Question about Pentair Minimax NT Heater
I have a NT Pool and Spa Heater that does not work. I have power and gas going to the heater and they work fine. I’m pretty sure the pressure switch works because anything over 10-12 PSI (on Pool Pump) and the pressure light lights and the display goes from off to three dashes. When I set either the pool or the spa temp the heater will start a cycle. First the thermostat light will come on and the blower at the same time. Then about 2 minutes later the heater light will come on and I can hear the gas ignite. Hot air in now coming from blower. Then after about 2 to 3 minutes the water tube coming out of the heater starts to shake and knock. The pressure switch light starts to blink ( and I see the pressure move below 10 PSI ) and the heater turns off and blower stays on for about three minutes more and then turns off, then they cycle starts over. I have a taken out the valve assembly and reseated it and after I did that it performed differently by getting too hot and the HI game on in the display. After it cooled down I tried it again and got the same cycle on, knock and shut down.
My first question what is the recommended PSI for normal operation? Second is there a way to test the valve assembly, I thought I saw something in here about putting it in hot water to see if it moves. If it not the valve assembly could it be the PSI or scaling on the heat exchanger. If it is scaling is there a way to clean it? Sorry for all the questions but would really like to get my heater going. Thank you in advance for any advice.
There are two valves inside the water manifold. The one you are talking about is the thermal govoner.This can be checked by putting it into boiling water and it will control how hot the water stays inside the heat exchanger. It is the piece that looks like the thermostat in a car and works the same way.
The other part is a by-pass assembly this mixes the hot and some cold water comming from the heater. One, to keep the water comming from the heater from being to hot and scalding. Two, it keeps the flow threw the heater from moving to fast to heat correctly. Their are two things to check on this. If the flow control disc is not moving free you will need to sand the shaft on this so it moves smoothly. The other is the spring that controls this and you just need to be sure that it is not broken,
Also you need to check if you have an external by-pass. This will be a valve bridging the inlet and outlet pipes going to the heater. If you have this on your system the valve needs to be shut down 80-90%. It will help to control the flow if your pump is moving too much water for the heater to control on it's own. You just need to adjust this pretty close as the one in the heater will fine tune the water flow. Let me know how you do and good luck.
Posted on Feb 03, 2010
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Posted on Jan 02, 2017
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