I've got a new Bender LIM tester that I'm going to demonstrate in an upcoming video. I'd like to simulate an alarm fault and show how to quickly find the faulty device.
This is so important to know. I work in a hospital setting as a biomed. I used to think the guys never wanted to teach me anything. Then i realized, its because they dont know either. Keep sharing knowledge! It can save lives!
@Engineering Technology for Healthcare Can you, please explain: If you touch non-isolated systems live wire with your hand, you get a shock because you complete the circuit from your palm through you to the floor? If this is the case, why don't you complete the circuit in isolated systems case when you touch either L1 or L2? The potential difference between L1 or L2 to GND is 0V?
Hi, the reasons is if you touch the live wire of a traditional system you are at ground potential (since you are touching the ground - you are at the same potential as ground), because traditional systems are connected to ground there is now a "path" for current to flow. However in an isolated system you are at ground potential still, however the isolated system is not connected to ground (normally the neutral is touching/at ground potential). Therefore there is no path though you. Hope that helps. The key difference is a traditional system includes a ground bridge from the neutral to ground (making them at the same potential), where a isolated system is not connected to ground by either line 1 or line 2. However as soon as you touch line 1 or line 2 you have not created 1 point to ground - if there is a second point to ground through a nother fault current can now flow. Thus it takes two faults
The potential difference from L1 or L2 to ground is hard to say - it can actually change a bit depending on fault conditions and other. But in general most systems (some are different than others) may mantain roughly 60 V from ground from both L1 and L2 (postive and negative) - but that can change depending on system conditions. The very act of connecting a multimeter to the system creates a "fault" or connection so if you measure it you are disturbing the isolated system.
My Mom has been an OR Nurse for 40+ years so I asked her if there has ever been an alarm that interfered with a surgery. She said she has never experienced that. These systems must work rather well. She has never been notified of an alarm going off either.
Interesting, yeah I have not heard how frequently alarms go off but I do know that it does happen. May have been her unit had very good equipment with good BMET (combo of both), and good clinical staff who know what they are doing to keep leakage currents under control.
That is the whole point of the wiring, if wired correctly then there are no alarms. If someone interfers with the wirng to make it unsafe then fault alarm is initiated as with a fault. Generally safe electrical circuits remain safe.
Not sure how this is any different from regular power. You always need 2 fault conditions for an electrocution to happen. Hot to ground or hot to hot of different phase. Am I missing something?
Can you explain how or what are the requirements for test this and make sure they are funtioning propertly ? I know some had self test buttons and alarms but what are the code requirements on checking them
Hi J, tough question - depends on where you are located and what equipment you are using. Do you have the companies contact info - they can usually recommend a test procedure. Codes are going to depend on your location and your facilities goals (some adhere to certain standards that others do not - for instance in Florida we have to deal with the state policies which are often more stringent than the NFPA polcies)
I've got a new Bender LIM tester that I'm going to demonstrate in an upcoming video. I'd like to simulate an alarm fault and show how to quickly find the faulty device.
Great idea - I don’t have access to one but let me know when it’s up!
You guys are the best BMET channel
Keep up the good work 👍
This is so important to know. I work in a hospital setting as a biomed. I used to think the guys never wanted to teach me anything. Then i realized, its because they dont know either. Keep sharing knowledge! It can save lives!
Thanks again!
@Engineering Technology for Healthcare Can you, please explain: If you touch non-isolated systems live wire with your hand, you get a shock because you complete the circuit from your palm through you to the floor? If this is the case, why don't you complete the circuit in isolated systems case when you touch either L1 or L2? The potential difference between L1 or L2 to GND is 0V?
Hi, the reasons is if you touch the live wire of a traditional system you are at ground potential (since you are touching the ground - you are at the same potential as ground), because traditional systems are connected to ground there is now a "path" for current to flow. However in an isolated system you are at ground potential still, however the isolated system is not connected to ground (normally the neutral is touching/at ground potential). Therefore there is no path though you. Hope that helps. The key difference is a traditional system includes a ground bridge from the neutral to ground (making them at the same potential), where a isolated system is not connected to ground by either line 1 or line 2. However as soon as you touch line 1 or line 2 you have not created 1 point to ground - if there is a second point to ground through a nother fault current can now flow. Thus it takes two faults
The potential difference from L1 or L2 to ground is hard to say - it can actually change a bit depending on fault conditions and other. But in general most systems (some are different than others) may mantain roughly 60 V from ground from both L1 and L2 (postive and negative) - but that can change depending on system conditions. The very act of connecting a multimeter to the system creates a "fault" or connection so if you measure it you are disturbing the isolated system.
Thanx for the explanation,great info.
My Mom has been an OR Nurse for 40+ years so I asked her if there has ever been an alarm that interfered with a surgery. She said she has never experienced that. These systems must work rather well. She has never been notified of an alarm going off either.
Interesting, yeah I have not heard how frequently alarms go off but I do know that it does happen. May have been her unit had very good equipment with good BMET (combo of both), and good clinical staff who know what they are doing to keep leakage currents under control.
That is the whole point of the wiring, if wired correctly then there are no alarms. If someone interfers with the wirng to make it unsafe then fault alarm is initiated as with a fault. Generally safe electrical circuits remain safe.
Not sure how this is any different from regular power. You always need 2 fault conditions for an electrocution to happen. Hot to ground or hot to hot of different phase. Am I missing something?
Hot to ground is a single fault. So in an isolated system you can have line one (kind of like hot) to ground and there are no issues.
Really! be very careful my friend.
Can you explain how or what are the requirements for test this and make sure they are funtioning propertly ? I know some had self test buttons and alarms but what are the code requirements on checking them
Hi J, tough question - depends on where you are located and what equipment you are using. Do you have the companies contact info - they can usually recommend a test procedure. Codes are going to depend on your location and your facilities goals (some adhere to certain standards that others do not - for instance in Florida we have to deal with the state policies which are often more stringent than the NFPA polcies)
@@HTMWorkshop ok thank you , I will do that we have to deal with the AAAHC here in Texas.
@@ip5232 Let me know how it goes and if you learn anything interesting