Applicable Systems
MAGNA1
Symptoms
The Grundfos MAGNA1 pump displays alarm code 29, indicating forced pumping. Other pumps or sources are forcing flow through the pump even though it is stopped and switched off, causing it to run as a turbine.
Possible Causes
- Defective non-return valve allowing backflow through the pump
- Non-return valve installed in wrong position or direction
- Multiple pumps on common manifold with no non-return valves
- System pressure from other sources pushing flow backward through stopped pump
Troubleshooting Steps
- Step 1: Check if the pump is running in turbine mode (Grundfos Eye lit)
If the Grundfos Eye is on while the pump is stopped, the pump is being driven backwards by flow - Step 2: Inspect non-return valve for proper operation
Valve must close fully when pump stops; replace if stuck open or damaged - Step 3: Verify non-return valve installation direction is correct
Arrow on valve body must point in flow direction toward the discharge - Step 4: If system has multiple pumps, ensure each has a non-return valve
Each pump on a common header must have its own non-return valve to prevent backflow
How to Reset
To reset: 1) Switch off the pump on the main switch. 2. Repair or replace defective non-return valves. 3) Power cycle the pump. Caution: Forced pumping can damage the pump bearings and electronics through uncontrolled rotation.
Frequently Asked Questions
- Q: What is forced pumping on a Grundfos circulator?
Forced pumping occurs when flow from other pumps or system pressure drives the stopped pump backwards, causing it to act as a turbine. This can damage the pump.
- Q: Will code 29 clear automatically after fixing the non-return valve?
The alarm may auto-reset once the backflow stops, but a manual power cycle is recommended to fully clear the fault state.
Source: Grundfos MAGNA1 Installation and Operating Instructions, Fault Finding Table, Document 6908923
Category: Pump