Two Gensets . . . Why ?

[ViribusUnitis]

In my looking at yachtworld, and dreaming about how the "other half" lives, I've noticed that many of the larger motor yacths have 2 gen sets.

Typicaly they seem to have 1 small one, and another large one. Something like a 7k unit, and then a 20k unit.

What is the advantage to 2 units? I assume that they can't both be used at the same time, as load ballancing between two gen sets is typicaly difficult without expensive electronics. Expecally gen sets with very diffrent power ratings.

Thanks!

[witzgall]

Run the small one when you have lighter electrical needs. Run the big one when you need more. Lightly running any diesel engine without load is bad for it.

Chris

[slacker]

Very large and comercial boats will have at least two similar sized gensets. Port side is run 10 days (240hrs) then starboard for 10 days. When one is off it can be serviced within the 10 day down time.

[roverhi]

Having the ice machine fail to get electricity is considered reason enough to end a cruise and sell the boat. After all, how can you expect the guests to live without A/C. Captains have been keel hauled, first mates mutinied, and the CG called in because of the immediate threat to life. You have to have two gen sets, one to back up the other. The second smaller one is probably only used as a back-up and wired directly to the A/C.

[ViribusUnitis]

Originally Posted by roverhi

Having the ice machine fail to get electricity is considered reason enough to end a cruise and sell the boat. After all, how can you expect the guests to live without A/C. Captains have been keel hauled, first mates mutinied, and the CG called in because of the immediate threat to life. You have to have two gen sets, one to back up the other. The second smaller one is probably only used as a back-up and wired directly to the A/C.

If you were from Houston, I might belive you...

[Palarran]

I have two, a 12kw and 8kw. We typically run the 8 kw at night and the 12 in the morning as the loads are higher. We can also run both and then turn on pretty much everything on the boat. If I would have designed the system, I would have put in a 5kw instead of the 8.

Why would I want two? Because if one breaks while I'm on vacation, I don't what to spend 3 weeks in a marina waiting to get it fixed. And, I can use it to very the costs of operation depending on loads.

[Gracies]

I am the Captain of a 35 metre yacht, 5 crew, 12 Guests. Therefore huge electrical consumption when we are at full load, in the region of about 63 amp peaks. We therefore have 2 gensets of 33 kw each, which run on a 50/50 basis. This allows for continuous operations when at anchor of about 30 days before servicing. Having the 2 gensets is vital for safety reasons, as you always have a back up. The gensets also provide the vital power to the service battery chargers which allow a ´get me home´power supply last just under 48hours.

[anjou]

Ive got two but think im going to sell one.

I wish I had developed an electric drive system running off a large genset instead of a diesel propulsion and separate genset.

Always useful though as you can never make tooo much electric.

[savoir]

It isn't just gensets. Big boats with pro crew have backups for everything.

You can't blame them because charter passengers are very wasteful with everything, particularly water and electricity.

[RaySea Lady]

I only have one 12.5 kwh but I wish I had two when I lost 4 days this summer replacing my generator head when my raw water hose split and sprayed water all over the genny. Motor was fine but fried my genny. A second unit would have been great...

[David M]

On medium and larger commercial vessels, two generators are a backup for each other. Many larger vessels even have more than two generators. Unlike most smaller pleasure boats, large power driven vessels cannot function without a generator. They are dead in the water without one.

Generators can be phase matched relatively easy so they can share the house load if necessary. This is very common.

On some older ships they even had a generator high in the ships superstructure in case of below deck flooding or a fire.

[capngeo]

Originally Posted by David M

On medium and larger commercial vessels, two generators are a backup for each other. Many larger vessels even have more than two generators. Unlike most smaller pleasure boats, large power driven vessels cannot function without a generator. They are dead in the water without one.

Generators can be phase matched relatively easy so they can share the house load if necessary. This is very common.

On some older ships they even had a generator high in the ships superstructure in case of below deck flooding or a fire.

+1 on that... On our tugs EVERYTHING ran off the AC Buss.... steering, everything.... even the main engines started off compressed air, from a compressor that ran off the genny! Our VHF radio had a gizmo that stepped down 120VAC to 12VDC!

[Gracies]

+2 on that, all my emergency services, and most running services run on 24v or 12v DC. Therefore the generators are as important to the safety of the vessel as having the emergency fire fighting pump (24v DC). The Generators provide the charge to the battery chargers which charge the service and emergency battery banks which then power the ship. Of course we also have dedicated engine start banks which have their own chargers also from the generators, and / or alternators. The genny´s can be run in parralel but were commissioned to be big enough to carry the ship at full load so therefore i never have to run them together.

[markpierce]

Originally Posted by Palarran

I have two, a 12kw and 8kw. We typically run the 8 kw at night ....

If your genset kept me awake at night, I'd shine my searchlight on you unless there was a more convenient way to communicate the harm you have caused. If worse came to worse, I'd put the air horn on automatic signaling I was anchored and we could all stay up all night until reason prevailed.

[Dockhead]

Originally Posted by markpierce

If your genset kept me awake at night, I'd shine my searchlight on you unless there was a more convenient way to communicate the harm you have caused. If worse came to worse, I'd put the air horn on automatic signaling I was anchored and we could all stay up all night until reason prevailed.

Seems kind of aggressive to me. You could always move, couldn't you?

I don't have AC on board my boat and don't run my genset at night. But my genset -- a 6.5kW Kohler which runs at 1500rpm -- is practically inaudible anyway. It's in two sound enclosures and exhausts through a massive hydrohush muffler. Many people have this kind of installation -- why do you assume that anyone running a genset at night is causing a ruckus?