Automatic water feeder that won’t fail in on position

But nothing is infallible.

You did not say what type you have.

Folks here seem to like the Hydrolevel VXT. To me they all can fail, there is too many reasons an Automatic water feeder unit can fail and flood the boiler. The valve could stick open or leak, the electrical switch or electronics could fail. Some have timers too, but depending what fails the timer may be useless.

If you have a probe type LWCO, the lack of maintenance or the electronics could fail commanding the feeder to fill the boiler indefinitely. If it is a float type LWCO the float can leak and sink.

How did yours fail ??? What type do you have ?

If you just want to deal with the Automatic water feeder you could pipe two in series with a common electrical trigger. Chances are they both won't fail at the same time.

There is a thread here on HH that someone modified a LWCO to act as a high limit (I can't find it so far). I don't recall how it stopped the water flow.

Another backup plan is a Normally Open contact type pressuretrol (like the ones on eBay that nobody wants) and a Normally Open Magnetic valve. At 56 inches (2 PSI of water pressure above the pressuretrol) the pressuretrol's switch would close, energizing the Magnetic valve, closing its valve cutting off the water flow. If the normal pressuretrol trips at 1.5 PSI there will be no heat anyway stimulating an investigation.

There is many ways, how reliable, only time will tell.

The question is — what failed, or could fail? The feeder? Or the switch that controls the feeder? You have to address both potential failures, and the water level sensor (whether float or probe) is just as likely to fail as the feeder valve is to stick open.

The idea of two feeders in series, triggered by the same trigger, has merit, as it reduces (does not eliminate) the chance of the feeder failing open. It does nothing to address the problem of the probe or float failing on. Better would be to add another trigger (preferably of a different type) in addition to the two you have (I hope you have two, one manual, if this is a rental/commercial properly?) and use that to control the second feeder. All of the three sensors would also be low level cutoffs for the boiler as well, of course.

Better yet is regular maintenance and attendance on the equipment…

Steam boilers should be checked daily! The more you add the more there is to fail.

OK…. Isn't the cg400-2090 A LWCO (Low Water Cut Off), not an auto feeder ? " cg400-2090 is what was on there. "

So the LWCO actually failed ?

What is your Auto feeder ?

No wonder you had a problem.

Redo it correctly.

I suspect the relay inside the CG400 LWCO is not rated for the load of a solenoid coil and eventually the relay's contacts weld closed causing constant water feeding. Comparably the VXT Auto feeder's Feed Signal input load is probably quite small and non inductive.