Do I need a genset and if so what size?

[impi]

oh and I almost forgot ... a mate of mine is using a similar genset to the pic you posted on his cat called Champollion ... he hates the petrol fumes and hardly uses it anymore

[impi]

Originally Posted by senormechanico

With all the great design of your boats, I'm a little taken back about your rather mastodon genset idea.

My 33' Dragonfly needs no genset.
320 watts of solar (2 Aurinco 100 watt and 1 solarblvd rigid 120 ) with Aerogel insulation on a "from scratch" apartment sized fridge and hot water tank, almost all lighting LED and we're golden.
I even make hot water using the inverter.
Genset?? NO WAY !!!
We went on vacation for a month using the above and didn't even bring along a shorepower cord. Who needs it?
We also used our sine wave inverter to plug in a new friend's catamaran which was having alternator problems. We gave him an hour of shorepower while we were at anchor.

Some people may not believe the above, but it's their loss....

I'm seriously impressed ... I have 5 x 135 Kyocera panels pushing through a MPPT controller ... gets no where close to sorting out my power needs but then again we idle on 25 AH

[cat man do]

Originally Posted by impi

2 Balmar 150 AH alternators wired through a center fielder and smart regulator. The alternators would be a 'just in case' and good back up. Nice thing is that when you need to motor you are getting 'kick ass' charge ...

Well I do have 100amp bosch alts on the motors, but they dont help when parked for a week at a time.

[cat man do]

Originally Posted by impi

oh and I almost forgot ... a mate of mine is using a similar genset to the pic you posted on his cat called Champollion ... he hates the petrol fumes and hardly uses it anymore

Just as well the gennys pictured are diesel

[impi]

Originally Posted by cat man do

Just as well the gennys pictured are diesel

Ok ... sorry I had not picked that up. Yeah, I guess if you are parked weeks at a time that's fair and well but you would only have to fire up when the solar panels can't keep up?

[cat man do]

Originally Posted by impi

Ok ... sorry I had not picked that up. Yeah, I guess if you are parked weeks at a time that's fair and well but you would only have to fire up when the solar panels can't keep up?

I reckon that's what I am trying to find out.

This vessel Stanyon 40' Power Catamaran has

80amp/hr alternators on mains
Honda Eu20i genset
Air-X 400 wind generator
4 x 80w Solarex panels with Plasmatronic regulators
Xantrax 1800watt sine wave inverter and Ctek 2500 switch mode charger
2 x 12v start batteries
4 x trojan 6v 200 a/h batts giving 400a/h

I have 100 amp alts
and plan on more panels and battery than that but no wind generator

It does have a Kelvinator split sytem a/c which I assume runs on the 2kva honda
It does have expensive and small 12 volt refrigeration
It also has washing machine, desal and an icemaker.

[Dockhead]

Originally Posted by cat man do

Its a $$$ and weight thing
$700 vs several thousand for a "marine" genset

The problem is noise. Air- cooled industrial gensets with no sound enclosures make a hell of a racket. You might be able to rapid charge a very large bank and run your AC overnight off your inverter, but this will require a lot of batts (weight and cost again) and you will spend your life managing power and spoiling your cocktail hours with noisy charging sessions. Even if it works at all (and for that, you must do the maths, as others have suggested).

If you don't believe me, listen to one of those Yanmar industrial frame gensets running some time. Then listen to a properly installed marine set. You will immediately understand why the marine genset is more expensive - as is so often the case, because it's really worth it!

I think you've got two practical choices:

1. Be resigned to no AC at anchor. In that case, a big solar installation will do you fine.

Or

2. Bite the bullet and install a proper sea water cooled, sound marine genset which you can run all night if necessary.

[cat man do]

Originally Posted by Dockhead

The problem is noise. Air- cooled industrial gensets with no sound enclosures make a hell of a racket.

Wouldn't the well insulated and vented engine room that I planned on installing it in act as a sound enclosure?

1. Be resigned to no AC at anchor. In that case, a big solar installation will do you fine.

Like I said, that powercat linked to above reckons they run a household split system on a 2kva honda pullstart

2. Bite the bullet and install a proper sea water cooled, sound marine genset which you can run all night if necessary.

Love to, this one was available
yanmar turbo diesel 11 kva genset | eBay
but a bit to big methinks
or one like this one that may or may not have existed on this very forum
http://www.cruisersforum.com/forums/...tor-77286.html
If I can find a good 2nd hand one at around 100kg I'll be all over it

[Dockhead]

OK, let's work through this together. First of all, the maths. Take a small, top quality marine air conditioning unit like the Cruisair Turbo Stowaway. Take the smallest unit available -- assume you will be cooling one small cabin for sleeping on a hot night. The 18,000 BTU model draws 5.5 amps at full load at 230 volts. Let's assume a 30% duty cycle over 12 hours -- you need 4.5 kW/hours of power delivered at the unit, to get from 20:00 to 08:00 on battery power.

4.5kW/hours of power is 360 amp/hours of power at 12.5 volts. Let's increase that by 20% for the inefficiencies of inversion, storage, and transmission -- 432 amp/hours.

Let's assume you are rapid charging, so you won't get the bats beyond 80%. You have the range of 80% to 50% to work with -- 30% of the nominal capacity (and this assumes that the batts are brand new and providing 100% of their nominal capacity). So in order to supply 432 amp/hours of power you need 432 * 100/30 = 1440 amp/hours of battery capacity. Now that is just the power for the aircon -- this is what you need on top your capacity for ordinary loads like lighting, refrigeration, electronics, etc.

