Hydratec Inc.

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Standalone HydraCALC (Location)

Button: Calculate Function: Add New Authorization Error Type: Source calc

Description:

When trying to run a source calc calculation (find the maximum possible denisity) with a pump as one of the water supplies, you get the error message; 

 

A source calc cannot be performed if a pump is present.  Please remove the pump or uncheck 'Source Calc' to continue.

Solutions:

Cause:

Due to the slightly inaccurate results which could result at the end of the calculation if more tests weren't run, the option of running a source calc when a PUMP was part of the water supply was removed.  With the latest update (50.55), it will only allow you to run a Source Calc when your water supply is a CITY only.  

 

While using a city water supply, the residual pressure can be calculated as the demand flow changes because it is a straight line supply curve.
The same equation can be used to calculate the pressure at any point along any water supply curve.

 

While using a pump, the residual pressure cannot be calculated easily.  As the demand flow changes the pump curve slope also changes.
An equation would be similar but different for each pump....Due to different Churn Pressures, variable speed pumps and/or pumps regulated with a PRV would make this more difficult. 


A check would also be required to prevent a new flow demand that exceeds the pump capacity.
Solution:

The source calculation can be done manually by increasing the start pressure from  the remote sprinkler until the safety margin goes to zero (ie. use trial and error with your densities until you get a zero safety margin).

 

In the example below, on the left side you'll see that different densites are used until a safety margin close to zero was found.
Updated: Sept. 20, 2022, 4:34 a.m. Created: May 10, 2021, 9:56 a.m.