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Posted by rbeck on October 21, 2008 at 14:11:12:
In Reply to: L8124 triple aquastat posted by Rick on October 21, 2008 at 13:18:03:
If this is an L8124CXXXX it will have 3 knobs. High limit, low limit and a differential.
The high limit will stop the boiler on a call for heat at the desired temperature. When the temperature drops 10f it will re-fire the boiler providing the thermostat is still asking for heat.
The low limit will maintain a lower temperature normally if there is a domestic hot water coil used. When this temperature drops 10f it will start the burner and shut off the circulator if it is running.
The differential is the amount of temperature increase when the boiler fires off low limit minus 10f. For example;
High limit 200f. Boiler shuts off on high limit. Refires at 190f
Low Limit - This is also called a maintaining limit. The boiler will maintain this temp -10f plus the diferential.
If set at 150f boiler will fire (and circulator shuts down if running)at 140f. If the differential is set at 20 the boiler will shut down at 160f providing it did not recieve a call for heat.
150f(Low limit) - 10f(built-in) + 20(Dif) + 160 shut off
The high limit is used for heat only, the low limit is used or maintaining the lower temperature and controls the circulator on a call for heat to verify there is enough hot water in the boiler so the domestic hot water coil will supply enough hot water.
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