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.
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.