Hwa CMY
"Lopaka Nane"
San Francisco
-----Original Message-----
From: Paul H.P. Christen
Sent: Wednesday, September 29, 2004 5:50 AM
To: trawlers-and-trawlering@lists.samurai.com
Subject: T&T: genset vs. inverter
So the new boat needs a complete electrical system overhaul. No small
matter, and I would like to get it right. I have talked to several people,
including some of you offline, regarding many aspects of the system, but the
biggest brain bender for me right now is: do I install a genset or no?
Quoting Al Thomason athomas@sns-access.com:
3rd (or 2.5) alternative.
Inverter + small DC generator
-al-
REPLY
I'm surprised more people did not suggest this option.
As I recall Paul expressed the intent to cruise in the North East from Long
Island to Maine. This is not normally considered A/C climate the way
Florida and teh Gulf states are.
Charging batteries becomes the main function of a genset when not used to drive
air conditioning. However this is probably the worst operating condition you
can provide. Even a 100 amp charger will only draw about 12 amps when
produicing full bulk charge. This is only 20% of the normal 60 amp output from
the genset.
We have in the past discussed all the problems attendant with running a genset
at light load but constant RPM.
People like Andina who also load down the gense twith a water maker etc are
making much more efficient use fo the available power because they have
carefully configured the system so all the parts match and work together.
DC gensets by contrast are variable speed units that speed up or slow down
with loading. This the same principle now used by the new generation of Honda
sets. The benefits are several.
Typically you end up with a smaller lighter genset. It runs quieter, and burns
less fuel. (mainly a consideration if fuel range is a concern)
The maximum benefit is less wear and tear, prolonged service life on the gense
and since the unit is not being run light load at high RPM you do not get the
internal glazing and coking from poor load factor.
These tow wear conditions are amont th emost frequent contributiors to genset
failure to start. Since most posters express the sentiment that th egenset is
the option of last resort if the rest of the boat goes dead electrically I
should think the overall reliability of the genset would be of paramount
concern.
I will admit that when you use a DC genset then you are relying on inverters to
produce all your 120V AC. But if you use dedicated inverters instead of one
single unit this does not pose as much risk of total catastrophic failuer.
I should also mention that with large battery banks a DC genset can usually
recharge thi sbank faster because a 200 - 300 amp alternator is mor3 ecommon
that a shore power charger of the same size.
Most inverters or large dedicated chargers only produce 100 - 130 amps at 12V.
To acquire 200 amps capacity in a charrger will cost a great deal.
For the cruising boats with single diesel propulsion, A DC genset offers anothe
radvantage. It is easier to adapt the DC genset to also serve as a get home
wing engine. It is already configured to run at variable speed.
Using a conventional AC genset is not as practical because the motor is only
designed to run at a singe speed. Changing that requires modifying the whole
governor mechanism but then you lose the ability to produice AC power while
using it as a get home engine.
Cheers
Arild
Mark Richter did exactly that to my boat ...I have 2 6 volts golf carts
dedicated to starting the 7.5kw onan, and the 14 6volt golf carts do
everything else, start the mains and run the heart 2500. During Ivan
something happened to make the big bank go down to 11.6 v...I started the
Generator, and waited in 30minutes or so I could start the Lehman's.
Ted Brustowicz MD(ret)
trbrustowicz@cox.net
"MOONSHINE", DeFever 43
Niceville, Florida
Paul,
Genny, inverter or both???
If you travel to stay out of the really hot weather, then the choice depends
on how you cook.
I choose to carry one fuel: diesel. So I have 2 gensets and I inverter.
Normal electric household stove/oven is 240v. Best of both worlds, but
initially expensive.
If you choose to carry two fuels (diesel and propane/LNG), then you can get
away with just an inverter.
Bob
Robert Calhoun Smith Jr
M/V MARY KATHRYN
Hatteras 58 LRC
Chesapeake Bay