Raypak P-R406A-EN-C Pool Heater

[Fitchinator]

Hi,

Hoping someone has an idea of how to fix my pool heater. I have a Raypak P-R406A-EN-C Pool Heater that wont stay lit. I turn the unit on, the pilot lights, the main burner lights and runs for a short time, then goes out. The pilot then tries to light but doesn't. Just clicks over and over.

Units faults are the following that alternate over and over
High Limit 2 Fault
No Pilot Sensed

I recently replaced the heat exchanger and then began having problems with the unit. It was turning off and on the same as it is now however with large explosions. I replaced the circuit board and pilot light thinking that might take care of it. It stopped the explosions but not the failure to stay lit. I broke down and had a local technician out to work on the unit and he thought the gas valve might be faulty and replaced it. He also said the pressure on both sides of the gas valve was low, likely due to the 3/4" supply line. I have been running this size of unit on this pool for 10 years and have never had these problems so while it appears that the gas pressure isn't what is called for, i'm skeptical that it is the problem. This particular unit is 3 years old. I am also getting banging in the unit when heating. One would assume this would be from scaling however I just cleaned it all out when I replaced the heat exchanger. Thanks for any help you can offer.

 

[1poolman1]

You may find that your small gas line to be a part of the issue. The flame at the pilot may not be large enough to be sensed, regardless of how well it worked in the past. Is this propane?

Start with no pilot sensed. If the flame is good, that is usually caused by a bad flame sense circuit. First, be sure that there is a good chassis ground and that the "green" wires at the valve and the burner tray are tight and have no corrosion at their connecting points. If they are, the flame sensor on the pilot burner may need to be cleaned. It is the fork above the actual pilot flame. It does require the burner tray to be pulled to get to it. It can be cleaned with a "Scotch" scrubber just to remove any coating that may be on it. Do NOT use sandpaper. There is a picture below.

A banging in the unit is water boiling in the exchanger. That will also cause a HiLimit 2 fault. Dirty filter, slow pump, clogged pump, anything that interferes with proper water flow can cause that. Internally it could be the UniTherm Governor. That is under the castle nut on the side of the manifold. Here is a video of how to get to it, though the poster calls it the thermostat.

Could also be the internal bypass.

 

[Fitchinator]

It is a natural gas unit. I am at a loss as to why, but the unit has remained lit and heating for approximately 18 hours for no apparent reason. Weather has gotten colder is all and I had a SW Open error code just prior to starting it up again.

 

[1poolman1]

It is a natural gas unit. I am at a loss as to why, but the unit has remained lit and heating for approximately 18 hours for no apparent reason. Weather has gotten colder is all and I had a SW Open error code just prior to starting it up again.

Do you have a VSP? SW Open is the pressure switch not closing. That is a water-flow issue, possibly the heater is calling for heat before the pump has started moving enough water to close the switch. Or the system has not completely filled with water after being off. Once there is enough flow the error goes away.
It will also show up at times if you try to turn the heater on and the pump is not yet running.