(related?) - refrigerator on (living room), non-dedicated 15A circuit?

[user 246304]

Total incompetent with electrics. I know.

So, trying to put together a motley assembly of two full-sized fridges as fermentation chambers. One, basically, an ale fridge and the other, lagers. Both are controlled with dual-control Inkbirds, and have germination mats for heating and obviously, cooling.

The lager fridge is currently outside, on our back porch, exposed. The outlet, which draws on our LR 15A circuit, is a GFCI outlet and it's this where I have a heavy-gauge (can't recall which one, but heavy) extension chord out to the inkbird, which controls in turn a Fermentwrap (40W) and the full-size fridge.

The ale fridge is actually in our BR and is drawing on our 15A BR circuit. Not much else there, except lights.

My question, would a typical 15A circuit handling a fridge at power up, a television and a few lights pose a problem? Or am I better off stringing the lager line to one of our two 20A circuits - kitchen, but it has its own fridge, or BR, for the fan - so these would be shared?

 

[odie]

I think you will be fine. I have 3 fridges and a freezer in my living room. they draw very little power running. Start up is the only brief peak and even that is not a lot. Not sure if they are all on the same circuit but I also got sizable stereo amps in the same rooms.

old 1940s vintage...they rarely run. very efficient.

 

[user 246304]

I think you will be fine. I have 3 fridges and a freezer in my living room. they draw very little power running. Start up is the only brief peak and even that is not a lot. Not sure if they are all on the same circuit but I also got sizable stereo amps in the same rooms.

old 1940s vintage...they rarely run. very efficient.

Great, thanks Odie.

You sound like me, lol. Thank god my wife loves beer.

 

[mac_1103]

I also think you'll be fine. If you want some extra reassurance, there should be labels either inside or on the back of the refrigerators telling you how many amps they draw. I have a 25 cf refrigerator/freezer, a 7 cf refrigerator and a 7 cf freezer in my basement on a single 20 amp circuit. I could probably double the load and still not trip the breaker.

OTOH, a microwave and a toaster oven on the same 15 amp circuit is an entirely different matter. I could never get my wife to understand that, so I finally ran another line to the kitchen.

 

[day_trippr]

I'd put in a new home run...

Cheers!

 

[user 246304]

Thanks much fellas.

 

[mac_1103]

I'd put in a new home run...

8 gauge 4 conductor. Might as well future-proof it.

 

[passedpawn]

Don't put on a bandaid if it isn't bleeding.

That is, just do it. If your breaker trips, well I guess you need to move to plan B.

 

[Tony B]

Amps X Volts = Watts
15 amps X 120 volts = 1,800 watts
You should plan on using no more than 80% of that on the reg to avoid issues. So, 1.440 watts with everything on that circuit running at the same time.

If you know what all is on that circuit, you'll be able to see where you stand.

 

[user 246304]

Amps X Volts = Watts
15 amps X 120 volts = 1,800 watts
You should plan on using no more than 80% of that on the reg to avoid issues. So, 1.440 watts with everything on that circuit running at the same time.

If you know what all is on that circuit, you'll be able to see where you stand.

Thanks Tony.

 

[Mark3885]

This will explain your problem.

 

[user 246304]

This will explain your problem.

Loved that show and had a crush on her as a kid. I actually ran into Eddie Albert, stood in line next to each other going to see a show at the Mark Taper Forum in L.A. Nice guy.

 

[whoaru99]

Amps X Volts = Watts
15 amps X 120 volts = 1,800 watts
You should plan on using no more than 80% of that on the reg to avoid issues. So, 1.440 watts with everything on that circuit running at the same time.

If you know what all is on that circuit, you'll be able to see where you stand.

Adding more detail to this since the "80% rule" comes up fairly often.

Circuits are rated for 100% of their capacity, but the continuous* load part of total load is not to exceed 80% of the circuit rating.

Then there is another 80% rule irrespective of the one above, that says cord and plug connected devices on circuits with multiple outlets are not to exceed 80% of the circuit rating.


