Near Intersection of I-35 & I-90 Southern Mn. | Low limit will set a minimum value for a control valve that is controlling the flow via a valve in the product line. With a PWM controlled pump, the speed of the pump is changed to control the output. There are settings that pertain to a PWM controlled pump. The PWM settings may be "overriding" the Low Limit setting.
One such setting is sometimes referred to as PWM offset. This is the PWM value that should keep the pump spinning but at the point where it develops no pressure. The idea is that better response is achieved if the pump is always spinning. If the hydraulic flow to the pump is allowed to go to zero or quite low, there may be an unacceptable delay as the pump speed increases to deliver product from a dead stop. It would be better if the pump were still spinning but just on the edge of delivering product. This can be set to keep some product moving at all times for agitation.
A problem with this is if this PWM offset is set too high, the pump may be running too fast at times. Your Low Limit may be trying to reduce the output flow but the PWM offset may be keeping the pump speed up and thus not allowing the Low Limit to work as expected.
Edited by tedbear 7/12/2020 06:45
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Rogator 1254 Raven 661 Low Limit
