Hi all,
I am sure this question gets asked weekly and I know the correct answer is to never do this but I am in a situation where I am on the fence. I have a small server rack in a home that draws around 9.5 amps at max load. The stack that is powered by its own 15 Amp circuit is as follows:
Ubiquiti UDM Pro
Ubiquiti USW-48-Pro-POE (yes I know this switch is overkill)
2 * NanoHD
1 * FlexHD
4 * G3 Pro
2 * Flex Mini
Rpi 4 POE
Arris SB8200
Telephone Modem
Dell Poweredge R510 (Max 370W recoded)
2 * AC Infinity AirFrame T7
1 * AC Infinity Cloudplate T7-N
** Future plans for a Synology **
I have an Eaton 5PX3000RT2U that I am looking at using one of those NEMA 5-15P to L5-30R adapters to connect it to the circuit. According to Eaton TS, the 5PX3000RT2U only pulls 1.6 Amps after a power outage when it is recharging its batteries. Assuming an 80% safety factor of 12 Amps, that leaves me with 10.4 Amps for equipment. If all the equipment I tend to use is what I have above and it is below 10.4 Amps at max load (if my math for the current draw is correct) which won’t always be the case, is it safe to use the UPS?
I know this is very frowned upon and most would say just upgrade the circuit but this is in a finished basement and it is not an option. I have this UPS so I am looking to see if I can safely use it or I should stop while I am ahead.
Thanks
7 Spice ups
Circuit breakers exist to protect the wiring , not the equipment. If you pull more than 15A on the circuit, it will trip. Assuming the breaker is working, you can’t hurt the circuit by overloading it.
A device that requires 20 or 30 amps will have a plug that matches a receptacle rated to deliver that. Adapt that down to a 15A receptacle and you will trip the breaker if it draws over 15A.
In your case, if you’re drawing 1.6A, there should be no issue.
3 Spice ups
The UPS is rated at 30 Amps with a L5-30P plug for the power input you would need a 30 Amp breaker for it to connect to.
bob2213
June 18, 2020, 7:03pm
4
The Roberts seem to have differing opinions on this.
I agree with @rhummel ’s statement - the wiring for the house circuits can handle 15 amps max, so that’s what the circuit breakers are protecting. You won’t hurt anything (in my non-electrical opinion) by adapting the L5-30P to a 15A receptacle - it’ll either work or trip the circuit breaker if the load draw is too high.
Don’t just replace the circuit breaker with a higher-capacity one though without verifying the wiring in the wall is rated for the breaker you want to install. If the wire is 15A rated, you will need to pull new wire rated for 30A.
2 Spice ups
From a purely mathematical and electronic perspective (I have a degree in EE), it should work. I do support those who say “put it on a 30 amp breaker” simply to protect yourself. You void the warranty by “adapting” the plug on it.
gregghill
June 18, 2020, 7:36pm
6
The UPS is rated at 30 amps MAXIMUM draw. For it do that SAFELY, it needs a 30 amp breaker AND at least heavy enough building wiring to handle that load, which a 15-amp breaker likely is NOT wired to. However, stating that “you would need a 30 Amp breaker for it to connect to” is incorrect. He CAN physically connect to the 30-amp outlet using the adapter he noted. As long as the draw stays under the 15 amps, he’s OK. The PROBLEM with that is it could lead an inexperienced person to just use the plug adapter and then install a 30-amp breaker connected to 15-amp rated wiring.
As Robert5205 said, “Circuit breakers exist to protect the wiring, not the equipment. If you pull more than 15A on the circuit, it will trip.” So, if he used the adapter to connect his 30-amp-maximum UPS to the wiring protected by a 15-amp circuit breaker, then he drew 14 amps, he’d be safe for a while (that much load could overheat the breaker with time). If some other equipment got added and it pulled 20 amps, hopefully the breaker would pop. If he had installed a 30-amp breaker on that 15-amp wiring, then he forgot about the breaker vs. wiring mismatch and added equipment later, he could burn the building wiring. We used to have property in the desert and a guy did exactly that when his belt sander kept popping his 15-amp breaker. He installed a 30-amp breaker and went about his business until he smelled smoke. By the time the “slab savers” (local fire dept) got there, well, there was not much more than the slab left, hence their nickname.
Gregg
gregghill
June 18, 2020, 7:42pm
7
One other thing to consider. Even though you could do it physically and keep the load low enough not to blow the 15-amp breaker, if you EVER have a fire, your insurance will investigate and probably find the remnants of your setup, then deny coverage.
Also, a 15-amp breaker will pop when there is a sudden current over-draw, but sometimes when pulling near capacity, they just get REALLY HOT and can melt if the connections are not really good and tight.
Gregg
jblair
June 18, 2020, 8:48pm
8
I think you’re fine. If the ups can put out 30 amps, that means it can handle what little bit of surge you might have on powering up equipment even with NO power coming into the ups. So the wall Jack only needs to handle a constant load of the 12.4 Amps you stated. You’re a “little” over the “normal” 30% safety margin if there are no ups. But as already stated, the worst thing that would happen is the breaker kicks.
