Mastertemp 200 - 3 cracked manifolds!!

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alleycats

Member
Mar 16, 2021
21
Antigua, Guatemala
Hi There,
Posting the first time.
I have a mastertemp 200 that is installed on a concrete platform that is the roof of a small machine room where the pump, filters, etc are located (also installed on concrete). The heater is for a large 8 person spa, and is located in Antigua, Guatemala (which makes everything like finding parts and service trickier). I'm having a very frustrating and strange problem that I hope someone here can advise me with.
The system was not in use for several months before I took over the property, which is an Airbnb. A maintenance technician came and replaced the in-line filter with an entirely new unit. After just a few uses of the jacuzzi, it developed a very small leak. I called the owner and rather than send someone to fix it, they took the whole unit away. They notified me there was a small crack in the manifold.
They replaced that unit with their own Mastertemp 175 from their house, and lo and behold within just a couple of uses the manifold cracked, a big crack, like 3 inches long and water sprayed out of it like a geyser.
I had a replacement manifold sent down from the USA for the original heater, and that was installed back into the original mastertemp 200. After just a few weeks BANG, again the brand new OEM manifold suddenly cracked and sprayed out like a geyser.
The owners were sending their own technicians and to be honest I don't think they were spa heater specialists, but even still this seems like a very strange problem. The heater seems to be on a stable service and I certainly don't notice any vibrations. That said, when they installed the second, provisional heater I did immediately tell the installers I was hearing a very deep base sound, which stopped when the heater turned off, but they didn't seem to think it was an issue (obviously wrong).
Does anyone know what could be happening? I'm hesitate to install another new manifold without solving the problem because I feel like I'll just be throwing away another quick $400. I don't even want to install a new heater because we've used two different heaters in this situation and BOTH have ended up with the same cracked manifolds.
I called Pentair and all they could tell me was probably some pressure or force on the tubes that was putting pressure on the manifold to twist and coupled with some kind of vibration, maybe that was happening...but that was all they could suggest.
I'm going to have to close my place without the jacuzzi (it's big selling point) and that will mean losing money hand over fist...so I would be really grateful for any input!
Thanks!
 
Are you sure that the water is going into the inlet and coming out of the outlet instead of going in reverse?

Are you sure that water is actually going to the heater instead of through a bypass?

Are all of the valves set correctly?
 
Well, the only thing I'm sure about from your questions is that the water enters through the top in the picture you see of the heater, and comes out the bottom.

The water is definitely going into the heater (rather than not when it's by-passed to just filter) because the water gushes out of it (the crack) like a geyser.

If by valves you mean all of the valves on the PVC/pump system below, yes, they are all set correctly. If you are referring to anything else that goes beyond my expertise...which is nil hahaha...
 
I can't see anything obvious.

You could try an ASME model, which comes with a bronze manifold, but the recurring cracks point to a problem that needs to be figured out.

For any heater, I would want to install a flow switch instead of the pressure switch that comes with the heater.

The flow switch ensures that there is really flow going to the heater instead of just pressure.

I would install a flow meter on the line to verify the actual flow rate in gpm.

I would install a pressure relief safety valve. On the same pipe, I would install a T and a pressure gauge so that I could see the actual pressure.

I would install a temperature sensor on the pipe going to and from the heater to see what the temperature rise is.

Maybe the heat exchanger is clogged or maybe the manifold is installed incorrectly or has defective or missing pieces.

Check the internal bypass and the thermal regulator.

Make 100% sure that the water is actually going into the inlet and coming out of the outlet.

Check the gas pressure.

Check the gas meter to verify that the actual amount of gas being used is correct.

Check the stack flue temperature during operation.

Does the heater run continuously without shutting down before reaching the set temperature?

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com www.troublefreepool.com
 
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img_2138-png.315774


Are these the lines going to the heater?

The valves are closed.

Are the lines going to the heater open when the heater is on?

Is the bypass valve closed while the heater is on?

Which line goes to the heater top inlet port?
 
JamesW said:
img_2138-png.315774


Are these the lines going to the heater?

The valves are closed.

Are the lines going to the heater open when the heater is on?

Is the bypass valve closed while the heater is on?

Which line goes to the heater top inlet port?
Click to expand...

The valves are closed in this picture because it was taken when the jacuzzi was being emptied through that hose from the filter. When the heater is running those vertical valves are open and the horizontal one between them is closed.

The line on the right goes into the inlet port.
 
JamesW said:
I can't see anything obvious.

You could try an ASME model, which comes with a bronze manifold, but the recurring cracks point to a problem that needs to be figured out.

For any heater, I would want to install a flow switch instead of the pressure switch that comes with the heater.

The flow switch ensures that there is really flow going to the heater instead of just pressure.

I would install a flow meter on the line to verify the actual flow rate in gpm.

I would install a pressure relief safety valve.

Maybe the heat exchanger is clogged or maybe the manifold is installed incorrectly or has defective or missing pieces.

Check the internal bypass and the thermal regulator.

Make 100% sure that the water is actually going into the inlet and coming out of the outlet.

Check the gas pressure.

Check the gas meter to verify that the actual amount of gas being used is correct.

Check the stack flue temperature during operation.

Does the heater run continuously without shutting down before reaching the set temperature?

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com www.troublefreepool.com
Click to expand...
All interesting thoughts. The most curious thing of all is that a manifold broke when we installed a completely different heater. Granted, it may also have had some of these issues, but after this happening three times it really does feel like it's something related to the pump system or something. Just hard to believe that there could be that much pressure to break the manifold coming after the filter (my understanding is that the filter would prevent any pressure surges between itself and the heater).
 
alleycats said:
Propane, from 100lb tanks.
Click to expand...
Those tanks might be a little bit small.

Propane needs to absorb heat from the tank walls, which depends on the amount of liquid propane in contact with the tank walls.

If the propane does not get enough heat, the gas pressure will drop too low, especially when the tank is less than 50% full.

If the tank is getting any frost buildup, the tank is definitely too small.

Make sure that the gas pressure is always good down to the lowest level in the tank that will happen.

Verify the water flow is at least 30 gpm.

Make sure that the plumbing isn't somehow stressing the heater unions.
 
FWIW, the official rep for Pentair came today and said that he though the issue was from the flow switch, or the lack of having one. Specifically because the heater was several feet above the jacuzzi, it was necessary and he said that you only get cracks like mine (it actually was in two pieces once unscrewed, when the outlet pipe has a valve closed or from the lack of the flow switch. He said the flow switch should be installed in the outlet pipe after the heater. Does that sound reasonable?
 
JamesW said:
img_2138-png.315774


Are these the lines going to the heater?

The valves are closed.

Are the lines going to the heater open when the heater is on?

Is the bypass valve closed while the heater is on?

Which line goes to the heater top inlet port?
Click to expand...
The problem with this bypass setup that he could very easily dead head the heater. He would need a three way diverter valve to avoid dead heading.
 
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If the heater was below the water level, that could cause the heater to run with no flow due to the water pressure, but being above the water level would require more pressure.

So, it really doesn't explain why the manifold cracked.

It's possible that the bypass was left open or maybe the valves were closed when they should have been open.

In any case, I agree that a flow switch should be used for safety.

In my opinion, all heaters should come with a flow switch and not a pressure switch.

A pressure switch is a foolish choice, especially now that plumbing systems are more complicated.

SWGs have a flow switch, why can't heaters come with a flow switch?

In any case, adding a flow switch was one of the suggestions that I wrote earlier.
 

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