Circuit Breaker 22AIC

On 9/25/2023 12:34 PM, Ralph Mowery wrote:
> In article <uesltr$22gfl$2@dont-email.me>, blockedofcourse@foo.invalid
> says...
>>
>> [Anyone who has lived in a dorm room can appreciate "active
>> power management"!  :-( ]
> 
> When my son was in a dorm room he could rent what they called a
> 'microfrige'.  It was a microwave on top of a small refrigerator.  I
> would assume it was set up so both of them were not drawing power at the
> same time. Due to the cost of the rent we decided just to buy a
> microwave an small refrigerator.

No microwaves when I was in school.  But, our kitchen had a
(laughably) small refrigerator.  Silly considering college kids
likely used the fridge more than the stove (oven?  what's THAT??)

I'm not sure how much "smarts" I would read into a combination
product's design.  It may literally be little more than a
simple repackaging of two *independant* products into a more
convenient form factor.

E.g., our fridge has three evaporators but one compressor.
I wouldn't be surprised if the control algorithm was much
more than:
     if (any zone calls for cooling)
         compressor(on)
(where compressor() had buried state that included a timer
since last activation)

Too often, control algorithms are naive and live entirely
in the moment.  E.g., your irrigation system *may* cut back
on water use if it detects that it has rained, recently.
*BUT*, will gleefully water your flora despite the
growing storm clouds overhead!  (isn't watering just BEFORE
a rain as wasteful as just after?)

Sad that so many products don't "open" their implementations
as I'm sure there are lots of optimizations that are possible
with multiple eyes/criteria looking at a problem!

mandag den 25. september 2023 kl. 20.44.39 UTC+2 skrev Eddy Lee:
> On Monday, September 25, 2023 at 11:22:16 AM UTC-7, Don Y wrote: 
> > On 9/25/2023 9:05 AM, Eddy Lee wrote: 
> > > If I unplug the fridge, or when it's silence, microwave is fine. Sound like I need a relay circuit to disable the fridge from the microwave. Namely, a fridge outlet on the microwave. 
> > What's the nameplate rating of the microwave? Does *it* say 
> > it requires a dedicated circuit? (because it draws more than 
> > half of the rated branch circuit's ampacity) 
> > 
> > The countertops, in kitchens, tend to see lots of large 
> > loads that are often running concurrently. Toaster, 
> > toaster oven, countertop oven (e.g., all the toaster 
> > ovens on steroids that you see advertised on TV), 
> > stand/hand mixer, electric frying pan, *TV*, etc. 
> > 
> > Add to this the other large loads that folks tend to 
> > think nothing of activating: dishwasher, garbage disposal, 
> > microwave, "instant hot water", etc. Imagine mindlessly 
> > turning on the garbage disposal (for 10 seconds) and 
> > tripping a breaker because it shared a branch circuit 
> > with some other appliance... 
> > 
> > You *don't* want to unplug/replug the refrigerator 
> > (which is what a relay would do) as this can confuse 
> > the defrost timer and (for poorly designed controls) 
> > lead to the compressor starting under a (mechanical) 
> > load that hasn't yet had time to dissipate (smart 
> > controls will inhibit the compressor for its required 
> > dead time on initial application of power for exactly 
> > this reason -- but, then, you would risk the compressor 
> > always "waiting" even without cause) 
> > 
> > [Microwave ovens tend to see frequent, brief use. 
> > Would you want your refrigerator being unplugged 
> > each time you throw something in the microwave 
> > for 15 seconds?] 
> > 
> > And, refrigerators (if disabled due to a tripped breaker) 
> > risk having their contents spoil. So, you'd like the 
> > refrigerator to be the sole item that can cause *its* 
> > breaker to trip (imagine the instant hot water unit 
> > thermostatically cycled on and silently took out the 
> > breaker for the refrigerator... which you happen to 
> > discover the next *morning*). Ditto the dishwasher 
> > or any other appliance that can "safely" sit, powered 
> > off, with no ill effects (e.g., the dishes are still dirty 
> > but aren't getting any *dirtier* in the absence of mains!)
> Fridge: 310KWhr/year = 35W average (no info on motor) 

probably more that 20x that when running (google says US average fridge is 725W), 
and the start up current can be 3x that

> Microwave: 1500W 

the start up current can be 3x that for a few cycles

> Laptops: 60W to 90W. 
> 
> No dishwasher or coffee pot.

