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Old 01-12-16, 08:34 PM   #21
ToddT
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I'd like to add a couple of tips for long term generator operation. I run my small business off the grid, mostly on renewable energy. I was running a diesel generator on biofuels and it had a 30 gallon fuel tank. That runs for days and days! But for now am having to use different gasoline generators. One has a 6 gallon fuel tank. Not bad, able to pour a full 5-gal can of gasoline in there without fear of overflow. Now I'm using a smaller one and the tank must be less than four gallons. Having to watch the fuel level is a drag.

I'm a stickler for filtration and heartily recommend the Mr. Funnel fuel filter. It has a filter element that I believe goes down to 30 micron (not quite as good as an oil filter but still worthwhile) plus a sump to catch any water.

For the gasoline generators, I'm thinking of setting up a gravity feed system. Using a universal low pressure fuel pump, I'll draw out of an old car fuel tank and pump through a filter and up to a small tank positioned slightly higher than the generator. I repurposed a stainless steel tank from an oil-fired hot water pressure washer. It has a drain on the bottom as well as a drain on the side. The bottom goes to the carb on the generator and the side port goes back to the fuel tank as an overflow. This way, there won't be any more gravity fuel pressure on the carb than regular. It also gives a way to continuously polish the fuel with a good 6 micron spin on fuel filter. Again, a stickler for filtration!

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Old 01-13-16, 02:30 AM   #22
WyrTwister
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https://www.johnstonesupply.com/stor...ep?pID=B18-842

https://www.johnstonesupply.com/stor...ep?pID=B18-843

Have not tried these . So no personal experience . I have wired / installed 3 phase soft starts & VFD's .

My cost on either of these is $ 235.00 .

You can probably google search soft starts for more information .

God bless
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Old 01-13-16, 07:46 AM   #23
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It is my understanding that "softstarts" reduce the initial current peak (6-7 times nominal running current) from a few msec to a couple hundred msec. By spreading out the starting load/torque, the peak current is reduced, the undervoltage minimized and electric motor/compressor is less stressed both electrically and mechanically.

This could be a very good item to add to a deep well submersible water pump.

What I don't know is the amps x time characteristic of deep well pumps vs a standard above grade compressor/electric motor.

I do see a softstart on the geothermal units I have here and the start up voltage drop is much reduced as there is little start up "blink" observed on house lights (compared to a unit with no softstart).

My clamp on current meter only tells me peak current or steady state current - not the time issue. I suppose I could drag out my storage oscilloscope to the pump house and look at starting current with a limiting resistor to get the time duration of this start up current surge.

Again, the issue is supplying the well pump with generator power during grid power loss. Even though the start current is only a fraction of the run current, I have observed what happens when the generator is not large enough to supply start up pump current.

During a former power outage (spring storms), my neighbor burned out his deep well pump by having a generator that was big enough to supply running steady state current, but not the starting peak current. In addition to being out of power, he was then out of water.

He was using a small Honda (~1.5 kW) generator only to the well pump (1 HP). At pump start up, the pump house electric light bulb would noticeably dim for 8-10 seconds and the generator slowed considerably. Then, the generator would speed up, the light brightened and he had water. Then, about two days later, the pump died while on this generator. When we pulled it and did the tear down necropsy, the motor windings appeared burned. My belief was that this repeated starting high current and low voltage fried his pump (caused by the too small generator).

Of course, this could just be coincidence, but the pump was only three years old.

I clearly want to avoid that situation . . . That is why I have been using larger PTO generators and running through lots of fuel.

Bottom line - do you think that a softstart would be beneficial for the water pump when running on emergency power?. $235 is a lot for just a "look see". Maybe it would also extend water pump life . . .

Steve
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Old 01-13-16, 07:55 AM   #24
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soft starts use older large capacitors of about 1 farad but new super/ultra capacitors have about 350 farads at 2.7 volts in the size of a d cell battery so they can run support loads for longer periods.

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Old 01-13-16, 08:20 AM   #25
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The time from the initial application of voltage , to full motor speed is known as ramp up . The 3 phase soft starts & VFD's I have been involved with , ramp up was adjustable / user set-able . Do not know about the small single phase units ?

I do not know but just a tiny bit about single phase submersible pumps . I know they have a " box " with a start capacitor and maybe a run capacitor ? And a relay that I think switches the start windings out of the circuit when the the motor reaches full speed .

