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Generators & Electric Motors General Discussion Antique Generators and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Electric Motors General Discussion

3600 rpm vs 1800 rpm


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  #11  
Old 02-21-2018, 09:37:33 PM
Mikey NY Mikey NY is offline
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Default Re: 3600 rpm vs 1800 rpm

I have a Honda powered air compressor. 26 yrs and counting. I don't use it all the time, but when I do, it runs 5 to 6 hrs a day for 5 or 6 days in a row. I religiously change the oil after a weeks worth of running. And the compressor oil also. Fresh oil is the answer to longevity.
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  #12  
Old 02-24-2018, 11:48:25 AM
dkamp dkamp is offline
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Default Re: 3600 rpm vs 1800 rpm

This is kinda off-topic, but all the generators in my shed have the oilpan drain plug removed, I replaced them with a 90 degree elbow, and a length of pipe long enough to reach an inch or so past the side of the machine. At that point, is a T, placed inverted, with a barb-type hose fitting facing up. On the remaining segment, is a 90 degree turn valve, a short piece of pipe, and a thread-on cap.

From the barb, extends upward a clear plastic tube, and atop that, a simple filtered breather.

I fill the crankcase to the dipstick ADD point, then mark the side of the engine, and the clear plastic tube, with a RED magic marker. I continue filling until the dipstick identifies FULL, then roll the engine over a dozen times to make sure the oil galleries, etc., are all full. Then I mark the block and tube again with BLACK marker.

This allows me to walk by, while the machine is running, and observe the oil level without pulling the dipstick. It also allows me to remove the cap, place a recovery jug under the discharge, then open the valve, fill the recovery jug, shut off the drain flow, switch to a second jug, open the valve, etc, and when all done, I replace the cap. The cap is there just in case someone or something smacks the valve handle, and it keeps residue in the pipe from dripping on my generator shed floor.

The one thing I have NOT done, is installed a sensor that detects oil level in the pan. I should, but I haven't found a level sensor that I've really felt worthy of drilling a hole in the machines' oilpans over yet. All the new fancy electronic sensors use ultrasonic infrared microprocessor-based controlled retroreflective mass-spectrograph inferometry via online smart-phone app, while my generators work in a mercury-rocker switch, mechanical bell and timer-relay-kill-switch world... (sigh)

But this has nothing to do with 3600 vs 1800. My answer, though, is NEITHER.

1200rpm.

Aside from the oil capacity (I think the Herc JXLD's fill takes uh... 38 quarts or so?) is that slow-spinning generators have a very high polar inertia, that means the windings will NOT be as able to pull down the armature speed on short-term start loads... even when those loads exceed the machine's rated output, it's sag frequency is very small.

I really like the fact that the 1200rpm, liquid cooled, multi-cylinder generators running inside my shed, with two mufflers separated by about six feet of pipe, are just-barely-audible inside the house with the windows open. My neighbors each have 3600rpm units of the 'permanent mount' flavor (looks like an AC compressor on a pad) about 1000' away, and through rows of trees, are rattling away, I can tell every time their wells and furnaces kick on.
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  #13  
Old 02-24-2018, 01:17:50 PM
armandh armandh is offline
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Default Re: 3600 rpm vs 1800 rpm

sure 1200 rpm 6 pole
mostly the 271 refer rail car pull out
not super on the fuel bill
but built to run for years with little down time
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Old 02-24-2018, 04:51:44 PM
Vanman Vanman is offline
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Default Re: 3600 rpm vs 1800 rpm

Yes, absolutely 1200 rpm, something that else I've been preaching on here for ages.

The trouble is, most folks here will not deviate from Onan. They're good machines, for sure, but they're no 1200 rpm Kohler. Most are air cooled too, making it considerably more difficult to salvage the waste heat.

A 271, 1200 rpm Detroit is definitely cool, but is WAY too big for a house. For ANY house.
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Old 02-24-2018, 05:16:34 PM
Wayne 440 Wayne 440 is offline
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Default Re: 3600 rpm vs 1800 rpm

Quote:
Originally Posted by Vanman View Post
...A 271, 1200 rpm Detroit is definitely cool, but is WAY too big for a house. For ANY house.
You guys must have different houses than we do in my community. A 2-71 at 1200 RPM is about 20kW. In the ball park for my little house, with a bit of load management.
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  #16  
Old 02-24-2018, 05:39:41 PM
Vanman Vanman is offline
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Default Re: 3600 rpm vs 1800 rpm

Wayne, what are you running in your house? I'm not going off of service or main breaker size, but rather actual load. All heating appliances here except the usual small appliances are gas.

We have digital watthour meters now, and they also scroll past a watt reading. It's Very rare to see it reach 2 kw, and usually just a few hundred watts. With the A/C on it my read around 5 kw, and rarely reach 6 kw.
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  #17  
Old 02-24-2018, 09:22:06 PM
Wayne 440 Wayne 440 is offline
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Default Re: 3600 rpm vs 1800 rpm

Right now it is 56 degrees outside, the loads in my house are not much, it is pulling just under 1600W. That means that the 2 refrigerators, freezer, sump pump and 4500W water heater were not running when I checked. Likely just a few lights, 3 TVs, a couple of computers, plus the associated accessories and one of two dehumidifiers.

The heat pump compressor and fans are about 3600W, and 7.5kW for the strip heat when it runs the defrost cycle in winter. On wash day, a clothes washer, electric dryer and that 4500W water heater for a few hours. When meal time comes around, add a few stove burners and the oven.

My shop/garage heater is manually shed for outages, it is 10kW.

I have seen my house pull 32kW in winter on utility power.
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Old 02-24-2018, 11:23:22 PM
Vanman Vanman is offline
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Default Re: 3600 rpm vs 1800 rpm

Ah, yes, I can see an all electric house taking that much power on occasion. What is your cost per kwhr? How does that cost compare to oil fired heat? I assume no natural gas or propane available.
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  #19  
Old 02-25-2018, 01:28:28 PM
dkamp dkamp is offline
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Default Re: 3600 rpm vs 1800 rpm

Golly, Wayne... that electric heat's gotta HURT...

My house is pretty big, but with all LED lighting everywhere, propane furnace blower and ceiling fans running, I pull 2.3kw. The well pump kicks it up a little, sump pumps do too. Aside from the motor loads, my lighting and electronics can run off a 1400w inverter and four 8D truck batteries... suffice to say the big six cylinder gennie only gets to work when SHE decides it's time to do laundry, run the dishwasher, and make pizza. I've got the big air compressor and workshop set up so that they won't kick on when we're not on utility power, but still... if I needed to, I could run a big tool or two and not worry about overrunning my generating capacity.

I'm pretty certain my systems are quieter than a 2-71...
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