*continuous defined by NEC as 3 hours or more in duration

 

[mac_1103]

Then there is another 80% rule irrespective of the one above, that says cord and plug connected devices on circuits with multiple outlets are not to exceed 80% of the circuit rating.

As if the average homeowner or apartment dweller even knows which outlets are on which circuits, much less the rule.

 

[whoaru99]

As if the average homeowner or apartment dweller even knows which outlets are on which circuits, much less the rule.

Lots here must be above average because it comes up on a somewhat regular basis.

Way I look at it is just because there may be general ignorance we shouldn't perpetuate it if/when possible.

 

[mac_1103]

Way I look at it is just because there may be general ignorance we shouldn't perpetuate it if/when possible.

Of course. My comment was about the silliness of having a rule that nobody bothers to make the general public aware of.

 

[whoaru99]

I think it largely sorts itself in the end. Overloaded circuits trip out and sooner or later people figure out the space heater and vacuum cleaner (or whatever) don't play well together on the same receptacle or certain other ones.

Even though they many not know the rule directly they run headlong into the reason it exists if they don't abide.

 

[sbro]

I believe those 80% rules are for design purposes to determine how many circuits to install for various purposes. Once installed, a homeowner has no idea what a circuit load is and may actually be using 90% continuously which would probably work just fine unless you have a high resistance connection or faulty breaker.

 

[whoaru99]

The continuous load 80% thing stems from breakers being rated 100% in free air but they're normally in a panel along with a bunch of others. With continuous loading there is higher temp rise than with intermittent albeit possibly higher load, hence the derate for the continuous condition.

The number and type of circuits is usually based on VA per square foot for general/lighting circuits and the requirements of the larger appliances.

 

[passedpawn]

Loved that show and had a crush on her as a kid. I actually ran into Eddie Albert, stood in line next to each other going to see a show at the Mark Taper Forum in L.A. Nice guy.

you know, the number of living people who have said "I had a crush on zsa zsa" goes down exponentially with time. It will reach zero, and it will be absolute (not asymptotic) in not too many years.

 

[Dland]

I'd probably also just run a new circuit, it is not that hard to do. But if you want to assess current draw, get a Killowatt P-3 or similar device they are cheap and can tell you a lot.

 

[passedpawn]

I'd probably also just run a new circuit, it is not that hard to do. But if you want to assess current draw, get a Killowatt P-3 or similar device they are cheap and can tell you a lot.

So, you apply a bandaid to your hand BEFORE you start working on a piece of wood? I think that's a wasteful idea. But not a bad idea.

 

[mashdar]

So, you apply a bandaid to your hand BEFORE you start working on a piece of wood? I think that's a wasteful idea. But not a bad idea.

I think it's called a glove : )

(edit: says the guy that was just sawing something with a dozuki saw 2mm from a finger.)

 

[user 246304]

you know, the number of living people who have said "I had a crush on zsa zsa" goes down exponentially with time. It will reach zero, and it will be absolute (not asymptotic) in not too many years.

HAHAHAHA...........tell me about it brother.

 

[Dland]

So, you apply a bandaid to your hand BEFORE you start working on a piece of wood? I think that's a wasteful idea. But not a bad idea.

No, as I stated, I'd a run a new (20A) circuit. Just suggesting a inexpensive measuring tool to someone who might want to quantify extent of problem.

A good tool to have around in any case, can monitor amps actually used by device, as well as line Hertz and voltage. The latter measurements pretty important if running off remote or standby power source, of it utility line power is suspect. And inexpensive compared to other "should have" measuring tools such as toxic gas meters, EMF detector and Geiger counter, But I digress....

 

[whoaru99]

FYI/FWIW, we have a fairly large fridge. Data plate on that lists 6.5A.

My question, would a typical 15A circuit handling a fridge at power up, a television and a few lights pose a problem?

Even though startup current can be much higher than nominal, breakers are not "brick wall" in terms of tripping immediately at the nominal rating.

Breakers can pass many times their rated current for short duration without tripping. Square D / Schneider Electric (and I'd guess others too) publish curves where you can see the range of current vs. trip out time.

 

[mashdar]

FYI/FWIW, we have a fairly large fridge. Data plate on that lists 6.5A.