Are the bearings or seals on submersible pumps " cooled " or " lubricated " by the water . When I worked maintenance , we had hot water pumps and chill water pumps in which the seals were water lubricated & maybe cooled ?

Where I am going with this line of question , is , would ramping up have a negative effect on the pump ? I doubt it would harm the electric motor .

Should you seriously consider this , I recommend you ask the vendor for recommendations as to your application .

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Old 01-13-16, 11:45 AM   #26
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You don't want to run VFD on single phase.
Typically for high starting torque motors you use capacitor start. Capacitor start uses a mechanical centrifuge to turn the start circuit on and off. During run up the start circuit does not cut out until the motor is almost at operating speed.
If the motor runs for more than 5 or 10 seconds with the start circuit powered up it will fry something in the start circuit, usually the capacitor or the windings.
If you drop the motor speed down too low the start system will reengage, frying the starter.

This is why industrial pumps are pretty much always use 3 phase inverter duty rated motors connected to VFDs. The motors and what ever they drive can be soft started and ran at variable speed, usually any speed between 20hz and 60hz. Some VFDs can produce 100hz.
You can get a 3 phase VFD that can be powered single phase 240vac power.
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Old 01-13-16, 11:51 AM   #27
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Quote:
Originally Posted by stevehull View Post
using a small Honda (~1.5 kW) generator only to the well pump (1 HP). At pump start up, the pump house electric light bulb would noticeably dim for 8-10 seconds and the generator slowed considerably. Then, the generator would speed up, the light brightened and he had water. Then, about two days later, the pump died while on this generator. When we pulled it and did the tear down necropsy, the motor windings appeared burned. My belief was that this repeated starting high current and low voltage fried his pump (caused by the too small generator).

Of course, this could just be coincidence, but the pump was only three years old.
No coincidence.
That sums it up pretty well.
The motor was in startup for too long.
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Old 01-13-16, 01:53 PM   #28
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Thanks for posting very interesting. I really liked the info about your cattle and their water requirements.
I have a small generator but I have been thinking about a PTO generator. I have a small diesel 36 HP tractor.

This guy is a drivable distance for me to pick up.
St 10KW Gen Alternator PTO Gear Box Coupler Combo | eBay

I have been watching craigslist and natural gas one come up once in a while usually someone upgrading and the installer it selling the old one.
Or an office building but those are usually too big for me but would work for you.
You might fine a propane generator that a office building no longer needs on craigslist that would fill your requirements and not break the bank.
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Last edited by pinballlooking; 01-13-16 at 02:33 PM..
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Old 01-13-16, 02:29 PM   #29
WyrTwister
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Quote:
Originally Posted by oil pan 4 View Post
You don't want to run VFD on single phase.
Typically for high starting torque motors you use capacitor start. Capacitor start uses a mechanical centrifuge to turn the start circuit on and off. During run up the start circuit does not cut out until the motor is almost at operating speed.
If the motor runs for more than 5 or 10 seconds with the start circuit powered up it will fry something in the start circuit, usually the capacitor or the windings.
If you drop the motor speed down too low the start system will reengage, frying the starter.

This is why industrial pumps are pretty much always use 3 phase inverter duty rated motors connected to VFDs. The motors and what ever they drive can be soft started and ran at variable speed, usually any speed between 20hz and 60hz. Some VFDs can produce 100hz.
You can get a 3 phase VFD that can be powered single phase 240vac power.
Not sure if single phase VFD's are made ?

You are right , some single phase motors have centrifugal switches , but not all do . The submersible pump motors do not , there is a relay in the " box " that senses when it is appropriate for the start winding to be turned off .

Will have to check , but I think single phase A/C compressors do not use centrifugal switches .

Most single phase motors have capacitors .

With motors larger than a few hp , 3 phase is almost always better . It is certainly simpler .

With a VFD , the power AC is rectified to DC . The electronics then convert it back to a semblance of AC . Usually 3 phase . The VFD could be built to be feed single phase or DC from a source like wind turbine or PV cells .

God bless
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Old 01-14-16, 01:04 AM   #30
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A single phase VFD could be made but I don't know what the application would be or where you would buy one.

I work with rooms full of VFDs in all sizes. Little ones for up to 10hp and the big ones are for 700hp motors.

For home use I only ever use capacitor start, capacitor run for my air compressors I built to run sand blaster and orbital sander.

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