Repair the pump “Gnome”: an overview of popular breakdowns and how to fix them

With proper operation, the pump “Gnome” can serve its owner for more than one decade. And even if a breakdown occurs, do not rush to replace it with another unit or call a repair technician.

Most malfunctions can be eliminated on their own, because repairing the Gnome pump is not difficult if you know the cause of the occurrence and how to fix the malfunction. In our material we will talk about the design features of the electric pump, the most common causes of equipment failure and how to eliminate them.

General Information about Gnome Pumps

Gnome Pumps for pumping clean and dirty water are very often used by summer residents and owners of country houses. These are reliable and durable electric pumps that do not require complicated and expensive maintenance.

Under this brand, centrifugal submersible pumps are available that have various technical characteristics:

• productivity is from 7 to 200 m³/hour;
• nominal head from 7 to 50 m;
• electric motor power from 0.6 to 21 kW.

In everyday life, the most commonly used models are “Mini Gnome”, “Gnome 16-16T”, “Gnome 10-10T” and “Gnome 20-25”, therefore, we will continue to talk about these household electric pumps. These models are small in size and weigh from 10 to 32 kg.

Most Gnome pumps are equipped with float switches with devices that perform the functions of a water level sensor - the pump automatically shuts off when the level drops

Gnom portable centrifugal pumps have a monoblock design and are used for pumping clean and dirty water with a density of up to 1100 kg / m3 and containing solid mechanical particles up to 5 mm in an amount not exceeding 10%. The maximum density of solid particles is 2500 kg / m3.

Pumps are used to supply water from open reservoirs, wells, and wells. They are used to drain pits and trenches, to irrigate agricultural crops, to pump groundwater from flooded rooms.The temperature of the pumped water for ordinary models is up to 35 ° C, for models “T” - up to 60 ° C.

The electric motor of the pump “Gnome” is equipped with a thermal fuse, which turns off the unit when overheating occurs, it is possible to resume pump operation only after it has completely cooled down

Centrifugal submersible pumps “Gnome” have a simple design and consist of the following main parts:

1. An electric motor that includes a stator, bearing shield and rotor.
2. Pump assembly, with an impeller located on the rotor shaft, with an intake mesh and a branch.
3. Sealing system to protect against ingress of water.
4. Housing made of metal, cast iron or plastic.
5. Power cable.

The motor is cooled due to the external environment and oil, which is located in a special oil chamber of the electric motor. Oil also performs the function of lubricating the rubbing parts. The rotational speed of the rotor and impeller is 3000 rpm. During rotation, a centrifugal force is generated, which pushes water through the discharge pipe.

Water enters the pump through a filter screen that traps large particles. Then the water moves through the channels to the branch, from which it enters the branch pipe. The electric pump is started by a starting device, which is connected to the power cord. Electric pumps “Gnome” have a capacitor and an automatic switch that protects the electric motor from overload.

Gnome pumps are submersible typeTherefore, their launch is carried out only after complete immersion in water. An exception is the “Gnome” electric pumps with a “cooling jacket”. Most electric pumps are equipped with float switch, which is mounted on the handle of the unit and provides a minimum suction height of 15 cm.

Typical Causes of Failure

According to statistics, 95% of cases of failure of the pumps “Gnome” are associated with improper operation and installation. The most common causes of malfunctions:

Number 1.Wrong motor protection circuit breaker

An incorrectly selected and installed circuit breaker does not respond to critical voltages in the mains. To protect the electric motor, it is necessary to install a special machine, which is purchased separately.

The type of protection device recommended by the pump manufacturer in the operating instructions. According to the manufacturer’s recommendations, for example, for the “Gnome” brand electric pump, the use of a VA 101-3 machine is mandatory. You can also use machines ABB series MS.

No. 2. Reflow insulation of thermal protection winding

Thermal protection is built into the winding and when the motor is heated, it turns off its power. If the pump often overheats for some reason, then each time the insulation melts. This is an irreversible process, which can lead to a short circuit and inevitable breakdown of the electric motor.

