Hot tub will not reach set temperature

Jump to latest Follow Reply
C

cerios2015

Member
Aug 21, 2024
10
Texas
I have a Pentair Mastertemp 400 heater that I've set to a 104 degree set temperature but when I run the heater, it operates per normal; however, the Screenlogic app says the water only gets to 100 degrees and the water itself feels less than 100 degrees (as I continue to troubleshoot, I'll measure with a thermometer). I've read other threads that this is a possible control board issue and a replacement fixes the problem but are there any other troubleshooting steps that I should do to see if it fixes the problem before ordering another board and replacing it?

Thank you in advance.
 
Screenlogic? Is it on a controller, such as an intellitouch? If so, the controller overrides the heater settings. You want the heater set to max but actual temp control is done at the controller, which if set to 100 will heat to 100.
 
Update: I just came from testing the spa. A couple of more pieces of information for background. The other day I had to replace the stack flue sensor due to a rodent chewing the wires (I've since blocked every hole with 1/4" wire mesh and laid some mouse bait). I read that you may have to reset the control board by following the steps in the first picture; this was not an issue as I received the SF1 reading. I don't believe the stack flue sensor replacement has anything to do with the current issue but I include this just in case.

Secondly, I turned on the spa and heater. The Pentair Screenlogic app had the set temperature at 104 degrees but the temperature on the heater itself was at 99 degrees. I manually raised it to 104 degrees so that the app and the heater as well as the panel were all showing 104 degrees. I let the heater run for about 30 minutes and saw the temperature raise to 104 degrees (it even got to 106 degrees at one point) but the water never got hotter than 98 degrees using a manual thermometer. I watched the app and the panel and noticed the temperature reading would fluctuate every couple of minutes; it would be at 100 degrees then raise to 104 then to 106 then drop back down to 98 and then start all over again, all within a couple of minutes.

If there are any questions on this latest post please let me know. Otherwise, again thank you in advance.
 

Attachments

  • image6.jpeg
    image6.jpeg
    29.7 KB · Views: 4
cerios2015 said:
saw the temperature raise to 104 degrees (it even got to 106 degrees at one point)
Click to expand...
Where? At the heater or controller? They use different sensors in different locations.
It sounds like a flow restriction causing the heater to overheat internally, turn off via the heater control then turn back on once heater temp has dropped with sufficient water replacement. The tub would heat very gradually, perhaps not even keeping up with ambient loss.
So I'd check flow. Clean or bypass filter, check for debris in the pump, etc.
 
RDspaguy said:
Where? At the heater or controller? They use different sensors in different locations.
It sounds like a flow restriction causing the heater to overheat internally, turn off via the heater control then turn back on once heater temp has dropped with sufficient water replacement. The tub would heat very gradually, perhaps not even keeping up with ambient loss.
So I'd check flow. Clean or bypass filter, check for debris in the pump, etc.
Click to expand...
Thank you RDspaguy. Any recommended videos on how to do this?
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply