Pentair Mastertemp 400 SFS Error - Heater Won't Fire Up

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Machiavelli1512

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Nov 3, 2022
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Hi All,

I have a 9 month old Mastertemp 400 Pool and SPA heater that will not fire up. My chlorine pool is also 9 months old, it was all new equipment. Some facts:

Observations
1. When turning the heater on the panel flashes "ERR SFS" (I get the same error if trying to heat the pool or spa).
2. The heater does not fire up at all, the vent does not blow any air
3. Water quality has been great and maintained weekly.
4. 2 days prior to this issue, the heater may have turned on by istelf overnight, i shut it off. I have experienced this error ever since.
5. The heater control panel is not responsive to any button pushes when the heater is powered on or off. I'm not sure if this is due to me using controls via automation and app. The Heater powers on/off via both the app and pentair main control panel.
6. There has been no change to the gas line leading to the heater, other gas appliances work fine branching off the same main feed
7. I see no leaks or corrosion on any equipment, all equipment is in a shed and protected from the elements

What I have tried so far
1. I've checked the Thermal Regulator, it was seated correctly and functions
2. I noticed the GPM flow on the pump was 38 GPM, below the minimum 40. I increased it to 50 and there was no change.
3. Ive tried to hold down buttons on the heater membrane panel to get the stack flow sensor temp (to see if it is giving an incorrect high reading even though the heater is not running) but the panel does not respond and just flashes the ERR SFS code.
4. I power cycled the heater by flipping the breaker on/off
5. Ive been on hold with pentair multiple times for over an hour, requested call backs. But am yet to get a response.

Any guidance would be greatly appreciated.

Cheers
 
Machiavelli1512 said:
Hi All,

I have a 9 month old Mastertemp 400 Pool and SPA heater that will not fire up. My chlorine pool is also 9 months old, it was all new equipment. Some facts:

Observations
1. When turning the heater on the panel flashes "ERR SFS" (I get the same error if trying to heat the pool or spa).
2. The heater does not fire up at all, the vent does not blow any air
3. Water quality has been great and maintained weekly.
4. 2 days prior to this issue, the heater may have turned on by istelf overnight, i shut it off. I have experienced this error ever since.
5. The heater control panel is not responsive to any button pushes when the heater is powered on or off. I'm not sure if this is due to me using controls via automation and app. The Heater powers on/off via both the app and pentair main control panel.
6. There has been no change to the gas line leading to the heater, other gas appliances work fine branching off the same main feed
7. I see no leaks or corrosion on any equipment, all equipment is in a shed and protected from the elements

What I have tried so far
1. I've checked the Thermal Regulator, it was seated correctly and functions
2. I noticed the GPM flow on the pump was 38 GPM, below the minimum 40. I increased it to 50 and there was no change.
3. Ive tried to hold down buttons on the heater membrane panel to get the stack flow sensor temp (to see if it is giving an incorrect high reading even though the heater is not running) but the panel does not respond and just flashes the ERR SFS code.
4. I power cycled the heater by flipping the breaker on/off
5. Ive been on hold with pentair multiple times for over an hour, requested call backs. But am yet to get a response.

Any guidance would be greatly appreciated.

Cheers
Click to expand...
Your stack flue sensor has gone bad. Replaced one yesterday on a heater that was only 12 months old. Same symptoms. You can find them online for about $15.00 (aftermarket, try Optimum Pool Technologies of Amazon, especially if you have Prime for free shipping). That's what I have been using. Heater fired right up. OEM is over $100.00 (suggested retail is about twice that).
Easy to do, just takes opening the cabinet, 5/16" nut driver or flat-blade screwdriver, and a 1/2" wrench for the sensor, its on the side of the flue. Doesn't matter which wire is plugged in to which.
 
1poolman1 said:
Your stack flue sensor has gone bad. Replaced one yesterday on a heater that was only 12 months old. Same symptoms. You can find them online for about $15.00 (aftermarket, try Optimum Pool Technologies of Amazon, especially if you have Prime for free shipping). That's what I have been using. Heater fired right up. OEM is over $100.00 (suggested retail is about twice that).
Easy to do, just takes opening the cabinet, 5/16" nut driver or flat-blade screwdriver, and a 1/2" wrench for the sensor, its on the side of the flue. Doesn't matter which wire is plugged in to which.
Click to expand...
Ty for the quick reply, part ordered! Will report back.
 
1poolman1 said:
Your stack flue sensor has gone bad. Replaced one yesterday on a heater that was only 12 months old. Same symptoms. You can find them online for about $15.00 (aftermarket, try Optimum Pool Technologies of Amazon, especially if you have Prime for free shipping). That's what I have been using. Heater fired right up. OEM is over $100.00 (suggested retail is about twice that).
Easy to do, just takes opening the cabinet, 5/16" nut driver or flat-blade screwdriver, and a 1/2" wrench for the sensor, its on the side of the flue. Doesn't matter which wire is plugged in to which.
Click to expand...
Fired right up with the new sensor! Owe you a frosty one 1poolman1!
 
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Machiavelli1512 said:
Fired right up with the new sensor! Owe you a frosty one 1poolman1!
Click to expand...
So why did you go this route vs having pentair fix under warranty? I am in the same boat, pool was installed in May and I am getting the SFS error. Heater will kick on and then go off.
 
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Jejunum said:
Warranty through my pb through another company. So yes?
Click to expand...
Yep exactly...I called my PB who is running it through pentair. Not sure how long that will take but might as well use the warranty vs going amazon route right now. Sounds like Pentair had a bad batch of sensors.
 
4x4tx said:
Sounds like Pentair had a bad batch of sensors.
Click to expand...
Thousands.

We replace piles of them under warranty. Happened during COVID disruption. Pentair is through the bad inventory but there are still heaters at supply houses and in PB storage lots with bad SFSs.

Visually, bad sensors have a plain rubberized coating on the wire. Replacement OEM have a braided sheath.

The cheap ones on Amazon may work but their longevity is a gamble. Buying a cheap couple to have on hand is a great way to keep your heater running while you wait for warranty. The install is dead simple.
 
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bradgray said:
Thousands.

We replace piles of them under warranty. Happened during COVID disruption. Pentair is through the bad inventory but there are still heaters at supply houses and in PB storage lots with bad SFSs.

Visually, bad sensors have a plain rubberized coating on the wire. Replacement OEM have a braided sheath.

The cheap ones on Amazon may work but their longevity is a gamble. Buying a cheap couple to have on hand is a great way to keep your heater running while you wait for warranty. The install is dead simple.
Click to expand...
Good post. I want pentair to fix it but may order one off amazon to have on hand.
 
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