Pentair Mastertemp 300

[sad_story]

First season maintaining my pool myself. Main issue: will not ignite/fire.

Running a Pentair Mastertemp 300.

Opened the pool and started up the heater.
The blower went on but never fired. And a very funky smell from the exhaust! Equal to the funky smell from the entire insides once the cover was removed

No error codes just the red service light.

Opened up the unit and found a massive mouse nest on the heater and baby mice inside the heater box.

Cleaned everything up and same result. tried to check the wires is all looked good.

Now... I may or may not have dropped the top cover at one point. And since then the display (temp display) started working intermittently then not a all. All the indicator STILL work, but the LCD display is not longer working but the unit still starts up and still tries to fire.

Original pool Installer put a small wire screen in venturi and the plastic is clean and white so pretty sure nothing got into the blower. (shame he didn't do the same for the vents on the entire heater!)

questions

1) regarding the membrane/lcd display. Do i need to replace just the membrane, or does the the entire controller board? (no mouse destruction evidence on either.

2) what is the yellow button the controller board

3) notice rust and a water leak on the 3rd from the top and maybe 4th from the top bolt on the left side of the manifold, just about the level of the by the sensor

4) given the smell when the blower is going does that mean I am going to have to open and check the combustion chamber - and is that hard? And if so when reassembling, to I need to

 

[ajw22]

Welcome to TFP.

Rodents can wreck a heater and make it uneconomical to repair. Rodents can chew on wires and their urine can cause corrosion on boards and ground issues.

Lots of helpful information at Pentair MasterTemp Heaters - Further Reading

1) regarding the membrane/lcd display. Do i need to replace just the membrane, or does the the entire controller board? (no mouse destruction evidence on either.

The membrane keypad just has a cutout for the LCD screen. The LCD screen is on the main PCB.

Replacing the LCD screen will require replacing the PCB and keypad.

2) what is the yellow button the controller board

The yellow button is used to set the maximum temperature setpoint.

3) notice rust and a water leak on the 3rd from the top and maybe 4th from the top bolt on the left side of the manifold, just about the level of the by the sensor

That is not a good sign and could indicate a leaking heat exchanger.

There are YouTube videos showing how to disassemble the heater.

4) given the smell when the blower is going does that mean I am going to have to open and check the combustion chamber - and is that hard? And if so when reassembling, to I need to

I suspect that the baby mice did get into the sealed boiler pot and you are going to need to disassemble the can and see what is going on.

Also look and see if the rodents ripped the insulation and used it for their nest. If the insulation is damaged then the heater will overheat and self destruct when you run it.

Let us know what you find as you dig into the heater.

 

[sad_story]

So, I am about embark onto this heater disassembly project, any pointers welcome!

Before I go, a few things,
1) new pcb
2) new thermal regulator

NEW INFO: I did notice that when I turn off the heater bypass (i.e. run water to the heater, my pressure jumps from about 14 to 18psi. Does that all lineup to the same conclusion? DO I proceed with the take apart?

 

[sad_story]

So I finally had the time to open up the heater …

This is water the inside looks like…

I ran the water nothing seems to drip inside …. The only water is still on the outside /manifold.

One thing I did notice though was that the water pressure goes from 14psi to 18psi when I turn off bypass and run through the heater…

Any observations or suggestion can be gleaned from this?

 

[sad_story]

I did order a new manifold kit (full kit with the 77707-0015)

 

[ajw22]

One thing I did notice though was that the water pressure goes from 14psi to 18psi when I turn off bypass and run through the heater…

That is normal. PSI goes up when heater is in the water loop due to the added restriction.

 

[sad_story]

The red mastic around the manifold. What is that? What to do I need to buy (additionally to the manifiold kit) to replace manifold? Is that a special sealant?

Any advice on the manifold replacement?

https://www.troublefreepool.com/attachments/8434cf21-764c-48a5-929c-4bf65b646180-jpeg.416378/

 

[ajw22]

The red mastic is not normal and someone added it. The O ring around the manifold should seal it.

 

[1poolman1]

The lid to the combustion chamber is sealed with red hi-temp silicone sealant. They come from the factory using it.

 

[ajw22]

The lid to the combustion chamber is sealed with red hi-temp silicone sealant. They come from the factory using it.

Must be something new. My MasterTemps never had it but then mine is a few years old.

 

[1poolman1]

Must be something new. My MasterTemps never had it but then mine is a few years old.

They do a very clean installation at the factory, but take a few apart and its always there. If it wasn't combustion gasses would escape into the heater cabinet as the combustion chamber is under positive pressure from the blower.

 

[ajw22]

They do a very clean installation at the factory, but take a few apart and its always there. If it wasn't combustion gasses would escape into the heater cabinet as the combustion chamber is under positive pressure from the blower.

I realize now where I was confused.

I thought we were looking at the header bolts not at the seal of the combustion chamber.

Got it now.

 

[Poolbreh]

Yea loctite red sealant or something similar the top of the chamber used to have it as well.

 

[sad_story]

Ok… so sadly, after putting in the new manifold, leaking stopped.

But… I’m still not up and running.

Heater still fires up 2 or three times .. keeps cutting off, then “service heater” light pops on… no error codes on the screen, and I don’t see any lights on the the bottom of the board.



To recap
1)New circuit board
2)new manifold & sensors

Any help or suggestions welcome

 

[ajw22]

Rodents can trash a heater.

You need to figure out which one of the safety's is shutting down the heater. It takes a lot observation and poking around in it.

 

[Poolbreh]

Any lights on the fenwal? Can you post a video of the heater firing?

 

[sad_story]

You need to figure out which one of the safety's is shutting down the heater. It takes a lot observation and poking around in it.

Can you help (specify) about the poking around? I've exhausted what I know and read so far.

Any lights on the fenwal? Can you post a video of the heater firing?

I'll try to get a video posted, but in short is it fires up normally, then stops after about 20 seconds. It then continues this 3 times then stops trying to fire up and the red "Service Heater" light goes on on the main display. There are no lights on the underside of the PCB lighting up.

(PCB is new)

Other than spending the 1K and getting a new heating core, any suggestions? any tests? All the sensors on the manifold are new (came with the new manifold kit). For example is there a test that can be done with a voltage/ohm meter on the sensors to see which is being triggered (e.g. pressure switch).

Thank you

 

[Poolbreh]

It sounds like a flame rectification issue. I would look at hsi. This is also assuming thermal regulator is new and functioning.
@JoyfulNoise with @JamesW help wrote a good post on testing the flame sense on mastertemps.

MasterTemp 400 Failure To Ignite Issue - SOLVED

I wanted to document this on the forum threads since this issue got diagnosed and solved via PM. First, let me give total credit to our esteemed forum expert @JamesW for helping me to diagnose, test and fix this heater issue. James' help saved me from calling in a "pool service" guy and...

www.troublefreepool.com

 

[Poolbreh]

And in this case seemed to be flame rectification but it happened a few minutes after ignition. Cannot confirm but it flew under the radar. Mastertemp 400 cycling No codes or service light

 

[ajw22]

Read Heater Flame Sensing - Further Reading