Question about Pentair 150k Minimax Ch Ng Mv Heater

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Burners won't ignite

Replaced pressure switch last season and it worked. This year, pilot stays lit but can't get the burners to ignite. I have had problems with the toggle switch but can usually get it to work. Thermocouple is really rusty. I bypassed the breaker and no change. This is an older heater. Not sure what to do next. Please advise.

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Posted on Jan 02, 2017

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SOURCE: Have a Triton Millivolt pool heater pilot is lit and nothing!!

Low out put voltage from the pilot generator and/or an open circuit in the control circuit...the most common is a bad pressure switch (dirty filters can hamper pressure switch operation).

Posted on Jun 28, 2009

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SOURCE: Mini max 150 has pilot lit but will not heat

If you read Ohms across the TH circuit with the thermostat(s) turned up and the switch in the on position with the pump running you should have about 1.0 Ohms. Anything higher than 2-3 Ohms and you have too high a resistance reading and will need to find the bad part/connenction. If you have about an Ohm and the burners are not lighting be sure you have enough voltage off the generator. With no call for heat it should read around 500mV. Once you turn everything on it should drop to about 300mV.

If all these reading are correct try striking the gas line near the valve. The solenoid may be sticking. If it frees up you may get more use from it. If not, the valve needs to be replaced.

Posted on Jul 28, 2009

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SOURCE: Pilot is lit, burners will not go on

clean t burners

Posted on Sep 18, 2009

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SOURCE: I have a Pentair 200M

Thank you for posting your question here on

First you will need to get a hold of a digital or analog multimeter and set it for the lowest range of Ohms you can. Your safety circuit is a string of several switches all strung together in a row with the gas valve at the end and the beginning of said string. Any one switch being open or a bad connection anywhere in the circuit and the heater will not fire.

You task is to remove one end of the circuit from the valves TH or TT post and put one end of you meter on that wire and the other end on the TH/PP terminal. It will likely read infinite resistance. Leave one meter lead where it is and remove the other. Follow the circuit from the connected lead up to the first switch. Check continuity from the lead left connected to both sides of the switch. If there is continuity to both sides the switch is fine. Keep moving from switch to switch until you find the bad switch or connection. There may be more than one. When the circuit is working properly and there is nothing within the heater to cause it to shut off you should have 5 ohms or less across the entire circuit. Once you get the reading to that level the heater will work as it should

If you are not familiar with the process I described you would be better served hiring a pool technician to perform this repair as you can cause significant damage to the heater if you do not repair it properly.

If this answer does not fix your problem, please comment with additional details prior to rating the answer. Positive feedback is appreciated once your problem is solved!


Posted on May 30, 2011

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SOURCE: I have a Pentair Mini Max 250 pool heater which I

Hi,you can try and troubleshoot the heater to find out what exactly is the problem...

Heater won't reach the desired temperature?

The thermostat may be set too low. If the heat loss is greater than the heater input - the heater may be too small, outside air temperature is too low, or your heater may have an inadequate gas supply. You may want to install a solar pool cover to slow heat loss from your pool. All pool heaters have high limit switches to prevent overheating. A faulty high limit switch could shut off the heater, or the problem could be that the heater is truly overheating, perhaps from improper exhaust out of the top of the heater.

The heater cycles on and off before it reaches the desired temperature?

Your heater may have inadequate water flow due to a dirty filter, closed valve, external bypass, reversed water connections, or pressure switch out of adjustment. It is also possible that your thermostat is out of calibration or needs to be replaced.

I hear "clicking" or "sparking," but my heater will not ignite.

Review to the pool heater owner's manual. If you do not find your answer, turn the heater off and contact a qualified service company. Make sure that the gas valves are all in the on position, and if LP (Propane) is being used, check the gauge on the tank.
The heater is leaking water.

The pool heater heat exchanger may be leaking because of chemical or sanitizer damage. The damage may be from winter freeze - usually leaking upon spring start-up, and usually on the return manifold, aka rear header. There could be a gasket leaking, or a loose connection to the pressure switch.
The heater appears to leak only when the burner is lit.....

This may be caused by condensation (occurring when heating very cold water); a missing or damaged internal bypass in the front header; or excessive water flow through the heater from an oversized pump. Check the heat exchanger for sooting, and make sure the internal bypass is working. Install an external pool heater bypass if necessary to reduce the water flow coming into the heater.
Heater top blackened and/or emitting dark exhaust?

Either low gas pressure and/or inadequate air supply and venting. Review the installation requirements in the pool heater Owner's Manual. Both conditions may need to be evaluated by a qualified service technician. This is called sooting and could lead to other problems or hazards.
The heater has damage due to excessive heat. Why?

One, or a combination of the following: low gas pressure, down-drafting, air supply, and venting. The pool heater may need a high wind stack, if installed near a vertical wall or windy area. Make sure that the heater is installed with proper clearances all around the outside. Pool Heaters can catch adjacent structures on fire, and pool heaters should not be located near windows, where carbon monoxide from the pool heater could be drawn into the house.

How much fuel does my heater use?

Propane heaters use one gallon of fuel per hour for each 91,000 BTU's of heater input. Example: A 250,000 BTU heater uses: 250,000/91,000 = 2.75 gallon per hour. Natural gas heaters use one therm (100,000) BTU per 100,000 BTU's heater size. Gas invoices are usually billed by therms.

Posted on Jun 16, 2011

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