PAC Display Alarm Issue

Hi all,

Currently, I’m having an issue with the PAC display alarm. When there is a low flow alarm or a high flow alarm, I set the alarm point to show up on the alarm screen. When the system is started, if the pump doesn’t start and the flow remains at 0 for 10 seconds, the alarm window pops up and shows a flow alarm. However, when I tried to simulate the situation, I set the low flow alarm at 5 and the high flow alarm at 60. You can see that the flow rate is 0 with the alarm turned on. Even though the alarm window is open, I don’t see any alarm on the screen.

When i make a slight change to the flow rate but still remaining under low flow alarm i get the notification in the screen.

The alarm point setup monitor the change in value inorder to show the alarm in the screen?. Attaching my alarm point setup too for the reference.

Is the tag an I/O point or a strategy variable?

I recall that the alarm is based on the ival, so it will be activated only when it’s read/updated.
One ‘trick’ is to make sure that point is always read frequently by putting a move command in a looping chart somewhere. It does not matter where you move it to (for example, to a variable called ‘trash’); it just needs to be read and thus update its ival.

Its looking for strategy variable. Which is uolowflowalarm = 1, Even though the variable is set to 1. The alarm shows only when the flow rate (Which is also an strategy variable not an io point) has some changes.

The value can’t be evaluated until it changes.

If its a float, you could try and set it more sensitive, but you run the risk of alarming on noise.

“The value can’t be evaluated until it changes.” So the alarm variable cant be an integer? Even though the alarm variable is set to 1. Still the alarm point looks for change in flow rate variable to show the notification?

The alarm can be an int.
Let me call up the users guide and see how it explains it. Im clearly not doing a very good job…

What do you have configured on the value tab of the alarm setup?

What is the logic for uolowflowalarm (how is it evaluated)?


When ever the flow rate drop below the low flow alarm setpoint with delay timer. The uoLowFlowAlarm goes high.

I would need to test this, but this is my guess as to what is going on.

You are enabling the alarm with the uoLowFlowAlarm tag (note that this isn’t the alarm point - just a flag telling PAC Display you can start reading the alarm point and evaluating for an alarm condition).

Once the alarm is enabled, then PAC Display will watch your fFlowRate tag - it is waiting for it to change before it will alarm (hysteresis is not set, so my guess is that it is still in play at a value of 0.0). So your fFlowRate tag needs to change slightly to get the alarm to trigger. It probably won’t be a problem in production since this value will vary, but when you are testing and feeding it a fixed value you see this behavior.

An alternative would be to setup a Discrete alarm on the uoLowFlowAlarm tag and always leave the alarm enabled, but then you won’t see the flow rate value in your alarm window, if that is important to you.

1 Like

This issue has been in the customer software for atleast a decade. Usually flow rate goes to 0 when pump isn’t running. We randomly get the alarm without showing any values on it. More like blank screen.

We need to have the flow rate as at what flow rate the alarm was triggered.

So the uolowflowalarm = high is more like condition to see change in flow rate and trigger the alarm?

How are you setting the value for fFlowRate and uoLowFlowAlarm? Make sure you are not performing interim calculations on them before you reach a final value - such as reading the value, then scaling it in the same variable, or setting your uoLowFlowAlarm to 0 at the top of your chart and recalculating it every time. It could be PAC Display is picking up values you don’t expect.

fFlowRate is water sensor which is in different chart which monitor the flow rate every 1 sec. All the flow alarm is in different chart. We dont reset the variable every time the chart loops. The uoLowFlowAlarm is locked in 1 when alarm is triggered. But the pac display still looks for change in flow rate to trigger the low alarm is weird. There is no way the value will chage for flow rate as its 0.0 when pump is not running. I use the same alarm in groov view. Which works fine. I assume logic over there is completely different than the groov view.