No. 3. Operation of an electric pump without water

One of the most common causes of malfunctions. Operation of the “Gnome” submersible electric pump without a “cooling jacket” on dry should not exceed 15 minutes. Also, you cannot use the pump to pump high-temperature water (above +35 ° C for ordinary and +60 ° C for “T” models). In both cases, overheating of the pump and its failure quickly occurs.

No. 4. Use of the pump out of operating ranges

The pressure and capacity issued by the electric pump must not exceed the parameters specified in the passport. If the equipment works with a significant excess of technical characteristics, then the operating current on the motor windings increases significantly, which leads to its overheating. For a long time, the pump will not be able to work with overload and will quickly fail.

The operation of a powerful pump with a lower load also leads to overheating and failure, so you should not buy an electric pump with a “margin” for performance

No. 5. Pump operation on a valve or a narrow pipe

Savings on pipes and their purchase of a smaller diameter leads to a decrease in the performance of the electric pump, i.e. he begins to work outside his working range.

At the same time, a very narrow pipe may become clogged, which will also lead to an enormous load on the pump. To avoid this, it is necessary to use pipes of the appropriate diameter.

No. 6. Pumping unsuitable liquids

Such liquids include all liquids for which the Gnome pump is not designed:

• chemically aggressive;
• highly abrasive;
• with particles greater than 5 mm and a density above 2.5 thousand kg / m3;
• viscous, with sediment, high temperature, etc.

Transfer of such liquids leads to breakdown of many parts of the pump: from the strainer to the electric motor, therefore it is strictly forbidden to use the “Gnome” electric pumps for fecal effluents. If you need an aggregate specifically for this purpose, then you will be interested to read this material.

No. 7. Frequent on / off pump

When starting the pump, it simultaneously consumes a large amount of electricity than subsequently with uniform operation. This leads to the melting of the windings, and then to overheating of the electric motor.

If the pump is in the well, then with frequent changes in the water level, the pump can automatically turn off and then turn on. This significantly reduces its working resource. For such wells, with water level differences, they are more suitable surface pumps.

Number 8. Power Surges

With a voltage deviation of more than 5-10%, the operating current in the motor windings increases significantly, which leads to overheating. This may be due to unstable power supply or when using the wrong cable cross-section.

In the first case, the purchase of a voltage stabilizer will help, in the second - the selection of the optimal cable cross-section, depending on the power of the electric motor.

Installing a voltage stabilizer will protect the “Gnome” pump motor from fluctuations arising in the power supply network, significantly extending the pump life

No. 9. Removing the pump from the power cable

Another common cause of submersible pump malfunction. When pulling the power cable, leakage occurs at the point where the cable is connected to the pump housing.

This leads to the fact that water enters the motor and disables the unit. The same damage occurs when transporting the “Dwarf” over the cable or when objects fall onto the power cord.

No. 10. Wrong direction of rotation of the impeller

When starting the pump, make sure that the shaft rotates in the right direction. It is very simple to determine the correct rotation: when switched on, the pump will rotate in the opposite direction indicated by the arrows on the unit body (or in the figure in the passport).

If the pump rotates in the direction of the arrow, the connection is incorrect and the impeller will soon fail. To solve the problem, it is necessary to open the circuit breaker and switch two of the three wires of the cable, and then again check the direction of rotation.

Diagnostics of malfunctions and their elimination

Before proceeding with the disassembly of the pump and its repair, it is necessary to correctly determine what exactly caused the breakdown. Consider the most common symptoms that occur when the “Gnome” pumps malfunction.

The electric pump does not start

Possible causes and methods for their elimination:

1. The impeller is jammed.
2. Faulty capacitor in the power supply circuit.
3. Open circuit, burning contacts.
4. Blown stator winding.
5. Failure of the electric motor.
6. Jammed motor bearings.
7. Lack of voltage in the network or interruption in power supply.

After making sure that there are no problems with the power supply, it is necessary to disconnect the Gnome pump from the mains and disassemble it to identify the reason why it does not start. Inspect bearings, impeller, evaluate the condition of the motor windings.

If the pump worked for a long time, and then turned off and does not start, then before you take the unit out of the water and begin repair work, you must wait for it to cool completely

The engine is running, but the pump does not pump water

The engine of the Gnome pump works, but it does not pump water. The sound of a running engine may be weaker, uneven.

