Boiler Burner Problem

Surprised to hear about boiler controlled by/controlling not temperature but pressure (you prob need to give more info about it)

It is obvious that some other safety device is keeping the burner off untill the pressure (or maybe temp ?, or flow ?) reaches a certain level.

well we enter our desired pressure not temperature and ofcourse you are forgetting gay lussac's law but the boiler remembers :P

How is the burner restarted? What sort of ignition system is used? Is the valve regulating the flow of fuel stuck or sluggish with deposits? Is there a control output signal present from the card under the stated condition?

The boiler is controlled by PLCs. Everything is automated like raw water tank filling, feed water tank filling, filling of boiler with water, blow down.

I have checked gas supply is ok, sensors are working fine, they even indicate burner need to be turned on and pressure need to be increase but burner just doesn't start. There is no indication of any electronic component over heating. Electric spark works fine. I am so confused.

It sounds like a PLC input problem. If the lower setpoint is determined by a pressure switch, you may be using the wrong contacts. If the setpoints are controlled by the PLC based on a single pressure transducer, you will need to look at the program loop which controls the restart.

Hope this helps. Without a LOT more information (PLC type, sensor type(s), program version, etc.), remote troubleshooting is just guessing.

Hi Everyone: Here are some thoughts from an Old Boiler-man that may help with your burner ignition problem. I am assuming that your boiler is Industrial Steam Boiler that is fueled by Natural Gas. If the boiler is an oil fired unit the ignition sequence will be a little different.

In your post you indicated the spark works fine. This would indicate to me that all of the external operating and safety controls are calling for the the burner to start the ignition sequence. This would mean to me that that your burner has actually started and completed the prepurge of the combustion chamber.

The next step in the ignition sequence would be to turn on the spark and the fuel supply to a small pilot ignition burner. Under normal conditions this burner would immediately ignite. The Pilot Flame would then be proven to exist, allowing the main gas valve to slowly open igniting the main burner.

It is important to remember that all automatic burners are ignited using several programed steps that are part of an overall firing sequence. Each step must be proven before the sequence is allowed to continue to the next event.

I hope these thoughts will help.

Good Catch, JDH. I missed that in my first read.

If the spark is working, it eliminates pretty much everything in my previous post. I'll go a step further & say can't be the flame prover or it wouldn't light in the first place.

I need more information on the state of control. Is any error showing in your display? Is the sequence of ignition running correctly? If so, is the electrode receiving voltage? If so, is it burned? Is the gas going through the burner? What does your manometer or pressure sensor say? Have you looked through the window opposite to your ignition unit to see what happens? If gas is not going through, are there elements that are closed or plugged?

Vital questions that must be answered.

One more thing, although it is a little aspect of the burner it could well be the problem. Have you checked the position of the electrode? Is it in the direction of the gas way or not?

Since most boilers are fired on temperature setpoint control it is important to check the temperature setpoints in the PLC programming. Make sure the temperature limits on the boiler controls are congruent with the pressure setpoint you have selected. It could be the burner is waiting for the temperature to come down to another firing setpoint to before starting.

Thanks all. I found one of the Programming switches were not working. Replacing it worked.