How to Bench Test a Jet Pump

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Dixon

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I want to test a couple of used shallow well pumps and would like a brief tutorial on the best method.
I have an amp meter, verified pressure gauge, electrical supply and an adequate water reservoir with supply/return plumbing. A ball valve is installed on the pump discharge side and a 30/50 pressure switch is installed. No pressure tank is plumbed into the test setup. Check/foot valve installed on suction side.
- I think I'm supposed to test amperage draw under load? Also, if using a clamp meter, L1 & L2 must be separated and either L1 or L2 clamped but not both.
- What kind of amperage should I be looking for? I realize this is motor/hp dependent, is there a basic guideline? During the amp test am I suppose to slowly close the discharge ball valve with the pump running and note the amp draw under pressure?
-For pressure diagnosis, do I record discharge pressure with the pump running and ball valve wide open then again with the pump off? After the pump is off how long should I time the pump under pressure to determine if there is a slow leak?
 

Valveman

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It will say SFA or Full Load Amps on the side of the motor. That is how many amps it should draw when running a full pipe of water at its design pressure. It should draw less amps when the ball valve is closed or nearly closed. You want to check amps at full flow and little or no flow. You will have to bypass the pressure switch to get a max pressure reading. Yes only L1 or L2, not both for the reading. With no pressure tank a leak will cause the pressure to drop off instantly. But a leak should also be obvious as water will be dripping on the floor.
 

Reach4

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It occurs to me that a ball valve in the suction line followed by a vacuum gauge could be informative... giving info as to how the pump performs with the water surface lower. I don't know how fancy your test setup should be.
 

Dixon

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Thank you gentleman for your advise.

"I don't know how fancy your test setup should be."
Fancy is definetely not me, In my book KISS is the way to go. I'm guessing simple would be to eliminate the check/foot valve and pressure switch? All I really want to know is amperage draw under load and pump pressure performance.
 

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If the pump will reach its max pressure it will draw from the well as it should. You will need the foot valve just to get it primed, and just wire to the output side of the pressure switch for the test.
 

Dixon

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" You will need the foot valve just to get it primed, and just wire to the output side of the pressure switch for the test."

Gotcha Valveman. Again, thank you for sharing your knowledge.
I'm developing a household "how to" notebook and your information is filling the well so to speak.. My memory isn't what it used to be and things I don't do frequently must be recorded. Keeping the house supplied with fresh water pretty much tops the list.
 

Dixon

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  • Got around to rebuilding/testing a Sta-rite SNE-L, 1 hp shallow pump.
Cleaned all parts, treated volute interior with 0spho.
Impeller/diffuser looked good enuff so they're in it.
Replaced mechanical seal, splash seal, and volute to back plate seal.
Pretty paint on pump, not motor.
Test run: (max amps motor rating = 7.40)
Motor runs 5.5 amps unloaded, no pump connected.
Runs 6.24 amps wide open with 1" discharge (@ 3')
Runs 6.72 amps and pressure switch chatter begins at @ 50 psi while closing valve three quarters +/-

Zero leaks after 10 minute run.

Would this be considered a sound backup pump? I turned it upside down and blew it out with pressurized air hoping so..
 

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DonL

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  • Got around to rebuilding/testing a Sta-rite SNE-L, 1 hp shallow pump.
Cleaned all parts, treated volute interior with 0spho.
Impeller/diffuser looked good enuff so they're in it.
Replaced mechanical seal, splash seal, and volute to back plate seal.
Pretty paint on pump, not motor.
Test run: (max amps motor rating = 7.40)
Motor runs 5.5 amps unloaded, no pump connected.
Runs 6.24 amps wide open with 1" discharge (@ 3')
Runs 6.72 amps and pressure switch chatter begins at @ 50 psi while closing valve three quarters +/-

Zero leaks after 10 minute run.

Would this be considered a sound backup pump? I turned it upside down and blew it out with pressurized air hoping so..

For safety purpose, You may want to add a electrical ground wire to the motor.

That will also let you test the motor for a shorted winding. There should be Zero current flowing on the ground wire.

Have Fun. Be safe.
 

Dixon

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Thanks for the advise folks. I did ground the motor while testing but did not test for current through ground. That can be done.
One question when bench testing without a pressure tank Is there anyway to prevent pressure switch chatter as I approach cutoff pressure while closing the discharge ball valve?
 

Dixon

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Gotcha, wire directly. Too easy. Also, wouldn't a simple resistance test between L1/ground, L2/ground with a multimeter indicate a short in the windings?
 

Reach4

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Gotcha, wire directly. Too easy. Also, wouldn't a simple resistance test between L1/ground, L2/ground with a multimeter indicate a short in the windings?
That would find a winding to case short, but not an inter-winding short.

Ideally you would check with a megger. Usually a short would show with a volt or two from the regular multimeter, but the megger provides hundreds of volts to detect the short that has a tiny tiny gap. Not worth buying one of those for a one- or two-time test. 100,000 ohms (1oo kohms) is about the cutoff between OK and not.
 

Dixon

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I havn't reconnected/primed the SNE to test current leak at ground but I did put another pump together, a used Sta-Rite SND and tested it.
SND Data plate indicates 6.2 max amps, I measured 5.1 pumping wide open and 5.38 amps with the discharge valve nearly closed (50 + psi). The clamp meter on the ground wire indicates .063 amps while the pump is running?
 
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Reach4

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The clamp meter on the ground wire indicates .063 amps while the pump is running?
Hmmm. stray magnetic fields affecting the meter? Yes, look things over. If you powered the pump via a GFCI, it would trip at 0.005 amps of mismatch.
 

Dixon

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No GFCI. The ground wire I clamped around had @ 6" free length from the motor to the cord. I moved the clamp up and down the free running length and the reading did vary somewhat, .05 to .10
The meter is a compact, 100 amp clamp, inexpensive but reliable I believe.
 

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Reach4

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Suppose you slide the clamp along the side of the wire, but with no wire encircled by the clamp. In theory, the meter should read zero. Does it?
 
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