Pentair Mastertemp 250 screaming/whining on ignite

[johnsonps08]

Have a Mastertemp 250 that I don't have a lot of history on (came with the house we moved into last August, wasn't hooked up). Heater was setup for propane and we finally got a large propane tank setup last week. Went to fire it for the first time yesterday and the heater kicks in fine, runs for a few seconds (maybe a minute), and then as soon as the fuel ignites a high pitched squeal/whine begins. The noise is pretty disorienting so it's a little hard to pinpoint where but it seems like the exhaust or gas valve as best as I can tell. The water does heat noticeably, I can feel the outlet lines getting warm and my wife said she could feel the warm water in the pool.

Things I've tried so far:
1. Remove thermal regulator - no change in sound.

2. Adjusted flow on the pump, up and down - no change in sound

3. Checked the pressure on the front side, where the propane comes in - getting static 10 inches WC which is, as I understand, within range. Expected to and still got the noise while testing. I don't have access to a differential manometer at the moment to check backside but I'm working on it.

4. Removed the union where the orifice lies and double checked the orifice was seated correctly and is smaller than the NG orifice. Check and check but still squealing on next fire.

At this point, the ONLY way that I've been able to even dampen the noise a little is by placing my hand over top of the intake. I don't fully block the intake, only cover it enough to reduce the air flow into the system and then the scream/whine disappears.

I'm guessing this is an issue with pressure in the gas valve but I'm wondering if anyone has experienced something similar or if anyone has any idea of other debugging tools to try. Thanks in advance!

 

[ajw22]

Get that manometer. Your dynamic gas pressure once the heater runs is not to spec.

Check the size of your gas lines or your gas valves.

 

[johnsonps08]

Get that manometer. Your dynamic gas pressure once the heater runs is not to spec.

Check the size of your gas lines or your gas valves.

The line coming in is 3/4" up to a regulator that the propane company installed. I'm not an expert but it looks right based on the explanation I received from someone who dealt with pool equipment regularly.

Re: the manometer - is there anyway to test the differential pressure on the backside with an analog manometer? Is there any value to getting the static pressure?

 

[ajw22]

See this post for what it looks like testing gas pressure before heater ignites and while running...

Pentair mastertemp 400 cycling due to low gas flow?

Google how to make a manometer. Simple tubing on a board. Water height differential in inches is the pressure. Plus you'll need a 1/8" threaded to barbed fitting to go into the test hole. You can buy a manometer if you want. Natural gas can be run two stage with a 2 psi first stage from the...

www.troublefreepool.com

 

[ajw22]

The pressure static should be about 7 to 10" w.c and it should drop only about 1 or 2 " w.c on call for heat.

Below, you can see that the initial pressure is good, but the pressure drops to zero on call for heat which indicates a gas supply issue.

 

[johnsonps08]

Oddly enough, I went to check out the pressure and take a video but now the system won't fire. The "Service System" light is on (a first for me) and when I flip the board the PS light is lit. The propane tank is running low because they didn't fill it completely yet but I don't think that's related to the PS led. I upped the pump speed and got nothing different. Any thoughts?

 

[ajw22]

Open up the heater and test the pressure switch continuity with a multimeter. It should be open with no flow and closed when your pump is running.

Your low propane could be causing the whine. You may not get the proper gas pressures when the tank is below 20%.

 

[johnsonps08]

Curiosity question on the propane hookup - does there need to be a sediment trap with propane? Do you know of any diagrams regarding propane install? The lines coming into the system aren't per the recommendation in the manual, however, I wrote that off before because the manual is talking about gas not propane. Maybe thats not the right line of thinking?

 

[ajw22]

I think gas is gas. Just with propane the source of the gas is closer.

You can easily get moisture in your propane tank over time, which is the purpose of the sediment trap. Especially if you regularly run your tank down low and allow much ambient air into it.

 

[Ahultin]

Curiosity question on the propane hookup - does there need to be a sediment trap with propane? Do you know of any diagrams regarding propane install? The lines coming into the system aren't per the recommendation in the manual, however, I wrote that off before because the manual is talking about gas not propane. Maybe thats not the right line of thinking?

2 stage propane , 10psi regulator at tank , 13" wc at heater

 

[johnsonps08]

So figured out the PS led was just some leaves clogging the basket inside the filter. Thankfully easy fix.

Propane tank has been filled... Still have the squeal/whine. Checked the front side reading with the manometer, seeing 10.5 before call for gas and a little above 8 after call for gas.

Tried hooking up the analog manometer to the backside port but I'm getting no reading. Not sure if that is because I need a special tool or something is wrong. I have to think the valve isn't shot because the water is def still getting hot. I checked the exhaust temp (I think) by holding down the Pool On button and it got up to 217 or so in the short time I ran the tests.

