Service instructions

MQ 3-35, MQ 3-45

50/60 Hz 1~

Image of a Grundfos MQ series self-priming centrifugal pump.

Contents

1. Type identification
   1. Nameplate
   2. Type key
2. Service tools
   1. Special tools
   2. Standard tools
3. Dismantling and assembly
   1. General information
   2. Replacing the shaft seal, chambers and impellers
   3. Replacing the pressure tank
   4. Replacing the electronic unit, flow sensor and pressure switch
   5. Replacing the motor unit
4. Operation
   1. Priming
   2. Start
   3. Stop
   4. Alarm
   5. Auto-reset
   6. Manual reset
   7. Control panel
   8. Overview
   9. Fault finding
   10. Fault finding overview
5. Wiring diagram
   1. Winding resistance measurement

1. Type identification

1.1 Nameplate

Diagram showing a pump nameplate with various labeled fields (1-15) indicating pump specifications.

1.2 Type key

Diagram illustrating the MQ pump type key breakdown, showing how different characters in the model name correspond to pump range, rated flow rate, max head, pump version, pipework connection, materials, and shaft seal.

2. Service tools

Series of illustrations depicting various service tools: A) Pressure gauge, B) Bit holder, C) Bits kit, D) Ring/open-end spanner, E) Screwdriver (straight slot), F) Screwdriver (cross-head), G) Hexagon socket driver, H) Circlip pliers.

2.1 Special tools

2.2 Standard tools

3. Dismantling and assembly

3.1 General information

Position numbers of parts (digits) refer to exploded views, sectional drawings and parts lists; position numbers of tools (letters) refer to section 2. Service tools.

3.1.1 Before dismantling

• Disconnect the electricity supply to the motor.
• Remove the electric cable in accordance with local regulations.

3.1.2 Before assembly

Gaskets and O-rings should always be replaced when the pump is overhauled.

• Clean and check all parts.
• Order the necessary service kits.
• Replace defective parts by new parts.

3.2 Replacing the shaft seal, chambers and impellers

3.2.1 Removing the shaft seal

1. Slacken and remove the strap pos. 92.
2. Remove the screws pos. 91.
3. Carefully remove the pump sleeve pos. 16 using a screwdriver.
4. Remove the inlet part pos. 6 from the pump sleeve or the top of the chamber stack.
5. Remove the nut pos. 67 and the washer pos. 66. Hold the shaft with a screwdriver in the shaft end.

Cross-sectional diagram of the pump showing components for shaft seal removal.

6. Remove the chambers pos. 4 and the impellers pos. 49.
7. Remove the washer pos. 107, the retaining ring pos. 111 and the washer pos. 102.
8. Remove the rotating shaft seal part pos. 104.

Exploded view diagram of shaft seal components (102, 104, 107, 111, 103).

9. Remove the stationary shaft seal part pos. 103 using a screwdriver.

3.2.2 Fitting the shaft seal

1. Fit the stationary shaft seal part pos. 103 with the groove against the intermediate part pos. 2.
2. Fit the rotating shaft seal part pos. 104.
3. Fit the washer pos. 102 (2 mm), the retaining ring pos. 111 and the washer pos. 107.

4. Fit the chambers pos. 4, O-rings pos. 37 and impellers pos. 49 on the motor unit/shaft pos. 150, see drawing. Note: There is no O-ring on the chamber next to the intermediate part pos. 2.

Exploded view diagram of pump chambers, O-rings, and impellers (parts 2, 4, 37, 49, 66, 67, 150).

5. Fit the washer pos. 66 and the nut pos. 67 and tighten it with 7 Nm. Hold the shaft end using a screwdriver.

Cross-sectional diagram of the pump showing assembly of components.

6. Fit the O-rings pos. 37 to the back of the inlet parts and fit the inlet parts to the chamber stack.
7. Fit the O-ring pos. 37b and lubricate it.
8. Fit the O-ring pos. 37a on the intermediate part pos. 2 and lubricate it.
9. Lubricate and fit the pump sleeve pos. 16. Check that the pin at the bottom of the intermediate part fits the hole of the pump sleeve.
10. Push the pump sleeve into position and tighten the three screws pos. 91.
11. Fit and tighten the strap pos. 92.

