Pentair Mastertemp 400 SFS error, need help

[ajw22]

The HLS is just an On/Off switch and not a thermistor.

Got it.

 

[Zizzam]

So today I tried using the heater in pool mode and it continuously runs without erroring out but the water entering the pool is barely warm, only slightly higher than the pool is which is 60 degrees. Back to spa mode, heater kicks on, everything seems fine but the same issue persists, water entering the spa is only barely luke warm and after 5 minutes or so the system errors HLS, shuts off then kicks on again after a minute or two. SFS temp runs up to right around 380 and stays there now which I guess is an improvement over running 480+ and shutting down with SFS error. It just really seems like the heat isnt going into the water but exiting the exhaust. I'll pull the salt cell out today and look at it, after that I'm at a loss. Thanks all for your feedback

 

[ajw22]

It just really seems like the heat isnt going into the water but exiting the exhaust.

Don't get distracted by lower water temperature. I explained in a post #18 why when you improve water flow exit temp will go down.

You somehow improved the water flow but you still have high exhaust temp at 380F when normal is around 300-325F. Your water flow through the heater is not as designed.

I have lost track of what parts you have replaced.

If you have not replaced the bypass valve and HLS sensor I would replace those.

 

[Zizzam]

First, I know I'm a newbie at all this and learning as I go so thanks for your patience. I am learning a lot about how my pool works

I believe I improved water flow from cleaning the pool filters, they were very dirty and that's been taken care of.

So far I've relaced the SFS and the thermal regulator. I did the thermal regulator despite it functioning as expected under hot water because it looked corroded and I figured it couldnt hurt to replace it. I tested the new one under running hot water and it also worked fine so both of those components have been replaced.

I have a HLS sensor in the mail that should be arriving today so I'll do that next.

The bypass valve I inspected when I opened the manifold and it was all in tact and the spring functioned. I can replace that too but will need to order the part.

I just ran it again and pulled some water from the drain plug after I got the HLS error and the water was 68 degrees, which is the temp of the spa. Is that normal? I expected it to be hot...

 

[Zizzam]

Wow wow wow wow WOW! Well, I believe I found the problem. The screen cap on the spa main drain came floating off earlier and looking inside I see the drain is completely clogged, I hopped in (cold!) and got down to the bottom and the drain is completely filled with epoxy. Apparently when the company came to open my pool we asked them to get the screen cover back on and instead of using screws they used epoxy, well it came off, floated to the bottom and is solidified in the drain. I smacked it with a screw driver a few times but its completely solid...

Just to confirm, the bottom hole shown in the pic here IS the primary drain back to the filter correct? In that case, no water returning from the spa to the pump/filter and that would explain my water flow issues. I dont even understand where the pump is drawing water back from in spa mode...

Hopefully I didnt create any new problems with part replacement or issues down the line with disassembling the manifold

 

[ajw22]

Glad you found it. You got an education in heater internals. Let us know how things run now.

Do you have any other drains in the bottom or sides of your spa? Many spas have two round drains that are T'd together to prevent entraption.

My spa has two sets of spa drains....

 

[JamesW]

The side hole is usually the suction and the bottom hole is usually not used or used for a hydrostat.

Is that the only suction?

If yes, you can't use the spa because it is way too dangerous to use with only one suction.

Also, do not use the spa with the grate missing as someone can get injured or killed.

 

[Zizzam]

Well, the pool company came out and proved that the suction from the drain and flow to the heater is correct. I replaced the HLS and still have the same issue so I'm at a loss now how to proceed. The only recommended part left to replace is the bypass value. It looked fine when I pulled it out but I guess it could be malfunctioning. I'll try that next

 

[ajw22]

Well, the pool company came out and proved that the suction from the drain and flow to the heater is correct.

How did they do that?

 

[Zizzam]

How did they do that?

