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wannasail 11-07-2002 01:27 PM

Gensets vs Inverters
Okay all you live aboards,
Opinions, thoughts and ideas all from experience.
Getting ready to move on board and looking to install one or the other.
Not looking for creature comforts of home but once in awhile or an emergency.
38'' CC Irwin.

Thanks in advance.

WHOOSH 11-08-2002 02:45 AM

Gensets vs Inverters
WS, I think you need to give yourself and us some more info. What will your AC needs be on the boat? Powering a tool or occasionally running a microwave? An inverter (and a properly matched DC electrical system) is the easy answer. Air conditioning, running an AC frig or heating the shower water are at the opposite end of the spectrum.

How will you be using the boat? If an occasional vacation cruise, you can purchase a lot of slip comforts enroute for the price of either one. Long term cruising? Then you may find it inviting to have a secondary power generation source (genset) or worry about being dependent on something that will possibly fail.

What about the budget? How important to you are things you will live & sail without if you buy the much higher cost genset? (Notice that''s "higher cost", not "higher price", since with gensets you keep on giving).

How easily can your Irwin swallow the genset? Where will you put it and what effect will that have on trim? On sailing in a lumpy sea or a steep chop? Do you have adequate fuel tankage? Will extra room need to be found for fuel jugs or an extra tank?What storage do you give up, and how will you feel about access for servicing if you install the genset. (The inverter is usually an ''install & forget'' item provided you give it adequate ventilation). And when thinking storage, don''t overlook the fuel & oil filters, impeller kits, special tools and the other items a genset will expect of you eventually.

And finally, what ''emergencies'' do you hope to cope with better by using the genset? Perhaps that''s where I should have started, since I can''t think of any and would worry about a genset being considered ''emergency equipment''.

In my limited experience, a boat, her crew and her budget all experience heavy compromises when bringing a genset aboard. Which doesn''t mean it''s a bad thing for some boats & crews.


petercra 11-10-2002 05:17 AM

Gensets vs Inverters
In my view a 38 foot boat is too small for a generator. The only circumstance where it should even be considered is if you have air conditioning. In that case it''s only because the power drain is just too great for any reasonably sized inverter or battery bank.

You can get 1000-2000 watt inverters which are very light and compact. Pro Watt makes a line. Heart also has a line of inverters, but they''re older technology (low frequency, requiring a bigger transformer) and much bigger and heavier. I believe Heart was selling the Pro Watt line at one time.

Dashew''s Sundeer line of boats (up to 65 feet or more) are designed for live aboard world cruising, and generally rely on big alternators, huge battery banks and an inverter to provide power, rather than a generator.

If you couple the inverter with an oversized alternator you can run the engine while the inverter powers big loads. In effect you have a generator, at much lower cost, and consuming much less space and weight. I have a 1000-1200 watt Pro Watt and use it that way all of the time. The bonus is that you don''t need to start the engine at all if the load is small or for only a few minutes. With a generator only you have no a.c. at all without starting the generator.

Diesel generators are very, very expensive. Non marinized gas generators are fairly inexpensive. The only way a gas generator could ever even be considered would be if the fumes could not leak into the bilge. This would probably mean leaving it on deck or draining all of the gasoline out of it. Neither is a good solution except for emergency or backup use only.

wannasail 11-10-2002 05:32 AM

Gensets vs Inverters

Wife and I intend to live aboard and travel the ICW south from MD with intentions of visiting various ports south into the Gulf and eventually into the Caribbean.
We have intentions of mostly anchoring along the way except when in areas where we want to spend longer then usual sightseeing then we would look for a marina as a transient.

Would like to have a cell phone which will need it''s battery charged from time to time. TV/DVD/Tape combo with minimul usage. Laptop computer for "e" mail and weather or other sailing issues again minimul usage. Female electrical devices from time to time again minimul usage. Man stuff, power tools when needed.

No microwave, electric coffee pot, etc.

Have AC/Heat aboard but have not used it since purchasing the boat with the exception of testing from time to time while in the slip.
Don''t care to use it but from what we are hearing the AC may be useful in areas further south. Issue we are not certain about.
Is it possible to have a small genset to run the AC only leaving the inverter for all other uses?
Have room in lazaret depending on size of genset. Also have room in engine compartment.Assuming genset can run off diesel have two 30 gal tanks.

Emergency use! Since I''m just starting research unfamilier with total usage of a genset.

