Sta-rite Pool Heater Problem

[Steve Mead]

I have a 10 year old Sta-Rite 400k BTU heater. Recently it started shutting off before it reaches the programmed temperature. It will fire up fine, run for a couple minutes, the burner shutes down and the heater act as though it has reached temperature and starts to shut down. It then fires up again and repeates the process. It eventually reaches the programmed temperature (a long process with all the shut downs) and shuts down as normal. There are no error codes. I'm thinking it's the control board. Any other possibilities?

Thanks

[Pool Clown]

The thermostatic by-pass has failed

Remove the by-pass here.

use a screwdriver and remove like so. Be careful as when the plug reaches the end of the threads, the spring will take over and snap the assembly out with a little force, so keep the fingers clear.

This is what should come out.

What you are looking for is any corrosion or erosion at the brass bulb. Could be rust or a kind of teal color and a crack that proves the bulb had been compromised. Replace the assembly as a whole (thats how it's sold). And you are good to go.

Forgive the dog hair, these pics were taken in my shop , which doubles as the dog house... or is it the other way around?

[Steve Mead]

Thanks very much Pool Clown, I'll give that a try.

The thermostatic by-pass has failed

Remove the by-pass here.

use a screwdriver and remove like so. Be careful as when the plug reaches the end of the threads, the spring will take over and snap the assembly out with a little force, so keep the fingers clear.

This is what should come out.

What you are looking for is any corrosion or erosion at the brass bulb. Could be rust or a kind of teal color and a crack that proves the bulb had been compromised. Replace the assembly as a whole (thats how it's sold). And you are good to go.

Forgive the dog hair, these pics were taken in the dog house, Which doubles as my shop.. or is it the other way around?

[sharon333]

Very helpful pics. Thanks!

[Steve Mead]

Thanks Pool Clown! That fixed my problem

[ggman]

Thank You. About 10 minutes for a solution. What took you so long. Seriously very impressive.

Greg

[Beachbreeze]

I had the same problem last year and changed the by pass valve, it was corroded, and that solved the problem. When I went to turn it on again this year, the same problem occurs. I checked the by pass and it looks fine. Tested it in a pot of boiling water and it opens and closes fine. I put it back in and still have the same problem. Any suggestions?

[Pool Clown]

Was the bypass a little difficult to remove? Like the spring was hung up on something? That is an indication that the flow bypass(different by-pass) is broken. That would cause the heater to fire, run less than a min, then shut off.

[Beachbreeze]

No, it came out fine and went back in okay.

[Pool Clown]

when it shuts off, are either of the trouble lights on? (service system, or service heater)

[Beachbreeze]

The service heater comes on. I tried it today and it ran for about seven minutes before shutting down. First the gas shuts off and after the cool down, the blower shuts off.

[Pool Clown]

Does it shut off at the same temp each time? If you take the control board off (top of the heater) the underside may give clue as to what is up. There may be an LED lit with a corresponding 3 letter code printed on the board.

[Beachbreeze]

Temperature doesn't seem to be an issue. I'll check that tomorrow. I was told in the past that you could check the flue temperature by holding down to buttons on the control panel, but I can't remember which ones they were. I was thinking of taking the flue stack sensor from my working one and swap it and see what happens.

[Pool Clown]

It would be easier to look under the board for a fault light. BTW one of the fault lights is the stack flue sensor (SFS).

[Beachbreeze]

Today I went back and took the covers off and started it up. After running for five minutes the entire unit shut down and the AFS led on the back of the control panel was on. The diagnostic led on the ignition module flashes repeatedly one time indicating air flow fault. A few things I noticed was a bunch of yellow insulation around the bottom and by the gas module. I also noticed a few bite marks on a couple of wires, nothing broken. I noticed this a month ago and cleaned most of the insulation out. I did leave behind a poison rat pellet that is gone. Everything seems to point to the blower unit. Any ideas? Oh, I did not swap out the stack sensor.

[Pool Clown]

Rats could have chewed on the air flow switch hoses, check those, also make sure they are connected well( don't slip off easily). They are the clear ones. Otherwise could be the blower if it is not putting out enough air flow. Hard to tell if you don't have a good known air flow to compare it to.

[Beachbreeze]

I checked the air flow hoses and they were intact. I'm thinking maybe the first time I turned it on some insulation may have gotten sucked into the blower. I'm going to pull it off and see if there is anything blocking it.

[Pool Clown]

Look closely at the motors' windings. you might even want to bend down and smell them. If they smell or look burned, then it is the blower. They should be a shiny copper color all the way around. You can have a burnt phase in the motor and it will still turn on. It just wont spin as fast. If you ever noticed the blower before, and remember how it sounded when it started up, then you may be able to tell now if it sounds differently when it comes on. When the blower is burnt, it spins up a bit slower, but if you never noticed it, you probably wouldn't be able to tell.

[Beachbreeze]

I've already had to change two blower motors. I did look at the windings and everything looked fine, no burnt smell. I have two units, one working and this one so I can compare them. Been raining for two days now, I'll let you know how I make out taking the blower off and cleaning it. Thanks for the help.

[Pool Clown]

Hmmm. Just for the heck of it, take the lower flange bolt out and see if any water comes out.

Look at the very first post of mine on this thread. See the four shiny bolts under my hand? Take the lowest one out.

[Beachbreeze]

I did not see any pictures in your first post on this topic. Are you referring to the bolts that hold the water inlet/output manifold. I see in the diagram that there are four insulation blankets. Like I said, there was quite a bit of chewed up insulation around the outer part of the heat exchanger. I'm thinking instead of taking the blower off, just removing the one piece metal elbow/combustion chamber cover assembly. I'm wondering if there may be a nest or torn up insulation in there that is restricting air flow form the fan to the flue stack.

[Pool Clown]

[Beachbreeze]

I'm sorry, I thought you said in your hand. That's the bolt I was going to remove. What will that indicate?

[Pool Clown]

That will tell if you have a hole in the exchanger. If you do, the box could be full of water up near the outlet of the blower. the blower pushing air into a full box of water will not allow the proper flow of air through the blower to keep the airflow switch closed. It is a stretch, but something to check/rule out and only takes two min.

I think at this point its the blower, or the switch. Unfortunately, I've replaced more blowers than air switches.

[Beachbreeze]

Well, took off the blower and everything looked good in there, no blockage. No water in the exchanger. Looks like I'm going to have to start looking for prices for the blower online. Cleaned out more insulation and left the rats another treat.