Unitherm governor blowout

[31003]

Hello,
I am not an expert, but am doing maintenance for a place with a Rheem/Raypack millivolt pool heater in the basement. The other morning I woke up to the sound of a flowing river along with the pump sound the other morning. Luckily I was able to shut it off before too much got wet. Luckily the floor drain was well cleaned out too!
The unitherm governor had blown straight out of the manifold, so it was pumping directly into the basement.
I ordered the new parts, but is there a chance that it is the manifold itself that has become warped?
I sure don't want to risk that happening again. Has anyone else had this happen? There were no warning signs, no little leaks or drips
Thank you.

 

[ajw22]

Welcome to TFP.

Never heard of the unitherm governor blowing out of the manifold and it is not good.

I would examine the threads on the old part and manifold carefully as well as the new governor.

Let's see if @1poolman1 @JamesW @ps0303 has seen it.

 

[JamesW]

Since it is in the basement and lower than the pool, the pressure switch can be closed from static pressure with no flow and that would be the first thing to check.

You need a real flow switch and not a pressure switch.

How old is the heater?

How high is the pool surface above the bottom of the heater?

Can you show the system?

 

[JoyfulNoise]

A plastic body with standard pipe threaded fittings would need a huge amount of pressure to blow out. Most pool pumps don’t typically create that much pressure.

I would carefully inspect the manifold or the cap that enclosed the thermal regulator. It sounds to me like the plastic cracked.

 

[JamesW]

It might have been overheated and under pressure, which can cause failure.

 

[Poolbreh]

This happened to me with Raypak digital 2100. The equipment is about 10ft below pool level. All valves were open and no indication of any blockage. The heater was 15years old and I couldnt say with confidence that threads on the manifold werent compromised. He has a neighbor that lives directly below the equipment easement. So we opted for a new heater.

 

[JamesW]

The equipment is about 10ft below pool level.

Did you install a flow switch?

https://www.royalswimmingpools.com/rp2100manual.pdf

 

[1poolman1]

Welcome to TFP.

Never heard of the unitherm governor blowing out of the manifold and it is not good.

I would examine the threads on the old part and manifold carefully as well as the new governor.

Let's see if @1poolman1 @JamesW @ps0303 has seen it.

Saw it once on a RayPak about 15 years ago. A health club was doing their own maintenance and adding a gallon of liquid chlorine daily to a 2000-gallon spa. Six-months of that (I did the install, not the sale) and the heater was shot, all the plastic parts of the header were warped and the Unitherm governor would not stay tightened. That's one reason an ASME rated heater should be used on a commercial application, especially with a below-pool installation. RayPak uses metal (now bronze) headers on those. I wouldn't trust using the old manifold if I were responsible for heater maintenance. Unless the cap was un-threaded, the threads in the manifold are suspect and would probably fail again.

 

[JamesW]

Raypak Flow Switch Kit - 007142F - INYOPools.com

Flow Switch Kit - 007142F

www.inyopools.com

 

[Poolbreh]

Did you install a flow switch?

No, the heater was replaced with a mastertemp. He has a jandy rs5 and I couldn’t tell you if there was a cooldown period now that you mention it. So it’s definitely possible for the manifold or cap to warp over time from no cooldown. Just thought I would share that this happened to me.

 

[JamesW]

No, the heater was replaced with a MasterTemp.

The Raypak pressure switch is set to 1.75 psi, which can be triggered by 4 feet of water.

The MasterTemp pressure switch is set to 3 psi, which can be triggered by 6.9 feet of water.

 

[Poolbreh]

View attachment 464743

The Raypak pressure switch is set to 1.75 psi, which can be triggered by 4 feet of water.

The MasterTemp pressure switch is set to 3 psi, which can be triggered by 6.9 feet of water.

I did not know this, thank you. Neither the old or new heater was my installation. But I will check and see if a flow switch was installed.

 

[JoyfulNoise]

It is still puzzling that the heater manufacturers use pressure switches. The incremental cost in using a flow switch can hardly justify not having one. Given that system pressures are mostly meaningless in pool plumbing (aside from the gauge sitting on top of the filter), it just makes no sense.

 

[JamesW]

It is still puzzling that the heater manufacturers use pressure switches.

Back when all pumps were single speed and the systems were simple and mostly at pool level, a pressure switch worked well enough for most applications.

Today, with variable speed pumps, complex plumbing and other issues, it's idiotic (in my opinion) to not use a flow switch.