Possible reasons:

1. Clogged strainer or outlet.
2. The engine is running with insufficient power.
3. Bearing wear and motor speed reduction.
4. There is no pumped liquid or it has become too viscous and dense.
5. Damage to the water supply line (pipes, hoses).

In this case, you need to make sure that there is no damage to the pipes and hoses, there is water in the water source. If everything is in order, it is necessary to disconnect the equipment from the power supply and inspect the inlet filter and outlet pipe.

If necessary, clean them and try to start the pump. Bearing wear will require replacement.

The pump starts and switches off immediately

When starting up, the “Gnome” pump works for several seconds, and then it switches off spontaneously.

This may be a symptom of the following malfunctions:

1. Failure of the float switch.
2. Short circuit in the electric motor circuit.
3. The pump has overheated and the thermal fuse has tripped.
4. Extremely low voltage.
5. Impeller lock
6. The liquid into which the pump is immersed does not correspond to its operating ranges (too hot, viscous, with a high density, etc.).

In this case, it is necessary to disconnect the “Gnom” electric pump from the mains and repeat the attempt to turn it on after 30-90 minutes, after making sure that the necessary voltage is available in the mains.This time is enough for the superheated pump to cool. If the pump stops, it must be removed and disassembled to identify and eliminate the malfunction.

The use of a machine to protect the motor is recommended by the manufacturer and allows you to protect the pump “Gnome” from short circuit and voltage surges

Pump is running but pressure is small

The “Gnome” pump pumps water, but the pressure of the water is significantly lower than before.

Possible reasons:

1. Leaking water lines (hoses, pipes).
2. Low voltage in the mains.
3. Impeller contamination and insufficient rotation speed.
4. Wrong impeller rotation direction.
5. Large clearance between the wheel and the movable disk.
6. Impeller wear.

If low head is not a consequence of low voltage or leakage on the line, the pump should be disconnected from the power supply, removed from the pumped liquid and disassembled for inspection and repair work.

When the impeller is worn, it is replaced. If clogging or improper installation after self-assembly, disassemble the unit, clean and set the wheel in the correct position.

Assembly disassembly rules

The design of the “Gnome” pump is very simple, and the casing is quick-disconnect, which makes it possible to disassemble it without problems. No special tools are required for this. They begin to disassemble by unfastening the three nuts of the intake filter mesh and removing the mesh itself.

Then the cover fastening nuts are turned away, and it is removed together with the installation-movable disk. The impeller nut is untwisted, after which the wheel is freely removable.

All parts should be dismantled carefully without excessive force. Symmetrical parts must be numbered and marked (left / right, top / bottom) to avoid incorrect installation during assembly. It is recommended to replace the rubber parts during the assembly process with new ones using the repair kits intended for this model.

During long-term operation of the “Gnome” pump, problems may arise with loosening the nuts on the housing, they rusted or covered with a layer of calcareous sediment. In this case, the nuts can be cut off with a “grinder”, and when assembling, use new ones that are suitable in shape and size.

When assembling the pump, it is necessary to pay special attention to the place of seating of the replaced parts, they should not hang, compress, their size must strictly correspond to the brand of the pump

Repair of parts of the pump “Gnome”

Having examined the causes of malfunctions of pumps of the brand “Gnome”, you can see that almost all problems are solved by replacing the following parts: bearings, impeller, impeller shaft. Also, some malfunctions are eliminated after adjusting the clearance between the impeller and the diaphragm.

Bearing replacement sequence

When the bearings are abraded, the pump can pump water, but at the same time emit unusual sounds arising from friction and swaying of worn bearings. Bearings must be replaced if there are gaps greater than 0.1-0.3 mm. Usually this happens after 3-6 years of operation of the “Gnome” electric pump.

The process of replacing bearings is very simple: the pump is disassembled, the bearings are removed and replaced with new ones taken from a special repair kit. Do not use a home-made similarity of bearings or from analogues from repair kits of other modifications, as this could damage the equipment again in the very near future.