There is far too much “if someone did this” and plain fearmongering going on.
If there was no UPS in the picture and he hotwired it right to the main feed and bypassed the electric meter, something could go wrong!
The problem, as stated, will neither void the UPS warranty nor imperil his home owner’s insurance.
A 14ga circuit with a 15A breaker can, by code, have up to 10 receptacles on it. Each one could have (could have) a 15A load plugged into it. That’s 10 x 15 = 150A!!! OMG! Obviously, the point is that circuit capacity is not the same as circuit load.
In this case, the wiring inside the UPS is sized to carry 30A (let’s use that number for discussion). It’s designed to pass through up to 30A to attached equipment. That doesn’t mean it draws 30A. It only draws what it needs to pass through, plus charging current, plus a little to run the fan and make some waste heat. If you plug nothing into the UPS, it draws a trickle current plus whatever it takes to run the smarts built into it.
If the max load on the UPS is 12A, it’s never going to draw more than 15A. If OP had a 30A receptacle and a 15A breaker, it would run fine. It would never know that it was being shorted-amped.
Sure, if someone added 20A more load to the UPS, it would trip the breaker. Exactly the same as if OP was using a powerstrip.
Are these load-adders the same people who sneak into your data center and add roles other than hyper-v to your host?
3 Spice ups
Thank you all for your opinions on the situation. It really helps me make my decision. I want to clear a few things up and say that first of all the unit is the 2014 model of the Eaton 5PX3000RT2U so it is out of warranty already. I am more worried about protecting my house. I understand how bad of an idea it is to install a 30 amp break and receptacle on the 14 AWG wire in the walls. That will not be happening, all I am thinking about doing is putting an adapter on the end so I can use the L5-30P on the UPS.
I have confirmed that at max my equipment will be around 10A. What I am trying to determine is if the max charging current of 1.6 amps that I was told my an Eaton representative is accurate or not. @rhummel I have the same opinion on the UPS only using what the equipment draws which is less than the 80% safe zone. However, what I am most worried about is if there is a power outage and the UPS uses up all of its battery. When the power comes back on the circuit will need to support the equipment load as well as charging the UPS. I have seen other posts about some UPS (mostly APC units, however) that draw a ton of current when charging. I am worried that will be my downfall because as @gregghill stated the breaker can get very hot if it is close to the 15 amps and not trip if there is not a spike. This is all dependant on if the charge current is truly 1.6 amps. If that is true I should be sitting right under 12 amps which I believe wouldn’t overheat the breaker. If the UPS does pull more current, best case scenario the breaker pops, worse case it melts. Even though I am sure this makes them uncomfortable maybe an @Eaton representative could comment on the charge current of the 2014 5PX3000RT?
Obviously I will be monitoring the system with a Wattmeter and observing the current and heat of the breaker if I went through with this but I was just hoping to get some feedback.
@seanwolsey and @jblair I was also looking at this from a mathematical standpoint and it does seem that as long as I don’t add more equipment down the road (which I don’t have much intention of doing) I should be right under the 80% load WHEN the UPS is charging, which is only for a few hours and I can turn off equipment (I know, not ideal) to keep it lower. When the UPS is not charging a sustained load of 10A seems reasonable. Maybe I am wrong as I am rusty on my EE but mathematically it seems okay for 66% sustained load. My sever draws 3 amps max and the Ubiquiti gear doesn’t draw a lot of power so I am already being very generous with 10 amp
If circuit breakers rated for X amps got “very hot” at X-1 amps, don’t you think you would have heard about it by now? Wouldn’t the papers be full of stories of houses burning down because of hot breakers? You have to use some logic here.
@mikedecamp , what’s the charging current for a fully discharged 5px3000 on the AC main?
If it uses 4 9Ah batteries, it would need 36Ah to charge them. or .36Ah at 120V (assuming 100% efficiency). I’d guess it’s < 1A @ 120V.
2 Spice ups
I’m with Robert…5205 to clarify
At the end of the day, if you were to plug in several things into a residential wall outlet all backed from the same breaker and it pulled more than 15amps, it would pop…that’s what your essentially talking about.
@rhummel
2 Spice ups
mike-eaton
June 19, 2020, 10:01am
14
Robert5205:
If circuit breakers rated for X amps got “very hot” at X-1 amps, don’t you think you would have heard about it by now? Wouldn’t the papers be full of stories of houses burning down because of hot breakers? You have to use some logic here.
Mike (Eaton), what’s the charging current for a fully discharged 5px3000 on the AC main?
If it uses 4 9Ah batteries, it would need 36Ah to charge them. or .36Ah at 120V (assuming 100% efficiency). I’d guess it’s < 1A @ 120V.
I’m going to defer to the Eaton 5PX product manager on this one. Kevin is out this week though.
@kevin-eaton
2 Spice ups
Ethan6123
June 19, 2020, 12:54pm
15
IIRC it’s pretty common to replace a double outlet 15A receptacle with a single 30A receptacle and 30A breaker using existing wiring but it doesn’t hurt to test it as is. Either it will trip the 15A breaker or it won’t.