Even though startup current can be much higher than nominal, breakers are not "brick wall" in terms of tripping immediately at the nominal rating.

Breakers can pass many times their rated current for short duration without tripping. Square D / Schneider Electric (and I'd guess others too) publish curves where you can see the range of current vs. trip out time.

I have a relatively new ~22cu ft fridge/freezer in the basement rated 11.6A. It's even an energy star model! Maybe the defrost is a big part of that.

I tend to assume they're 12A for circuit loading purposes unless I know otherwise.

Re breakers, there's a reason why you get to size them at 250% motor FLC. Inrush is generally 6-8x FLA/RLA. Presumably any 15A appliance is tested to work with common 15A thermal magnetic breakers, but all bets are off if you're adding other stuff to the circuit with a >8A motor load, IMO.

Personally, I'd walk around and add up some nameplates for a worst case load and peace of mind. Breakers are supposed to be the backup chute, not the primary : )

 

[whoaru99]

I have a relatively new ~22cu ft fridge/freezer in the basement rated 11.6A. It's even an energy star model! Maybe the defrost is a big part of that.

I tend to assume they're 12A for circuit loading purposes unless I know otherwise.

Re breakers, there's a reason why you get to size them at 250% motor FLC. Inrush is generally 6-8x FLA/RLA. Presumably any 15A appliance is tested to work with common 15A thermal magnetic breakers, but all bets are off if you're adding other stuff to the circuit with a >8A motor load, IMO.

Personally, I'd walk around and add up some nameplates for a worst case load and peace of mind. Breakers are supposed to be the backup chute, not the primary : )

FWIW, I've measured one of the stereo amps I have at just ~100A inrush. Works fine on a 15A circuit though because that high peak is only about 1/2 cycle.

 

[mashdar]

FWIW, I've measured one of the stereo amps I have at just ~100A inrush. Works fine on a 15A circuit though because that high peak is only about 1/2 cycle.

That's capacitive inrush. Motors basically look like a locked rotor until they get moving. It can take most of a second, depending on the system. Here's a little paper on fuse selection:
https://www.eaton.com/content/dam/e.../bus-ele-tech-lib-motor-starting-currents.pdf

 

[whoaru99]

That's capacitive inrush. Motors basically look like a locked rotor until they get moving. It can take most of a second, depending on the system. Here's a little paper

Yes, I have a reasonable understanding of why it (high initial current, then tapering) occurs in either case.

 

[user 246304]

Enjoying the discussion guys.

 

[day_trippr]

Oh, yeah, right. I think we all forgot about you there
So, whatcha gonna do then?

Cheers!

 

[whoaru99]

Perhaps a couple previous remarks I made bear some clarification or further detail.

When mentioned that breakers can handle high short term peaks then gave example of 100A for 1/2 cycle, the point to elaborate is the duration is not constrained to very short time 1/2 cycle.

Going again to the Square D QO example, the trip curve for 15A breaker shows 4.5x to 9x nominal rating (68A to 135A) for trip current at 1 second duration.

If you take that down to 1/2 second, it's 6x to 13x nominal rating (90A to 195A).

That's a lot of cushion for starting loads in residential/home appliance use case.

 

[user 246304]

Oh, yeah, right. I think we all forgot about you there
So, whatcha gonna do then?

Cheers!

Lol, no, this stuff eludes my brain but when I get the chance, I'd like to dig in and learn more. I ended up with the fridge outside, two mini-heaters on Inkbird, and the feed is an external outlet, on the LR circuit. So far, so good.

 

[whoaru99]

... So far, so good.

I'm all for learning, but when rubber meets the road whether the loading is OK or suspect/problematic, I suggest the comment above appears to answer the question from a pragmatic rather than academic perspective

 

[user 246304]

I'm all for learning, but when rubber meets the road whether the loading is OK or suspect/problematic, I suggest the comment above appears to answer the question from a pragmatic rather than academic perspective

Sorry, by "above," you mean your last post?

 

[whoaru99]

No, your words I quoted, "so far, so good".

 

[user 246304]

No, your words I quoted, "so far, so good".

Oh, OK, thanks.