To run or rest a generator set

[Pete]

Being located on the Neuse River, about 5 miles south of New Bern, NC, Irene took our power out for close to 4 days. Has happened before with storms, and each time I back feed power from the boat behind the house. And each time I do about the same routine, run the generator 8 hours or so, and shut it down for 4 hours. I am not doing this to conserve fuel as it is attached to a 275 gallon tank. Over the years I have just accepted that resting the generator is good for it.

Now I am questioning this theory from unkown sources. It sounds to me like treating a mechanical device as a human, that can benefit from rest between work periods. It also takes the generator set through a thermal cycle each rest/run period.

So, my question: Is it better for the generator set just to run, with an occassional short shutdown to check the oil level versus the run/rest cycle that I am using? BTW, the generator set is a Westerbeake 15.0 KW unit with about 700 hours on it since new, and the loading seldom exceeds 50%.

Pete

 

[jim rosenthal]

I'd keep it running. FWIW, on the Alaska Diesel Electric web site there used to be a writeup on a NL genset similar to mine that was on a fishing boat in the Gulf of Alaska, which had over 20K hours on it. It was in a small lean-to up on deck and they only shut it down to do maintenance and chip the ice off it when needed. It had not yet been overhauled.

I'd keep it running. Except, as you say, to do maintenance. Our power was out for two days and during that time my gasoline genset ran constantly here under partial load, only stopping to refuel. I think as long as they are within their load envelope, periodic rests aren't needed.

 

[captainwjm]

I agree that there is no need to rest the genny. This thread made me think, however, how long could I run in continous operation before I needed to shut her down to do an oil check? I generally run for an entire weeknd non-stop, say 50+ hours or more without shutting her down once. Should I shut her down any more frequently, ie, daily to do an oil check? My manual [Onan] says do an oil check every 8 hours, but that seems too much since I only have to add a quart once between oil changes [around 350 hours between changes]. What do you think?

 

[SKYCHENEY]

The only reason to rest it is to conserve on fuel and reduce the number of hours on the genset.

 

[krush]

All else being equal, an engine (and almost any mechanical device) that runs constantly will give more total running hours before having to be overhauled.

You may be able to figure out a system to check the oil while running (not lower spot on dipstick, etc)

 

[rsmith]

After Frances and Jeanne in 04 I ran my onan for almost 3 weeks continuous with a daily shutdown to check oil 12,000 hoursTT with only a top end RB.Added 1/2 qt / day. Did use close to 700 gal of fuel. I think it was over 500 hours before the power came back on.

 

[jim rosenthal]

3 weeks? Wow. Where were you located?

 

[MarioG]

No need to shut down. I sometimes run my generator for a week or more at a time during the summer. It gets shut down when we get back to the dock. every time i check the oil level it is at proper level. I do change the oil when I get back after about a 250-300 hour run. interestingly the oil isn't that dirty from a visual standpoint. I do shut down the generator in the evening during winter after recharging the batteries for our inverter. our 17Ni Norpro has about 1300 hours now. runs great.

 

[rsmith]

3 weeks? Wow. Where were you located?

Vero Beach. Surely youve heard of Frances and Jeanne. 2 cat 3 storms that hit 3 weeks to the day and hour apart.Sept 2004

 

[saltshaker]

I wouldn't shut it down to give it a rest. You do need to do a visual inspection of the strainer a few times a day. If you can't see if it is fouled then you need to shut down and clean the strainer. After a major storm it is pretty common for them to clog from sea grass and other debris. Periodic checks for water flow and operating temps should be SOP.

 

[spartonboat1]

There is no need to shut down a genset, unless it is going to be idling for long periods, say an hour or more; at least on a diesel genny. Idling for a long period can lead to "wet stacking", in which un-combusted materials build up in the exhaust, valves, etc. Also, it has been recommended by genny Pro's that you should try to run it at least at 40% of rated load, if you can; more is ok up to 90% of rated load. Starting and stopping quite frequently, esp. if allowed to cool all the way down, is harder on the unit, because of the thermal cycles, which over a very long period (years) causes various wear areas- gaskets, etc.

If your genny has a history of "using" oil or coolant, then a shut down and periodic checks (4 hrs?) would seem indicated.


My genny is happiest to be run periodically and taken up to full boat load of 7.5Kw, which is this unit's rating (Onan MDJE). If I stretch its legs, it starts and idles better, plus I can tell that the full range of controls are being reached, the injectors are fully cycling, so they don't "hang up" later. I have run synthetic Mobil 1 for diesels, although I have taken to using Texaco Ursa 40, same as the mains.

I did replace the coolant cap, which seemed to loosen, but otherwise it uses no oil or coolant. It had been bench re-built in 1996, before I bought the boat in 1997, so I have about 60-100 hours of use on it; very light for some owners here.