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Posted by barnstable1197 on December 02, 2006 at 18:25:37:
In Reply to: Re: FD Fan Operation posted by Rick on December 01, 2006 at 11:49:59:
The fd fan operation was controlled by the boiler o2. The new controller has another input(steam flow) along with the O2 input. It uses these to determine FD damper position. This controller can be set to favor one input or the other(not set by the operator). The persons setting up this controller were informed to set it with the the steam flow input dominating the fd fan controller. For example when boiler steam flow increases sharply, the fd fan follows instantly regardless of what the O2 is. This would probaly be ok with a boiler burning eithe gas or fuel oil. With these boilers, the increase in steam flows takes a long time to make a difference in the actual fire in the furnace. By this time, the load is decreasing with the fan following. This usually causes a drop in the boiler O2. If the boiler steam flow decreases the fd will follow even if the boiler is in a low O2 alarm(2%) condition.
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