(725+1500+60*10)/120V = 23.5A that's more than 20A .....

the AIC rating really only matters in a dead short

mandag den 25. september 2023 kl. 22.07.41 UTC+2 skrev Don Y:
> On 9/25/2023 12:34 PM, Ralph Mowery wrote: 
> > In article <uesltr$22gfl$2...@dont-email.me>, blocked...@foo.invalid 
> > says... 
> >> 
> >> [Anyone who has lived in a dorm room can appreciate "active 
> >> power management"! :-( ] 
> > 
> > When my son was in a dorm room he could rent what they called a 
> > 'microfrige'. It was a microwave on top of a small refrigerator. I 
> > would assume it was set up so both of them were not drawing power at the 
> > same time. Due to the cost of the rent we decided just to buy a 
> > microwave an small refrigerator.
> No microwaves when I was in school. But, our kitchen had a 
> (laughably) small refrigerator. Silly considering college kids 
> likely used the fridge more than the stove (oven? what's THAT??) 
> 
> I'm not sure how much "smarts" I would read into a combination 
> product's design. It may literally be little more than a 
> simple repackaging of two *independant* products into a more 
> convenient form factor. 
> 
> E.g., our fridge has three evaporators but one compressor. 
> I wouldn't be surprised if the control algorithm was much 
> more than: 
> if (any zone calls for cooling) 
> compressor(on) 
> (where compressor() had buried state that included a timer 
> since last activation) 
> 
> Too often, control algorithms are naive and live entirely 
> in the moment. E.g., your irrigation system *may* cut back 
> on water use if it detects that it has rained, recently. 
> *BUT*, will gleefully water your flora despite the 
> growing storm clouds overhead! (isn't watering just BEFORE 
> a rain as wasteful as just after?) 
> 
> Sad that so many products don't "open" their implementations 
> as I'm sure there are lots of optimizations that are possible 
> with multiple eyes/criteria looking at a problem!

and while you are busy optimising the irrigation system the plans dry out and die

there's; too late, too expensive and good enough

On Monday, September 25, 2023 at 12:31:34 PM UTC-7, Ricky wrote:
> On Monday, September 25, 2023 at 2:44:39 PM UTC-4, Eddy Lee wrote: 
> > On Monday, September 25, 2023 at 11:22:16 AM UTC-7, Don Y wrote: 
> > > On 9/25/2023 9:05 AM, Eddy Lee wrote: 
> > > > If I unplug the fridge, or when it's silence, microwave is fine. Sound like I need a relay circuit to disable the fridge from the microwave. Namely, a fridge outlet on the microwave. 
> > > What's the nameplate rating of the microwave? Does *it* say 
> > > it requires a dedicated circuit? (because it draws more than 
> > > half of the rated branch circuit's ampacity) 
> > > 
> > > The countertops, in kitchens, tend to see lots of large 
> > > loads that are often running concurrently. Toaster, 
> > > toaster oven, countertop oven (e.g., all the toaster 
> > > ovens on steroids that you see advertised on TV), 
> > > stand/hand mixer, electric frying pan, *TV*, etc. 
> > > 
> > > Add to this the other large loads that folks tend to 
> > > think nothing of activating: dishwasher, garbage disposal, 
> > > microwave, "instant hot water", etc. Imagine mindlessly 
> > > turning on the garbage disposal (for 10 seconds) and 
> > > tripping a breaker because it shared a branch circuit 
> > > with some other appliance... 
> > > 
> > > You *don't* want to unplug/replug the refrigerator 
> > > (which is what a relay would do) as this can confuse 
> > > the defrost timer and (for poorly designed controls) 
> > > lead to the compressor starting under a (mechanical) 
> > > load that hasn't yet had time to dissipate (smart 
> > > controls will inhibit the compressor for its required 
> > > dead time on initial application of power for exactly 
> > > this reason -- but, then, you would risk the compressor 
> > > always "waiting" even without cause) 
> > > 
> > > [Microwave ovens tend to see frequent, brief use. 
> > > Would you want your refrigerator being unplugged 
> > > each time you throw something in the microwave 
> > > for 15 seconds?] 
> > > 
> > > And, refrigerators (if disabled due to a tripped breaker) 
> > > risk having their contents spoil. So, you'd like the 
> > > refrigerator to be the sole item that can cause *its* 
> > > breaker to trip (imagine the instant hot water unit 
> > > thermostatically cycled on and silently took out the 
> > > breaker for the refrigerator... which you happen to 
> > > discover the next *morning*). Ditto the dishwasher 
> > > or any other appliance that can "safely" sit, powered 
> > > off, with no ill effects (e.g., the dishes are still dirty 
> > > but aren't getting any *dirtier* in the absence of mains!) 
> > Fridge: 310KWhr/year = 35W average (no info on motor) 
> > Microwave: 1500W 
> > Laptops: 60W to 90W. 
> > 
> > No dishwasher or coffee pot.
> I like that you provided the "average" power draw of the fridge. How do you expect to use that in solving your problem? 

