I have a brain teaser for you.

So I have a fairly large facility I maintain and have been at this site for a little over 12 years. They have a Trane control system that was installed in the mid '90's.

Recently the boiler plant has been flipping out anytime the emergency generator does a test run. Not a loaded test, just a maintenance run with the transfer switch in the "normal" position. The generator room is immediately adjacent to the pump room. The generator is mounted on a spring isolated inertia base as is the control box that the PCM is mounted in (separate bases 20+ feet apart).

When the generator runs, the hot water pumps, which are on a VFD, start and stop at random, the speed signal never drops off, but the start stop at the relay on the PCM drops out and comes back like it is possessed.

While looking into this today, I pounded the top of the enclosure with my fist and was able to get it to drop out, then about 15 seconds later, fires right back up... The light (led) for the binary output goes off, the relays drop out, then right back on... Watching it with my laptop logged into the controller you can actually see the output "off" then shortly back on (not real time, but I know it is something in the controller.

This was at that point encouraging, but was short lived, I was thinking I had a problem in the controller, after reprogramming another spare PCM and installing it, the new(er) one does the same thing, exactly the same.

I am at my wits end.. Anybody have anything?, I know I have not included everything I tested in this post, but I have tried numerous other things to try and hunt down the issue.

The programming is pretty straight forward, there is an averaging pressure differential system that takes two different pressure transducers, averaging them together then using the one signal to control the pump, the pumps have a bypass, one VFD, two pumps, so the outputs are pump 1 bypass, pump 1 VFD, pump two bypass, pump 2 vfd. The inputs are rotary switches mounted in the door, there is one for each pump that does VFD/off/bypass.

Thanks in advanced.

GT

HELP!!!