Pump problem - voltage drop

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olly

Senior Member
Location
Berthoud, Colorado
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Master Electrician
Hey guys,

I have a situation where a very expensive pump that is only lasting about 1 year before failing. The pump is pulling a load of 9A when working properly so I am told by the manufacture. It is on a dedicated 20A circuit. 12 AWG wire the entire length of the 150' circuit except a 18 AWG extension cord that was found 50' from the source. I removed the 18 AWG and installed a 12 AWG wire in its place. This is a 120v pump. It does run 24/7. Its an aeration pump for a lake. It blows air to oxygenize the lake for lake health
I am wondering if this fix / removing the 18 AWG week link will fix the issue?

The pump says voltage of 110v.

The damaged pump / not working pump was pulling 4 amps and I tested voltage while running and got 119v. 122V at the panel. The pump has no thermal overload just a capacitor and the pump.

Do you think removing the 18 AWG wire will fix the problem of the pump failing after a year?

Do you have any recommendations to where to go from here?

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I don't think that 18g section caused the problem, and it doesn't really matter where in the line it was. (Sounds like this pump isn't the right one for the job.)

When a new pump is installed, measure the current / voltage drop and record that somewhere so if there's a future problem you have the info.
 
I would get rid of the 18 gauge wire, but I agree the wire is not the problem. There's a lot of things that can go wrong with those aerator pumps. The first rule when it comes to something with a motor is that if there's a problem everyone blames the motor and the problem is usually mechanical.
Is it a vane pump?
When you say failing, what do you mean?
 
I agree that it is inappropriate to assume the problem is electrical. It could be the pump bearings for all we know. Perhaps foreign material in the lake clogging the impeller resulting in motor overheating.

So here again, what is the failure mechanism? Does the motor simply stop running? Are there any signs of overheating (perhaps not too likely if the motor is submerged)? Indeed is the motor submerged? OK, the pump is expensive, but that does not mean it is of sufficient quality. Do you know whether other similar installations with the same motor and pump combinations have the same problem?
 
Can you clarify the setup please?
Is it an air pump (low pressure compressor) which injects air into a bubbler or aerator or is it a water pump that feeds through a venturi to draw in air to mix with the water stream (like a Jacuzzi)

If it is an air pump, is it a positive displacement (cylinder or diaphragm)?
How is the pump cooled? Is there good air circulation around it?
The small cylinder-type aerator pumps I am familiar with have a service life of less than a year of continuous operation before a required/recommended maintenance procedure that replaces the piston seals and the cylinder liner. (Although the one I work with still seems to be in perfect condition at the time maintenance is done).
 
ActionDave said:
I would get rid of the 18 gauge wire, but I agree the wire is not the problem. There's a lot of things that can go wrong with those aerator pumps. The first rule when it comes to something with a motor is that if there's a problem everyone blames the motor and the problem is usually mechanical.
Is it a vane pump?
When you say failing, what do you mean?
Click to expand...
The pump is not pushing any air. It starts up, but sounds like there is something obviously wrong with the motor. It is pulling 3A but again no air flow. This has happen 2 years in a row now. It runs for a year then fails.
The pump sits above ground in a factory provided housing with a fan for ventilation and a HOA switch and an optional timer.
So what would be the next step?
 
olly said:
The pump is not pushing any air. It starts up, ...
Click to expand...
If the motor's turning at a normal-ish speed and the pump is not pushing any air, the primary problem is not electrical.

olly said:
... It is pulling 3A but again no air flow. ...
Click to expand...
The low current draw is probably a secondary result of not moving any air, not a primary sign of the root cause of this failure.

Air has mass. You're not pushing any. Nobody would be alarmed if the motor powering an empty conveyor belt was drawing significantly less than nameplate current.
 
olly said:
The pump is not pushing any air. It starts up, but sounds like there is something obviously wrong with the motor. It is pulling 3A but again no air flow. This has happen 2 years in a row now. It runs for a year then fails.
The pump sits above ground in a factory provided housing with a fan for ventilation and a HOA switch and an optional timer.
So what would be the next step?
Click to expand...
The next step is to find out what kind of pump it is. Vane pumps are common for this application and they need the vanes replaced regularly if that's what you have.
 
drcampbell said:
The low current draw is probably a secondary result of not moving any air, not a primary sign of the root cause of this failure.
Click to expand...
Bingo.
olly said:
Its an aeration pump for a lake. It blows air to oxygenize the lake for lake health
Click to expand...
Assuming this is a centrifugal machine (pump or blower, I still don't know), load = flow, so no flow = no load. If it WAS pulling 9A when it was working properly and now it only pulls 3A, there is no flow (of air or water, whatever it's supposed to do). Fix that first. If the flow of [product] is also used in cooling the machine, that could be a contributing factor to premature failure.

On a 9A load, 10ft of 18ga, although not ideal, is not going to cause enough VD to significantly affect the motor life by the way.
 
What kind of pump? Rotary, piston, or diaphragm? If the pump is not moving air and not drawing excessive current, and voltage is in permitters likely a mechanical issue not an electrical. Seen pump with seals leaking and just allowing blowby and not causing electrical load issue. Also seen something as simple as intake valve closed and it would not cause an electrical overload.
 
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