You answered your question in another post:

"Typically a refrigerator runs on 35% duty cycle, (65% for a freezer). This means that if you take the running watts and multiply it by 35%, you can get an idea as to how much power the average running amps will be."

> It just occurred to me. You have the fridge to chill all the laptops so you can overclock them!!! 

Not really.  They are air-cooled.
 
> Here's the most direct route to solving your problem. Get a microwave that is 600 watts, rather than the behemoth 1500 watt monster. Do you actual defrost turkeys in it? 

It's fairly standard sized microwave.  

I still don't understand Fred's concern about relay switching the fridge.  I got some 30A relay contacts that should be enough.  Half of the laptops have batteries, which I can also relay switch off while using the microwave.

On 9/25/2023 1:23 PM, Lasse Langwadt Christensen wrote:
> mandag den 25. september 2023 kl. 22.07.41 UTC+2 skrev Don Y:
>> On 9/25/2023 12:34 PM, Ralph Mowery wrote:
>>> In article <uesltr$22gfl$2...@dont-email.me>, blocked...@foo.invalid
>>> says...
>>>>
>>>> [Anyone who has lived in a dorm room can appreciate "active
>>>> power management"! :-( ]
>>>
>>> When my son was in a dorm room he could rent what they called a
>>> 'microfrige'. It was a microwave on top of a small refrigerator. I
>>> would assume it was set up so both of them were not drawing power at the
>>> same time. Due to the cost of the rent we decided just to buy a
>>> microwave an small refrigerator.
>> No microwaves when I was in school. But, our kitchen had a
>> (laughably) small refrigerator. Silly considering college kids
>> likely used the fridge more than the stove (oven? what's THAT??)
>>
>> I'm not sure how much "smarts" I would read into a combination
>> product's design. It may literally be little more than a
>> simple repackaging of two *independant* products into a more
>> convenient form factor.
>>
>> E.g., our fridge has three evaporators but one compressor.
>> I wouldn't be surprised if the control algorithm was much
>> more than:
>> if (any zone calls for cooling)
>> compressor(on)
>> (where compressor() had buried state that included a timer
>> since last activation)
>>
>> Too often, control algorithms are naive and live entirely
>> in the moment. E.g., your irrigation system *may* cut back
>> on water use if it detects that it has rained, recently.
>> *BUT*, will gleefully water your flora despite the
>> growing storm clouds overhead! (isn't watering just BEFORE
>> a rain as wasteful as just after?)
>>
>> Sad that so many products don't "open" their implementations
>> as I'm sure there are lots of optimizations that are possible
>> with multiple eyes/criteria looking at a problem!
> 
> and while you are busy optimising the irrigation system the plans dry out and die

Because you are incapable of using existing technology while
developing newer?  Sounds like a pretty limited intellectual capacity...
walk/chew (gum) -- pick one...

> there's; too late, too expensive and good enough

When you live where lack of water is a REAL issue, you think twice about
how it is misused or underutilized.  "Good enough" works when there *is*
enough!

