Sta-Rite SR200NA air flow sensor LED on

[faithie999]

When I turn the heater on, the blower comes on but the AFS LED is lit.

There are three plastic tubes attached to the blower inlet. One goes from a metal nipple on the bottom of the air inlet to the AFS, one goes from one of the plastic nipples on the plastic air inlet housing to the AFS, and the third goes from the other plastic nipple on the air inlet housing to the gas ignition module.

When I remove the tube from the metal nipple on the bottom of the air inlet and suck on it (keeping attached to the AFS), the Service Heater light goes out and after a short time delay the heater fires, and the blower seems to accelerate somewhat. When I suck on the other tube attached to the AFS, it has no effect.

When I remove the "metal nipple" tube from the AFS, with the blower running, and improvising a manometer using a plastic tube filled with water, I measure 1" of vacuum.

Does that condemn the blower or the AFS switch?

Thanks

Ken

 

[Poolbreh]

Are you on LP or NG? Any new additions to the stack flu? Is the heater inside or outside? Did you clean out all the barbed orifices where the tubing connects?

 

[faithie999]

Natural gas. no mods to flue. heater is outside. all 3 tubing connections are clear and clean.

it would be great if I could find the spec for the AFS, which is

Pentair 42001-0061S​

so I can determine at what vacuum (inches of water) the switch is supposed to close allowing the ignition sequence to start.

I'd like to know this so I can decide whether to take the fan housing apart and see if there is anything inside that is hindering the proper air flow. it doesn't appear to be a trivial task to disassemble the fan, starting with needing to take the gas piping apart.

 

[Poolbreh]

I think you need a manometer with a positive and negative. You would be measuring the differential between the suction and pressure. I don’t think you can do it with a slack tube accurately.

 

[Poolbreh]

@JamesW @ajw22 could you offer some insight

 

[Poolbreh]

No rat damage? No possible way of rats pulling debris into blower? You can check the flame holder and combustion chamber for soot buildup, it’s a big task though. But this could restrict airflow. If all is well I would say it’s the afs.

 

[faithie999]

I have an endoscope camera that I had forgotten I had. I will fish that down into the tank via the hot air outlet tomorrow and see what I find. there is no obvious damage on the outside. but I did find a snake skin under the top cover left behind by a snake that molted, and a nice hornets nest with a dozen very unhappy hornets.

 

[swamprat69]

You should not suck on the tubing attached to the pressure switch. You can suck a lot harder than the switch parameters can handle and might damage the diaphram. It would be easier to troubleshoot the air presure switch and other problems using a dual port differential manometer. The setting on the switch appears to be 1.25" WC as the 42001-0059 and the 42001-0061S seem to cross reference as the same part (Pentair may have changed suppliers).

Pentair 42001-0061S Air Flow Switch Replacement for MasterTemp and StaRite Max E Therm Swimming Pool and Spa Heater System Amazon.com : Pentair 42001-0061S Electrical System Air Flow Switch Replacement Pool and Spa Heater : Outdoor Spas : Garden & Outdoor Sta-Rite Max-E-Term Heater Air Flow Switch 42001-0061S Free Shipping Pentair 42001-0061S Air Flow Switch for Sta-Rite Max-E-Therm and MasterTemp Heaters

 

[faithie999]

I think I have my answer. I removed the blower and found that the diffuser receptacle that the air/gas mixture discharges into was packed full of fiberglass insulation. It is the type of insulation in R-11 batts, not the rigid insulation that is inside the combustion chamber. plus, the only way into that "cup" is through the fan.

after removing the "mouse house", the airflow is now normal and the heater ignites.

 

[faithie999]

on further reflection, I decided to take the temp of the top of the combustion chamber with an IR thermometer. there is a small section that measures about 300F so I guess that's where the mouse found his building material. I will be replacing the top and bottom insulation pads in the chamber.

 

[ajw22]

Look at rat proofing the heater. MK Rat Proofing sells wire mesh kits to cover the vents or you can fabricate your own using 1/4" mesh wire screen or simple chicken wire and some sheet metal

 

[faithie999]

Look at rat proofing the heater. MK Rat Proofing sells wire mesh kits to cover the vents or you can fabricate your own using 1/4" mesh wire screen or simple chicken wire and some sheet metal

since the nest was in the perforated cylinder into which the fan exhausts, the only way into there for the mouse would have been through the intake side of the fan, and then through the channels in the impeller, to reach the cylindrical chamber. so I will put some hardware cloth over the fan intake, as well as on the exhaust port. the mouse must have entered the exhaust port to gather the insulation from inside the combustion chamber and then carried the insulation into the fan exhaust cylinder to built the nest.