Pentair 400 heating problems

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Tonyjp

Tonyjp

Active member
Feb 22, 2022
26
Parker, Colorado
Pool Size
18000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I have a pentair 400. When i try to heat up the hot tub it gets to 80 degrees, usually from about 60, and then i get an E05 code. The thermal regulator was stuck open so I replaced it with a new one. I thought that would solve the problem but it does the same exact thing. Will a bad bypasss valve cause this symptom also? Any other ideas? Thanks
 
Tonyjp said:
I think I am going to try and clean the exchanger inside and out. Any tips?
Click to expand...
That is not the first thing I would do.

What type of filter and pump do you have?

When did you last clean your filter?

Did you measure your stack flue temperature?
 
I have a new Hayward c3030 filter. Maybe two weeks old. I have not cleaned them yet since they are new.
I have a Pentair VS pump.
I haven’t measured the stack flue temp. I checked the ohms on the sensor and it was good. How do I check the temperature?

Thanks for your help. This forum is great.
 
That reading material was good. I just checked the stack flue temp with everything set for the pool. Pump set at 1750. It got as hot as 352. It stayed around 350-352. Then I switched to spa. It went as high as 354. Pump for that was set at 2250. I am trying to heat up the hot tub now. It seems to work pretty well until it hits about 80. I started at 60 and it is about 70 now. As it gets closer to 80 I will check the stack flu temp again. It’s seems to work like it should until 80. I have only tried to heat the hot tub up also so I am not sure what it would do if I tried to heat the pool.

I have read that the heater requires 40gpm and I think at either of those rpm’s I should be safely getting it. And the hot tub which is where I have the problem now I am either at 2250 rpm or 3450 rpm.

Also when I switched between pool and spa an r02 came up on the screen.

I just checked the flue temp at a water temp of 74. It is at 357 now.
 
Last edited:
If the issue arises again, remove the thermal regulator and check the spring, etc. I had to reset my new one a couple times before it quit shutting down the heater prematurely.

Also, your filter has no minimum flow rate. The slower the flow through it, the better it filters.
 
I meant heater on the 40gpm. I fixed it.
I will definitely try and reset the thermal regulator. It seemed like it had more spring pressure going in than coming out. It was 10 degrees outside when I put it in so I was hurrying. Resetting it is a great thought. Thanks
 
The flue temp went to 359 at 78 water temp. It seems to go up a degree or two for every degree of water temp. I expect it to shut off soon since it is getting close to 80 water temp. I will reset the thermal regulator and see if it restarts and gets warmer.
 

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When the water temp hit 80 the flue temp started rising to about 380 then the heater shut off. I let it sit for a few minutes and restarted it. It turned off at 336 stack flue sensor this time. It was making a quiet rattling sound at the manifold when the pump was running and the heater had turned off. I also reset the thermal regulato. It felt like it was good where I set it.
it seems to work perfect until 80 degree water temperature.
 
I tested it. I also bought a Pentair one instead of generic even though they are probably the same. I will pull it out and test it again. Fortunately it is easy to get out. Thanks
 
I just tested the thermal regulator again. It worked perfect. I restarted it. The water started at 79 and went to 81. At 81 the flue temp hit 393 and the heater turned off.
What would be the next step?
I would rather fix this heater but I am getting close to just buying a new one.

Also when I had the thermal regulator out I stuck mu finger in to feel the bypass valve. It seems like it is in the correct position. I couldn’t move it. I am not sure how much spring pressure it should have.
 
I am not a heater expert but as I understand it if the Flue Temp is high, it is because you are not getting enough water through the heat exchanger. It works at lower water temperature but as the feed water warms, the flue temperature goes up. The thermal regulator is the easiest and likeliest source of that issue. Like I said, I replaced mine and had to take it out and put back in multiple times before it worked.

The other item I believe that can mess with this is the internal bypass. But I am not up on that effect.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com www.troublefreepool.com
 
I think cleaning the coils is my next step. I think I have plenty of water flow. I can see it and feel it in the hot tub. It looks like it is moving at a pretty good pace. The out pvc also feels warm like 80 but not not like 100+.
All the help has been awesome. It has helped me think through this logically.
If any at her ideas come up I am all ears. Thanks
 
Rattling noise is caused by the water boiling in the heater which it should not do. You don’t have fast enough flow through the heat exchanger to absorb the heat and move it out of the heater.

Your exhaust temperature is running too high.

You may have a broken bypass valve blocking flow to the coils.

You need to open up the header and see. I would have on hand a new bypass valve and new O rings for the header. You can look into the coil and see if it is calcified.

There are YouTube videos on replacing a MasterTemp bypass valve.
 
See posts #17 & 38 for links to YouTube videos but you may find the entire thread applicable to your problem…

Mastertemp 400 Shutdown Issue & E05 error

Hi all- So last week we had an issue with our heater that I thought we resolved but it happened again today when I went out to turn on the heater. Below is what happened, how we thought we resolved it and what happened since. Any advice is appreciated! Regards, Peter Last Week Issue - last...
www.troublefreepool.com www.troublefreepool.com
 
I finally got in there. It looks like my coils are clogged up pretty good. Interestingly it is mostly only the one that is bad. Have you seen that before?
 

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