On Monday, September 25, 2023 at 4:25:39 PM UTC-4, Eddy Lee wrote:
> On Monday, September 25, 2023 at 12:31:34 PM UTC-7, Ricky wrote: 
> > On Monday, September 25, 2023 at 2:44:39 PM UTC-4, Eddy Lee wrote: 
> > > On Monday, September 25, 2023 at 11:22:16 AM UTC-7, Don Y wrote: 
> > > > On 9/25/2023 9:05 AM, Eddy Lee wrote: 
> > > > > If I unplug the fridge, or when it's silence, microwave is fine. Sound like I need a relay circuit to disable the fridge from the microwave. Namely, a fridge outlet on the microwave. 
> > > > What's the nameplate rating of the microwave? Does *it* say 
> > > > it requires a dedicated circuit? (because it draws more than 
> > > > half of the rated branch circuit's ampacity) 
> > > > 
> > > > The countertops, in kitchens, tend to see lots of large 
> > > > loads that are often running concurrently. Toaster, 
> > > > toaster oven, countertop oven (e.g., all the toaster 
> > > > ovens on steroids that you see advertised on TV), 
> > > > stand/hand mixer, electric frying pan, *TV*, etc. 
> > > > 
> > > > Add to this the other large loads that folks tend to 
> > > > think nothing of activating: dishwasher, garbage disposal, 
> > > > microwave, "instant hot water", etc. Imagine mindlessly 
> > > > turning on the garbage disposal (for 10 seconds) and 
> > > > tripping a breaker because it shared a branch circuit 
> > > > with some other appliance... 
> > > > 
> > > > You *don't* want to unplug/replug the refrigerator 
> > > > (which is what a relay would do) as this can confuse 
> > > > the defrost timer and (for poorly designed controls) 
> > > > lead to the compressor starting under a (mechanical) 
> > > > load that hasn't yet had time to dissipate (smart 
> > > > controls will inhibit the compressor for its required 
> > > > dead time on initial application of power for exactly 
> > > > this reason -- but, then, you would risk the compressor 
> > > > always "waiting" even without cause) 
> > > > 
> > > > [Microwave ovens tend to see frequent, brief use. 
> > > > Would you want your refrigerator being unplugged 
> > > > each time you throw something in the microwave 
> > > > for 15 seconds?] 
> > > > 
> > > > And, refrigerators (if disabled due to a tripped breaker) 
> > > > risk having their contents spoil. So, you'd like the 
> > > > refrigerator to be the sole item that can cause *its* 
> > > > breaker to trip (imagine the instant hot water unit 
> > > > thermostatically cycled on and silently took out the 
> > > > breaker for the refrigerator... which you happen to 
> > > > discover the next *morning*). Ditto the dishwasher 
> > > > or any other appliance that can "safely" sit, powered 
> > > > off, with no ill effects (e.g., the dishes are still dirty 
> > > > but aren't getting any *dirtier* in the absence of mains!) 
> > > Fridge: 310KWhr/year = 35W average (no info on motor) 
> > > Microwave: 1500W 
> > > Laptops: 60W to 90W. 
> > > 
> > > No dishwasher or coffee pot. 
> > I like that you provided the "average" power draw of the fridge. How do you expect to use that in solving your problem?
> You answered your question in another post: 
> 
> "Typically a refrigerator runs on 35% duty cycle, (65% for a freezer). This means that if you take the running watts and multiply it by 35%, you can get an idea as to how much power the average running amps will be."

I'm pretty sure I didn't post that.  Regardless, that would be a combination of an average with a rule of thumb, so not of much value.  The point is, your appliance has a plate with the actual power rating while running.  Why don't you look at that?  Not the motor, the appliance.  You've also said nothing about the size of this appliance.  Is it a dorm room size fridge?  A massive double door kitchen behemoth?  Something in between?  As is usual with you, only the barest minimum of information is provided and then the guessing begins. 


> > It just occurred to me. You have the fridge to chill all the laptops so you can overclock them!!!
> Not really. They are air-cooled. 

LOL!  


> > Here's the most direct route to solving your problem. Get a microwave that is 600 watts, rather than the behemoth 1500 watt monster. Do you actual defrost turkeys in it?
> It's fairly standard sized microwave. 

1500W is not a standard size microwave.  That's as large as they get for home use.  600W to 1000W is much more typical.  Should I assume you actually read the rating plate to get the 1500W number?  Or is this another "average" you pulled off a web page, somewhere?  


> I still don't understand Fred's concern about relay switching the fridge. I got some 30A relay contacts that should be enough. Half of the laptops have batteries, which I can also relay switch off while using the microwave.

You will wear out the relays in relatively short order.  Maybe a few months, maybe a year, depending on how often you use the microwave.  The current rating does not mean you can open the circuit under load as much as you want.  Especially with motors, this causes an arc across the contacts, eroding and pitting them severely in a small number of cycles. 

