New Pentair Mastertemp 125 Heater Installation - Squeals like a pig when heating...

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alpineracing

alpineracing

Member
Jun 22, 2022
6
Ann Arbor, MI
Pool Size
8000
Surface
Vinyl
Chlorine
Liquid Chlorine
Good Morning Everyone,

My first post here, I just finished installing a brand new Pentair Mastertemp 125 (Natural Gas Unit) and although it is working (heats the pool correctly with no errors or faults) it is squealing very loudly when in heating mode (heater in burning phase).

This is so loud that it literally wakes us up at night!

With multiple calls to Pentair they won't help me and say I am on my own because I did a homeowner install so unfortunately they are not warranting anything.

They had suggested a most probable mis-installation, however I have since proved this not to be the case. They had me validate the following:
  1. Not large enough gas pipe - I showed photos of my installation showing 3/4 inch gas lines and total run from gas meter under 20 feet (they finally agreed that is not the issue)...
  2. Improper Gas Pressure at inlet - I took manometer readings for both static and dynamic pressures (they finally agreed that is not the issue)...
  3. Improper air volume - I looked around and could see the trees were still alive so...(they finally agreed that is not the issue)... (LOL)
When operating without call for heat (burner not on) it runs quiet as a whisper (cannot even hear the water cycling thru it), but when heat comes on, omg... horrible. I read on this forum that on the larger units, the Thermal Regulator may not be opening and saw it was an easy check/fix... unfortunately, on the Mastertemp 125 unit (their smallest heater) it is a big job, pulling the manifolds, etc...

I have included a video I did when doing the gas pressure tests, you will hear the whine (wait for it)...

Any other ideas out there?

Thanks very much in advance,

Gary

**Note, it would not let me attach the video (sorry, my first post, do I have to change it's format? it is a .mov file)...
 
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The thermal regulator is in the same spot and as easily accessible on that size heater as any other. It is under the "castle" nut to the left of the water inlet and outlet. Just takes a screw driver through the cap to loosen the nut and out it comes.
 
Hi 1poolman1, thanks for the reply, however, unfortunately, the thermal regulator on the 125 is NOT in the same place ... uploading diagram below... I wish it was, it would be an easy check...
 

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1poolman1 said:
The thermal regulator is in the same spot and as easily accessible on that size heater as any other. It is under the "castle" nut to the left of the water inlet and outlet. Just takes a screw driver through the cap to loosen the nut and out it comes.
Click to expand...
Sorry, replied in wrong post area...Hi 1poolman1, thanks for the reply, however, unfortunately, the thermal regulator on the 125 is NOT in the same place ... uploading diagram below... I wish it was, it would be an easy check...
 

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1poolman1 said:
The thermal regulator is in the same spot and as easily accessible on that size heater as any other. It is under the "castle" nut to the left of the water inlet and outlet. Just takes a screw driver through the cap to loosen the nut and out it comes.
Click to expand...
Hi Poolbreh, it is indeed the Natural Gas Unit (Not LP) as I did see that was a common issue... you think YouTube would get more people that know anything about this than here? I would think the experts are hanging out here... I may try that however and appreciate the assistance and recommendations.
 
Well, it might be a "big job" but, in reality, 6 bolts isn't such a bad deal. Give yourself 2-3 hours on a Saturday morning with cup of coffee and it should be a fairly quick check. Honestly, at this point, you can't use the heater anyway so you've got nothing to lose taking it apart. Undo the PVC unions, shove the heater over a bit to make some room, undo 6 bolts and a few wires for the pressure switch and thermistors and it'll come right off. And that way you can check to make sure the bypass valve and spring is still intact as those has a tendency to snap off as well as check the T-regulator and make sure all the internal diverters look healthy and the o-rings are all good. It's really a lot less complicated than it looks ...
 
I finally get it Poolbreh (took me a while to sink in lol)!

Here are the links I just posted on YouTube of me checking Static and Dynamic Pressure (and squealing during heating)...

Static to Dynamic:
Dynamic to Static:
 
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I would pull that regulator like stated above, if that doesn’t work you can to an gas/air differential test. You will need a differential manometer. Can you post a pic of your equipment pad as well? And you are certain of adequate water flow?
 
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Your going to need a differential manometer to do the pressure drop test across the gas valve. You'll also need a T, some tubing and a two hose barbed fittings. The test is described on pages 19-20 of the manual -


The differential pressure drop across the valve must be -0.2".

