APC 3000 UPS - does it really need 30A?

[BCinSC]

Got a SU3000RM that has funky L5-30A plug on end. In old location, I ran a dedicated circuit. In new location, don't have that option, even though I pulled the breaker and outlet when I left. If it's the ONLY thing on the line, could I simply replace the standard 2 outlet with the L5 one, even though the circuit is only 15A?

 

[ProviaFan]

Originally posted by: BCinSC
Got a SU3000RM that has funky 30A plug on end. In old location, I ran a dedicated circuit. In new location, don't have that option. If it's the ONLY thing on the line, could I simply replace the standard 2 outlet with the L5 one, ven though the circuit is only 15A?

You're asking for trouble when the UPS starts recharging its battery after a power outage...

 

[BCinSC]

Well, it was partially discharged from being unplugged for nearly a year. With nothing plugged in, I connected and charged. All seems fine for now. Perhaps under load, things will be different. The breaker will simply trip, right?

 

[Agamar]

Yeah, breaker should trip..but still, do you want your breaker to be tripping every time the lights go out...Might be better to just change out the plug.

 

[BCinSC]

Plug is changed. Breaker is the hard part.

 

[odog]

do you know the layout of the wire? and most important it's gauge?

most standard household circuits are 15A, but manys time the wire can handle more.(might not be 30A) if it's good quality wire it might be as simple as changing the breaker. are their any other devices off this circuit? if so add up everything on it, as you may not even have all 15A to yourself.

 

[BCinSC]

Solid copper 14-2 with ground, rated to 600V - same stuff I used for dedicated circuit in old location. It's a one room building and has 2 outlets and an overhead light on that circuit. There's a separate GFI circuit for bathroom, and a 20A circuit for A/C unit. Breaker box cover is partially covered by doorframe and thus swapping breaker would be difficult.

 

[syberscott]

Originally posted by: e-phex
do you know the layout of the wire? and most important it's gauge?

most standard household circuits are 15A, but manys time the wire can handle more.(might not be 30A) if it's good quality wire it might be as simple as changing the breaker. are their any other devices off this circuit? if so add up everything on it, as you may not even have all 15A to yourself.

Holy crap that's bad advice. For proper electrical safety 15amp circuits are really only suppossed to carry 12amps (an 80% of max is standard for any branch circuit). Never replace a breaker with a higher one unless you increase the wire size as well.
There are electrical standards for a reason!!! Don't think that something is safe just because it will work.

 

[BCinSC]

Isn't solid 14-2 w/grnd sufficient for 30A? I thought that met code/standard.

 

[syberscott]

Originally posted by: BCinSC
Isn't solid 14-2 w/grnd sufficient for 30A? I thought that met code/standard.

10 AWG wire is required for a 30 amp circuit. Please note that this is Canadian Electrical Code (table 2), but I doubt there is any difference in American standards.

 

[Mark R]

Don't forget that the size of the wire is not all that determines the current rating.

In the UK, 30A mains circuits are usually wired with a ring of 2.5 mm^2 cable. However, at work they were adding some new sockets - they were adding 15A circuits and used a ring of 4 mm^2 cable. Why? I asked them: the new cables were being laid in an electrical conduit with some other cables - the cable had to be oversized in order to avoid overheating because of the presence of nearby cables. Other situations also have to be taken into account, including the length of cable, whether it is buried in plaster or under insulation, etc.

Never assume that the a circuit already installed can handle an increased load. If you don't know enough about mains electricity, and have to ask about current carrying capacity, and overloads - then you should stay well away from it and pay a qualified and competant electrician to advise and to install a suitable circuit.

Remember, if the house burns down and you have performed a suspect modification, then may be liable - that means your insurance is void, and any liability for injury (even to a subsequent occupant/owner) rests with you.

 

[odog]

Originally posted by: syberscott

Holy crap that's bad advice. For proper electrical safety 15amp circuits are really only suppossed to carry 12amps (an 80% of max is standard for any branch circuit). Never replace a breaker with a higher one unless you increase the wire size as well.
There are electrical standards for a reason!!! Don't think that something is safe just because it will work.

you miss the part about check the quality of the wire? if the wire can't handle the extra amperage then don't use it. as mark said many times wire is laid in overkill with far more overhead then legally required. what would happen if he cracked it open and found 10 gauge wire? he shouldn't use it, and should replace it with 8 gauge wire?

 

[Mark R]

as mark said many times wire is laid in overkill with far more overhead then legally required. what would happen if he cracked it open and found 10 gauge wire? he shouldn't use it, and should replace it with 8 gauge wire?

I'm not sure you understood the point of my story.

Let's say I wanted to upgrade one of these circuits at a later date. I look at the breaker and it's 15A. I pull one of the sockets off, and there is 4 mm^2 wire in there.

Great, I think. This wire will easily cope with 30A because 30A only needs 2.5 mm^2. I'll have no problems changing the breaker for 30A.

WRONG!

Because the wire runs in conduit there is no air to cool it, and it runs next to other cables which act as insulators and themselves also produce heat, this wire has to be the size it is to prevent overheating. Despite the fact that this cable run is seemingly massively overrated, it is in fact the minimum allowed legally.

Cables are rated differently depending on how they are laid. Unless you know the exact route of the cable and the properties of the route, you don't know the maximum allowable current for the wire. There may be a good reason why it is the size it is.

You must also not forget that the main breaker is to protect the circuit and the cables to the appliances plugged into it. You cannot have a 30A breaker on a circuit which has 15A sockets on it (unless there are seperate breakers/fuses for each socket).

 

[syberscott]

Originally posted by: e-phex

Originally posted by: syberscott

Holy crap that's bad advice. For proper electrical safety 15amp circuits are really only suppossed to carry 12amps (an 80% of max is standard for any branch circuit). Never replace a breaker with a higher one unless you increase the wire size as well.
There are electrical standards for a reason!!! Don't think that something is safe just because it will work.

you miss the part about check the quality of the wire? if the wire can't handle the extra amperage then don't use it. as mark said many times wire is laid in overkill with far more overhead then legally required. what would happen if he cracked it open and found 10 gauge wire? he shouldn't use it, and should replace it with 8 gauge wire?

I think you're twisting what I'm saying here. To me, wire quality and guage are two different things. Second, the odds of finding 10 AWG wire in a 15 amp branch circuit are like 1,000,000:1.
Some things to consider when choosing wire size (gauge) are:
-maximum load
-ambient temperature
-number of conductors in cable or raceway
-length of conductor
-type of insulation
-type of wire
-safety factor

 

[BCinSC]

All right, all right already. I'll crack the breaker box and add new circuit using 10-2 w/ground. Maybe I'll tap right off the leads from the pole. ;-)