I got a few computers ( servers & workstations ) , DSL, hooked up to 2 APC UPS ( the smart ups - aka smups ). One smups is to suppose to remain on all the time to take care of the internet connection. The other smups is to take care of the other equiptment that does not need to be on all the time. Both APC smups is plugged into a bank of switched outlets ( 1900 boxes with switch & recepticles ) . Those bank of switches are connected to a GFCI/recptical. That GFCI is plugged into the wall outlet. The wall outlet, 2 wire BX, does not have a GFCI, but is protected by a 15amp CB.
I recently aquired a fancy 2000va smups that does double conversion of power ( ie AC->DC+BATT->AC ). The output voltage is regulated to a single voltage and frequency no matter what the input voltage is.
I plugged the fancy smups into the outlet. I removed the plug that fed the power to the GFCI and placed it into the output side of the fancy smups. Within 10seconds the GFCI tripped. The GFCI tripped a few times. I then set the fancy smups in bypass mode ( bypass mode is where the utility is directly connected to the output ). No more GFCI tripping.
A little later I placed the fancy smups in non-bypass mode. It appeared to do nothing till a few hours later, when the GFCI began tripping again.
I e-mailed the manufacture, and this was their absolute response:
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Hello again, George. This is a fairly common question asked by our sales team, so I've copied our explanation below. Also, you should never use a UPS system on a circuit required to have GFCI protection.
Q. Should I install a GFCI to protect my UPS and its connected equipment?
Ground Fault Circuit Interrupter (GFCI) protection is a system that shuts down the protected electric circuit -- opens it -- when it senses an unexpected loss of power, presumably to ground. In some countries a similar device is referred to as Earth Leakage Circuit Breaker. GFCI protection devices constantly monitor and compare the amount of power flowing from the panel on the hot (or phase) wire and the amount returning on the neutral wire. Any time the returning power drops even slightly below the amount being supplied, the protection device will trip and open the circuit. GFCI devices are employed in areas exposed to moisture such as restrooms, kitchens and garages and are designed to protect people - not equipment. GFCI devices are designed to protect against very low power leakage through people in locations where people are likely to have direct contact with worn electrical appliances or exposed conductors and ground; such as water pipes (bathroom, kitchen), concrete floors (garage, basement), or damp locations (including outside). Since wet conditions allow skin to conduct much better, these locations are more hazardous. When it is working properly, a GFCI device will open its protected circuit when the difference between the current coming in and the current going out reaches .005 amperes. That's 5 milliamp, an amount most of us can't even sense but is common in UPS applications since the UPS typically employs a front-end TVSS and EMI/RFI circuit. This makes GFCI inappropriate for electronic loads such as UPS, computers, or anything else with EMI filters. EMI filters needed to control emissions usually include small capacitors to ground. These pass small AC currents to ground similar to a ground fault, but since the action of the EMI circuit is intentional it doesn't represent a hazardous fault. Any single data-processing device is likely to leak 0.5 - 2mA during normal operation. Therefore, the combination of a UPS with multiple computer-type loads are virtually guaranteed to trip plug-in GFCI circuits. We advise against using GFCI or Earth Leakage Circuit Breaker circuits in UPS applications. GFCI devices provide no benefit to load equipment - again their primary intent is to protect people in potentially damp or hazardous conditions. The regular building grounding system protects equipment that is attached (or plugged in) to the circuit against a ground fault.
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Lots of this makes sense, lots dont make sense. I dont like the idea that 5ma leakage is just not something to worry about.
But in reality, some sites have a lot of blade servers in a single cabinet ( sales folks are very proud of that feat ). With current leakage from each one, it may reach lethal conditions if the manufacturers position is relied upon to be correct.
But I normally have the GFCI to protect me, as well as the equipment from abnormal conditions. Unfortunately, the fancy smups is causing the equipment, its protecting, to emit more current to ground, and tripping the GFCI.