It sounds like your water flow is fine and that the noise is in the gas line or blower as it seems to stop as soon as the gas valve shuts off. If it were water flow causing the noise, I would expect it to ramp up and down a bit, not be so immediate. I know you said that the unit is an NG unit but did you physically check the gas orifice to make sure it is for natural gas? While they are installed at the factory and you would think that it wouldn't happen, it is entirely possible that the wrong orifice was installed or the unit was labelled incorrectly. It can happen however unlikely it is.
 
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When the thermal regulator is fully open, it looks like this.

If it only opens a little, it basically creates a whistle.

The thermal regulator opens based on temperature.

The noise begins shortly after the burner fires and the water begins to heat up causing the thermal regulator to open.

1656625942479.png
 
Good Morning Everyone,

🥳 **UPDATE** SOLUTION FOUND!! 🥳

First, I want to thank all of those above that replied with suggestions and ideas to help me thru this endeavour. I thought that perhaps what I have ended up finding may help others who come upon a similar experience.
Before finding the solution, I had one additional call with Pentair and after days of them having me test *my* gas and water supplies, exits, etc (as if it was certainly my installation that was the issue) I met all of their challenges and they simply then told me they would not warrant a thing (because I installed it). They even told me like others here on this forum told me to check the gas orifice as they may have put the incorrect one in during manufacture. I said I would and asked if I indeed found this to be the case if they would send me the correct replacement part (they said no, I would have to purchase it!). I really like Pentair products but wow, caveat emptor.

Solution: A friend of mine works in the HVAC world for pool heaters and I called him. He told me to try a simple test and was 75% sure this could be the issue (as I walked him thru what I had tried and not tried to this point), he told me to simply bump up the RPM of the Pump (I have a Pentair VSP) to a higher number (I was running it just above the RPM that would allow the heater to fire without fault and that initial number was 2050 RPM). My particular pump has a max RPM setting of 3450 RPM. I slowly bumped up the RPM setting and found that the squeal was starting to subside. I ended up with it setting at 2800 RPM and it is quiet as a whisper.

*Additional note: I also have a restricter (ball swivel type) outlet at the bulkhead where the return pool water enters the pool. I have always had it and it created a strong nozzle type of stream. After the success of the above, I started thinking again that ~possibly this back pressure may have been contributing but am not sure as it had no effect when heat was off. I removed the restricting ball from the fitting and now it has little back pressure and still unchanged and whisper quiet. I am going to see if it will now allow a lower RPM setting and stay quiet (only as running my pump at a lower RPM will save energy and hopefully increase longevity).

PS: I thought FOR SURE it was a Thermal Regulator problem and was heading (with coffee in hand) toward that step next but now know it was not the culprit.

Does anyone have any info on why the lower RPM (but high enough to allow the heater to operate) would cause the squealing? I am guessing that it has something to do with the water "boiling" in the manifold and causing steam? (don't be too hard on me folks, it was only a guess!) lol.

Thanks,

Gary
Alpine Racing :)
 
Awesome!! Glad you got the unit working. Wow, obnoxious of Pentair to treat you that way … companies have no common sense nowadays when it comes to building up good will with customers. Sure, you did a self install and you own it, but they can clearly see from the paper trail of service calls that you were willing to do all the hard work and all you asked for was a little help. And they decided to treat you like Crud. That orifice part would cost them nothing to throw your way for free but, by standing their ground on their “rules”, they’ve potentially cost themselves a lot of future earnings … businesses run by people with no business sense whatsoever …

I suspect partial boiling of the water inside the heat exchanger likely caused vibrations that emanated as the “screeching” noise. A vigorous bool would sound like banging and hammering but a very mild boil could cause vibrations of the metal fins. Given their right spacing, higher pitched screeching is totally possible.
 
All water goes through the internal bypass (manifold bypass) until the water heats up and then the thermal regulator opens and some of the water begins to go through the heat exchanger and through the thermal regulator.

As the thermal regulator opens, the flow going through the manifold bypass slows and the manifold bypass closes some.

The thermal regulator is the silver thing.

If either one is only open a tiny crack, it can create a whistle effect.

The noise can be from the thermal regulator or the manifold bypass.

Higher flow can open the manifold bypass more and prevent a whistle effect.

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