Boiler intermittently not turning on

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Jersey5.0

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Hi All,

Hoping for some help here.

I have a newer Slant Fin boiler (3 years old) with a Carlin Model 99FRD burner. It uses a Honeywell L7224C 1004 aquastat. My boiler makes my hot water through a coil inside the boiler.

My issue is this: About once every 2 weeks I find that I have no hot water. I take a look at the boiler, and the water teamperature is the same as outside ambient temperature, and the boiler is not on.

I take a look at the aquastat, and it has set no error codes. The Aquastat has an board that displays the correct temperature. The temperature displayed on the board is roughly the same as the temperature that I see in the mechanical guage on the boiler, so I'm assuming the temperature sensor is reading correctly, and the aquastat is able to understand the temperature reading from the sensor. There are some LED lights on the aquastat that are blinking when the issue is occuring. I can't find any wiring damage or loose connections on the aquastat.

If I flip the service switch off and then back on, the relay for the aquastat clicks about 5 times, but the boiler still does not start.

My boiler uses an auto bleeding system with a clear bulb, so I can see that that oil is going to the burner, no issue with oil supply.

If I press the reset button on the burner, the boiler immediately fires up with zero issues, and will work correctly for weeks at a time.

I had the boiler recently serviced hoping the issue may be a clogged nozzle or filter. Filters and nozzle were replaced, boiler was cleaned inside, tuned, and given an OK health check. The problem still persisted after.

At this point I'm kind of stumped. I'm leaning towards having a bad aquastat, but don't want to throw $140 at it without something a little more concrete to test.

I can't see it being oil related, as I never have an issue using the reset button. I can't see it being wiring related for all the same reasons. I don't think it's the temperature sensor because the read out from the sensor diplayed in the aquastat is correct.

It seems as though the temperature sensor is telling the aquastat that the water temperature has dropped down, but the aquastat isn't commanding the burner on. I am not opposed to calling a professional, but to be honest I think it would be quite challenging being that it happens so intermittently and randomly.

Any insight would be amazing,
Thank you
 

Dana

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If resetting something the burner clears it and gets it to run correctly (for awhile) the problem is with the burner, not the aquastat. The aquastat doesn't seem to have an error code for the burner not firing, at least on the short-sheet reference guide but the flashing LEDs mean that it's algorithms have detected that something isn't right.

If resetting the aquastat cleared it and got it running again it could be either a bad aquastat or an undiagnosed intermittent elsewhere that put the aquastat in a state that caused it to inhibit the burner (a possible safety default for dealing with conditions that can't be properly dianosed in the aquastat itself.)

I assume you've pored over the specs/manual for the burner?
 

Jersey5.0

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If resetting something the burner clears it and gets it to run correctly (for awhile) the problem is with the burner, not the aquastat. The aquastat doesn't seem to have an error code for the burner not firing, at least on the short-sheet reference guide but the flashing LEDs mean that it's algorithms have detected that something isn't right.

If resetting the aquastat cleared it and got it running again it could be either a bad aquastat or an undiagnosed intermittent elsewhere that put the aquastat in a state that caused it to inhibit the burner (a possible safety default for dealing with conditions that can't be properly dianosed in the aquastat itself.)

I assume you've pored over the specs/manual for the burner?

Thanks for the response. I've gone through the troubleshooting guides for the burner and aquastat, but unfortuntately can't pin point the issue. I wish that whatever was going on would just happen consistently at this point so I could diagnose it a little easier.
 

BadgerBoilerMN

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Thus the need for a sharp tech.

I would lean to the faulty aquastat, but you want to make sure it is installed properly.

And, get rid of the tankless coil, a real waste of fuel. You want a proper indirect-fired water heater unless you live above the Arctic Circle.
I like Trin & Stor, SuperStor and MegaStor for a lifetime of carefree DHW.
 

Dana

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If it were a faulty aquastat I would have expected a power-on reset to have cleared the problem, not resetting something on the burner. I haven't looked at the manual for the Slantfin for hints on how they hooked it all up though.
 

Jersey5.0

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So, I dug a little deeper into the potential that something in the burner causing this.

What Dana is saying makes sense. A reset of the burner is actually what gets it going rather then a reset of the aquastat.

I took a look under the ignitor to see if I noted anything odd with the electrodes, which I didn't. Not burnt, carboned, etc.

I took a look at the spark produced from the ignitor when I turned the boiler back on quickly, and within a split second it lit up, so I don't think it's likely an issue with the ignitor, at least not what I would go for first.

At this point I'm thinking I may have it narrowed down to the CAD cell or the electronic oil burner controller, the control box that the reset switch is on and that the CAD cell wires into.

I think I'm going to replace the CAD cell and see what happens. For the price I think it's worth it to try that and see before I replace the controller.

Thoughts?
 
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