3.3 Replacing the pressure tank

3.3.1 Removing the pressure tank

1. Remove the cover pos. 43.
2. Remove the pressure tank pos. 42 including the O-ring pos. 44. It can be loosened using the fingers.
3. If the union nut including O-ring pos. 44 is not removed with the pressure tank, remove it using a 42 mm socket.

3.3.2 Fitting the pressure tank

1. If the pressure tank pos. 42 has been screwed out of the union nut, lubricate the threads of the pressure tank with Loctite 5331 and screw the tank into the union nut.
2. Fit the O-ring pos. 44 and screw the pressure tank pos. 42 into the motor housing pos. 180 by hand.
3. Fit the cover pos. 43.

3.4 Replacing the electronic unit, flow sensor and pressure switch

3.4.1 Removing the electronic unit, flow sensor and pressure switch

1. Slacken the screws pos. 166 and remove the terminal box cover pos. 164.
2. Disconnect the leads and pull them out of the terminal block on the electronic unit pos. 181.
3. Disconnect the flow sensor and pressure switch from the electronic unit pos. 181.
4. Disconnect the earth lead.
5. Remove the electronic unit pos. 181.
6. Remove the capacitor pos. 161 from the terminal box and disconnect the leads.
7. Remove the pressure switch pos. 174a using the fingers.
8. Slacken and remove the screws pos. 166a.
9. Remove the flow sensor cover pos. 184 including the O-ring pos. 187 and flow wheel pos. 185.
10. Pull up the flow wheel shaft pos. 186 and remove the washer pos. 185a.

3.4.2 Fitting the electronic unit, flow sensor and pressure switch

1. Fit the flow wheel shaft pos. 186 and the washer pos. 185a.
2. Fit the flow wheel pos. 185 with the magnet against the cover.
3. Lubricate the O-ring pos. 187 and fit it on the cover pos. 184.
4. Press the cover pos. 184 home. Check that the pin of the flow wheel chamber fits the hole in the cover.
5. Fit and tighten the screws pos. 166a.
6. Lubricate the O-ring pos. 174b with soapy water.
7. Fit and tighten the pressure switch pos. 174a using the fingers.
8. Pull the mains cable into the terminal box.
9. Lead the earth lead round the pressure switch 174a on the outside and the leads round the flow sensor pos. 184 on the inside.
10. Fit the capacitor pos. 161 into the retainer by means of the clip pos. 160.
11. Fit the electronic unit pos. 181 and connect the leads including the earth terminal pos. 176a, see 5. Wiring diagram.
12. Fit the terminal box cover pos. 164 including the O-ring pos. 165.
13. Fit and tighten the screws pos. 166.

3.5 Replacing the motor unit

3.5.1 Removing the motor unit

1. Remove the shaft seal, see 3.2.1 Removing the shaft seal.
2. Remove the electronic unit, flow sensor and pressure switch, see 3.4.1 Removing the electronic unit, flow sensor and pressure switch.
3. Remove the pressure tank, see 3.3.1 Removing the pressure tank.
4. Slacken and remove the screws pos. 152 and washers pos. 152a, -b and -c.
5. Remove the end cover pos. 51.
6. Remove the screw for the earth lead pos. 173 on the motor unit pos. 50.
7. Pull the leads to the motor unit out of the terminal box.
8. Press the motor unit pos. 150 out of the motor housing pos. 180.
9. Remove the screws pos. 26, washers pos. 27 and intermediate part pos. 2.
10. Remove the retainer pos. 40a and the O-rings pos. 40.

3.5.2 Fitting the motor unit

1. Lubricate the O-rings pos. 40 and fit the rings and the retainer pos. 40.
2. Lubricate the O-ring pos. 37a and fit it on the motor housing pos. 180.
3. Fit the motor housing pos. 180 to the intermediate part pos. 2.
4. Fit the screws pos. 26 and the washers pos. 27 and tighten diagonally.
5. Lubricate the recess of the O-ring pos. 53 in the motor housing pos. 180.
6. Roll the O-ring pos. 53 on the motor unit pos. 150 and lubricate it.
7. Fit the motor unit in the motor housing pos. 180.
8. Pull the leads from the motor unit into the terminal box.
9. Pull the earth lead into the terminal box. The earth lead lug must not touch the other leads.
10. Fit the earth lead to the motor unit and tighten the screw pos. 173.
11. Lubricate and fit the O-ring pos. 52 to the end cover pos. 51.
12. Fit the end cover pos. 51. The leads from the motor must fit into the slot.
13. Fit the screws pos. 152 and washers pos. 152a, -b and -c and tighten.
14. Fit the pressure tank, see 3.3.2 Fitting the pressure tank.
15. Fit the electronic unit, flow sensor and pressure switch, see 3.4.2 Fitting the electronic unit, flow sensor and pressure switch.
16. Fit the shaft seal, see 3.2.2 Fitting the shaft seal.

