Lochinvar Boiler Won't Light

luke0050

Seeing in anyone can help me out. I have a Lochinvar Noble Combi unit. Installed it about two years ago and it has worked great for both the heated floor and domestic hot water.

About a month ago, it started locking out with a 'Flame Fail: Ignition'. It would do it intermittently (about once a week), I would hit the reset and then it would fire off and be fine. However, not it will not fire. I hit the reset and it just cycles and locks out ever time.

I checked the ignitor and have spark (cleaned it anyways). Moved on to the gas valve and pressure switch, replaced each of them and still the same thing.

Thru some troubleshooting, I was able to get it running. If I remove disconnect the hose that connects the pressure switch, intake pipe and gas valve, blow a little pressure (and hold it) to the gas valve, it will fire off and run like it should until I release the pressure.

First I will admit I cannot figure this out as I would figure based on the routing of this hose that it would be a negative pressure, not a positive pressure, I checked the intake pipe to make sure that no nest is within the pipe (have bird screens installed on the outside regardless). Pipe is clear. Same with on the exhaust line. Unit is mounted right next to an exterior wall, so run is short (less than 4').

For the life of me, I cannot figure this out. Any suggestions or comments are greatly appreciated!

For reference, my unit is a NKC199, Series 110.

Ironman

Was the boiler setup with a digital combustion analyzer originally? If so, do you have the numbers?

pedmec

Are you getting 24 volts to the gas valve? remove the connector feeding 24v to the gas valve from the control board. initiate a call and measure the 2 pins on the control board. if your getting 24 volts listen for a click at the gas valve or hook up a manometer at the inlet pressure test port on the gas valve. check the pressure. pressure looks good then when it calls for heat check that the pressure drops a little. that would indicate the gas valve is opening. if nothing changes with the gas pressure and you have 24 on the control replace the wire feeding between the gas valve and control board.

HomerJSmith

Unplug the unit for 5 min. and reset it if need be. This sometime works. You can talk to Lochinvar Teks for a solution.

pedmec

Are you getting 24 volts to the gas valve? remove the connector feeding 24v to the gas valve from the control board. initiate a call and measure the 2 pins on the control board. if your getting 24 volts listen for a click at the gas valve or hook up a manometer at the inlet pressure test port on the gas valve. check the pressure. pressure looks good then when it calls check that the pressure drops a little. that would indicate the gas valve is opening. if nothing changes with the gas pressure and you have 24 on the control replace the wire feeding between the gas valve and control board.

hot_rod

Gas pressure?

pedmec

Sorry for double posting. Something is going wrong on my computer or with this thread

109A_5

Hello @luke0050, With what you did here,

luke0050 said:

Thru some troubleshooting, I was able to get it running. If I remove disconnect the hose that connects the pressure switch, intake pipe and gas valve, blow a little pressure (and hold it) to the gas valve, it will fire off and run like it should until I release the pressure.

And this text from the manual;
https://www.lochinvar.com/lit/163547100275091_2000533998_Rev_AC_Freeze Protection_PVC Purge_(42716).pdf



A normal differential pressure (probably generated by the prepurge) is missing or insufficient and you have found a way to simulate it.

Since the situation has gotten progressively worse with time and also you can 'Fake it out', I think something has become plugged up or restricted so possibly the prepurge pressure is not represented sufficiently or as @hot_rod mentioned the Gas pressure is now insufficient.

Something probably needs cleaning to get the system pressures in the normal operating range again.

hot_rod

Check intake and exhaust for obstruction, including termination cap

mattmia2

Look at the port you removed the tube from, make sure it is clear.