Currently budget okay since we are working. Once retired we will go day by day. Have pension and other assets.


wannasail 11-10-2002 05:47 AM

Gensets vs Inverters

When you cite coupling the inverter with an oversized alternator and running the engine at the same time, what load usage by the inverter is acceptable.


wgfi 11-10-2002 08:51 AM

Gensets vs Inverters
If your boats is 35'' or over your budget will be your controling factor.

WHOOSH 11-10-2002 04:13 PM

Gensets vs Inverters
Ray, based on your planned itinerary (ongoing cruising, ICW first but later the Caribbean), I think you''d be putting a lot of money and weight into - and taking a lot of space out of - your boat in order to have gear you will only occasionally wish you had. We used all the gadgets you mentioned in 2000-2002 on that same varied cruising route while relying on a Freedom 1000 watt inverter. There are ''those days'' on the ICW when the bugs are super small and get everywhere, and the heat sticky and relentless...but it''s not unreasonable to use a slip for a portion of just the maintenance costs of a generator at such times. Moreover, folks often tend to go north in the summers and travel the ICW in the Fall/Spring when frontal weather patterns provide frequent breezes and the weather is less oppressive. Once you depart the U.S. you''ll find the Trades to be a huge help in making the boat habitable in even mid-day hot weather. Better you think about a good bimini and awning arrangement, I think.

However, it''s important that you work your energy equation thoughtfully (e.g. see either of Calder''s two reference books) and be sure you''re sizing each piece of the electrical equation to be compatible to the overall system. Know your average daily consumption, understand the small span of actual stored amp/hrs that you can routinely use from the house bank(s), insure your alternator is capable of recharging the bank(s) over an acceptably short period of time, and use a smart regulator to help you with all this (the Link 2000R is excellent gear, e.g.). Alternators in particular can be a troublesome piece of the equation, eating belts, wearing bearings, etc. Plus the heat often kills the less stout ones; they become *very* hot at high output levels.

You''ll find a variety of (relatively) small gensets available, altho'' typically they are intended for DC power solutions (watermaker, battery charging). Your 12,000 or 16,500 BTU A/C unit will require a bigger, more conventional genset, I fear.

Good luck on The Plan!


manateee_gene 11-10-2002 06:50 PM

Gensets vs Inverters
I agree with you! on 38'' a big battery bank a stout alternator and a big inverter will do the job.
We use a 900watt microwave, toaster, coffee pot and other great electrical gear on our 32'' boat. 660 Amps of batteries,1500watt inverter,130 amp alternator, plus solar panels. P.S. never ever turn off our Alder Barber 12vdc refrig.
Gene S/V Teacher''s Pet III

petercra 11-11-2002 05:49 AM

Gensets vs Inverters

I believe your question is what sort of duty cycle an inverter would be good for, i.e. would there be a problem running the engine for extended periods to power the inverter. Inverters generally have a continuous and a peak rating which is higher. Inasmuch as they are electronic, they won''t wear out from overuse. Most, if not all, have protection from overcurrent or overheating built in; it should not be possible to damage them by overloading them or running them for too long. It is possible, however, that the continuous duty spec might be optimistic, meaning that the unit would eventually overheat and shut itself off, even though run at or below the specification. This is a function of how large the heat sink is, the ambient temperature, and the size of the cooling fan, if any. On my Pro Watt, the cooling fan comes on after 3 or 4 minutes of powering the microwave.

I would try to talk to the manufacturer to get a sense as to how conservative the continuous duty spec is, and oversize the inverter somewhat accordingly.

When powering the inverter from the engine, I''d be much more concerned about damage from the engine due to it being run at low loads for extended periods (assuming this is done while at anchor rather than underway).

If you have an air conditioner but aren''t sure if you want to use it away from a dock I''d stay away from a generator. However, depending on the size of the air conditioner I doubt that it would be viable to run it using the engine/inverter combination. At night you''d have to worry about carbon monoxide, and you''d have to worry about causing damage to your engine due to extended running at minimal load.

If you''re planning on recharging cell phone and other batteries, be careful that the type of charger is compatible with the inverter. Most should be OK, but there are some very inexpensive chargers that can be damaged by the modified square wave put out by most inverters, for example some rechargeable shavers. As I recall, chargers which have transformers in them are generally OK, but you may want to verify. To be 100% safe, and if possible, I''d recharge cell phones, etc. directly from the 12 volts rather than using an a.c. charger. Also, a few computers/TVs/VCRs have problems with the modified square wave, they usually won''t be damaged, but may do strange things. It is possible to get a sine wave inverter (ProWatt makes), but they''re a lot more expensive.

wannasail 11-16-2002 09:43 AM

Gensets vs Inverters
Thanks to all who responded. Your info. will be put to good use.
Thanks again.

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