Sta-Rite Max-E-Therm 400 cycling on and off, no error code

Jump to latest Follow Reply
M

masbem95

Member
May 15, 2014
5
Palo Alto, CA
We havd a 8-year-old 20,000 gallon salt water pool with an attached spa. We heat the pool w solar and although we could use our heater (Sta-Rite Max-E-Therm 400) for the pool as well, we only use it for our spa. Late last year something happened that caused the heater to cycle on and off.
I have the spa temp at 104F, starting at 72F it will heat for about 16-17 minutes until it reaches approx. 85F and then it will shut off, after about a minute it will ignite again. In the beginning it will typically heat for 75-80 seconds and then shut off for about 60 seconds. It takes me 30 minutes to get to 90F (before this problem I would have reached my set temp of 104F by then). I am able to reach 100F after 50 min but by then it is heating for 40 seconds and then shuts off for 80 seconds. After 1h I reach 102F.
I never see an error code.
The highest exhaust temperature I have is around 350F.
There is no rattling sound when I start it up, it sounds just like before.
I opened the casing and there is no debris, no rats nest and cables all look fine etc.

Any idea what I should look at next? I have read about the thermostat thing being corroded, but I am not sure how that would drive this behavior and not trigger an error? I am a newbie when it comes to trouble shooting heaters, so TIA for any help!
 
masbem95 said:
We havd a 8-year-old 20,000 gallon salt water pool with an attached spa. We heat the pool w solar and although we could use our heater (Sta-Rite Max-E-Therm 400) for the pool as well, we only use it for our spa. Late last year something happened that caused the heater to cycle on and off.
I have the spa temp at 104F, starting at 72F it will heat for about 16-17 minutes until it reaches approx. 85F and then it will shut off, after about a minute it will ignite again. In the beginning it will typically heat for 75-80 seconds and then shut off for about 60 seconds. It takes me 30 minutes to get to 90F (before this problem I would have reached my set temp of 104F by then). I am able to reach 100F after 50 min but by then it is heating for 40 seconds and then shuts off for 80 seconds. After 1h I reach 102F.
I never see an error code.
The highest exhaust temperature I have is around 350F.
There is no rattling sound when I start it up, it sounds just like before.
I opened the casing and there is no debris, no rats nest and cables all look fine etc.

Any idea what I should look at next? I have read about the thermostat thing being corroded, but I am not sure how that would drive this behavior and not trigger an error? I am a newbie when it comes to trouble shooting heaters, so TIA for any help!
Click to expand...
Sounds like a bad thermistor.
 
Remove the thermal regulator as a test and see if the heater runs normally.

Problem is likely a bad thermal regulator or bypass valve.

Water is overheating internally in the heater and tripping one of the safety. As soon as the heater shuts off it cools and reignites. It is an internal water flow problem in the heater.

I am assuming you have a clean filter and adequate pump water flow.

Do you have a VS pump?

What model filter do you have? What is your filter PSI?
 
ajw22 said:
Remove the thermal regulator as a test and see if the heater runs normally.

Problem is likely a bad thermal regulator or bypass valve.

Water is overheating internally in the heater and tripping one of the safety. As soon as the heater shuts off it cools and reignites. It is an internal water flow problem in the heater.

I am assuming you have a clean filter and adequate pump water flow.

Do you have a VS pump?

What model filter do you have? What is your filter PSI?
Click to expand...
We have a sta-rite system 3 filter. I clean it every 6 months, last time was about a month ago and it was a bit dirtier than usual.
PSI is 15 when I just run the pool filter plus solar heat (it is typically 11 when solar heat is not active), it goes up to 19 when I turn on the spa.
There is VS pump, it is currently set at 2750rpm for the spa.

Do those numbers seem ok enough for me to remove the thermal regulator and test it?
 
Which is easier? Cleaning the filter or removing the thermal regulator?

Do whichever is easier first.

A filter can clog with algae in a month.
 
Glad we were able to help solve your problem.

TFP is a registered 501(c)3 non-profit that is kept online by user donations. Please consider donating at Support TFP!.
 
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