-- 

  Rick C.

  ++ Get 1,000 miles of free Supercharging
  ++ Tesla referral code - https://ts.la/richard11209

On Monday, September 25, 2023 at 1:39:33 PM UTC-7, Ricky wrote:
> On Monday, September 25, 2023 at 4:25:39 PM UTC-4, Eddy Lee wrote: 
> > On Monday, September 25, 2023 at 12:31:34 PM UTC-7, Ricky wrote: 
> > > On Monday, September 25, 2023 at 2:44:39 PM UTC-4, Eddy Lee wrote: 
> > > > On Monday, September 25, 2023 at 11:22:16 AM UTC-7, Don Y wrote: 
> > > > > On 9/25/2023 9:05 AM, Eddy Lee wrote: 
> > > > > > If I unplug the fridge, or when it's silence, microwave is fine. Sound like I need a relay circuit to disable the fridge from the microwave. Namely, a fridge outlet on the microwave. 
> > > > > What's the nameplate rating of the microwave? Does *it* say 
> > > > > it requires a dedicated circuit? (because it draws more than 
> > > > > half of the rated branch circuit's ampacity) 
> > > > > 
> > > > > The countertops, in kitchens, tend to see lots of large 
> > > > > loads that are often running concurrently. Toaster, 
> > > > > toaster oven, countertop oven (e.g., all the toaster 
> > > > > ovens on steroids that you see advertised on TV), 
> > > > > stand/hand mixer, electric frying pan, *TV*, etc. 
> > > > > 
> > > > > Add to this the other large loads that folks tend to 
> > > > > think nothing of activating: dishwasher, garbage disposal, 
> > > > > microwave, "instant hot water", etc. Imagine mindlessly 
> > > > > turning on the garbage disposal (for 10 seconds) and 
> > > > > tripping a breaker because it shared a branch circuit 
> > > > > with some other appliance... 
> > > > > 
> > > > > You *don't* want to unplug/replug the refrigerator 
> > > > > (which is what a relay would do) as this can confuse 
> > > > > the defrost timer and (for poorly designed controls) 
> > > > > lead to the compressor starting under a (mechanical) 
> > > > > load that hasn't yet had time to dissipate (smart 
> > > > > controls will inhibit the compressor for its required 
> > > > > dead time on initial application of power for exactly 
> > > > > this reason -- but, then, you would risk the compressor 
> > > > > always "waiting" even without cause) 
> > > > > 
> > > > > [Microwave ovens tend to see frequent, brief use. 
> > > > > Would you want your refrigerator being unplugged 
> > > > > each time you throw something in the microwave 
> > > > > for 15 seconds?] 
> > > > > 
> > > > > And, refrigerators (if disabled due to a tripped breaker) 
> > > > > risk having their contents spoil. So, you'd like the 
> > > > > refrigerator to be the sole item that can cause *its* 
> > > > > breaker to trip (imagine the instant hot water unit 
> > > > > thermostatically cycled on and silently took out the 
> > > > > breaker for the refrigerator... which you happen to 
> > > > > discover the next *morning*). Ditto the dishwasher 
> > > > > or any other appliance that can "safely" sit, powered 
> > > > > off, with no ill effects (e.g., the dishes are still dirty 
> > > > > but aren't getting any *dirtier* in the absence of mains!) 
> > > > Fridge: 310KWhr/year = 35W average (no info on motor) 
> > > > Microwave: 1500W 
> > > > Laptops: 60W to 90W. 
> > > > 
> > > > No dishwasher or coffee pot. 
> > > I like that you provided the "average" power draw of the fridge. How do you expect to use that in solving your problem? 
> > You answered your question in another post: 
> > 
> > "Typically a refrigerator runs on 35% duty cycle, (65% for a freezer). This means that if you take the running watts and multiply it by 35%, you can get an idea as to how much power the average running amps will be."
> I'm pretty sure I didn't post that. Regardless, that would be a combination of an average with a rule of thumb, so not of much value. The point is, your appliance has a plate with the actual power rating while running. Why don't you look at that? Not the motor, the appliance. You've also said nothing about the size of this appliance. Is it a dorm room size fridge? A massive double door kitchen behemoth? Something in between? As is usual with you, only the barest minimum of information is provided and then the guessing begins.

