Raypak - High 2 limit fault - checked unitherm governor, now what?

[pgershon]

Today I changed the internal bypass too. No high limit errors today but we will see if this is a final fix. The old bypass had rusted and the spring looked stuck (see photo). I have now:

1) replaced both high limit sensors and added thermal paste
2) replaced unitherm governor
3) replaced internal bypass
4) added a heat shield

Not sure what else could possibly be done. Also have new board, pilot assembly and gas valve within last two summers. Heater bought in 2011 before the season.

 

[Pauls234]

Thanks for keeping this thread (and the other) up to date on your quest to resolve this issue. These two threads seem to be found often on google searches so adding the link to the other thread as well for those that may need it. (New Raypak LP heater issue. high limit fault)

How difficult was changing the internal bypass? Did you replace all the seals and o-rings as well since you took so much apart?

My most recent heater maintenance has been ensuring a mouse doesn't nest in there. It started building a nest right on the burners, which I learned when I fired the heater and incinerated the beginning of its build, though thankfully not any mice. Then a week later, I saw it moved up and built a nest right around the hi limit switches on top of the header, so I opened it up, cleared it out and then put some of those mesh screens around all openings (from Mkratproofing).

It might have been an interesting experiment to see if the nest provided the necessary insulation to the hi limit switches from the ambient air tripping them, but I didn't want to risk burning the mouse or it chewing up all of the wiring.

 

[pgershon]

It was actually very easy to change the bypass. There was one o-ring and while the old one looked good, I decided to replace it anyway. I needed a deep socket wrench to get into the header, but other than having to purchase new tools, there was nothing complicated.

Unfortunately I am still getting the high limit fault, last two days it happened as the internal temperature recorded by Raypak hit 107. It was very hot outside and my guess is that the high limit sensors registered 110 between the water, the outside heat, and the internal exhaust heat. I am going to try to improve the insulation and see if it helps.

 

[pgershon]

It was actually very easy to change the bypass. There was one o-ring and while the old one looked good, I decided to replace it anyway. I needed a deep socket wrench to get into the header, but other than having to purchase new tools, there was nothing complicated.

Unfortunately I am still getting the high limit fault, last two days it happened as the internal temperature recorded by Raypak hit 107. It was very hot outside and my guess is that the high limit sensors registered 110 between the water, the outside heat, and the internal exhaust heat. I am going to try to improve the insulation and see if it helps.

And the latest insulation…

 

[pgershon]

No high limit fault the last 3 days. But I got one the day after installation. Seems like the high limit error now is related to how hot and humid it is outside and the angle of the sun at the time I turn on the heater. I am hopeful that other who have insulated the high limit switch area will talk about how they did it. I wonder about putting some additional insulation material into the area under the heat shield (foam, fiberglass, etc).

 

[pgershon]

Fault today. Heater got water to 103, then started declining. Seems like it craps out at 106 (internal temp)

 

[Pauls234]

That is a bummer.... it's like it needs a cooling fan installed.

 

[pgershon]

Yes - exactly - a cooling fan. What I really dont understand is why I have the issue this year and not in past years. If the problem relates to the hot air exhaust, perhaps the nearby trees have gotten too close to the heater and are inhibiting the exhaust. I'll post a picture later.

 

[pgershon]

I have a new thought - might the exhaust from the unit be impeded by the trees growing on top of it? This might explain why the problem is new this year, as my trees get a bit larger every year. I tried to provide some color with these pictures. The evergreen branches are certainly about 1 foot over the heater, and that may cause the heat to stick around a bit. I have no issues on cloudy days, but the high limit fault kicks in right when the water has gone from about 85 to 107 continuously on sunny days when its particularly hot around the heaters. If the water shut off even one degree sooner today, the fault would not have come up. I was watching the temperature probe on my iaqualink and sp temp rose steadily to 104, then fell back to 100 before I had a chance to reset. And the RayPak is reading about 3 degrees hotter than the Jandy at all times (so 104 on iAqualink is 107 on RayPak). Spa heater is the far one from the camera in the photo below.

 

[Pauls234]

Certainly plausible given how sensitive these seem to be. My fault did not start occurring right away either, more like 3 years into ownership. Try trimming some of those branches maybe??

 

[Beeba]

If you want to replace the unitherm governor, get part 006719F.

Yes as Pool Clown said, the limits on the Raypak's are pretty robust.

