Pentair MasterTemp 400 Ignition Issue

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H

hangingout

Member
Mar 8, 2024
6
San Diego, CA
I am not a pool guy, but have a lot of knoledge of home heating systems. I have a Pentair MasterTemp 400 heater that sometimes fails to start up properly.
The process is you can hear it start up, the blower motor turns on, the gas valve clicks open, the heater lights (you can feel hot air out of the flue pipe), but then shuts down in about 5 seconds.
It does exact cycle 2 more times and then shuts down with the service heater light on, and no error number on the screen.
If I power off the heater and power it back on, it typically will start and stay on.

In a home HVAC system this is almost always a dirty flame sensor that needs to be cleaned. As I have googled around, I don't seem to be able to find if this heater has a flame sensor or where it would be.
Any help would be greatly apprecaited.
Thanks in advance.
Bob
 
Check the Fenwal LED blinking pattern.

Fenwal LED Light.

The LED will flash on for 1/4 second, then off for 1/4 second during a fault condition.

The pause between fault codes is 3 seconds.

The LED light on the Fenwal box can indicate the following problems:

Steady on - Internal Control Failure.

One flash - Air Flow fault.

Two flashes indicates flame no call for heat, then the Fenwal is detecting a flame current when it shouldn't be.

Three flashes indicates no flame current being sensed and ignition locked out.
 
hangingout said:
I am not a pool guy, but have a lot of knoledge of home heating systems. I have a Pentair MasterTemp 400 heater that sometimes fails to start up properly.
The process is you can hear it start up, the blower motor turns on, the gas valve clicks open, the heater lights (you can feel hot air out of the flue pipe), but then shuts down in about 5 seconds.
It does exact cycle 2 more times and then shuts down with the service heater light on, and no error number on the screen.
If I power off the heater and power it back on, it typically will start and stay on.

In a home HVAC system this is almost always a dirty flame sensor that needs to be cleaned. As I have googled around, I don't seem to be able to find if this heater has a flame sensor or where it would be.
Any help would be greatly apprecaited.
Thanks in advance.
Bob
Click to expand...
Get a piece of green wire and use it as shown in the instructions attached. Pentair made the kit to help solve this issue if it is a flame-sense issue, which it sounds like.
 

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thanks for your help. I hooked up the wire between the heat manifold and into the control box. Hopefully that does it. It is an intermittent problem, so i wont know if it is fixed for a while. I will give a final update in a couple weeks unless it fails earlier.
THANKS FOR EVERYONES HELP!!
 
The heater appears to be working fine, all set points, etc are working correctly when the heater is running and the temperature displayed in the phone based app or on the remote panel in the house always seems to be correct. However the RED LED read out on the panel sometimes will be correct and other times it is stuck at 32 degrees. I have even seen it rapidly count down from 75 to 32 degrees. I changed the Thermistor (Pentair 42001-0053S Electrical Systems Thermistor) but that didn't seem to repair the RED LED read out on the panel.
Is there a different temp sensor i should be looking for?
 

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The MasterTemp only has one thermistor to display the water temperature.

How did you determine the thermistor was bad and needed replacement?

Did you replace it with a genuine Pentair part? We see many third party parts that do not work well.

Does your heater have a genuine Pentair PCB?

That display is not an original Pentair part.

Put a 10K resistor connected to the temperature sensor wires. If the heater reads 76F then the sensor is bad.

If you don't get a good temperature then the wires or PCB are bad.

10k-resistor-test-rig1-jpg.481393

pentair-mastertemp-with-10k-resistor-test-jpg.481394

pentair-mastertemp-with-10k-resistor-temp-jpg.481395
 
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ajw22 said:
The MasterTemp only has one thermistor to display the water temperature.

How did you determine the thermistor was bad and needed replacement?

Did you replace it with a genuine Pentair part? We see many third party parts that do not work well.

Does your heater have a genuine Pentair PCB?

That display is not an original Pentair part.

Put a 10K resistor connected to the temperature sensor wires. If the heater reads 76F then the sensor is bad.

If you don't get a good temperature then the wires or PCB are bad.

10k-resistor-test-rig1-jpg.481393

pentair-mastertemp-with-10k-resistor-test-jpg.481394

pentair-mastertemp-with-10k-resistor-temp-jpg.481395
Click to expand...
I believe
ajw22 said:
The MasterTemp only has one thermistor to display the water temperature.

How did you determine the thermistor was bad and needed replacement?

Did you replace it with a genuine Pentair part? We see many third party parts that do not work well.

Does your heater have a genuine Pentair PCB?

That display is not an original Pentair part.

Put a 10K resistor connected to the temperature sensor wires. If the heater reads 76F then the sensor is bad.

If you don't get a good temperature then the wires or PCB are bad.

10k-resistor-test-rig1-jpg.481393

pentair-mastertemp-with-10k-resistor-test-jpg.481394

pentair-mastertemp-with-10k-resistor-temp-jpg.481395
Click to expand...
I beleive that is the original key pad, but i only inherited the system from the old owner. I did not test the old temp sensor, but figured at $25, and buying from the Pentair Store on amazon, it would be authentic and it was easier just to replace it. I will try the 10K resistor across the leads, thanks for that tip. But then I have to think it is the control board, because the keypad at the house and the android app are both displaying the proper temp. So how could I be showing 2 different temps if there is only 1 sensor, unless the board is bad.
THANKS AGAIN
 
The keypad in the house and the app gets its temperature from a different water temperature sensor in your pipe, usually after the filter.

The Pentair Store on Amazon is not run by Pentair and does not always sell genuine Pentair parts.
 
@hangingout having a combustion chamber infiltrated by water will also produce the behavior you're describing, including failing to provide an error state.

Remove the bottom right bolt on your manifold. If water exits, or your bolt is wet, you have another task ahead of you.
 
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