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Author Topic: Starting a Lister with or without load  (Read 5251 times)

cold comfort farm

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Starting a Lister with or without load
« on: May 16, 2007, 12:06:44 PM »
This may be a daft question but I will ask it anyhow.  If you are using a Lister and generator, do you start the Lister with the generator connected but no load or just start the lot generating whilst turning it over.

Stephen
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phaedrus

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Re: Starting a Lister with or without load
« Reply #1 on: May 16, 2007, 02:30:33 PM »
My procedure is to start with no load (other than the incipient mechanical load of the engine itself). Within a few seconds I bring the machine online by switching the main to the load. If there's only a small load to carry I add load by switching in a load bank - bringing the machine fairly promptly to about 30% of capacity. I try to add load by degrees.

My reasoning is to avoid carbon build-up as well as I can by creating a condition that will produce a good spray pattern and hot combustion and exhaust temperatures.
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ronmar

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Re: Starting a Lister with or without load
« Reply #2 on: May 16, 2007, 06:08:18 PM »
Start it without a load.  Most generators won't have an instant output anyway but will start producing greater power as the RPM increases.  The lister has aenough work just getting the spinning mass up to speed, let alone any added electrical load.  Besides, what electrical load would you want to subject to this terribly under voltage/under frequency condition?

In my case, the need for instant power is not there.  I personally give the engine a chance to warm up a bit before I start switching in the electrical load.

 
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xyzer

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Re: Starting a Lister with or without load
« Reply #3 on: May 16, 2007, 07:28:36 PM »
Start it without a load. 
In my case, the need for instant power is not there.  I personally give the engine a chance to warm up a bit before I start switching in the electrical load.

Same here! Although I will plug a 300w light to add a bit of a load to expidite the warm up. Without a slight load warmup seems to take forever.
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skeeter

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Re: Starting a Lister with or without load
« Reply #4 on: May 16, 2007, 08:38:16 PM »
I start my 12/2 with no load attached. Once up to speed, I switch in a 2.5k watt load bank. This along with thermostats, warms it up pretty quickly. Once head temp reaches 140 - 150 deg. I switch in house load, remove load load bank. I guess everyone has their own way of doing things. The common ground is no load at startup or shutdown.   
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phaedrus

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Re: Starting a Lister with or without load
« Reply #5 on: May 17, 2007, 12:10:36 AM »
I 'member a fella I used to know - had a pair of 12 V 92's in a boat. He'd light 'em off an' idle 'em for maybe 15-30 minutes before we cast off, but they never got past slightly warm. We'd complain "they're not warmed up yet". Cap'n would always say "we'll warm 'em up underway". Never got very cold there anyway, with the 2-71 genny screaming away. We were kids. Under 30.

Cap was right. Absent load or pre-heaters they don't really warm up, not like a otto cycle engine will. Warming a diesel without load means getting "lukewarm" due to the internal and external friction, air drag, oil pump - that sort of load - pretty small, might be a kw in a 6-1 l'iod but I bet it's more like 300 watts. Meantime the machine tends to wetstack and carbon up. On the boat we almost never ran past 12 kts, though she'd do something like 30 or a bit more at 100%. Cap had a stack fire eventually, we were trying to outrun a storm 'bout 120 miles off Longbeach CA and Cap opened 'em up for the first time since trials..purty flames, no damage. (That boat was built for $15 per bl oil, long gone now.)

I suppose what we're really looking at here in starting is letting the engine get oil circulation going and oil into the ring lands. Past that, which I believe takes only seconds, I honestly doubt that any gain accrues. Load obviously brings increased temperatures in an Nth engine, especially so in diesels. Avoiding extremes of thermal-stress, temperature change over time, means adding load gradually. Avoiding wetstacking and carbon problems means adding load quickly. These two goals are somewhat juxtaposed. Obviously there's a compromise rate. My guess, (which seems pretty close to Skeeter's way of doing this), for my very mild ambient temperatures is start plus 30 seconds to 30% - just a guess, but so far as I can tell it has not created any problems yet. If it were freezing I'd make it 60 seconds to 15%,90 seconds to 30% . (If it were freezing on a regular basis I'd think real hard about heaters - say the hot water heater from an old trailer thermosyphoning through the l'iod. Or maybe save some heat from the previous run and valve it in a few minutes prior to start)

The Enterprise engines at Rancho Seco back in the 1980's were kept warm with an auxiliary jacketwater circ pump and auxiliary L.O. pump pushing warm fluids through 'em at all times except while they ran, then the engine-driven pumps took over. Each of those engines went from stopped to 100% (6000 hp) in 10 seconds. I thought that was a bit fast and that the engines ought to have been set up with turning gear as is found in steam turbines if one wanted to go to 100% that fast. I suppose they ought to have been dual fuel designs and then used for peaks as well as standby emergency, but engineering and regulation are very conservative arenas - that was too experimental.
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cold comfort farm

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Re: Starting a Lister with or without load
« Reply #6 on: May 17, 2007, 09:09:27 AM »
Thanks everyone. Its easier to ask than play trial and error.

Stephen