Hayward H400FDN - partially ignites

[W. Thompson]

We have an H400FDN pool heater. It is 12 years old and is used about 4-8 times per year. It worked this summer but stopped this fall.

If we pull the small cover on the left side (igniter access baffle?), the unit will light but only the left half of the burners appear to be lit. The left side of the vent is hot. The right side of the vent is cool. If the cover is in place, it will not ignite. If we remove the cover, it will ignite and stay on until the cover is replaced.

We have replaced the regulator, thermistor, and blower vacuum switch. We have had people come out to troubleshoot/repair it but they have not been able to solve the problem. I have checked the burner orifice and the burners to make sure they were clean and they are.

Any suggestions on what to check next?

 

[ajw22]

Welcome to TFP.

Everything you said points to a restriction in your gas flow.

As much as you say you checked the burner orifice and the burners to make sure they were clean I would look again and the whole path from the gas valve.

@Pool Clown @ps0303 @swamprat69 @1poolman1

 

[swamprat69]

This seems to be the manual for your heater universal-h-series-asme-heater-service-installation-manual.pdf (inyopools.com) It has an exploded parts view and list near the end of the manual. If the part you are removing is the ignitor access cover " FDXLIAC1930 " which is listed as part list #16 when only the left side burners ignite it would seem that you have a gas/air mixture flow problem through the burners. A more complete description of exactly what is happening would be helpful. Photos would be helpful. I can see that the ignitor is positioned at the left side of the burners, but it is difficult to see the exact position of the flame sensor? Again photos would be helpful. The position of the flame sensor is important because when you say it will stay lit, in order for that to happen the flame sensor must be sensing that there is a flame present at its location/position. The manual also contains instructions for removing and cleaning the burners and burner orifices, although it doesn't explain to you how to clean the burners or burner orifices. The parts list does not seem to list the "air box" as a replacement part?? I have seen this with certain specific parts on some other Hayward heaters. If you do remove any parts that seal with a gasket make sure that the gasket is still in one piece and seals correctly when parts are reinstalled. Gasket kits are listed as "not shown" parts at the end of the parts list, but do have Hayward part numbers. It appears that the service techs that have been servicing your heater may be a bit below adequate (throwing parts at the heater until they get it to work). Will be happy to try to answer any questions that you may have.

 

[Pool Clown]

If we remove the cover, it will ignite and stay on until the cover is replaced.

So if you have the heater running without the cover and you replace the cover, the flame dies? Sounds like an oxygen deprovision issue.

These heaters need to have the correct mixture of gas AND air, especially in the case of forced air appliances. They are alot more temperamental than naturally vented heaters with respect to the air/fuel mix.
I'm not a Hayward guy, but i think that those heaters have their blowers post flame, meaning that they draw the exhaust out of the firebox instead of pushing it through or having the blower PRE flame.
Something may be up with how the heater is getting its (fresh) air. Recheck the air inlet all the way to the flame, or to the point of introduction of gas. It cant pass enough air to create the right mix through the intake (can you smell raw gas out of the exhaust when it is not firing, but is suppose to be?) , BUT when you open the cover, you are letting air in to get a halfway decent mix, and you get minimal flame. Its probably a real sooty or rich burn. Kind of like when you have a heater that is enclosed in a room with little or no make up air.

Just a guess...

 

[W. Thompson]

Swamprat69 - thank you for the link to the installation manual. That will be helpful for instructions on removing and cleaning the burners. Everyone else, thanks for your suggestions. I will take the heater apart again and get some pictures to share. Give me a few days. Thanks again.

 

[swamprat69]

Swamprat69 - thank you for the link to the installation manual. That will be helpful for instructions on removing and cleaning the burners. Everyone else, thanks for your suggestions. I will take the heater apart again and get some pictures to share. Give me a few days. Thanks again.

Glad that I could be of some help

 

[CPS Reno]

Those burner orrifices are famous for plugging up when not used regularly. You can even buy new burner tubes if they're damaged beyond cleaning/repair.

 

[W. Thompson]

Here are some images of the burners, nozzle, and box. I have not observed any soot, but the first 3 burners, from the right side, are more corroded than the other 4. Although the first 3 are rusty on the surface the small holes on the top of the burners are clear. All the nozzles are clear as well.

I purchased a manometer, to check the gas pressure. The inlet pressure was 7.3 WC, which meets the specs. The outlet manifold would peak at 1.3 WC during start-up and then go down to 0.53 WC. I increased the pressure on the regulator to get a peak value of 1.6 WC, with a steady-state of 0.55 WC. I had to max the regulator out (turned all the way in) to get the 1.6 WC peak value. This is a new regulator and I can only get the heater to stay lit with the ignitor access cover removed.

I would appreciate any other suggestions.




.

 

[swamprat69]

Is the regulator that you are adjusting the one that is part of the gas valve? You need 1.8 to 2.0 inches WC at the gas manifold to the burners for the heater to run correctly. If you are only getting 0.55 " WC at the manifold then you are either losing pressure across the gas valve or are losing supply pressure upstream of the gas valve. If you check the pressure at the inlet side of the gas valve while the heater is running/heating and it maintains 7.3" WC, then the problem is with the gas valve. When you say the regulator is new, do you mean the gas valve is new?

 

[W. Thompson]

Correct, the regulator I am adjusting is on gas valve (part #17 on the diagram). You bring up a good point, I need to check the incoming pressure (high-pressure side) while it is running to see if it can maintain the necessary flow of gas. Thanks for the tip.

Yes, I purchased a new gas valve. There was no change after it was installed. I can't imagine the new gas valve is bad.

 

[W. Thompson]

Well, it appears to be a gas supply problem. Under load, with the system on, the high pressure reads 1.2 WC. We will work on the problem from that end and see what we get. Thanks for the help and suggestions.