When you get a “flow” message as an error code on your hot tub panel, expressed in several ways, “FL” “FLO” or”FLOW” it indicates that there is no water flow or inadequate water flow through the hot tub heater. Having no flow or not enough flow through your hot tub heater is a critical event! If your hot tub heater came on without enough water flowing through it it would burn up quickly. Almost all hot tub systems have some means of determining water flow before allowing the heater to fire.
Digital systems may use pressure switches or temp sensors to determine if there is enough flow for the heater to fire. If the system detects no water pressure, or temp sensors detect temp levels outside the realm of their settings the system will return a Flow error. This is often expressed as “flo” on the digital panel of the hot tub.
When you get an error like this, the first thing you want to check is the pump. If the pump is either not coming on.. or running, without pumping, you will get this error code. If you’ve just drained your hot tub, and the pump seems to be running (as opposed to Humming) but you have no water flow, you need to check for an air lock at the pump.
To check for an air lock, turn off all power to your system at the breaker. Locate the pump plumbed to the heater and loosen the female nut part of the union on the front of the pump by unscrewing it slightly and wiggling it to break the oring seal. Keep your hand under the union so you don’t lose the Oring. If your pump is airbound, when you release the oring seal, you will hear air hissing out of the pump. Let all of the air hiss out until water starts to come out. Let the water leak a bit until it is a steady stream and then tighten the union nut back up to the pump. This should be hand tight only! When you have the union snugged up and the water is not leaking anymore, turn your breaker back on and see if the pump starts pumping water again. If it does, your flow error should be corrected.
If your pump is not running when you get the error code, you need to check for cause there. If the pump is not getting power, you could have a spa control issue. If the pump is getting power, you may have a pump problem. An electrical meter is the only way to know for sure if your pump is getting power or not.
Checking voltage to the pump is a little tricky because you need to know if the pump is a 120 or 230volt pump. ALL 2 speed pumps have 4 wires, usually a white, black, red and green. The green wire to the pump attaches to the pump ground screw. In both 120 and 230 volt pumps, the white is considered “common.” In a 120 volt pump the white will be “NEUTRAL.” Black and red on both 120 and 240 pumps are “switched lines” feeding low or high speed connections. The most common scenario is that the black feeds the high speed pump windings and the red feeds the low speed pump windings, but some control manufacturers may do it the opposite way with red being high speed and black being low speed. On the pump motor itself, you can see a small H for high and a L for low as well as a C for common where the wires attach to the motor.
The hot tub control system only feeds ONE speed at a time, either high or low, but never both. (if both high and low are fed at the same time which can happen if there is a bad relay in the system, the pump will sound buzzy, will not work efficiently and will eventually shut off by the motor overload.
Testing a 120 volt 2 speed pump, involves voltage tests between the COMMON (Neutral) and either High or Low speed connections.
Most systems will energize the low speed pump on startup and in heating situations. After energizing your hot tub, the pump should start on low speed. Your test to be sure the pump is getting voltage will be between the common and low speed connection on the pump. If the pump is to work properly, there should be 115 to 120 volts at this connection. If you have voltage here, but the pump is not coming on.. you have a pump problem. If there is no voltage here, the problem may be in the control system.
Testing a 240 volt 2 speed pump will also involve a test from the COMMON (LINE 2 in a 240 situation) to the Low speed connection on the pump. You should have 220 to 240 volts if the pump is to work properly. In a 240 volt pump, the common is always hot! Readings of 120 volts do not indicate that the pump is getting sufficient power. You are simply reading the voltage coming from line 2 that is always present. When the pump is energized for High speed, your 240 volts can be read between the common and high speed connections.
Always, disconnect power at the breaker before opening or removing any panels from any component. These tests are best performed immediately after energizing your system. High voltage can kill you! Plan your movesÂ and understand your multimeter! If you are uncomfortable with these tests hire someone qualified to do them for you but make sure they perform THESE tests.