What causes a Low Flow, HFL or HL error code in a hot tub?
The Balboa spa pack with the M7 heater will display a Low FLow, HFL or HL error code on the topside panel if it has detected this fault 5 times in the last 24 hours or less, and the heater is now disabled. The Low Flow error code will display when there is not enough water flow through the heater to carry the hot water away from the heating element. Diagnosing the problem and fixing the cause is required, resetting the hot tub breaker will not resolve the issue, it will only clear the code till it shows up again.
Possible causes:
• Low flow.
Water flowing through the heater at a lower than normal or required rate can cause the heater to stop working and the error code appear. If the Balboa spa pack is a new install that replaced and old unit with a pressure switch make sure that the plumbing size is at minimum 1-1/2” and the circulation pump is the correct size as the heater sensor require about 23 gallons per minute of water flow through the heater to activate.
• Low Water Level.
One of the most overlooked causes of these error codes is a too low water level in the spa. If the water level drops too far then air will be sucked in through the filter when the pump is running. Then, if the smallest of air bubble comes in contact with one of the sensors in the Balboa heater tube it will instantly disable the heater to protect it from over heating. If this happens five times in a 24 hour period it will trigger the error code and disable the heater.
• Blocked suctions.
All hot tubs have suctions in the foot well area where they suck water from to pump through the Balboa heater and to the jets. If the suctions become blocked it reduces the amount of water the pump can draw thus reducing the flow rate and when it drops below the minimum level it will trigger the HFL, HL, or HTR FLOW LOW error code and disable the hot tub heater.
• Blocked filter skimmer.
If the filter area or the skimmer is blocked or the water flow is restricted it will cause the pump to suck air in through the filter, which will cause these error codes and disable the hot tub heater.
• Dirty filter.
Dirty filter(s) can restrict the flow rate of the water and cause no heat problems. To see if the problem is related to a dirty hot tub filter, turn the power off to the spa, remove the filter(s) leave them out then turn the power back on and let the spa run regularly for about 24 hours and observe if the error come back. If no error codes appear after 24 hours of running then the spa filters were too dirty and caused the issue. Just replace or clean the filter cartridges and the problem should be solved.
• Too many jets closed.
If too many of the hot tub jets are partially or completely turned off or closed it creates severe flow restriction. The spa pump is running full speed but cannot push enough water through the plumbing. Because of the closed jets the water doesn’t flow through heater at the minimum required rate which triggers the Balboa heater shut down to protect the heating element from burning out.
• Closed valves.
Occasionally when a hot tub is serviced and the valves have been closed to replace a pump or heater the valves may stay partially closed even though they appear to be open, gate or knife valves are prone to this issue. If the hot tub has not been serviced and there are valves in the spa plumbing it’s always a good idea to inspect them to ensure the handle has not moved to a closed position from vibrations in the lines.
• Pump issue.
Some hot tubs have a 2 speed pump that does the heating when it is running on low speed and some hot tubs have a small designated circulation pump that runs continuously. In hot tubs with the larger 2 speed pump check to make sure the pump is running properly on low speed and quietly as well. If a pump is very loud when running it is an indicator that it is in need of service or possibly not performing at full level. For hot tubs that have a smaller circulation pump that runs continuously check the pump to confirm that it is running properly and quietly. A noisy pump can be an indicator that the pump requires service and also degrades its’ performance.
It's important to make sure that when the pump is running it is moving water. If the hot tub pump is running but very little or no water is moving then it’s possible the pump impeller has sheared off inside the wet end and will require replacing. Removing the pump and disassembling the wet end will expose the impeller, if it’s loose inside and can just be lifted out then it is broken.
• Air lock.
Often when the hot tub water is drained and the spa is filled with fresh water air can become trapped inside the pump. When the power is turned on the pump may run but will not be moving any water, as there is no water inside the pump only a trapped air bubble. The air trapped inside a pump can be stubborn to get out, the best method is to take out the filters, take the garden hose with the water turned on and push it to the bottom where the filter locks or threads in which will push water into the plumbing to the pump. This should push out the locked in air bubble.
• Incorrect size circulation pump.
On hot tubs with designated circulation pumps that run continuously, when the circulation pump is replaced it has to be replaced with the same size or a pump that has the equivalent Gallon Per Minute flow rating of the original one. Installing a circulation pump that has a lower Gallon Per Minute flow rate will result in not enough water flowing through the heater to allow it to function.
• Programming.
The configuration of the circulation system in the Balboa spa pack programming via topside requires proper set up. If not correctly configured the Balboa spa pack will not manage the pumps correctly for the heater and cause error codes to appear.
• Sensors.
The sensors in the Balboa M7 heater can, on very rare occasion, malfunction and cause no heat issues including error codes. Its best to retain the services of a professional with the proper equipment to test and trouble issues related to the Balboa sensors in the M7 series heaters.