Author Topic: ST Generator Head Question  (Read 192 times)

Randybee1

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ST Generator Head Question
« on: December 24, 2020, 07:45:35 PM »
I'm finally putting my Perkins/ST head together and have a question about ST heads in general. I know that typically you don't want to exceed 80% of the rated output of your head for long periods. Is this true for the massive ST heads? I have one of the old Power Solutions heads sold by George via Utterpower. It weighs well over 200 pounds (7.5 kw). I've read that these will run continuous for days and never get warm. So, can I run this at 7.5 continuous or should I down rate it?

hwew

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Re: ST Generator Head Question
« Reply #1 on: December 24, 2020, 09:22:02 PM »
Iíve always de-rated all my generator heads. I used an ST-10 on my S195 genset and it was a good match. It pulled 7.5kW all day long with no problem and the power was cleaner than the Kubota/Marken brushless genset I built. On full load (roughly 7.5kW) the Kubota/Marken was producing lots of trash. Myself, I would probably limit the ST-7.5 to 5kW continuous output. Especially if your going to use it on capacitive loads.
« Last Edit: December 24, 2020, 09:31:22 PM by hwew »

hwew

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Re: ST Generator Head Question
« Reply #2 on: December 24, 2020, 09:58:02 PM »
Randy, Remember this topic? I started it back in 2009 on the microcogen forum.

http://www.microcogen.info/index.php?topic=484.msg5302#msg5302

Edited 12/25/2020
I attached a spec sheet for the Cat C0.5 engine in the topic. (You have to be logged in to open it)  I presume your running the engine at around 2500 rpmís. The engine should be capable of running a 5000 watt load. The engine will be running close to its full recommended intermittent rating to accomplish this. Below I cut and pasted something that Iíve remembered in the attachment.

IND-C (Intermittent) is the horsepower and speed capability of the engine where maximum power and/or speed are cyclic (time at full load not to exceed 50%).

Itís been years since I started this topic and since reading the Cat spec sheet tonight I could of been wrong commenting that the setup I was thinking of building should put out 5000 Watts continuous.

The way I interpret it is full load run time is not supposed to exceed 12 hours in a 24 hour period.

How much of a load can this engine handle in a 24 hour period? I donít know.

 Might be a good question for a Cat application engineer.

Question, does your Cat C0.5 have the oil pan that extends approximately 4 inches from the front of the block below the front crankshaft pulley? This would make a difference. How much, I donít know.
« Last Edit: December 25, 2020, 01:04:13 PM by hwew »


Randybee1

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Re: ST Generator Head Question
« Reply #4 on: December 25, 2020, 12:54:11 PM »
Thanks for the info.
Yes my engine has about a 4 inch deep oil pan. I did not know there were other size oil pans. Why would that make a difference ?

I keep getting a warning from Malware bytes about Microcogen. I know it was hacked awhile ago. Is the site safe and I can ignore the warning?

Yes, I will be running my Cat at about 2400-2600 rpm. Can't remember the exact rpm but I remember having a pully made to coincide with the Cat's maximum torque.

I'm still a little confused about derating an older style ST head. It is my understanding that you derate so as to not burn up the genhead but since this head is so massive I'm somewhat confused. I don't think I'll ever pull 7.5kw from my house but I am just curious.

hwew

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Re: ST Generator Head Question
« Reply #5 on: December 25, 2020, 01:54:34 PM »
I did some tests running my S195 genset years ago and Bob G and I wondered why my S195 can pull a higher load with a ST-10 than his setup using a ST-7.5. Both setups were dependent on what the engines could produce. And both engines were similar. One of the things we thought about is that the generator heads are more efficient operating below 100% load. How much? We never got that far, but from the data I got it seemed considerable enough that I should of done more testing. Since that time I try to de-rate generator heads about 25%. I also find less voltage droop running below max rated output when no AVR is used.

It seems like your setup will be able to put out 5000 watts. I feel the ST-7.5 head is a good match.

The larger oil pan holds about an extra quart of oil. The extra capacity should allow some extra full load running time between full load cycles. The more oil the longer it will take to heat up to higher temperatures where the oil will start breaking down faster.

It would be nice to have an oil cooler installed and being able to keep oil temperature near 220-230 F. (104-110 C.) I would think you would be able to run near full output continuous if one is installed.

The microcogen forum software needs to be updated. Others, including myself had have no problems.
We hope to have updates done in the near future.
« Last Edit: December 26, 2020, 03:28:46 PM by hwew »