Drained the spa into the pool, tested suction at the spa drain, refilled spa. I dont know enough to call BS, seemed accurate to me

 

[Zizzam]

So I got a technician out to my house who checked all the same things I did (thermal regulator, HLS, water flow etc.) and he believes I have a sooted exchanger. I've been searching but dont see any posts or videos that show how to clean soot? I've seen plenty of stuff showing disassembly of the pot and cleaning out scale but nothing on soot. If there's any existing references that people are aware of I'd appreciate it. Thanks all

 

[ajw22]

So I got a technician out to my house who checked all the same things I did (thermal regulator, HLS, water flow etc.) and he believes I have a sooted exchanger.

Did you ask the technican if he ever actually saw a MasterTemp heater with a sooted heat exchanger?

I've been searching but dont see any posts or videos that show how to clean soot? I've seen plenty of stuff showing disassembly of the pot and cleaning out scale but nothing on soot. If there's any existing references that people are aware of I'd appreciate it. Thanks all

Disassemble the burner can so you can look at the heat exchannger. Black soot is obvious on the outside of the coils.

Soot is caused by a too rich mixture. Too much gas and too little air. It is hard to get that in the way a MasterTemp heater works.

 

[Zizzam]

I did not ask that question... I will say as part of my troubleshooting I found the regulator for the propane line had gone bad and had to be replaced so a propane flow issue was likely occurring for some undetermined amount of time.

I did end up pulling the thermal regulator the heater runs fine without it, SF temp stays around 320 and the spa will heat normally.

 

[JamesW]

So I got a technician out to my house who checked all the same things I did (thermal regulator, HLS, water flow etc.) and he believes I have a sooted exchanger.

A sooted exchanger can cause high stack temperatures, but it will not cause a high limit issue.

Everything points to a water flow problem.

I did end up pulling the thermal regulator the heater runs fine without it, SF temp stays around 320 and the spa will heat normally.

Try a different new thermal regulator.

 

[JamesW]

Here is what the normal exhaust temperature should be:

• Below 250 degrees...very low
• 250 to 290 ..................low
• 290 to 350.................acceptable
• 350 to 480 ..................high
• Above 480...................error/shutdown.

Note: HD models can be up to 75 degrees higher. HD models use a cupro nickel exchanger and the efficiency is slightly lower resulting in less heat transfer and more waste heat.

If you had a sooted exchanger, the stack temperature would be too high.

Since your stack temp is good with the thermal regulator out, the old and new thermal regulators are probably bad.

You might have a borderline low flow issue.

You should try to confirm the actual flow in GPM.

 

[Zizzam]

Here is what the normal exhaust temperature should be:

• Below 250 degrees...very low
• 250 to 290 ..................low
• 290 to 350.................acceptable
• 350 to 480 ..................high
• Above 480...................error/shutdown.

Note: HD models can be up to 75 degrees higher. HD models use a cupro nickel exchanger and the efficiency is slightly lower resulting in less heat transfer and more waste heat.

If you had a sooted exchanger, the stack temperature would be too high.

Since your stack temp is good with the thermal regulator out, the old and new thermal regulators are probably bad.

You might have a borderline low flow issue.

You should try to confirm the actual flow in GPM.

Ok thank you for that. The old and new (generic) thermal regulators both opened fine when run under hot water but I did not test them to 120 degree's exactly. I can do that though

 

[mknauss]

Ok thank you for that. The old and new (generic) thermal regulators both opened fine when run under hot water but I did not test them to 120 degree's exactly. I can do that though

Also, you need to be sure they are seated correctly when installing. It took me many attempts to get the regulator seated just right so it would let the heater operate continuously.

 

[Poolbreh]

Do you have eyeball fittings in your jet heads and are they aligned?

 

[Zizzam]

Also, you need to be sure they are seated correctly when installing. It took me many attempts to get the regulator seated just right so it would let the heater operate continuously.

Whats the correct seating look like? I replaced it, have it pretty flat. I'm not sure how you could tell if its seated correctly since its hidden once inserted?

 

[Zizzam]

Do you have eyeball fittings in your jet heads and are they aligned?

I do in the pool (not the spa) but I have no idea what proper alignment looks like.