Posted by Dan on September 28, 2000 at 23:19:40:
In Reply to: Re: boiler posted by mike on February 20, 2000 at 18:34:34:
: : : Today we had a boiler that had the o2 go from 4.2 to 9.2,also the sides of the boiler started pulsating. it was pulling about 40000. We have Preferred Instruments Controls.Any Help ?
: : The increase in O2 indicates an increase in excess air. I'd check the FD and/or ID fan controllers or the oxygen trim controller if you have O2 trim. The furnace was pulsating from an excessive amount of fuel-gas being carried through it.
: also check your safeties on feed water heater to make sure they are not drawing in air! thsi is were O2 might be coming in!
Try putting your ID and FD dampers on manual next time it happens, and open your id damper slowly to see if the pulsating stops. It is probably excess air in the furnace. I'm suprised it didn't
trip. You may have to play a little with each damper(FD and ID)to get a balance. It sounds like your ID fan damper is not opening, but your FD damper is, putting excess pressure on the furnace.
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