There is an energy guide tag saying 310 KWhr/year.  Nothing else.  Detail info might be at the back of the fridge.  Too heavy to pull the fridge out when loaded.  

We just need to agree that it's too much to have both the fridge and microwave running together.

> > > It just occurred to me. You have the fridge to chill all the laptops so you can overclock them!!! 
> > Not really. They are air-cooled.
> LOL!
> > > Here's the most direct route to solving your problem. Get a microwave that is 600 watts, rather than the behemoth 1500 watt monster. Do you actual defrost turkeys in it? 
> > It's fairly standard sized microwave.
> 1500W is not a standard size microwave. That's as large as they get for home use. 600W to 1000W is much more typical. Should I assume you actually read the rating plate to get the 1500W number? Or is this another "average" you pulled off a web page, somewhere?

Yes, rating plate at the back of the microwave.

> > I still don't understand Fred's concern about relay switching the fridge. I got some 30A relay contacts that should be enough. Half of the laptops have batteries, which I can also relay switch off while using the microwave.
> You will wear out the relays in relatively short order. Maybe a few months, maybe a year, depending on how often you use the microwave. The current rating does not mean you can open the circuit under load as much as you want. Especially with motors, this causes an arc across the contacts, eroding and pitting them severely in a small number of cycles. 

5 to 10 times per day. 3000 per year.  It should last at least a year.
I will put a filter cap in parallel with the contacts.

On Monday, 25 September 2023 at 09:39:26 UTC+1, Ricky wrote:

> The only individual heavy load is the microwave which ranges from 600W to 1,400W, depending on size. 

Output. Consumption is about 1.2kW - 2kW

On Monday, September 25, 2023 at 4:57:02 PM UTC-4, Eddy Lee wrote:
> On Monday, September 25, 2023 at 1:39:33 PM UTC-7, Ricky wrote: 
> > On Monday, September 25, 2023 at 4:25:39 PM UTC-4, Eddy Lee wrote: 
> > > On Monday, September 25, 2023 at 12:31:34 PM UTC-7, Ricky wrote: 
> > > > On Monday, September 25, 2023 at 2:44:39 PM UTC-4, Eddy Lee wrote: 
> > > > > On Monday, September 25, 2023 at 11:22:16 AM UTC-7, Don Y wrote: 
> > > > > > On 9/25/2023 9:05 AM, Eddy Lee wrote: 
> > > > > > > If I unplug the fridge, or when it's silence, microwave is fine. Sound like I need a relay circuit to disable the fridge from the microwave. Namely, a fridge outlet on the microwave. 
> > > > > > What's the nameplate rating of the microwave? Does *it* say 
> > > > > > it requires a dedicated circuit? (because it draws more than 
> > > > > > half of the rated branch circuit's ampacity) 
> > > > > > 
> > > > > > The countertops, in kitchens, tend to see lots of large 
> > > > > > loads that are often running concurrently. Toaster, 
> > > > > > toaster oven, countertop oven (e.g., all the toaster 
> > > > > > ovens on steroids that you see advertised on TV), 
> > > > > > stand/hand mixer, electric frying pan, *TV*, etc. 
> > > > > > 
> > > > > > Add to this the other large loads that folks tend to 
> > > > > > think nothing of activating: dishwasher, garbage disposal, 
> > > > > > microwave, "instant hot water", etc. Imagine mindlessly 
> > > > > > turning on the garbage disposal (for 10 seconds) and 
> > > > > > tripping a breaker because it shared a branch circuit 
> > > > > > with some other appliance... 
> > > > > > 
> > > > > > You *don't* want to unplug/replug the refrigerator 
> > > > > > (which is what a relay would do) as this can confuse 
> > > > > > the defrost timer and (for poorly designed controls) 
> > > > > > lead to the compressor starting under a (mechanical) 
> > > > > > load that hasn't yet had time to dissipate (smart 
> > > > > > controls will inhibit the compressor for its required 
> > > > > > dead time on initial application of power for exactly 
> > > > > > this reason -- but, then, you would risk the compressor 
> > > > > > always "waiting" even without cause) 
> > > > > > 
> > > > > > [Microwave ovens tend to see frequent, brief use. 
> > > > > > Would you want your refrigerator being unplugged 
> > > > > > each time you throw something in the microwave 
> > > > > > for 15 seconds?] 
> > > > > > 
> > > > > > And, refrigerators (if disabled due to a tripped breaker) 
> > > > > > risk having their contents spoil. So, you'd like the 
> > > > > > refrigerator to be the sole item that can cause *its* 
> > > > > > breaker to trip (imagine the instant hot water unit 
> > > > > > thermostatically cycled on and silently took out the 
> > > > > > breaker for the refrigerator... which you happen to 
> > > > > > discover the next *morning*). Ditto the dishwasher 
> > > > > > or any other appliance that can "safely" sit, powered 
> > > > > > off, with no ill effects (e.g., the dishes are still dirty 
> > > > > > but aren't getting any *dirtier* in the absence of mains!) 
> > > > > Fridge: 310KWhr/year = 35W average (no info on motor) 
> > > > > Microwave: 1500W 
> > > > > Laptops: 60W to 90W. 
> > > > > 
> > > > > No dishwasher or coffee pot. 
> > > > I like that you provided the "average" power draw of the fridge. How do you expect to use that in solving your problem? 
> > > You answered your question in another post: 
> > > 
> > > "Typically a refrigerator runs on 35% duty cycle, (65% for a freezer). This means that if you take the running watts and multiply it by 35%, you can get an idea as to how much power the average running amps will be." 
> > I'm pretty sure I didn't post that. Regardless, that would be a combination of an average with a rule of thumb, so not of much value. The point is, your appliance has a plate with the actual power rating while running. Why don't you look at that? Not the motor, the appliance. You've also said nothing about the size of this appliance. Is it a dorm room size fridge? A massive double door kitchen behemoth? Something in between? As is usual with you, only the barest minimum of information is provided and then the guessing begins.
> There is an energy guide tag saying 310 KWhr/year. Nothing else. Detail info might be at the back of the fridge. Too heavy to pull the fridge out when loaded. 