Still not really sure what to do.

 

[johnsonps08]

Adding a couple videos, hoping maybe this helps

This one shows the manometer test and gives a sense of the noise before/after call for gas:

This shows how putting my hand over the intake changes the sound and makes it disappear:

Also one more to show the stack temp is increasing

 

[Wiri0302]

JohnsonPS did you ever figure this out? I’m having the same issues. Gas company said the issue is within my heater and it’s Pentair's issue. I’ve got 11” WC pre fire and 8” post fire. Dropping 3” during the fire. The noise(squeal or whistle) goes away when I block the intake with my hand but not fully or it shuts down.

 

[wireform]

JohnsonPS did you ever figure this out? I’m having the same issues. Gas company said the issue is within my heater and it’s Pentair's issue. I’ve got 11” WC pre fire and 8” post fire. Dropping 3” during the fire. The noise(squeal or whistle) goes away when I block the intake with my hand but not fully or it shuts down.

Your problem could be related to pipe size issue too. Dropping that much is a supply problem.

 

[Wiri0302]

Your problem could be related to pipe size issue too. Dropping that much is a supply problem.

Turns out the heater was set up for natural gas so I need a propane “oriface”.

 

[johnsonps08]

I already had verified that I had the propane orifice. After that + everything I've posted above, I basically completely reworked the gas line coming into the machine. Added a sediment trap that the gas company didn't recommend, took out a couple unions. But STILL was getting the noise. I ended up finally getting a digital manometer that could measure differential flow. It was within spec.

Finally decided to remove the brass plug on the top of the gas valve. Even though I've read a few things advising against, I adjusted the screw underneath that plug about 3/4 a turn counter clockwise and after doing so the noise finally disappeared. I've not retested the differential flow since doing so but I plan to hook it back up again to verify that number is still within spec.

I was able to heat the pool up 2 degrees in the first hour of testing this configuration. I ran it again a few days later and had it go up about 5 degrees in about an hour and 45 minutes. Probably the last time we'll run it til fall though.

I'm curious if anyone here has thoughts on adjusting the valve?

 

[johnsonps08]

Your problem could be related to pipe size issue too. Dropping that much is a supply problem.

Worth mentioning - for me, the pipe size was 3/4" from the propane company's installed regulator to heater. This was unchanged from my first post until now. Only thing I changed from first post to today was adding the sediment trap and removing a union that was originally installed because of not having right length of pipe. Also, sadly, all the changes I made with the gas pipe had no impact on the issue.

 

[ajw22]

I'm curious if anyone here has thoughts on adjusting the valve?

Let's see what @JamesW @swamprat69 say.

 

[Ahultin]

Worth mentioning - for me, the pipe size was 3/4" from the propane company's installed regulator to heater. This was unchanged from my first post until now. Only thing I changed from first post to today was adding the sediment trap and removing a union that was originally installed because of not having right length of pipe. Also, sadly, all the changes I made with the gas pipe had no impact on the issue.

What is the distance from the tank to the heater? For a mt250, 3/4 pipe, propane, the max effective distance (actual pipe length plus 5ft per fitting) is 50ft per the pentair chart. If you exceed this then you need to have the regulators swapped to 2 stage (red high pressure regulator at the tank, green low pressure regulator at the heater). I have 13" water column at the heater static and it drops by less than .5" dynamic
Do you have a photo of the gas installation?
I've not futz'd with the gas valve on the mastertemp but the manual pretty implicitly says that it is an unconventional valve set at the factory and shouldn't be adjusted.

 

[johnsonps08]

What is the distance from the tank to the heater? For a mt250, 3/4 pipe, propane, the max effective distance (actual pipe length plus 5ft per fitting) is 50ft per the pentair chart. If you exceed this then you need to have the regulators swapped to 2 stage (red high pressure regulator at the tank, green low pressure regulator at the heater). I have 13" water column at the heater static and it drops by less than .5" active
Do you have a photo of the gas installation?
I've not futz'd with the gas valve on the mastertemp but the manual pretty implicitly says that it is an unconventional valve set at the factory and shouldn't be adjusted.

The propane tank is less than 20 feet from my heater and the regulator sits between the propane tank itself and the 3/4" black iron gas pipe I installed. There is maybe 4 linear feet of pipe from regulator to heater, excluding the sediment trap, but including an elbow.

I'm def getting more than .5" drop in WC, it was a approx 2" drop for me but I'm pretty sure the manual states that's within reason.

I'll report back with photos when I can but the propane company swears they've hooked up 1000s of machines the same way.