Natural Gas Pool heater experiencing delayed ignition - Troubleshooting

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J

JoshFink

Member
Jan 23, 2022
7
Atlanta, GA
Hi Folks, I'm hoping someone can point me in the right direction here.

I have a relatively new Pentair MasterTemp 400 Natural Gas Heater. The heater works well when running but I'm having a delayed ignition issue where ,sometimes, when it clicks to turn on it will delay and then start about 30 seconds later. When it does this I'm guessing the combustion chamber is filling up with gas and then igniting which creates a big boom. Sometimes flames shoot out the vent and sometimes it does not.

While it still works great, I hate having something that is new do this.

I've had the company out that did the installation and he seems to think it is low gas pressure. However, unless the specs on the MasterTemp are incorrect then it shouldn't be causing an issue.

I've tried a lot of difference scenarios to see if perhaps something was going on that might be dropping the pressure. The Pentair manual says that the minimum is 4in W.C. and Maximum is 14in W.C.
With the manometer hooked up to the inlet port:
  • Everything off at the house that uses gas:
    • Before ignition I'm right about 7in WC. Which is right where it is set from the gas company.
    • Turned on and heating - 4.62in WC
  • Running the Tankless + the Pool Heater - 4.58in WC
  • Tankless + HVAC Heater1 + Pool Heater - 4.46in WC
  • Tankless + HVAC Heater 1 + HVAC Heater 2 + Pool Heater - 4.33in WC
  • Tankless + HVAC Heater 1 + HVAC Heater 2 + All 5 burners on my stove top + Pool Heater - 4.32in WC
Any ideas here? I mean it could be low gas pressure but I'm hoping it's something else as the gas regulator is outputting as the designated specs of the gas company and the 7in WC is where they would expect it coming directly off the meter. It's a small run from the meter to the pump.

Thanks for the help
 
You may not have a large enough meter at your house. Most residential meters are able to allow 175-250 cubic feet of gas per hour. Your meter will have a rating plate on it. Your heater alone wants 400. You are barely meeting minimum requirements when other appliances are on.
Just because a manual says it can doesn't mean it will work.
 
You can check the manifold gas pressure.

Maybe check the voltage and current going to the ignitor.

Is the supply voltage 120 or 240 volts?

You can watch the gas meter to see how much gas is being used.

The amount should be about 400 cubic feet per hour or 6.67 cubic feet per minute.

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1poolman1 said:
You may not have a large enough meter at your house. Most residential meters are able to allow 175-250 cubic feet of gas per hour. Your meter will have a rating plate on it. Your heater alone wants 400. You are barely meeting minimum requirements when other appliances are on.
Just because a manual says it can doesn't mean it will work.
Click to expand...
I would have normally thought that but the gas company came out 3 months ago and installed a meter for 1000 cubic feet per hour.
 
JoshFink said:
I would have normally thought that but the gas company came out 3 months ago and installed a meter for 1000 cubic feet per hour.
Click to expand...

Post a pic of your gas meter showing the label on it with its CFH rating.

Also show the size of your gas line feed to the heater. While your meter may have capacity your gas line may be undersized.
 
Last edited:
The inlet gas pressure is staying above 4" wc, so that seems ok.

The delay is a concern.

Can you post a video of the heater trying to start?

Are there any error codes?

You can check the flame current to see if it is good.

Check the stack flue temperature to see what that shows.
 
Since it's new, file a warranty claim with the installer or Pentair and let them figure it out.

You should get a properly working heater, not a problem that you need to diagnose and fix yourself.

The installer seems unsure about what the problem is and if they are not going to deal with it effectively, ask Pentair to assign a certified warranty service center to get it right.
 
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I posted this and then went to the airport shortly after. I really didn't expect such a fast answer. THANK YOU ALL.

I do have some of the info with me and i'll be back home tomorrow to get the rest.
JamesW said:
You can check the manifold gas pressure.

Maybe check the voltage and current going to the ignitor.

Is the supply voltage 120 or 240 volts?

You can watch the gas meter to see how much gas is being used.

The amount should be about 400 cubic feet per hour or 6.67 cubic feet per minute.
Click to expand...
The voltage is 120. I should probably watch the gas meter and see how much is being used. Good idea. I will do that.

Using the manometer is how I got the numbers about.

ajw22 said:
Post a pic of your gas meter showing the label on it with its CFH rating.