Ok, but that's not the same as "nothing else".  It just means you don't know the wattage and you won't do what it takes to find it.  Can you read a model number somewhere?  Did you look inside the fridge?  

You still didn't say how large the unit is, but I suppose it's not a small unit if you can't move it.  Maybe buy less groceries and eat your way to lightening it? 


> We just need to agree that it's too much to have both the fridge and microwave running together.

That's not the question. 


> > > > It just occurred to me. You have the fridge to chill all the laptops so you can overclock them!!! 
> > > Not really. They are air-cooled. 
> > LOL! 
> > > > Here's the most direct route to solving your problem. Get a microwave that is 600 watts, rather than the behemoth 1500 watt monster. Do you actual defrost turkeys in it? 
> > > It's fairly standard sized microwave. 
> > 1500W is not a standard size microwave. That's as large as they get for home use. 600W to 1000W is much more typical. Should I assume you actually read the rating plate to get the 1500W number? Or is this another "average" you pulled off a web page, somewhere?
> Yes, rating plate at the back of the microwave.

Ok, end of discussion.  You only have a small amount of reserve on your 20 amp line when the microwave is in use.  I doubt you can use the ten laptops with the microwave.  

So now, the only question is if the laptops can be used with the fridge.  If so, you need to circuits.  If not, you need three. 


> > > I still don't understand Fred's concern about relay switching the fridge. I got some 30A relay contacts that should be enough. Half of the laptops have batteries, which I can also relay switch off while using the microwave. 
> > You will wear out the relays in relatively short order. Maybe a few months, maybe a year, depending on how often you use the microwave. The current rating does not mean you can open the circuit under load as much as you want. Especially with motors, this causes an arc across the contacts, eroding and pitting them severely in a small number of cycles.
> 5 to 10 times per day. 3000 per year. It should last at least a year. 
> I will put a filter cap in parallel with the contacts.

Good luck and enjoy

-- 

  Rick C.

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On Monday, September 25, 2023 at 7:39:07 PM UTC-4, Tabby wrote:
> On Monday, 25 September 2023 at 09:39:26 UTC+1, Ricky wrote: 
> 
> > The only individual heavy load is the microwave which ranges from 600W to 1,400W, depending on size.
> Output. Consumption is about 1.2kW - 2kW

I've never seen a 120V appliance draw over 1440W.  But then here it's very uncommon to see 20A circuits. 

-- 

  Rick C.

  --+ Get 1,000 miles of free Supercharging
  --+ Tesla referral code - https://ts.la/richard11209