Lochinvar kbn150 lockout

merimar1

Hope someone has an answer. I have a Lochinvar KBN 150 that was installed in 2007. The boiler locks out with error displayed as "high fan speed". The manual says to check vent blockage, wiring, replace fan and or replace control board. If I restart the boiler it will function properly. The lockout happens once the zones are satisfied and the boiler goes to standby. I notice the problem occurs more often when outside temps are higher, 40 degrees or more.
I do have an outside sensor. I have disconnected the sensor and get the same error.

The manual states the high fan speed error is displayed when fan exceeds 30% more then needed. When the boiler is operating the fan speed shows the fan running between 2000 and 5200 rpms depending on the firing rate. I have cleared the error codes, rest the boiler as well as de-energized the unit with hopes of clearing the board memory.

I hate to replace the wrong part since each part is about 500. Thanks in advance.

Jeff W_2

I know that a dirty burner can cause this lockout as well. Has the burner and HX been cleaned and serviced? I would pull it and take a look- this might solve the issue. If you still get the error after cleaning try testing the ignitor cable resistance (should be 1,000 ohms +/-50, then move on to other parts to be replaced.

Ironman

The heat exchanger in that boiler boiler requires annual maintenance and cleaning by someone who's trained to do it. Has that been done?

merimar1

Thanks guys for responding. When I got home today I cleaned the burner and HX. This has not been done since the unit was installed. Overall, it was not that dirty. It had some crud on the coils and light surface build up on the burner.

I cleaned and restarted the boiler. The unit locked out again. I was able to spend time and observe the conditions prior to locking out. I had three zones calling for heat. I shut down one zone and within a few minutes the unit went into post purge which is typical if the water temp is high enough. Normally the display will say "set point met" but now it went right back into a pre-purge mode, fired up and ran a few seconds and then back to post-purge mode. It did this three times before it locked out. It appeared to be cycling. The system has worked perfectly for 7 years. I have not changed anything i.e. new stats, change of settings, etc..

I am open to other suggestions. If you have no other ideas then I would value your opinion on which item you would replace first, the control board or the fan. The fan seems to be working so I would lean towards the control board.

Thanks

Ironman

Did you use some CLR, a brass bristle brush and a credit card to get between the coils when cleaning? If not, then it hasn't been cleaned properly and that still may be your problem.

Was a combustion analysis done when the boiler was installed?

I don't believe in recommending parts be changed in an attempt to stubble upon the problem by chance. There are proper procedures for diagnosing the issue, but it takes someone who's trained with the right tools and equipment.

I would highly recommend that you get a tech who knows that boiler to repair it. You'll come out better in the long run.