Edit: Correction, it was a 20A receptacle I was thinking of. 30A may require different wiring.
mike-eaton
June 19, 2020, 12:58pm
16
With Kevin, our product manager out this week, I did ping our tech support crew and they actually responded in all caps:
“DON’T DO THAT!!! STOP, NO!!! STOP!!! EATON STRONGLY RECOMMENDS THAT YOU DO NOT VOID NATIONAL ELECTRICAL CODE.”
gregghill
June 19, 2020, 1:59pm
17
Robert5205:
If circuit breakers rated for X amps got “very hot” at X-1 amps, don’t you think you would have heard about it by now? Wouldn’t the papers be full of stories of houses burning down because of hot breakers? You have to use some logic here.
Mike (Eaton), what’s the charging current for a fully discharged 5px3000 on the AC main?
If it uses 4 9Ah batteries, it would need 36Ah to charge them. or .36Ah at 120V (assuming 100% efficiency). I’d guess it’s < 1A @ 120V.
I have been in two homes where the current was that high or very close to it but did not pop the breakers. We could smell the breakers or the wiring behind them and the breakers were HOT to the touch. That was when multiple people used floor heaters on their highest settings. When those heaters were all on medium, it was not an issue.
The wall outlets also get hot and melt long before breakers pop, especially if connections are loose.
Gregg
@rhummel
@mikedecamp I figured they would say that. Please note that I do not intend to use a 30A receptacle and breaker with the 14 AWG wiring. The breaker and receptacle will NOT be changing. I simply want to know if a 15A circuit with 10A of equipment load can support the UPS charging itself. Please let me know what Kevin says when he gets back, it will be very much appreciated
1 Spice up
greggmh123:
Robert5205:
If circuit breakers rated for X amps got “very hot” at X-1 amps, don’t you think you would have heard about it by now? Wouldn’t the papers be full of stories of houses burning down because of hot breakers? You have to use some logic here.
Mike (Eaton), what’s the charging current for a fully discharged 5px3000 on the AC main?
If it uses 4 9Ah batteries, it would need 36Ah to charge them. or .36Ah at 120V (assuming 100% efficiency). I’d guess it’s < 1A @ 120V.
I have been in two homes where the current was that high or very close to it but did not pop the breakers. We could smell the breakers or the wiring behind them and the breakers were HOT to the touch. That was when multiple people used floor heaters on their highest settings. When those heaters were all on medium, it was not an issue.
The wall outlets also get hot and melt long before breakers pop, especially if connections are loose.
Gregg
I cannot respond to your personal anecdotes except to point out that you appear to be exceptionally unlucky. Or, lucky, if you consider that you have survived this long.
If you have loose connections, the solution is not to reduce your current usage, but to fix the connection, no? Perhaps on every single post where someone proposes connecting something to an electrical source we should add the disclaimer Before connecting any equipment to a power source, have your entire electrical system inspected by a competent professional. Let’s ignore the fact that those loose connections were probably installed by a professional in the first place.
Overheating was a real problem when aluminum wire was used in residential construction between 1965 and 1972. While the wire itself isn’t an issue and can still be used, the connections were a problem. Oxidation of the aluminum created resistance which creates heat which induces “wire creep” as the aluminum expands more than copper. Here’s an example of a really crappy connection in a breaker box that’s obviously been exposed to water (note the rust on the breaker and on the bus bar rivets) where the wire overheated.
However, in the case of the OP, he’s not running multiple space heaters. He is, in fact, currently running the same load he is proposing and planning on adding one more small device. If he proposed adding another desktop PC to his rack to run Squid, would you tell him not to because his breakers might overheat and catch fire?
1 Spice up
greggmh123:
Robert5205:
If circuit breakers rated for X amps got “very hot” at X-1 amps, don’t you think you would have heard about it by now? Wouldn’t the papers be full of stories of houses burning down because of hot breakers? You have to use some logic here.
Mike (Eaton), what’s the charging current for a fully discharged 5px3000 on the AC main?
If it uses 4 9Ah batteries, it would need 36Ah to charge them. or .36Ah at 120V (assuming 100% efficiency). I’d guess it’s < 1A @ 120V.
I have been in two homes where the current was that high or very close to it but did not pop the breakers. We could smell the breakers or the wiring behind them and the breakers were HOT to the touch. That was when multiple people used floor heaters on their highest settings. When those heaters were all on medium, it was not an issue.
The wall outlets also get hot and melt long before breakers pop, especially if connections are loose.
Gregg
I believe what @gregghill is stating is correct, I have heard many cases of a constant high current draw (not a spike) not tripping the breaker and causing a lot of heat. What I am attempting to do is basically the same thing as plugging say 11.5 amps of equipment into the circuit. I am still relying on the breaker to pop at 15 amps so I want to remain under the 80% load of 12 amps. I believe at 80% load, while existent, the heat is not as much of concern whereas when you creep up to 14.5/15 amps you have issues. This is no different than plugging a bunch of hairdryers into the circuit and causing excess heat. As long as I can remain below 80% (dependant on UPS charge current) I should be safe.
