A.O. Smith 100 Series, Руководство по обслуживанию

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Servicing should only be performed by a Qualified Service Agent
The LL master may be aware of slave Burner Control’s minimum firing rate and use this information for some of its algorithms, but
when apportioning rate it may also assign rates that are less than this. In fact, the add-stage and drop-stage algorithms may assume
this and be defined in terms of theoretical rates that are possibly lower than the actual minimum rate of the Burner Control. A Burner
Control that is firing and is being commanded to fire at less than its minimum modulation rate will operate at its minimum rate: this is
a standard behavior for a Burner Control in stand-alone (non-slave) mode.
If any slave under LL Master control is in a Run-Limited condition, then for some algorithms the LL master can apportion to that stage
the rate that it is actually firing at. Additionally when a slave imposes its own Run-limited rate, this may trigger the LL Master to add
a stage, if it needs more capacity, or drop a stage if the run-limiting is providing too much heat (for example if a stage is running at a
higher-than commanded rate due to anti-condensation).
By adjusting the parameters in an extreme way it is possible to define add-stage and drop-stage conditions that overlap or even
cross over each other. Certainly it is incorrect to do this, and it would take a very deliberate and non-accidental act to accomplish it.
But there are two points in this:
1. LL master does not prevent it, and more important;
2. It will not confuse the LL master because it is implemented as a state machine that is in only one state at a time;
For example:
— If its add-stage action has been triggered, it will remain in this condition until either a stage has been added, or
— The criteria for its being in an add-stage condition is no longer met; only then will it take another look around to see what state it
should go to next.
ASSUMPTIONS
Modulating stage The modulating stage is the Burner Control that is receiving varying firing rate requests to track the load.
First stage: This is the Burner Control System that was turned on first, when no slave Burner Controls were firing.
Previous stage: The Burner Control that was added to those stages that are firing just prior to the adding of the Burner Control that
is under discussion.
Next stage: The Burner Control that will or might be added as the next Burner Control to fire.
Last stage: The Burner Control that is firing and that was added the most recently to the group of slaves that are firing. Typically this
is also the modulating stage, however as the load decreases then the last-added stage will be at its minimum rate and the previous
stage will be modulating.
Lead boiler/water heater: The Lead boiler/water heater is the Burner Control that is the first stage to fire among those stages which
are in the equalize runtime (Lead/Lag) group. If a boiler/water heater is in the “Use first” group it may fire before the Lead boiler/water
heater fires.
First boiler/water heater: A Burner Control may be assigned to any of three groups: “Use First”, “Equalize Runtime”, or “Use Last”.
If one or more Burner Controls are in the “Use First” category, then one of these (the one with the lowest sequence number) will
always be the first boiler/water heater to fire. If there is no Buner Control System in the “Use First” category and one or more are in
the “Equalize Runtime” category, then the First boiler/water heater is also the Lead boiler/water heater.