Ground Fault Interupters (GFI) effect on mains?
Posted by: ET on 07 February 2003
Does anyone know how much, if at all, the GFI outlets would impact your mains power? I would assume that they are a positive thing in that they would prevent spikes to your equipment? I am contemplating putting in hospital grade GFI for my system (sistem), but don't want to harm the sound. Don't know if this will apply to the non-north american crowd or not. thanks for any input.
Tim E.
Tim E.
Posted on: 07 February 2003 by phil. S
In the UK I think these little devices are called RCDs'. They are fitted in the electrical installations in newer or re-wired houses (at least on the downstairs ringmain). In my setup they are vital as I have upgraded the fuses in my hifi eqipment. In the unlikely event of a fault the RCD should prevent my house from burning down!
Phil
Phil
Posted on: 07 February 2003 by ET
the GFI's are either built into the outlet itself, or can be part of the fuse in your circuit box. Legally in the U.S. it is needed in new kitchens or baths, mainly so if an appliance gets dropped into the sink/tub you will hopefully not be electrocuted as the GFI will cut off the spike of power in a fraction of a second. Since I have a young ankle biter, and I worry about my gear getting zapped by a spike/surge since I have a bare outlet strip, it seems like a good idea, coupled with a possible improvement as I goto a hospital grade outlet also
Posted on: 07 February 2003 by ejl
Hi ET,
A GFI is not a surge protector. A GFI works by measuring the current (Amps) difference between the hot and neutral lines. If a difference above a certain level is detected, then it will trip because this indicates a "ground fault" (thereby protecting you/your kids from getting killed).
Anyway, although GFIs do sometimes trip with a lighting strike, you shouldn't expect it to protect your gear from lightning.
I've never plugged my stereo into a GFI, but I strongly suspect that the effect would be negative. GFIs are typically rated at 15 amps, so there is a current restriction right there.
Unfortunately I don't think there is any way to protect gear from lighting that doesn't involve a sound-degrading surge supressor or, safer yet, turning it off, although I'd be glad to hear otherwise.
[This message was edited by ejl on SATURDAY 08 February 2003 at 01:08.]
A GFI is not a surge protector. A GFI works by measuring the current (Amps) difference between the hot and neutral lines. If a difference above a certain level is detected, then it will trip because this indicates a "ground fault" (thereby protecting you/your kids from getting killed).
Anyway, although GFIs do sometimes trip with a lighting strike, you shouldn't expect it to protect your gear from lightning.
I've never plugged my stereo into a GFI, but I strongly suspect that the effect would be negative. GFIs are typically rated at 15 amps, so there is a current restriction right there.
Unfortunately I don't think there is any way to protect gear from lighting that doesn't involve a sound-degrading surge supressor or, safer yet, turning it off, although I'd be glad to hear otherwise.
[This message was edited by ejl on SATURDAY 08 February 2003 at 01:08.]
Posted on: 10 February 2003 by NAIM-Collector
eji
I noted with interest your reluctance to connect to a power circuit in conjunction with a RCD.
Your resistance is based on the 15 amp limitation of the RCD, what is the rating of the circuit breaker or fuse on your existing circuit.
Out of interest I recently checked the current draw on a circuit with a NAP-135 six pack, at idle the amplifiers draws a little over one amp, at a realistic volume the current draw rises between two to three amps.
If we considered running all six amplifiers at maximum transformer capacity (500 Watt) we would demand 3,000 watts, this translates to about 12.5 amps (3,000 / 240), still within the 15 amp rating Ummmmmmm.
I noted with interest your reluctance to connect to a power circuit in conjunction with a RCD.
Your resistance is based on the 15 amp limitation of the RCD, what is the rating of the circuit breaker or fuse on your existing circuit.
Out of interest I recently checked the current draw on a circuit with a NAP-135 six pack, at idle the amplifiers draws a little over one amp, at a realistic volume the current draw rises between two to three amps.
If we considered running all six amplifiers at maximum transformer capacity (500 Watt) we would demand 3,000 watts, this translates to about 12.5 amps (3,000 / 240), still within the 15 amp rating Ummmmmmm.
Posted on: 10 February 2003 by ejl
Hi,
I think the idea behind larger fuse box fuses is that the peak current draw on transients actually can go to 20 or 30 times the average current (although only briefly), and that as a result even 15 amp fuses can be a bottle-neck. There is an old thread discussing this, I think it's called "30 amp fuses" or something. I myself haven't experimented with 15 amp fuses (nor have I ever measured actual transient peak current draw for an amp -- have you?); so I'll rephrase my point as a conditional: If larger amperage (over 15 amp) ratings on fuse-box fuses make a difference (as several on this forum have asserted), then one limitation imposed by a typical GFI is the requirement of a 15 amp fuse. There might be others as well; certainly the introduction of the extra control circuit in a GFI prima facie isn't a good thing.
Keep in mind also that your computations assume a separate spur; if for instance the original poster has his computer and 'fridge on the same circuit (and nothing he said implies a separate spur), then it would be pretty easy for him to exceed 15 amps
I think the idea behind larger fuse box fuses is that the peak current draw on transients actually can go to 20 or 30 times the average current (although only briefly), and that as a result even 15 amp fuses can be a bottle-neck. There is an old thread discussing this, I think it's called "30 amp fuses" or something. I myself haven't experimented with 15 amp fuses (nor have I ever measured actual transient peak current draw for an amp -- have you?); so I'll rephrase my point as a conditional: If larger amperage (over 15 amp) ratings on fuse-box fuses make a difference (as several on this forum have asserted), then one limitation imposed by a typical GFI is the requirement of a 15 amp fuse. There might be others as well; certainly the introduction of the extra control circuit in a GFI prima facie isn't a good thing.
Keep in mind also that your computations assume a separate spur; if for instance the original poster has his computer and 'fridge on the same circuit (and nothing he said implies a separate spur), then it would be pretty easy for him to exceed 15 amps
Posted on: 10 February 2003 by plynnplynn
quote:
Originally posted by NAIM-Collector:
eji
I noted with interest your reluctance to connect to a power circuit in conjunction with a RCD.
Your resistance is based on the 15 amp limitation of the RCD, what is the rating of the circuit breaker or fuse on your existing circuit.
Out of interest I recently checked the current draw on a circuit with a NAP-135 six pack, at idle the amplifiers draws a little over one amp, at a realistic volume the current draw rises between two to three amps.
If we considered running all six amplifiers at maximum transformer capacity (500 Watt) we would demand 3,000 watts, this translates to about 12.5 amps (3,000 / 240), still within the 15 amp rating Ummmmmmm.
Any problem there may be with an RCD and current flow (if there is a significant problem - and I am not saying there is) may come from a 'choking' effect resulting from the physical make-up of the RCD. In an RCD the current flows through a coil which may have an effect on the impedance and in turn the current. There may be a current rate of response issue in relation to the demands of the amp or power supply within the hifi system.
Terry