Delay Device Output

[JonathonB]

Hi, 

I am working on trying to implement a Rate-of-Rise heat detector in FDS. I have gone through the User Guide and can't find a built-in function that achieves this directly. What I am trying to achieve is a control that checks whether a heat detector has increased by a set temperature over a set time period (for example increase by 8° over 60s). 

To achieve this I was thinking to use a SUBTRACT control of the output from a heat detector with the output 60s previously. 

Is there a way to create a device with a delayed output? Or is there a way to output the results from a device from a previous simulation time? 

Regards,

Jonathon Beardmore

[dr_jfloyd]

A rate of rise detector is looking to see when temperature is increasing at the rate of 8 C/min, not that it has actually increased 8 C over the last 60 s. One potential option is you could put a large diameter THERMOCOUPLE at the detector location and use the PID function to monitor the derivative of the THERMOCOUPLE. The tricky part would be figuring out what mass to give the TC so its temperature response matches the response expected from the physical detector.

[JonathonB]

Thank you for the recommendation. Spent some time experimenting with different arrangements. Was able to get it working reliably. 

Much appreciated.