I Have a brand new pool heater one season old and when I turned it on this year it kept giving me the High limit fault. I took out the unitherm governor And it was bad, I replaced it with the part listed above and now everything is all good. Not sure why it went bad after one year but it was an easy fix

 

[Pool Clown]

Keep in mind that everything that the (pool) water hits is subject to the effects of your chemical dosing, good or bad. This is why some parts fail quickly and, coincidentally not covered under warranty.

 

[Pauls234]

Just to keep this thread updated....

Brand new Ray Pak 406a installed a few days ago and tripped the hi limit 2 fault. Water temp was set to 86.

After 7 seasons I replaced my heater with same model and it has been in intermittent use past few days. Pump was on high and filter was recently cleaned (pressure reads about 10% above clean) so no flow issues and yet the hi limit 2 fault tripped last evening. That seems to suggest a design flaw as we discussed where high ambient air temperature hangs around that switch and trips it? I know some experimented with creating a heat shield around the switch.

Even though these are outside I also understand there could still be venting issues, so perhaps something along the lines of an uncommon lack of air current in that part of our yards that allows hot exhaust to hang around? Just seems this is recurring to several of us, but clearly not everyone.

My ongoing issues with this are really just a nuisance, as evidence by me buying the same model again - I'm still getting +2 degrees/hour. It is curious though and not sure I can do much about it.... maybe I'll experiment with putting a fan out there next time I plan to run it more than a couple hours.

 

[pgershon]

I never fully solved this either. I have two side by side 406a units for spa and pool. Spa runs maybe every other day and periodically trip HL2 near 104 degrees. Does not seem to be any rhyme or reason as to
Why some days and not others. I replaced UG, bypass, limit switch and upgraded insulation last year and issue persists. Pool heater only heats to 85 and does not have the issues at 100 degrees. However, pool heater trips HL2 when filter dirty or I don’t run pump fast enough. 2800 RPM seems to keep heater from the error.

 

[ps0303]

I never fully solved this either. I have two side by side 406a units for spa and pool. Spa runs maybe every other day and periodically trip HL2 near 104 degrees. Does not seem to be any rhyme or reason as to
Why some days and not others. I replaced UG, bypass, limit switch and upgraded insulation last year and issue persists. Pool heater only heats to 85 and does not have the issues at 100 degrees. However, pool heater trips HL2 when filter dirty or I don’t run pump fast enough. 2800 RPM seems to keep heater from the error.

I always suggest to my customers to run their variable speed pumps at 3000 RPMs. That appears to be the best speed for making sure the heater doesn't over heat. Also check to make sure your heat enchanger is clean and not partially filled with soot.

BTW, I stopped selling the Raypak/Rheem units due to similar issues with the HL2 sensor.

 

[Old Guard]

Over the weekend I was getting a high limit 2 fault after the heater was running for maybe a couple of hours. It was not a particularly hot day and water flow was about as strong as it gets (no blockages and freshly cleaned filter). After the first fault, I left the heater off for about 30 min with the pump running, then turned it back on. It fired up fine, ran for a few hours and then I got another high limit 2 fault.


So, after some researching I decided to pull the unitherm governor and inspect. It had some cottonwood on it, but not so much that would seem to interfere with its operation. I cleaned it off, took it in the house and put it in some hot water and it appeared to be operating correctly in that it was opening/closing with the temp changes. The gasket for the governor was pretty mangled however - could this be the source of my problems? Maybe it is letting in some outside temperatures that are causing the fault?

Any suggestions on next steps or is it best to replace the gasket and see if that solves things? (Open to suggestions on where to get the gasket as well.)


Thanks,
Paul

I just installed a P-M406A-EN-X (400BTU Outdoor) two weeks ago. In the last 24 hours, I have gotten 5 of these Hi Limit 2 faults every one of which shut the heater down and disabled my lock out code. I'll circle back when I get a proper diagnosis. The guy who put it in is coming to look Sunday or Monday but I can't get a tech before Thursday. I discovered the first of these faults early Friday morning. Not feeling so smart about getting away from Hayward now.

 

[Pauls234]

I removed the small panel that gives access to the hi limit when running the heater and then put it back in place when I'm done (without screws) and I don't recall getting another hi limit 2 fault since doing so. Consistent with findings on this thread suggests that the sensor is being tripped by ambient temps.