ABOUT THIS PROJECT
We have been asked to compile an investigative quotation into the viability of retrofitting safety flow switches to the Water Hydraulics to each of the 251 Indoor Colt Air-conditioners on site.
We undertook some preliminary testing with regards to integration of a Safety Flow Switch giving an LED Indication when flow is present. This is to give a quick visual indication of whether flow is present after works have been completed on a Colt unit to ensure all Water Hydraulic Isolation Valves have been re-opened to system; subject to the Primary Water Pumps running at the same time.
QUALIFICATIONS:
We have measured several current daws on the PCB Card and have come up with the following Design Criteria:
* 24VDC Rail powering the IC’s and ancillary devices on the above PCB.
* There are 5 Digital Inputs not being utilised, these channels are OPEN. Each channel draws 7 mA when MADE. This being the case we have 28 mA spare current capacity on the PCB Card.
The Ancillary Devices we plan to install have the following Current Ratings:
* The Mechanatronic Flow Sensor requires 3 mA supply.
* The Relay Coil we plan to install will draw 9 mA when Water Flow is present.
When flow is present the relay will ENERGISE and open circuit the FLOW INPUT TERMINALS. (Net effect is 2 mA additional current draw from the 24 VDC Rail.
When flow is missing the relay will DE-ENERGISE and short circuit the FLOW INPUT TERMINALS. (Net effect is 0 mA additional current draw from the 24 VDC Rail.
The FAIL SAFE MODE of the relay is to short circuit the FLOW INPUT TERMINALS, putting the Colt Unit in Alarm.
A quotation was drafted and submitted where we received an order to proceed.
