Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 27-08-2011, 12:55   #1
Registered User

Join Date: Jun 2009
Location: STX and Portland, until refit finished
Boat: 1999 Steel (Tom Collin's design)
Posts: 371
Two Gensets . . . Why ?

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!
__________________

__________________
ViribusUnitis is offline   Reply With Quote
Old 27-08-2011, 12:57   #2
Vendor
 
witzgall's Avatar

Join Date: Oct 2006
Location: Eastern Shore, MD
Boat: Camper Nicholson 44 Ketch
Posts: 1,775
Re: 2 Gen sets, why?

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
__________________

__________________
witzgall is offline   Reply With Quote
Old 27-08-2011, 13:06   #3
Registered User
 
slacker's Avatar

Join Date: Nov 2006
Location: San Diego and Mazatlan
Boat: Gulfstar 37 "SLACKER"
Posts: 147
Re: 2 Gen sets, why?

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.
__________________
slacker is offline   Reply With Quote
Old 27-08-2011, 13:13   #4
Senior Cruiser
 
roverhi's Avatar

Cruisers Forum Supporter

Join Date: Aug 2005
Location: Kona, Hawaii, Carlsbad, CA
Boat: 1969 Pearson 35 #108 & 1976 Sabre 28
Posts: 6,003
Send a message via Yahoo to roverhi
Re: 2 Gen sets, why?

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.
__________________
Peter O.
'Ae'a Pearson 35
roverhi is offline   Reply With Quote
Old 27-08-2011, 13:23   #5
Registered User

Join Date: Jun 2009
Location: STX and Portland, until refit finished
Boat: 1999 Steel (Tom Collin's design)
Posts: 371
Re: 2 Gen sets, why?

Quote:
Originally Posted by roverhi View Post
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...
__________________
ViribusUnitis is offline   Reply With Quote
Old 27-08-2011, 23:28   #6
Elvish meaning 'Far-Wanderer'
 
Palarran's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: Me - Michigan / Boat - Tenerife
Boat: 56' Fountaine Pajot Marquises
Posts: 2,641
Re: Two Gensets . . . Why ?

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.
__________________
Not all who wander are lost

http://www.sailblogs.com/member/palarran/
Palarran is offline   Reply With Quote
Old 28-08-2011, 01:42   #7
Registered User

Join Date: Jan 2011
Location: Palma Mallorca
Boat: Fisksatra Havsfidra
Posts: 72
Re: Two Gensets . . . Why ?

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.
__________________
www.alonearoundtheworld.com
Gracies is offline   Reply With Quote
Old 28-08-2011, 05:46   #8
Registered User
 
anjou's Avatar

Join Date: Apr 2009
Location: Malvernshire, on the sunny side of the hill.
Boat: 50' steel canal and river cruiser
Posts: 1,905
Re: Two Gensets . . . Why ?

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.
__________________
www.amy-artimis.blogspot.com
anjou is offline   Reply With Quote
Old 28-08-2011, 06:20   #9
Registered User

Join Date: Jan 2010
Location: Narragansett Bay
Boat: Able 50
Posts: 3,057
Re: Two Gensets . . . Why ?

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.
__________________
savoir is offline   Reply With Quote
Old 28-08-2011, 17:38   #10
Registered User
 
RaySea Lady's Avatar

Join Date: Oct 2009
Location: Windsor, ontario, Canada -Cape Coral, Florida
Boat: Bluewater 5800, Novatec 52
Posts: 191
Images: 5
Re: Two Gensets . . . Why ?

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...
__________________
Ray Sea Lady, 2001, 58 Bluewater, while in the Great Lakes (Fully updated 2012/13).
Ray of Sunshine, 2008, 52 Novatec Classic Sedan while in Florida (Fully updated 2016).
Album http://www.cruisersforum.com/forums/...69-albums.html
RaySea Lady is offline   Reply With Quote
Old 28-08-2011, 18:41   #11
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,150
Re: Two Gensets . . . Why ?

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.
__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 28-08-2011, 20:16   #12
Mooderator
 
capngeo's Avatar

Cruisers Forum Supporter

Join Date: Jul 2010
Location: Key West & Sarasota
Boat: Cal 28 "Happy Days"
Posts: 4,211
Images: 12
Send a message via Yahoo to capngeo Send a message via Skype™ to capngeo
Re: Two Gensets . . . Why ?

Quote:
Originally Posted by David M View Post
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!
__________________
Any fool with a big enough checkbook can BUY a boat; it takes a SPECIAL type of fool to build his own! -Capngeo
capngeo is offline   Reply With Quote
Old 29-08-2011, 01:15   #13
Registered User

Join Date: Jan 2011
Location: Palma Mallorca
Boat: Fisksatra Havsfidra
Posts: 72
Re: Two Gensets . . . Why ?

+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.
__________________
www.alonearoundtheworld.com
Gracies is offline   Reply With Quote
Old 29-08-2011, 02:30   #14
Registered User
 
markpierce's Avatar

Join Date: Aug 2010
Location: Central California
Boat: M/V Carquinez Coot
Posts: 3,413
Re: Two Gensets . . . Why ?

Quote:
Originally Posted by Palarran View Post
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.

__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 29-08-2011, 03:06   #15
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,743
Re: Two Gensets . . . Why ?

Quote:
Originally Posted by markpierce View Post
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?
__________________

__________________
Dockhead is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Gensets & Solar Panels Vessna Electrical: Batteries, Generators & Solar 6 15-08-2011 15:36



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 20:17.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.