Also show the size of your gas line feed to the heater. While your meter may have capacity your gas line may be undersized.
Click to expand...
gas meter.png

I called the gas company before I got the pool heater installed. I told them all about the appliances that I had that used gas and they installed the 1000 C.F.H. meter. They also came out and replaced my line from the street to the meter. It was originally a 1/2" line and they replaced it with an 1.25 or 1.5" line. I think 1.25" line.

JamesW said:
The inlet gas pressure is staying above 4" wc, so that seems ok.

The delay is a concern.

Can you post a video of the heater trying to start?

Are there any error codes?

You can check the flame current to see if it is good.

Check the stack flue temperature to see what that shows.
Click to expand...

I do have a video that I can upload. I need to find it. It doesn't show much other than it not starting and then a boom.

I didn't see any error codes but I can check again. I have no clue how to check the flame current and stack flue temperature but I'll do some looking around to see what I can find to get it.

JamesW said:
Since it's new, file a warranty claim with the installer or Pentair and let them figure it out.

You should get a properly working heater, not a problem that you need to diagnose and fix yourself.

The installer seems unsure about what the problem is and if they are not going to deal with it effectively, ask Pentair to assign a certified warranty service center to get it right.
Click to expand...

This is probably what I will do. I had called Pentair yesterday, before I posted this, but their systems were down for some reason and teys aid to call back today. I'll probably do that when I get done typing this out.

Thanks for all the help.
 

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JoshFink said:
They also came out and replaced my line from the street to the meter. It was originally a 1/2" line and they replaced it with an 1.25 or 1.5" line. I think 1.25" line.
Click to expand...

What about the line from the meter to the heater?

Especially the line into the heater where some isntallers use flex pipe that is too restrictive?
 

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com www.troublefreepool.com

If you hold down POOL or SPA button for at least 10 seconds it displays the exhaust temp. Normal temps should be ~290-350.

Turn the heater on. The fan will come on for about 30 seconds, then you will hear a click, and the heater should fire. At that moment, which ever thermostat you are using (POOL or SPA) hold that button down for ~10 seconds. Display should change from water temp to exhaust temp. Normal temps should be in the range of 290-350.

While running, press and hold the On button will display the exhaust temperature display.

Here is what the normal exhaust temperature should be:

  • Below 250 degrees...very low
  • 250 to 290 ..................low
  • 290 to 350.................acceptable
  • 350 to 480 ..................high
  • Above 480...................error/shutdown.
Note: HD models can be up to 75 degrees higher. HD models use a cupro nickel exchanger and the efficiency is slightly lower resulting in less heat transfer and more waste heat.
 
JamesW said:

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com www.troublefreepool.com

If you hold down POOL or SPA button for at least 10 seconds it displays the exhaust temp. Normal temps should be ~290-350.

Turn the heater on. The fan will come on for about 30 seconds, then you will hear a click, and the heater should fire. At that moment, which ever thermostat you are using (POOL or SPA) hold that button down for ~10 seconds. Display should change from water temp to exhaust temp. Normal temps should be in the range of 290-350.

While running, press and hold the On button will display the exhaust temperature display.

Here is what the normal exhaust temperature should be:

  • Below 250 degrees...very low
  • 250 to 290 ..................low
  • 290 to 350.................acceptable
  • 350 to 480 ..................high
  • Above 480...................error/shutdown.
Note: HD models can be up to 75 degrees higher. HD models use a cupro nickel exchanger and the efficiency is slightly lower resulting in less heat transfer and more waste heat.
Click to expand...
I'll check this out tomorrow when I get home.
 
JoshFink said:
Maybe it's 240. It's whatever it came with. I didn't change a thing.
Click to expand...
You need to make sure that the correct plug is installed.

Do not change the plug unless you are 100% sure.

Low voltage can make the fan run slow and the ignitor to not reach full temp.

Low voltage usually means that the heater won't work at all, but it might.
 
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JoshFink said:
I've had the company out that did the installation and he seems to think it is low gas pressure.
Click to expand...
A vague guess about the problem is not an acceptable answer to the problem.

If they are a competent installer, they need to take responsibility for making it work 100% correctly and not expecting you to figure it out and fix it yourself.

Is the installer a competent qualified licensed installer with the correct licenses and permits?
 
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