New Raypak LP heater issue. high limit fault

[JamesR]

Just installed my new heater. It keeps tripping the high limit 2 switch. I think it’s a 135 degree trip. I put a thermocouple on that switch and noticed that if the side cover is off, it runs 120 - 128 degrees. If I put the cover back on it runs 127 - 137 degrees and trips. Why would it run so hot. I think the switch just to the left of it is the higher temp switch and that area runs much cooler. Are they installed wrong or is it an issue with the governor? Pics below. Temp with cover off and cover on. Flow is about 60 gpm

 

[JamesR]

I just realized I put this in the wrong area. Mods, please feel free to move over to “Everything Else”
Thanks, Jim R

 

[JamesR]

TTT. Thanks.

 

[JamesR]

one more try......

 

[MITBeta]

What speed is your pump running?

 

[JamesR]

What speed is your pump running?

It is a single speed 1.5 HP Hayward Super pump. GPM flow through the heater is roughly 60gpm.

 

[MITBeta]

Seems like there isn't enough flow through the heater. Is there a bypass, either internal or external?

 

[JamesR]

This Raypak heater has an internal bypass and some controlling valve called a Unitherm Governor. I'm pretty handy and fixing stuff, but I have not taken anything apart to check them because it is under warranty. Too bad Raypak is not getting back to me though.

 

[pgershon]

Did this get figured out? Lots of people on this board trying to solve raypak high limit 2 issues, including me

 

[1poolman1]

Had this issue on too many RayPak heaters before I stopped using them. Always the same, remove the panel, no problems, restore the panel, hi-limit trips. The answer I always received from tech support was to put some fiberglass insulation around that particular switch or fill the cabinet area just below the switch at the header (not the whole cabinet). That was it. I did that a few times (because I had some insulation left over from a small remodel) and it always worked but that is not the type of solution I expected from a company that I had used for over 25 years.

 

[pgershon]

You mean put insulation around the hi limit sensor? I am not sure what other "switch" you might be referring to.

 

[1poolman1]

Yes, they are hi-limit switches, they "open" and "close" and that's it. Loosely packed to keep the heat in the cabinet from reaching the switch. The first time I heard of this a customer called the factory and he was told to do it. Heater was only two weeks old. Since I had installed it, and thought that solution somewhat strange, I checked the entire heater for issues and found none except the same as you found. Called tech support and was told the same thing. I wasn't happy, but did it and it worked and is still working. Had to do the same thing 3 more times over 2 years with heaters I installed. Call-backs are a waste of my time and energy so I now use another brand of heater. I don't recommend brands, just sell what I believe will be best for the customer's particular installation.

 

[JamesR]

Sorry for being late to respond but yes I got it figured out. A couple issues. 1) there was no heat sink compound on the thermal switch where it mounted to the polymer manifold. So I yanked both switches and applied thermal paste to them as it should have had to begin with. 2) the design tends to have exhaust gas and heat trapped in that area so I added high temp insulation to the heat shield. The kind you would use on headers of a cars race motor. I did a lot of temp measurements with an accurate thermocouple mounted at that high limit switch and determined the issue was not the actual water temp, but the switch getting hot from the surrounding area. It’s been fine ever since and my temp meter shows it runs much cooler. My temp meter would show that switch hitting close to 150F after 30 minutes of run time. Now it never goes over 130F even with the heater on continuously for several hours straight heating the pool.

 

[pgershon]

How did you build your insulation? That seems like a great approach

 

[JamesR]

That’s the factory metal heat shield that I wrapped with high temp header wrap insulation, drilled holes in the plate, used large fender washers and riveted it in place. It may be overkill, but I sometimes get carried away with my “fixes”. Applying the proper thermal compound in the well where the switches mount helped as well.

 

[pgershon]

I just ordered thermal compound. I guess I will start there. And I have new high limit switches on order too.

 

[pgershon]

I dont believe I have that factory metal heat shield. I have the the metal shelf like you above the polymer manifold, but that is it. I see two levels in your photo, with the heat shield between that metal shelf and the in/out polymer

 

[JamesR]

I thought of defective switches also so I removed them, hooked up and ohm meter, placed them in a pot of water on the stove with a thermocouple in the water at the switch. Then slowly heated the water. They both “opened up” at 138f. So they were good. That’s made me realize that the area around the switch was getting unusually warm. Yank that access cover off and run the heater so the ambient temp drops. See if your issue goes away.
…. You don’t have the shield? It’s called out in the parts diagram.

 

[pgershon]

No, I dont have it - not on either of my two heaters (I will look again tomorrow but I am pretty sure). This is the diagram I have followed and its not on that one - but I found the diagram you sent in my manual as well. I wonder if the lack of this part is the cause of my problem.

 

[JamesR]

That picture indicates heaters built prior to 10/2019. How old is your heater? Mine is a 2021 build.