Raypak heater whining... how to increase water flow?

HappyAuer

Member
Jul 9, 2014
21
Rochester, NY
I bought a Raypak heater for my new AG pool last summer, based largely on advice from ps0303 (Paul) that I read in this forum. It works great. Thanks, Paul! However, it makes a whining/whistling noise. I’m pretty sure the noise is caused by insufficient water flow (thanks again to Paul’s posts). I’d like advice on the best course of action. Here are some options I’m considering:

  • Live with it. The noise is a minor annoyance. Apparently the real downside is not the noise itself, but the fact that it’s a symptom of the temperature being too high inside the heater, which can accelerate scale buildup. Would this be very likely to shorten my heater's life?
  • Set the filter multiport to recirculate when heating. I tried this for a few minutes, and the noise was almost eliminated—reduced to an occasional very quiet squeak. But that would send unfiltered water through the heater. Bad idea, right?
  • Optimize plumbing layout. The pool builder used 1.5” flexible hose, and I added a heater bypass made of 2” PVC. The flexible hose has some tight turns that could be improved by adding supports, and there’s a 90 degree elbow at the pump inlet that points away from the skimmer (***?) that I think should be eliminated anyway.
  • Replace all 1.5” flexible hose with 2” PVC. Could this increase flow rate substantially?
  • Upgrade my 1HP pump. I’d likely go to a 1.5HP VS and run it at a much lower speed when not heating. My concern here is whether I could damage my filter. My SD40 sand filter is rated for 40gpm maximum, according to the brochure on the Pentair website. I fear that I may be caught between a rock and a hard place… maybe the filter can’t handle the water flow that the heater needs? Will I need to upgrade both the pump and filter to satisfy the heater’s water flow demand?

One more related question: besides low flow, the other documented cause of whistling in the Raypak heaters is a faulty unitherm governor (UG). I removed mine and tested it in a bowl of hot water and it expanded like it’s supposed to. However, the UG gasket was twisted. I straightened it and lubed it, but it’s still crimped and imperfect. Is there any chance that a new gasket would solve the noise problem?

Thanks in advance for any and all advice.
 

ps0303

TFP Expert
In The Industry
Jul 6, 2011
4,001
FL
Issues with the unitherm governor have been more of an issue with their professional series. Seems like you tested it right and it's working as it should. The gasket you speak of is common and an annoyance for sure. No lube is really needed for that gasket.

I would get rid of the flex hose as much as possible. Use the correct PVC piping as much as possible. I know is common on AGP pools but it can create issue especially since you can twist and bend it more than it should. Your pump size is adequate and I would not worry about upgrading it.
 

HappyAuer

Member
Jul 9, 2014
21
Rochester, NY
Thanks, Paul. It's a relief to know that I don't need a new pump. I will start taking measurements and working on a plan for new plumbing in 2" PVC.
 

HappyAuer

Member
Jul 9, 2014
21
Rochester, NY
The plot thickens: I just found a way to eliminate the whining noise without setting the multiport to recirculate. But I'd like expert opinions on why it worked and if it's ok to run it this way.

My heater bypass is made of 2" PVC and includes 3 ball valves. I read in another thread that a Raypak owner made the noise go away by increasing back pressure. So I tried the same thing by slowly closing the valve just downstream from the heater while the heater was running. The noise got quieter as I went and stopped altogether when the valve was about 2/3 closed. I checked the flow at the return eyeball and found it reduced but still decent... I'd say similar to the way it feels when my filter is due for a backwash.

I'm confused because I'd already tried reducing flow to the heater by opening the bypass and got a very different result. The noise dropped in pitch (the valve was like a musical instrument) and got even louder.

Here are my questions:

1. Can too much water flow cause a whining noise? If so, why?
2. How come restricting flow upstream of the heater (opening the bypass) doesn't stop the noise, but restricting it downstream does?
3. Would I be introducing any risk by running it this way all the time (with the ball valve partially closed)?
 

Jaerock

New member
Aug 14, 2018
1
San Francisco CA
The screeching is small amounts of water boiling and turning into vapor. Increasing flow prevents this and stops the noise. Water boils at lower temps at low pressure and higher temps at higher pressures. Closing inlet lowers pressure inside boiler and closing outlet raises pressure inside the boiler.Probably best not to use as a permanent fix.


The plot thickens: I just found a way to eliminate the whining noise without setting the multiport to recirculate. But I'd like expert opinions on why it worked and if it's ok to run it this way.

My heater bypass is made of 2" PVC and includes 3 ball valves. I read in another thread that a Raypak owner made the noise go away by increasing back pressure. So I tried the same thing by slowly closing the valve just downstream from the heater while the heater was running. The noise got quieter as I went and stopped altogether when the valve was about 2/3 closed. I checked the flow at the return eyeball and found it reduced but still decent... I'd say similar to the way it feels when my filter is due for a backwash.

I'm confused because I'd already tried reducing flow to the heater by opening the bypass and got a very different result. The noise dropped in pitch (the valve was like a musical instrument) and got even louder.

Here are my questions:

1. Can too much water flow cause a whining noise? If so, why?
2. How come restricting flow upstream of the heater (opening the bypass) doesn't stop the noise, but restricting it downstream does?
3. Would I be introducing any risk by running it this way all the time (with the ball valve partially closed)?