Brand New Pentair MasterTEmp 250 wont fire up

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Rebelyelljr

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May 15, 2022
11
Pittsburgh PA
Help.

We replaced our previously blow Pentair MasterTemp 250 with the exact same model, thought 5 years newer, same plumbing same position everything and when we set it up exactly as is out of the box, it wont kick on. We have put a manometer to the test port on the outsdie the heater and there is plenty of gas there. Is there a way it calls for gas or primes the heater itself? We can seem to figure out the issue. We've tested all the electric and seems everything out of the box is working fine but it just does call of for the gas or prime it into the heater. Any help is so appreciated. I feel like we are just missing something simple.
 
This a NG or propane heater?

On a new gas heater hookup there can be air in the gas line that needs to be purged before you get a consistent gas flow. People have reported it taken 20 or more tries before the air is purged.

How many times have you reset the heater and tried to start it?
 
ajw22 said:
This a NG or propane heater?

On a new gas heater hookup there can be air in the gas line that needs to be purged before you get a consistent gas flow. People have reported it taken 20 or more tries before the air is purged.

How many times have you reset the heater and tried to start it?
Click to expand...
we went 2 hours letting it attempt to run. at least 100 start up cylces. No dice.
 
Just to clarify, I have 12"WC gas at the valve assembly. I have checked it on the output side and have 0 at all times. It has been started up and cycled at least 100 times by now. Checked all the applicable sensors. Still have 0 psi output through the burner/valve assembly. Checked voltage and it is correct also. After about 20 mins of trying to ignite I will get an AGS error. I have checked the AGS sensor as well and it is working correctly. Reset system and it repeats the same process. Flame status read N/A as well. Ignitor checked out good 50 Ohms.
 
Do you have 24v at the main gas valve? Do you hear a definite "click" of the gas valve opening? If not no gas is getting to the burner.
Please check again that the main gas valve in the heater is in the "on" position.
 
Rebelyelljr said:
.After about 20 mins of trying to ignite I will get an AGS error.
Click to expand...

This says the heater lit and ran for 20 minutes. The AGS error is an overheat that causes the gas valve to close. Water temperature after the 2nd pass thru the heat exchanger is more than 140°F.

A failure to ignite should give an ignition error - ERR IGN.

Does your heater keypad have six buttons or five buttons?

If this is a new heater why not make a warranty claim with Pentair?
 
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ajw22 said:
This says the heater lit and ran for 20 minutes. The AGS error is an overheat that causes the gas valve to close.

A failure to ignite should give an ignition error.

Does your heater keypad have six buttons or five buttons?

If this is a new heater why not make a warranty claim with Pentair?
Click to expand...
0" water column on the valve output side means there can't be combustion, no fuel. Something not right here.
 

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The manifold pressure will be -0.2" wc.

The manifold pressure is tricky to test as shown in the manual.

What happens to the inlet pressure as the heater tries to fire?

Does it stay the same or drop?

Can you show a picture of everything and a video of the heater trying to start?

Is the input voltage 120 or 240?

Did you change the voltage selector plug?

Note: Do not use the wrong selector plug or you can seriously damage the heater.

Do not change the plug unless you are 100% sure.
 
1poolman1 said:
Do you have 24v at the main gas valve? Do you hear a definite "click" of the gas valve opening? If not no gas is getting to the burner.
Please check again that the main gas valve in the heater is in the "on" position.
Click to expand...
If you are not feeling heat at the exhaust, but smell gas, no ignition. If no heat and you don't smell gas at the exhaust, the valve, most likely, isn't opening.
 
If the inlet pressure stays the same during attempts to fire, the gas valve is not opening.

The inlet gas pressure should drop a little bit, but not too much, if the valve is opening.

If the pressure drops too much, the problem is the gas supply.

You can also check to see if the ignitor is getting current during attempt to fire.
 
Rebelyelljr said:
Just to clarify, I have 12"WC gas at the valve assembly. I have checked it on the output side and have 0 at all times. It has been started up and cycled at least 100 times by now. Checked all the applicable sensors. Still have 0 psi output through the burner/valve assembly. Checked voltage and it is correct also. After about 20 mins of trying to ignite I will get an AGS error. I have checked the AGS sensor as well and it is working correctly. Reset system and it repeats the same process. Flame status read N/A as well. Ignitor checked out good 50 Ohms.
Click to expand...
Please show a picture of your installation, including the gas supply.
 
Testing the manifold pressure is tricky and usually not necessary.

The gas is introduced before the blower (suction side), which causes the manifold pressure to be below zero (vacuum).

In any case, the inlet pressure will usually tell you enough if you watch it while the heating is trying to fire.

In the video below, you can see the inlet pressure go below zero due to a gas supply problem and the blower trying to pull in the gas through the valve.

If the pressure did not drop at all, then the gas valve is not opening.

The pressure should drop by about 2 or 3 inches of wc from static if the gas valve is opening and the gas supply is sufficient.

 
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I see a flexible gas line leading to your gas regulator.

The Installation Manual says "The use of Flexible Connectors (FLEX) is NOT recommended unless they are properly sized according to the supplier recommendations for the heater rating."

Do you know what the capacity rating of that flex line is?
 

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