This is generally not a SunPump issue, because it is a sensor that says it cannot detect adequate flow through the SunPump Heat Exchanger to satisfy compressor safety requirements. Nearly every time I hear of a P03 it is because of the installer or plumber having a pump issue, and SunPump get blamed for the lack of flow. The fixes for no flow have been:
- Attaching the wires to the pump
- Removing an air lock from a water pipe that was shaped like an upside down U - that trapped air at the top.
- Pointing the pump flow in the right direction
- Turning a Grundfos 3 speed pump to the middle speed setting.
- Pump cavitation from being installed in the incorrect location. (should be on cooler water supply pipe at the lower entry to SunPump, flowing into the SunPump HX).
The wires into the flow switch are sealed, the leads are in the Electrical Box and requires cutting a dozen zip ties to trace the wire location by tugging it gently. When you find the end wire leads, you can test for continuity. It should be Normally Open "NO" without pressure, and Closed when the paddle touches the contact with very little force. Do not replace the switch if it is NO and Closes without too much pressure. We do not recommend using a jumper wire to bypass the Flow Switch for a short test, but do so at your own risk, never for very long because it is important protection for the Compressor to not start before verified water flow. Bypassing the switch will void the warranty.
The Flow Switch unit is located inside the SunPump at the top pipe for hot water return. It is about 3/4" threaded like a garden hose with a swivel arrangement that allows the paddle to be put across the stream flow. It is critical to have the switch arrow in line with the water pipe, not backwards or significantly sideways to work - as shown below.
We have had one bad switch for Shore Energy in Nanaimo, it was intermittent for a month, and worked when the wire was pulled or bent indicating a bad wire connection. We swapped it for another and it was fine.( Update Dec 2016: the same install has had the replacement flow switch jumpered to test again).
- Do consider that removal will open the water line, so be prepared by shutting off isolation ball valves, and have a towel or bucket to catch the water. The only reason to remove it is to pop in a replacement, which is the way to go, if done quickly there should be minimal water escape.
- Do not try to open the flow switch, it is sealed waterproof and not serviceable.
- Because flow switch failures are rare, having a replacement is debatable, knowing how to jumper it and test is sufficient since there are just a few dozen SP2.2 models using this Harwil style Paddle Flow Switch.
SunPump models SP2.3 - SP3.1 made after 2015 that are 6 foot tall and have an integrated tank do not have a flow switch because there is no pump or water piping by design, the heat exchanger is internal and immersed in water rather than a flat plate HX.