Is this an issue that needs to be addresed by UL, or NEC?
setup:
wall-outlet->fancy-smups->utlity-box(GFCI)->utility box(switches/outlets)->various computer equipment ( 2 APC smups, TV, modem, servers, workstations, laser printer,.... ).
I recently aquired a fancy 2000va smups that does double conversion of power ( ie AC->DC+BATT->AC ). The output voltage is regulated to a single voltage and frequency no matter what the input voltage is.
I plugged the fancy smups into the outlet. I removed the plug that fed the power to the GFCI and placed it into the output side of the fancy smups. Within 10seconds the GFCI tripped. The GFCI tripped a few times. I then set the fancy smups in bypass mode ( bypass mode is where the utility is directly connected to the output ). No more GFCI tripping.
A little later I placed the fancy smups in non-bypass mode. It appeared to do nothing till a few hours later, when the GFCI began tripping again.
I e-mailed the manufacture, and this was their absolute response:
------------------------------------------
Hello again, George. This is a fairly common question asked by our sales team, so I've copied our explanation below. Also, you should never use a UPS system on a circuit required to have GFCI protection.
Q. Should I install a GFCI to protect my UPS and its connected equipment?
Ground Fault Circuit Interrupter (GFCI) protection is a system that shuts down the protected electric circuit -- opens it -- when it senses an unexpected loss of power, presumably to ground. In some countries a similar device is referred to as Earth Leakage Circuit Breaker. GFCI protection devices constantly monitor and compare the amount of power flowing from the panel on the hot (or phase) wire and the amount returning on the neutral wire. Any time the returning power drops even slightly below the amount being supplied, the protection device will trip and open the circuit. GFCI devices are employed in areas exposed to moisture such as restrooms, kitchens and garages and are designed to protect people - not equipment. GFCI devices are designed to protect against very low power leakage through people in locations where people are likely to have direct contact with worn electrical appliances or exposed conductors and ground; such as water pipes (bathroom, kitchen), concrete floors (garage, basement), or damp locations (including outside). Since wet conditions allow skin to conduct much better, these locations are more hazardous. When it is working properly, a GFCI device will open its protected circuit when the difference between the current coming in and the current going out reaches .005 amperes. That's 5 milliamp, an amount most of us can't even sense but is common in UPS applications since the UPS typically employs a front-end TVSS and EMI/RFI circuit. This makes GFCI inappropriate for electronic loads such as UPS, computers, or anything else with EMI filters. EMI filters needed to control emissions usually include small capacitors to ground. These pass small AC currents to ground similar to a ground fault, but since the action of the EMI circuit is intentional it doesn't represent a hazardous fault. Any single data-processing device is likely to leak 0.5 - 2mA during normal operation. Therefore, the combination of a UPS with multiple computer-type loads are virtually guaranteed to trip plug-in GFCI circuits. We advise against using GFCI or Earth Leakage Circuit Breaker circuits in UPS applications. GFCI devices provide no benefit to load equipment - again their primary intent is to protect people in potentially damp or hazardous conditions. The regular building grounding system protects equipment that is attached (or plugged in) to the circuit against a ground fault.
-------------------------------
Lots of this makes sense, lots dont make sense. I dont like the idea that 5ma leakage is just not something to worry about.
But in reality, some sites have a lot of blade servers in a single cabinet ( sales folks are very proud of that feat ). With current leakage from each one, it may reach lethal conditions if the manufacturers position is relied upon to be correct.
But I normally have the GFCI to protect me, as well as the equipment from abnormal conditions. Unfortunately, the fancy smups is causing the equipment, its protecting, to emit more current to ground, and tripping the GFCI.
Is this an issue that needs to be addresed by UL, or NEC?
setup:
wall-outlet->fancy-smups->utlity-box(GFCI)->utility box(switches/outlets)->various computer equipment ( 2 APC smups, TV, modem, servers, workstations, laser printer,.... ).
