BP501 controller - heater dry error

[Thomee]

I just replaced the heating element on my spa. When I turn it on now, I get an error message "The heater may be dry".

The control unit is a Balboa BP501. The heater unit is a Balboa 15" M7 5.5kW. The spa was not heating. I determined that the old heater element had failed (it measured as no connection). After replacing the heating element (just the heating element, not the whole tube), I now consistently get the heater dry error message. I did not drain the hot tub before replacing the heating element - I just closed the slide valves on either side. They leaked some, but not terribly. This hot tub has a separate circulation pump from any of the main seat jets.

The new heating element measures about 10.5 ohms.

When I first turn on the breaker, the spa goes to the pump priming screen. The first time after replacing the heater, I got some bubbles through when turning on the circulation pump. The circulation pump turns on and has good flow. I loosened one of the temperature sensors on the top of the tube, and water comes out, so the heater tube is definitely full. The filters are clean, the water level is good, the gate valves are open, and I have good flow coming from the heating inlets.

After leaving the priming screen, the spa goes to the main screen. After a few seconds, it reads the water temperature correctly (about 55F). After a few more seconds, the screen indicates the heat is turning on. When it does, I can hear the relay click, and I measure 240VAC at the heating element. Just a few seconds later, the relay clicks back off, and I get the error message.

If I clear the message and wait a little while, it will try again, with the same results.

Powering off the breaker for a few minutes before trying again had the same result again.

I turned the breaker off, and disconnected each of the temperature sensors from the control board. Each one measures about 55k ohms, which seems to be about right for the temperature. After reconnecting the sensors and powering back on, I still have the same problem.

Any suggestions?

Thanks!
 

[CanadianSpaTech]

When you installed the element did you look down the tube and make sure the element was centered in the tube and in line with the sensors and not touching the tube side wall?

Disconnect the element from the circuit board and lift the copper tabs up so they don't touch anything and go through the start up again and see if you still get the error. Wait until the heat indicator led is solid and not flickering then test the copper tabs for 240v.

Remove the filters until issue is fixed. Take them out of the equation

[Thomee]

Well, this is embarrassing. When initially researching this problem, I found several threads which discussed filters and insufficient flow. I felt the flow at the heating inlets, and decided it felt fine, so I left the filters alone. After seeing your comment, I went ahead and pulled the filters before proceeding, just to make it clear that wasn't the problem. Sure enough, that resolved it, and everything seems to be working fine now.

Thanks for not trusting me that the flow was "good", and pushing me to remove the filters.

To any future people like me finding this thread: no matter how confident you are that the filters aren't the problem, go ahead and pull them - it only takes a minute, and if they really aren't the problem, it was a trivial amount of effort to prove it. Doing so initially would have saved me hours of troubleshooting, needless research, and stress.

[CanadianSpaTech]

On 12/23/2023 at 3:23 AM, Thomee said:

Doing so initially would have saved me hours of troubleshooting, needless research, and stress.

You are not the first. 60% + of the calls I get for flow related errors are dirty filter related. Could be independently wealthy if I didn't tell people over the phone and went and charged a service call to remove the filters. I ask when was the last time you cleaned the filters and then there is usually a long pause as they think back weeks/months. I usually stop them before they answer.