So besides the massive battery bank, you will need a way to get that power into those batts every day. At a 25% acceptance rate (and that's probably somewhat optimistic), you will need a battery charger (on top of what you have for ordinary purposes) of 360 amps of power. That's about 5 kilowatts, and with inefficiencies will draw probably 6 kilowatts of power to run, maybe more. Depending on the type of genset, you will need 7 to 10 kilowatts of generator capacity (a heavy duty 1500 rpm genset can be run safely at 80% to 90% of nominal capacity; a 3000 rpm genset much less; a cheap frame genset even less). This will put into the batts the necessary power in about two hours, I guess.

So I think we can agree that this doesn't look too good, right? Namely running air conditioning on inverted power.

So if you want to run the aircon from a genset, the question is what type and how big.

The Yanmar frame genset you showed will be extremely noisy and will vibrate a lot. It is designed for running construction equipment or water pumps on an intermittent basis; it is in no way designed to run for long periods of time while people are sleeping. I don't think putting it in any amount of soundproofed room will help much, especially considering the vibration. You can get the dB numbers and figure it out for yourself -- remember, the dB scale is logorhythmic.

A Honda 2.0kW suitcase gen will be probably 10x quieter and will vibrate less. This is in fact designed to run for long periods unobtrusively. I think it is rated for 1600 watts, so you should be able to run a load which is 80% of that without any problem -- 1280 watts. Well, the small Crusair aircon draws 1265 watts at full load -- bingo. On a 30% duty cycle, I think the little Honda should do fine (but double check with people who have actually tried it). I think this would be a much, much better solution than a Yanmar construction generator. You might require an inverter/charger with power boost to deal with startup loads, in order for that genset to work comfortably.

But far, far better would be a real marine genset, a heavy-duty 1500 rpm one like a Northern Lights. The smallest one they make would be enough for this application (I think it's 4.5kW). This one has a three-cylinder Lugger engine which you will hardly hear when running, as it lopes along at 1500 rpm, and which will not produce any kind of harsh vibration. And it's made to be run continuously, so 10,000 or 20,000 hours will not be a problem -- you can just run it whenever you need it and for however long you need it (but make sure to keep a load on it). Yes, it's expensive, but don't compare such a piece of equipment to a crappy construction genset. You won't fit within your 100kg budget for weight -- this thing will weigh probably 250kg after you add the weight of the sound enclosure and exhaust system. It will be expensive to install, too -- you will need raw water in and out, an exhaust system, an antisiphon loop, etc., etc.

But if I needed aircon (I don't have it), I wouldn't even consider any other way to power it.

I don't have aircon, but living off shorepower (my boat is on a mid-river mooring) and anchoring out a lot, I find our 6.5 kW heavy duty Kohler genset to be an absolutely essential piece of kit. At anchor, I run it for a couple of hours every day at the time when we are using AC power for other purposes, or even just to heat water with the immersion heater, and it gets the batteries up and simply deals with all of our electrical needs on board. The biggest benefit of this is you don't have to constantly worry and manage power -- you just use what you need with confidence.

I hope that is at least somewhat helpful.

[sailinglegend]

Some good maths there Dockhead. Puts things in perspective.

We run our 12,000 Btu air con for an hour or so off our batteries via an inverter and 1050 Ah Lifeline AGMs. We only have 150 watts of solar, but charge with our Fischer Panda DC genset that pumps a continuous 250 amps into the batteries. Installed with extra insulation under the bed and is quiet enough to lie there watching TV, but have never needed to run it all night.

[DeepFrz]

How much does a bank of 1050ah Lifeline AGMs cost and how much do they weigh?

[savoir]

Roughly USD4000 and 1000 lbs

OUCH !

[Sailmonkey]

I had one of those yanmar gennys in the past........If you think an Gasoline powered industrial generator is loud, you ain't heard nuthin!!!!

Beyond that, the amount of heat created by this thing is about 1.5 to 2 times the amount of the gasoline counterpart.

[DeepFrz]

There was a guy who used to come on this forum a number of years ago that had an air cooled diesel gen. on his deck. Couldn't figure out why his charter business wasn't doing well or why all the other people in the anchorage were upset with him. I think a rod went through the block. Go figure...

[Pete7]

Originally Posted by Dockhead

A Honda 2.0kW suitcase gen will be probably 10x quieter and will vibrate less. This is in fact designed to run for long periods unobtrusively. I think it is rated for 1600 watts, so you should be able to run a load which is 80% of that without any problem -- 1280 watts. Well, the small Crusair aircon draws 1265 watts at full load -- bingo. On a 30% duty cycle, I think the little Honda should do fine (but double check with people who have actually tried it). I think this would be a much, much better solution than a Yanmar construction generator. You might require an inverter/charger with power boost to deal with startup loads, in order for that genset to work comfortably.

We used our honda 20i to run electric oil heaters until we added a Webasto. The Honda will run for 7 hours under load on a full tank of fuel, but CO2 fumes were a worry, only just noticeable below decks but wouldn't want to sit in the cockpit with it running. It would have to go in the dinghy on a long line.

There are some amazing numbers in this thread, like Seniormechico with his dragonfly we manage with somewhat less, 125w of solar kept us fully topped up at anchor for 5 days recently and I still had a glass of cool French wine each evening from the fridge.

Do you really need aircon? after a couple of weeks in Hong Kong I turned the damned thing off because it sounded like a B52 on take off (window mounted unit). Also I used to have problems with condensation if my next door neighbour ran his. The wall between us would run with condensation on my side, just wondered if a boat with warm and cold rooms will have the same problem. Go native

Pete