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Utica UB90-150 wont stay fired

CHLuke Member Posts: 2
Hi everyone,
I need help getting my boiler running. Utica UB90-150.

I was investigating my breaker switches and flipped off and on the switch for my basement/ boiler and the boiler failed to restart.

The IBC LEDs displayed the second to the last light blinking "valve"

I reset it and it ran through the sequence and it shuts the gas control valve down after only 6 seconds of blue flame. After three failed attempts it blinks red code "valve" on the IBC

After several attempts to get it running and reading the manual I replaced the ignitor/flame sensor and I blew compressed air into the venturi valve  to attempt to clear out obstructions and gasses. Also made sure the intake pipe was clear. 

When I removed the plug and cleared out the exhaust pipe cleanout Tee a whole bunch of water and grey sludge came out. Then i reset it and it fired up.

The boiler stayed running for a month and when the weather warmed we turned the Thermostats all the way down.  The boiler shut off and couldn't start back up. It did the same exact thing it did last time.
I again, blew out the boiler with compressed air and knocked on the valve and inspected all the connections and cleaned out the pipes. Then after several attempts to fire it up, it stayed lit for about 24 hours and shut off again. 

I had a friend (who was a boiler tech) look at it and he and I agreed that it could be the gas control valve failing to put out the gas needed. So I replaced the gas control valve.
The problem didnt change.
So I pulled out the burner cylinder and found a leaf stuck between the blower and the entrance to the burner cylinder obstructing half the entrance. I removed the leaf and cleaned the burner cylinder. After putting it all back together, the same issue persisted. 

I'm pretty much stumped. 
I would like to clean the heat exchanger inside the block out by flushing or something but I have no idea how I would do that on this boiler.

Any suggestions or instructions on how to clean the grey sludge out of this unique block?


  • Ironman
    Ironman Member Posts: 6,868
    What do you mean that you "blew compressed air into the Venturi valve"? There's no such part by that name and nothing on the boiler should have had compressed air blown into it.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    EBEBRATT-Ed Member Posts: 11,989
    Sounds like your flue pipe or air intake is blocked and may not be pitched correctly. Finding a leaf in the burner is telling you at least part of whats wrong. There shouldn't be standing water in the flue pipe.

    If you shoot the parts cannon at the boiler you will be broke before it's fixed
  • mattmia2
    mattmia2 Member Posts: 5,511
    Did you make sure all the condensate lines and passages were clear? Did someone adjust the combustion after you replaced the valve?
  • CHLuke
    CHLuke Member Posts: 2
    Utica UB90-150 
     I got the boiler up and running for good yesterday. 

    I removed the red rubber tubes that feed the pressure switches to make sure they had no obstructions. While blowing through each end I found the one end has a little check valve in the tube and the other doesn't.  Then I found that when I blew through the tube in the direction away from the pressure switches I got air flow. Then,  when I blew through the tube in the other direction that should have air flow going to the pressure switches, the check valve stopped any flow. So I flipped the tube assembly around, hooked it back up and the boiler fired up like a champ and has been running strong. The home owner before me had replace a worn out blower and installed the tubes on backwards. 
    The only reason the boiler ever ran after that is either he jumped the switches long enough for the boiler to get passed the ignition sequence and stay running (I bought the house in the winter) or there was enough pressure in the system from blowing it out to get it through the ignition sequence and run until I came along and killed the power causing the ignition sequence to start over and fail once it got the the final pressure switch analysis. 

    I hope this thread helps somebody out there that has this boiler and cant figure out what the heck is wrong with it.