Pentair Pool Heater makes a loud bang (backfire?) when it ignites.

[Pdxonthego1]

Thanks @Pdxonthego1. I’ve had to put this on hold for a bit as my son just got married, but I’ll be tearing into this shortly. Not sure how the 206a compares to the pentair or if there is a similar “sping in the heater core of the bypass line” but it’s with checking out. I’m also wondering if it’s related to the gas valve. But I’m going to pop open the can and check the coils first.

016194F KIT-BYPASS VALVE PLASTIC 206A-408A​

that is the spring (on the bypass line in the manifold) is for the banging when starting up from cold water only…

not the explosion noise (like delayed ignition of the burner tray

the explosion noise is air gas mix and is a danger to not fix for Sure.

 

[Poolbreh]

The only time I have ever heard that is when there was water in the gas line. Yes, it can happen.

Or the chamber is full of water, you can pull the bottom bolt on the manifold and see if water comes out.

 

[RJS3]

@ajw22 @swamprat69 @1poolman1

So I have an update on this heater. I had a wedding in July and life got in the way of taking some next steps on this problem. But I borrowed a manometer and hooked it up to the valve today. I turned on the gas and found that the static pressure (the pressure before the heater was turned on) was between 5.6 and 5.8 inH20. I understand that it should be about 10 inH20.




When I turned on the heater it dropped down to about 2.5 inH20 and then I heard the bang or backfire.

So my assumption is that the meter is not pushing enough gas through the pipes (which would be odd I think) or there is a clog in the pipes. Should I start unscrewing the gas piping back to the valve and see if there is any blockage. Or should I call the gas company and have them check the meter?

This heater has been running fine for many years, so unless something happened to the gas pressure, I am assuming there is a clog, maybe at the valve. While I have the manometer, I can at least unhook the pipe from the value and test for pressure. Thoughts on this strategy.

 

[ajw22]

Call the gas company and have them check the gas meter. I had a gas meter fail and stop the gas flow.

If the gas meter checks good then you may have a collapsed line between the meter and heater.

 

[RJS3]

Thanks @ajw22
Wondering if @ps0303 has a thought on this. He helped someone earlier in July with a gas flow issue.

 

[john4]

My next suggestion was going to be to inspect the burner. I've never heard or seen rodents in the combustion chamber, but maybe. Also, look for a cracked burner. That would allow too much gas into the chamber and cause explosive ignition. Again, never seen it in a Max-E-Therm/ MasterTemp.

I have the same backfire problem. Finally got some time to disassemble it and found a blowout on the burner.

 

[kyleross]

So here is an update to this issue. At the suggestion of @1poolman1 I checked the gas line for water (don't smoke ), and all looked good. The cap to the gas trap looked brand new, gas flowed out normally and I could not detect any gurgling sounds or water dripping or anything out of the ordinary.

Following the Pentair tech advice, I checked the Termal Regulator as well. I pulled it out and tested it under hot and cold running water. It worked flawlessly. I reinstalled it. The new ignitor came. I installed that. (FYI: The Pentair tech told me I probably didn't need an ignitor because when they go, they don't light at all. And this one is lighting as was the old one.

So after everything was back together, I tested it. Same issue happened. Heater turns on, the valve opens, the ignitor lights, and there is a bang and it does not stay lit. Now that I am a bit more used to this and not thinking it is going to blow up, I did pay closer attention to the blower when it did this, and I noticed that the air orifice/intake blew off when the bang happened. Here is another short vid illustrating this: <

>.

The fan is spinning freely so I doubt there is an issue with the fan or housing. But I am wondering now about the AFS or tubing in and out of the AFS. Not getting an error code, but I wonder if that is the problem. Any thoughts?

did you ever sort this out\/ i have the same issue, only the odd time, runs fine for about 10min then bang, blows off the intake screen and shuts down

 

[AlanLi]

I had exactly the same issue. Finally, I found the reason is a broken air orifice connection as attached pictures showing. There is no more backfire after replaced with a new air orifice.

 

[canada001]

I had a similar issue with my pentair mastertemp heater. When it would startup, there would be a loud bang after the gas ignition.
I had a technician look at it, couldn't find the issue. Gas pressure was ok.
So I decided to change the igniter, just in case. Turns out, the old igniter had become loose, with only one of the screws tight. And there had been rust in the area where the seal should be. I think this would allow gas to escape and then ignite outside the chamber.
Hope that info helps someone else with similar problem!

 

[Reynoldsrl]

Pentair Mastertemp 400 had loud gas bang when first starting up. Found that the gas igniter measured too high resistance of 150 ohms. Resistance should not exceed 80 ohms. Lower current draw caused the igniter to delay reaching the critical temperature necessary to ignite the gas. So gas was flowing before the temperature was reached then BANG!!