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Pentair Heater shuts off prematurely when warming spa

I have the spa set to 100 degrees. Prior to turning on the spa heater the water temperature is about 60 degrees. The heater warms the spa fine until the water temperature reaches about 94 degrees. At this point the heater flame shuts off for a couple minutes. The blower keeps running. The Service Heater lignt comes on. The heater flame comes back on for about 20-30 seconds. During this time the Service Heater light goes off. The flame then shuts off and the heater fan keeps blowing. The Service Heater light comes on. This keeps repeating itself for a dozen or so times until the spa reaches 100 degrees.

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rcampsr
  • 90 Answers

SOURCE: Heater cycles on and of, pool/spa does not reach desired temp

hello, It sounds like you may not be getting circulation thru the heater. Make sure the valves are open to allow water to pass thru the heating system. Some systems use a bypass on the heater so there is not a lot of wear on the coil system in the heater. If it is not circulating it will get too hot and the safety shut down will occure. If you are getting water circulating thru the heater, then the thermocouple or auto start igniter system is not working correctly. It is trying to start and can't then recycles. If the burners are igniting on the startup and then shutting back down you may have a bad control unit or thermal sensor unit. Since the unit is gas have a professional service it for you. Good Luck, RAC

Posted on Apr 20, 2009

  • 990 Answers

SOURCE: Pool Heater Mis-reading Temp.

Your temp sensors are on the heater, a small tube that slides into the water manifold, usually on the left side. On the remote it will be in one of the pipes coming from the pump or the filter. If it is after the heater you should move it to between the filter and heater. It will be a tube that is in the pipe with a stanless steel clamp holding it in place.
To find out wich one it is you will need to remove the remote from the system by takeing the wires that go to it from the wireing inside the heater and wire nuting the wires in the heater together. If the heater runs normal then it is the sensor for the remote if not it is the sensor for the heater. Let me know how you do and if need be we can get a little more specfic for your system. good luck.

Posted on Mar 29, 2010

  • 1 Answer

SOURCE: Pentair matertemp 400,000 BTU heater cycles on & off

My pentair matertemp 400,000 BTU natural gas heater cycles on and off before reaching desired temperature. I completely cleaned the DE filter and flow should not be an issue. When running the spa the pressure is 25. When running the cleaning system (polaris pop ups) the pressure is 30. Burner fires for 80 seconds then shuts off, reignites after 53 ceconds.Any tips on what might be the issue with the heater

Posted on Jul 23, 2011

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1 Answer

My Pentair Mastertemp 400 temperature is reading 20 degrees too low. I've replaced the thermistor already. Any ideas?


bummer hi limit wont do that but tep sensor will or control board also make sure water is flowing freely,
you will want to check the manifold bypass and thermal regulator

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Have a brand new Master Temp 400K Propane with an Intellitouch and the heater shuts off at 84 degrees. Do I need to set a max temperature from the heater control panel?


If this heater has pool mode and spa mode as an option, and you need the water higher than 84 degrees, you must set it to spa mode even if it is a pool. As a regulation, these heaters come pre-set to max out at 84 degrees as a safety feature. However, in spa mode it can reach 104degrees.

Jan 11, 2011 | Pentair Mastertemp Heater

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Have pentair easy touch controls just installed new water temp sensor. spa is 88 degrees but master temp heater shuts off because it reads 104. what should i check? the thermistor/


If the Easy Touch is reading the correct temperature, but the heater is not - you need to double check the temperature of the pool water with a standard pool thermometer.
Other things to consider:
1) The water is traveling too slowly through the heater. If the water is heating too quickly, then it will shut it off. If it takes a while for this to occur, then this would not be the issue.
2) Thermostat/thermistor is incorrectly reading the temperature of the water prematurely shutting the system down.
Make sure you really are checking the temperature of the water and matching this temperature up with one of the two readings that you are getting. Don't just take the word of the displays on either unit.

Dec 10, 2010 | Pentair Mastertemp Heater

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My pool heater keeps showing e-05 and the heater will shut off in about 2 minutes. How can I resolve this problem myself?


The E-05 code sets when the exhaust gas temperature goes too high. This is often caused by a insufficient water flow. Ensure that you have good water flow before turning the heater on. Ensure that all valves are set to allow that to happen.

Dec 04, 2010 | Pentair Minimax NT Heater

1 Answer

My heater ignites and blows really hot exhaust


The water is mixed on the back side of the heater and will exit the heater at 7-11 degres hotter than it came in. This will keep people from being scalded at pool side. So what you have sounds normal.

Apr 05, 2010 | Hayward H Series Pool & Spa Heater 400k...

2 Answers

Pool Heater Mis-reading Temp.


Your temp sensors are on the heater, a small tube that slides into the water manifold, usually on the left side. On the remote it will be in one of the pipes coming from the pump or the filter. If it is after the heater you should move it to between the filter and heater. It will be a tube that is in the pipe with a stanless steel clamp holding it in place.
To find out wich one it is you will need to remove the remote from the system by takeing the wires that go to it from the wireing inside the heater and wire nuting the wires in the heater together. If the heater runs normal then it is the sensor for the remote if not it is the sensor for the heater. Let me know how you do and if need be we can get a little more specfic for your system. good luck.

Mar 29, 2010 | Pentair Minimax NT Heater

2 Answers

Digital display shows LO what should i do


LO is a limit string open. This is what I refer to as a saftey circut. It will peobally be a dirty filter or a plugged up basket. The heater need enough water flow to run or it will overheat and cause damage to the heater. Without enough flow the saftey circut shuts the heater down before this can occur. If it is more than this it is probally time to get a repairman involved. Good luck and remember this is a box full of fire that runs on high voltage.

Mar 05, 2010 | Pentair Minimax NT Heater

2 Answers

Minimax pool heater cuts out at 91 degrees when remotely set for


Turn the temp set knobs on the front of the heater all the way up do both pool & spa temp.
If that doesn't help flip the selector switch on the front of the heater the pool temp. This switch doesn't control what heats up Pool or spa it just selects the heater on and which thermistat to use

May 23, 2009 | Pentair Minimax Ch 400,000 Btu Propane...

1 Answer

Pentair Mini-Max NT Pool Heater does not get very hot


The thermistor is a common failure on this heater. With a setting of 104 and the heater shutting off early, the sensor is bad. If you have a digital display, check the water temp with a thermometer and compare that ot the display. Odds are that they are different. The thermistor plugs into the back of the thermostat board and is a thin whire wire set or thibker yellow wire. The white wire sensors are old and most have fialed by now.

Dec 15, 2008 | Pentair MINIMAX NT TSI IGNITER

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