Water vs. Air: Safety Concerns with VRV-VRF Systems
In our continuing discussion of water vs. air systems, particularly with regard to hydronic chilled water systems vs. DX-type air systems like VRV-VRF, the issue of safety arises as a concern. That’s due to the presence of toxic refrigerant used in VRV-VRF systems. Your author relates a personal experience below, one that I was fortunate enough to have survived to tell about…
The major concern about VRV-VRF systems is the safety factor stemming from a refrigerant leak. As refrigerant is a toxic fluid, applicable codes (ANSI/ASHRAE Standard 1502001 and the IMC) restrict the amount that can be used in a single refrigerant circuit. Refrigerant is classified as a hazard to human health and the codes place restrictions on how much can be discharged into a living or work space. Refrigerant fluid is heavier than air and because of that it displaces oxygen in a room – if it takes enough oxygen out of a space a person exposed to it can suffocate. Because refrigerant can’t be readily detected by human senses – it cannot be seen or smelled – codes require refrigerant alarms in spaces where the concentration of the fluid is enough to cause a lethal accident. Years ago that was not the case.
This author, in an earlier career phase, had a potentially lethal encounter with leaking refrigerant. As a manufacturer’s rep agent back in the 1980s I had supplied a large DX system to a school. One day I was called out to the school because there was a problem with the system’s refrigerant distribution. I was joined by a factory representative who discovered that a check valve had been installed backwards in the refrigerant receiver.
Being younger men we decided we could fix the unit on the spot – unscrew it, screw it back in correctly and walk out of there, job done. So the tech unscrewed the valve from the piping. Being a fairly large receiver there were many pounds of refrigerant under pressure. With the pressure so high and the velocity of refrigerant coming out being so great, the tech found he could not get the valve screwed back in. The fluid was literally streaming out into what was a rather small mechanical room. In less than a couple of minutes the escaped refrigerant had built up in that room to make both of us pass out.
What saved us was an alarm going off which woke me up. I was still standing but the tech was on the floor. I literally dragged him out of the room and got the door shut. The alarm that saved us was not a refrigerant alarm but rather a fire alarm – positioned outside the mechanical room – which thankfully could detect gases as well as smoke.
Next Up: Liability Concerns for the Engineer
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