Heater cycles, will not bring spa up to proper temp

[dthdth_2000]

Hello-

I have a Purex Triton Minimax 350 NG heater. It has recently began to shut itself off before bringing the spa up to the proper temp. Regardless of control box temp setting the water in the spa tops out about 95 degrees. When the heater first fires up, all LEDs come on, the heater ignites and runs like a champ. It operates fine for awhile then shuts off. Once it shuts down only the LED for Power remains green. The service light has never come on. I have taken the top off and cleaned out the heat exchanger, taken the front of the unit off and cleaned it, and replaced the temperature sensor for the control panel - no luck. Any advice would be appreciated, thank you.

 

[ps0303]

Sounds like maybe one of the high limit sensors is bad. They are on the right side of the header. You need to remove the ride panel to get to them.You can try jumping one of them at a time and see which one it is.

 

[OldPoolMan]

Probably the high limit sensors are causing the cycling but they may be the symptom and not the problem. They are detecting over heated water which may be caused by low flow, a broker bypass valve, dirty filter, or plugged heat exchanger tubes.

 

[ps0303]

If you are going to provide a POSSIBLE cause to the issue, please tell the poster how to check each one of them. I told the OP how to check for the possible sensor. You left it open ended and now when the OP looks at your post and it will generate more question. Lets help the OP and give them the detail things to look for.

Yes it could be all of the above also. So, make sure your filter is clean, then if you want to check the flow control you would need to remove it from the heater. It is located on the right side of the heater. Check out this PDF as it will help you. https://www.parts4heating.com/v/vspfiles/images/pdfs/MiniMaxCH.pdf

What you want to look at is the spring and the element power. Parts4heating.com: Pentair 470178 Element Power To test the element power you can take a lighter and hold it under it and you should see the little pin on the other end move. If it doesn't move, replace the element. Other issues like the spring, if broken, will be obvious.

 

[dthdth_2000]

Thank you and I'll see what I can do with is.

 

[dthdth_2000]

Thanks again and here's an update....btw, filter is clean, flow is good.

Yep...the unit has two high-temp sensors, but only one of them was hooked up. I jumped it - no behavior change. Next, flow control valve/element power. Pulled it and no springs are broken, but the element had corrosion all over it and does not move. I scraped the corrosion off it and some chunks of it came off in my hand, so I'm assuming it's bad. It looked to be in poor shape. Also, I could not get the valve to move at all (not sure if that's how it's supposed to be or if I'm just not strong enough to move it). The gasket was about shot as well, so I bit the bullet and have a whole new assembly on order. I'll let you guys know what happens in a few days.

 

[dthdth_2000]

Update.....Well guys, this stinks. New valve assembly has been installed - no change whatsoever. Exact same behavior.......fires up, runs like a champ, then shuts off around 98-99. It eventually will start back up but won't get any hotter than that. High temp sensor is still jumped. I sat and looked at the unit, and notice that every few minutes, there is a "click" sound. Like the control box in the house is sending a signal to the unit to fire up, but it just doesn't. Considering these things are almost $2K new, I'm willing to hear any more ideas you may have. Thanks again....

 

[wjr75]

Make sure you have the temp setting at the heater set to the max it can go before using an external controller. I had this happen to me when I replaced my heater.

 

[dthdth_2000]

Thanks - yes, it's cranked all the way up.

 

[wjr75]

My controller has a thermistor on the outside of one of the pipes and I keep the spa set at 98deg. The heater readout actually shows over a hundred. I wonder if you are maxing out the heater. If you measure the water temp directly I wonder what it reads. I'm by no means a pool heater expert just what I have experienced over the years with frustrations with different heaters we had..

 

[ps0303]

There are two high limit sensors. Which one do you have jumped out?

 

[dthdth_2000]

Hi Paul – The lower sensor is jumped out, the other one is completely removed. The one I removed had a wire hooked to itself only, and that wire was broken, so I just pulled the sensor. Should I have both sensors installed? Thanks.

 

[ps0303]

So both of the high limit sensors on the header, where the pipes connect up, are jumped out?

 

[dthdth_2000]

One is jumped out, the other is removed.

 

[pool&spatech]

I will assume that you have a multi-meter, and that you completely understand all of it's test function's for electrical measurements (know how to use it) If you don't have a meter and/or don't know how to use one, then be honest with your yourself and accept you are in over your head, heater's are best left to qualified EXPERT repair techs, find your local pentair heater warranty rep, (call, or go online to pentair to find a rep in your area) and pay them to come out to your home, this is the best way to ensure you will have a skilled heater tech with pentair experience to efficiently, and accurately, solve your heater problem. stop throwing good money after bad when trying to solve this problem.

 

[ps0303]

I'm pretty sure this heater isn't under warranty any more and honestly, most techs will come out and condemn it as is on it's last leg. When you start looking at replacing the control boards and items like that it becomes throwing money at something that isn't worth it. Yes new units aren't cheap but when you add up all of the service calls you will be saving by installing something new. The fact that one of the sensors is totally missing tells me someone had an issue and just removed it which is not good. All of those sensors need to be in place to prevent any accidents from occurring.

 

[dthdth_2000]

I have a meter and know how to use it. Tested the thermistor and it's in range. You guys are right, time to waive the white flag and call in an expert or replace the unit - it is in poor shape. Thanks again for all the help and advice.