4. Operation

4.1 Priming

Before initial start-up, pour approx. 5 litres of water into the pump through the priming port, see the installation and operating instructions. When started, the pump will start to evacuate the air contained in the system. Once it starts to deliver water, the pump will change over to normal operation (start/stop).

If no water is delivered within 5 minutes after start-up, the pump will stop automatically as protection against dry running, and alarm will be indicated.

4.2 Start

The pump starts when

• the consumption is higher than 1.2 l/min or
• the pressure is lower than 2 bar.

4.3 Stop

The pump stops when

• the consumption is lower than 1.2 l/min.

4.4 Alarm

The pump stops in case of

• dry running (if the pressure falls below 2 bar and the consumption below 1.2 l/min, an alarm will be given after 60 seconds)
• overtemperature (thermal switch in motor)
• overloaded motor (thermal switch in motor)
• seized-up motor/pump (thermal switch in motor).

4.5 Auto-reset

If activated, the auto-reset function will cause the pump to restart automatically every 30 minutes for 24 hours in case of any type of fault. After this period, if the fault has not disappeared, the pump will remain in the alarm condition and can only be reset manually, see below.

4.6 Manual reset

The pump can be reset manually by

• pressing the on/off button twice or
• interrupting the supply voltage briefly.

4.7 Control panel

Diagram of the pump control panel with 'On/Off' button, 'Pump on' (green), 'Auto-reset' (green), and 'Alarm' (red) indicator lights.

Note: The pump settings are stored. After supply failure, the pump will automatically revert to its operating condition when the electricity supply is connected again.

4.8 Overview

Before starting the fault finding procedure, check the external installation conditions of the pump. For this purpose, see the installation and operating instructions.

Note: It is important to read this section as well as 4.9 Fault finding and 4.10 Fault finding overview thoroughly.

The pictures below show the essential parts that control the MQ pump.

4.9 Fault finding

If the pump does not start when the fault has been corrected, contact your pump supplier or GRUNDFOS for further information.

4.10 Fault finding overview

Start the pump and allow it to run for a minimum of 5 minutes with the tap turned on. Then observe how the system reacts.

4.10.1 Observation A

1. Illustration of a tap being turned off.

   Turn off the tap.

2. Illustration of a pressure gauge on the pump.

   The system is closed; the pressure must be minimum 2.5 bar. If 2.5 bar is not reached, check the hydraulics. If the pressure is above 2.5 bar, continue the fault finding procedure.

3. Illustration of a non-return valve and a timer showing approx. 15 seconds.

   Wait approx. 15 seconds to see what happens when the pump stops. If the pump does not stop, even when the start/stop button is on, replace the controller. If the pressure falls below 2.5 bar, check the non-return valve in the suction line. If the pressure does not fall, continue the fault finding procedure.

4. Illustration of disconnecting the electricity supply by pulling out the plug.

   Disconnect the electricity supply by pulling out the plug.

5. Illustration of removing the pressure switch plug from the controller.

   Remove the pressure switch plug from the controller.

6. Illustration of a multimeter measuring the pressure switch with the pump under pressure.

   At a pressure above 2.5 bar, the switch is closed, and the multimeter must show approx. 0 Ω. If the multimeter shows "OL" or MΩ, the contact is open, and the pressure switch must be replaced.

7. Illustration of turning on the tap to remove pressure from the system.

   Turn on the tap. The pressure is removed from the system.

8. Illustration of a multimeter measuring the pressure switch with no pressure.

   At a pressure below 2 bar, the switch is open, and the multimeter must show "OL" or MΩ. If the multimeter shows approx. 0 Ω, the contact is closed, and the pressure switch must be replaced. If the pressure switch is OK, replace the controller.

4.10.2 Observation B

1. Illustration of a tap being turned off.

   Turn off the tap.