Impeller Replacement

To replace the impeller, it is necessary to disassemble the electric pump “Gnome” and remove the impeller. Then install a new impeller and assemble the pump in the reverse order.When mounting the cover with the installation-movable disk, it is necessary to screw the fasteners onto the studs and screw them at the same time until the minimum clearance between the impeller blades and the cover with the disk is achieved.

After assembly, it is required to check for leaks and, if it is broken, then refuse to use a permanently damaged electric pump.

In some cases, if you have experience and the appropriate equipment, you can not replace the impeller with a new one, but try to fix the existing ring workings using surfacing and then process it on a lathe.

Defects in the impeller of stainless steel or cast iron can be corrected by electrode welding, followed by turning the welding spot on a lathe

Repair impeller shaft and housing

If there is damage to the working shaft (bending, crack), it is best to completely replace it. The building of the “Dwarves” is theoretically repairable, but in practice it is practically impossible to implement it correctly.

In nine out of ten cases, the tightness of the case will be violated, and this defect can be corrected only at the factory or in a service center.

Given that such breakdowns occur in pumps that have worked for a considerable time, and therefore are not subject to warranty service, it is necessary to think about the feasibility of repair. In most cases, it is faster, cheaper, and easier to purchase a new submersible pump.

Clearance between impeller and diaphragm

The main reason for the decrease in pressure and performance of the “Gnome” electric pump is the increase in the gap between the impeller and the diaphragm during operation. To reduce the gap, it is necessary to adjust it.

To do this, remove the filter bottom and unscrew the upper nut. Then tighten with the nuts located on different sides the parts of the diaphragm until it contacts the impeller.

Then unscrew the lower nuts half a turn. With this adjustment, the gap will be 0.3-0.5 mm. The adjusted location of the diaphragm relative to the impeller is secured by the upper nuts. After completing the adjustment, it is necessary to check the ease of rotation of the impeller, it should rotate without applying force.

The clearance between the diaphragm and the impeller is necessary after the repair work related to disassembling the “Gnome” pump

Repair of the electric motor of the pump "Gnome"

Gnome brand pumps are equipped with a reliable asynchronous electric motor. It is very difficult to independently repair an electric motor. The maximum that can be done without special stands is to determine the resistance of the motor windings using a household multimeter.

If the resistance indicator tends to infinity, then this indicates that the winding is damaged and its replacement is necessary. To replace the winding will require complex disassembly of the electric motor and the presence of a rewinding machine.

But the main difficulty lies in the assembly process - the unit must be assembled in such a way as to provide a perfect barrier against the penetration of water into the electric motor. That is why it is better to entrust the repair of the “Gnome” pump engine to professionals.

The most difficult repair of modifications of the Gnome pumps is the restoration of the engine's operability. You should not take up this business without skills and auxiliary equipment.

Maintenance and overhaul

In order to avoid malfunctions, it is necessary to timely carry out maintenance of the “Gnome” electric pump recommended by the manufacturer.

THAT includes:

• oil change every 200-250 hours of operation;
• checking the level and quality of oil - 2 times a month;
• flushing the pump with clean water after pumping water with a high solids content;
• adjusting the clearance between the impeller and the diaphragm;
• inspection of the housing, bearings, impeller and shaft.

Maintenance of the pumps “Gnome” is carried out when there are signs of a malfunction or when the pump is idle.

Overhaul must be done after 25 thousand hours of work. Overhaul begins with the dismantling of the unit and determining the feasibility of carrying out repair work.

To fill the oil, put the pump on its side and unscrew the plug (17), then drain the used oil and fill in fresh industrial oil

Conclusions and useful video on the topic

Video on how to quickly disassemble a submersible electric pump “Gnome”:

The device and principle of operation of the pump “Gnome”:

Electric pumps "Gnome" - reliable units for pumping clean and dirty water, capable of serving its owner for more than 25 years. Proper operation and installation, as well as timely maintenance and elimination of the causes that lead to breakdowns, guarantee uninterrupted operation of the equipment. Most failures of the Gnom pumps can be fixed on their own without the involvement of repair technicians.

If you have already encountered repair of pumping equipment and have the necessary knowledge or skills, please share with our readers. Leave your comments and questions in the box below.