Using a generator to power a water well pump

[SPYDERLK]

I have 7000 watt/8750 starting power generator with a transfer switch. Electrician turned the well on while testing it, he flushed the toilet a few times until the tank bladder was down enough that the pump kicked in. He wanted me to hear what happens. Generator made a quick louder blip sound. But once the pump stopped it quickly stabilized. Around here we mostly have propane heat and water heaters and most neighbors have generators 5500-8000 watts (continuous). As long as we have gas to run a generator, it'll do what we need to stay comfortable.

What you heard was the gens response to the quick high starting load imposed by the pump. The gen should immediately stabilize to the diminishing load as the pump starts. Maybe you meant, "once the pump stopped starting it quickly stabilized".
larry

 

[Boeing]

Question for Curly Dave. I too have hill top land. Drillers have said that I may have to go 700-800' to get water. One suggested a THREE phase pump thru an inverter? to convert my SINGLE phase electricity to run this pump....thereby....running a smaller gauge wire. Does this sound reasonable? The well will be anywhere from 100 to 300' from house and then down 500-800'. ALOT of wire. Thanks

 

[SPYDERLK]

My well is 710 feet and I have the pump at 670, even though my water level is closer to 60', just like yours. The reason is that water levels fluctuate over time and this way I can withstand a large drop and still be OK. Also, the amount of water stored in the well bore is significant.

It requires very little extra energy to pump, only the friction losses in the extra pipe, the hydrostatic head only depends on the actual water level and is the same no matter what the pump depth.

Under steady state pumping conditions this is absolutely true. During startup however it prolongs the high current startup phase of pump operation. There is, 1st, the very high [3 or 4 times motor rating] locked rotor current drawn, and 2nd the longer termed but lower overcurrent due to the motor being under overload while it accelerates a column of water more than a tenth of a mile long from zero to a speed of several feet per second. In combination, when other motor loads are present [particularly compressor type] this can be telling on a marginal gens ability to complete a pump startup.
larry

 

[Carl_NH]

It is a a double throw with a metal bar attaching the two 20 amp breakers. It is not the ones I have seen that has one switch for a breaker that takes up two spaces in the panel.

I checked just now it IS 12-2 wiring I guess it is SLIGHTLY larger than the regular romex going through the rest of the house. I also have a 220 plug for pottery Kiln thatthe PO used to have. But it is armored sheathing over the wiring. That and the electric water heater are the only 220v run in the house. The oven and range is gas.

So guess i will have to look through my paperwork to see what type of Gould pump is down there.

Shortlid, sounds like the breaker is one of the double type with the metal bar allowing you to have two 220 V circuits in the space of one double pole. Thats fine. The pottery kiln wiring may be 30 amp (10 gauge wire) if so you could wire the generator plug/wire into this circuit and back feed the panel - making sure you shut off the main breaker and other house feeds first, before you connect the generator. Most portable gensets have a 4 wire either 20 amp or 30 amp cable. The 5KW will have 20 AMP and those above 5KW will have 30 amp typically. If you go for a 6KW unit a 30 amp circuit with #10 wire would be fine.

They make transfer switches $300 that have 4-6 circuits which is the norm for setting up a panel and generator, but many just backfeed the panel thru a spare breaker.

On your pump, its probably a 1/2 or 3/4 HP based on your well depth of 200' which is 5-6 amps 1/2 HP or 7-8 amps 3/4HP.

 

[Larry Caldwell]

Question for Curly Dave. I too have hill top land. Drillers have said that I may have to go 700-800' to get water. One suggested a THREE phase pump thru an inverter? to convert my SINGLE phase electricity to run this pump....thereby....running a smaller gauge wire. Does this sound reasonable? The well will be anywhere from 100 to 300' from house and then down 500-800'. ALOT of wire. Thanks

Rather than a submersible pump, you might take a look at a turbine pump. The motor sits on top of the well head, and runs the pump by drive shaft down the bore. Typically it requires at least a 6" well to install. They are common in irrigation applications, but they also manufacture small models for domestic water.

 

[TheGoose]

Setting a sub that deep is no problem, just takes time and materials. Setting a turbine pump that deep would be a huge PITA for home use.

 

[shortlid]

Carl, again thank for info. I was thinking the EXACT same thing when I was the armored 30amp 220v plug for the old kiln! As always make sure when ever you are using a generator shut off the main!

 

[BobRip]

Under steady state pumping conditions this is absolutely true. During startup however it prolongs the high current startup phase of pump operation. There is, 1st, the very high [3 or 4 times motor rating] locked rotor current drawn, and 2nd the longer termed but lower overcurrent due to the motor being under overload while it accelerates a column of water more than a tenth of a mile long from zero to a speed of several feet per second. In combination, when other motor loads are present [particularly compressor type] this can be telling on a marginal gens ability to complete a pump startup.
larry

I have seen this situation. The column of water is like a flywheel and it takes energy to accelerate. My 8kw generator would not start my 1.25 Hp after hurricane Isabel. We ended up changing the wire size from 12 guage to 10 gauge. Now a 5kw will start it. The pump is 300 feet down.

 

[5030]

The only thing I see that's wrong is in the first post of the thread.

Starting amperage is THREE times running amperage, not two times. That's standard acceptable practice according to the NEC.

 

[hosspuller]

There have been several posters speaking of back-feeding their electrical panel. I do not recommend it and speak against it. This practice is risky for several reasons. There is nothing to prevent fatal errors. Only a single switch that must be operated by a person that knows the system.

it is easy to overload the generator if an automatic device were to turn on.

If you don't kill a lineman, your generator will be destroyed when the power is restored.

How will you know if your power is restored if your main is off ...

All to save a few dollars... Nuts..

Take those same few dollars and wire a receptacle and plug for the well pump. Locate it between the circuit breaker and the pressure switch. When the power is out, disconnect the well from the receptacle and plug it into an extension cord to the generator. About the same cost as back feeding a panel without the risk...