2. Illustration of a timer showing 15 seconds.

   If the pump enters an alarm condition after 60 sec., replace the pressure switch. If the pump stops within 15 sec. and does not enter an alarm condition, continue the fault finding procedure.

3. Illustration of disconnecting the electricity supply by pulling out the plug.

   Disconnect the electricity supply by pulling out the plug.

4. Illustration of turning on the tap to remove pressure from the system.

   Turn on the tap. Remove the pressure from the system.

5. Illustration of removing the controller.

   Remove the controller.

6. Illustration of checking the flow sensor housing for impurities.

   Check for impurities in the flow wheel housing. Replace the flow sensor if defect.

7. Illustration of fitting the magnet on the flow wheel against the sensor.

   Make sure that the magnet on the flow wheel is fitted against the sensor in the flow sensor cover.

8. Illustration of fitting the controller and cover and connecting electricity supply.

   Fit the controller and the cover. Connect the electricity supply.

9. Illustration of the On/Off button being pressed.

   Press the on/off button. Do not forget to turn on the tap.

10. Illustration of water flowing from a tap.

    If the pump delivers water without stopping/starting at intervals of 15 seconds, the pump is OK. Otherwise, the controller must be replaced.

4.10.3 Observation C

1. Illustration of a non-return valve in an inlet pipe.

   Check that the inlet conditions are satisfactory.

2. Illustration of pouring water into the pump (priming).

   Prime the pump.

3. Illustration of disconnecting the electricity supply by pulling out the plug.

   Disconnect the electricity supply by pulling out the plug.

4. Illustration of checking if the pump is seized-up with a screwdriver.

   Check if the pump is seized-up by means of a screwdriver. If it is impossible to turn the motor and pump, the hydraulics must be checked. See the exploded drawing.

5. Illustration of bypassing the controller by connecting motor lead to mains cable.

   Bypass the controller by connecting the motor lead to the mains cable.

6. Illustration of fixing the cover on the pump and connecting electricity supply.

   Fix the cover on the pump and connect the electricity supply.

7. Illustration of a timer showing max. 5 minutes.

   Wait approx. 5 min. or until water comes out of the tap.

8. Illustration of two scenarios: pump delivers water or not.

   If the pump delivers water, the controller must be replaced. If the pump delivers no water, continue the fault finding procedure.

9. Illustration of disconnecting the electricity supply by pulling out the plug.

   Disconnect the electricity supply by pulling out the plug.

10. Illustration of a capacitor with wires (White, Red, Blue).

    Replace the capacitor. If available, a measuring instrument capable of measuring 25 microfarad can be used to measure the capacitor for failures before it is replaced. The blue wire from the capacitor must be connected with the red wire to the motor. The white wire is not connected to other wires.

11. Illustration of fixing the cover on the pump and connecting electricity supply.

    Fix the cover on the pump and connect the electricity supply.

12. Illustration of a timer showing max. 5 minutes.

    Wait approx. 5 min. or until water comes out of the tap.

13. Illustration of two scenarios: pump delivers water or not.

    If the pump delivers water, it is OK. Connect the controller correctly. If the pump does not deliver water, continue the fault finding procedure. The controller continues to be bypassed.

14. Illustration of disconnecting the electricity supply by pulling out the plug.

    Disconnect the electricity supply by pulling out the plug.

15. Illustration of dismantled hydraulic parts.

    Dismantle the hydraulic part and check for defects, dirt and wear.

16. Illustration of connecting electricity supply by plugging the pump into the mains.

    Connect the electricity supply by plugging the pump into the mains.

17. Illustration of checking if the motor can rotate.

    Check that the motor can rotate. If the motor cannot rotate, replace it. If the motor can rotate, the hydraulics are faulty. See the exploded drawing.

18. Illustration of connecting the controller correctly.

    Do not forget to connect the controller correctly after completing the fault finding procedure.

4.10.4 Observation D

1. Illustration of the controller.

   Replace the controller.

5. Wiring diagram

Detailed electrical wiring diagram for the Grundfos MQ pump, showing connections between the electrical motor, capacitor, ground, phase, neutral, flow sensor, and pressure switch. The diagram includes labels for White (aux), Red (main), Yellow-green, Black, Blue, Orange wires, and indicates connections to Mains, Flow sensor, and Pressure switch.

5.1 Winding resistance measurement

The measurement can be done with or without cables connected to the PCB and the capacitor.

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