Pulling enough Watts

ryshark

ryshark

Active member
Please help me understand this. I am upgrading my tank and need to pull power from two circuits. The extra circuit I am going to use is 20amp and it is shared with my microwave and refrigerator.

I think it might already be maxed out though because my refrigerator says it is 11.6 amps and my microwave says it is 1.6kw. So 1.6 kw = 1600 watts or 13.3 amps.
If I add the two 13.3 amps and 11.6 amps I am already over the 20amp circuit breaker. Shouldn't my breaker have tripped? And this is the circuit I need to draw about 450 more watts out of for my new 180-gallon tank.
PLEASE HELP!
 
I just did a little test. I opened the refrigerator/freezer doors until it kicked on, then I turned the microwave on and then I went to the socket I am planning on using that is tied in with the micro and refrig and I plugged in a 200w heater and 2x 50w heaters in a bucket of water. The breaker did not trip.
Next I am goig to try the same test with my 440 watts of VHO lighting and plug it in there.
 
I am surprised it didn't trip, from what I know it should of... maybe they are just not pull as much as they say. You could grab a meter.
 
I just did the test again, this time with 440watts of VHO, the microwave on and the refrigerator doors open. Still didn't trip. Is it possible even though the refrig says 11.6 amps it is not using all the amps? Or that even though the micro says 1.6kw it is not using all 1600watts?
 
ryshark, lots of things are possible.

The average full size autodefrost refridgerator/freezer combo is likely someplace in the 500-700 Watt Range depending on the actual size.

The microwave oven is likely in the 1500W range. It may draw more power on "defrost" or depending on the mode.

A 20A circuit breaker can handle 2400W, but should NEVER be loaded to more than about 1900W to allow for overhead. So with both devices running, you are somewhere near 2000W of continuous load with both appliances running.

So a few notes:
1) The fridge and microwave likely do both run together for long periods. If they did the breaker would run "warm" and be very prone to nuisance trips.

2) When the compressor motor kicks in, the inrush current can be many times the continuous current rating. If the circuit is already being pushed too hard, then the compressor startup or microwave defrost capacitor/coil can easily kick the circuit into overload.

So adding your 400W of heaters did not trip the circuit right away, but clearly would put it well into the red zone if both appliances and your heaters need to run at the same time.

Do yourself a favor and find another circuit to use, or have one pulled in for your new tank. You don't want your life support system to rely on a clearly overloaded circuit breaker. The crash will cost you much more than the new circuit!
 
Thanks BeanAnimal.... I had 3-electricians look at it already and they all said that my tank is in the worst possible spot in the house to get another circuit to. I may just have to bite the bullet and pay one to do it. If I was to use the 20-amp circuit that is shared with my refrig and mircowave, at least it would only trip while I was home, because the microwave is what would make it trip at 1600 watts. We don't use it that often, maybe I can just put one 250-watt halide ballast and maybe my protein skimmer on the circuit that is shared with the micro/refrig... then worst case I will only be out 1-halide and my skimmer until I can flip the breaker switch.
I am spending close to $4000 already on my 180-gallon upgrade so I am trying hard to find ways to avoid an electrician bill too.
 
BeanAnimal, or anyone else... How about this question? The 250-watt Galaxy ballast comes in both 120v and 240v. Is the 240v more efficient and use less amps because 250watts/240v = 1.04amps
and 250watt ballast / 120v = 2.08ams. So the 240v ballast actually uses less half the electricity??? Is that right? If that is the case that is way I could save amps
 
They both use the same amount of electricity :) You are billed in WATTS, not AMPS.

Watts measure POWER, AMPS simply measure current. You buy water buy the gallon, not by the pressure and rate of delivery.
 
ok, thanks... I am just going to have to hire the electrician for $500. At least I feel now that I have exhausted all options.
 
Good plan. I don't know about the electrical code in your area, but where I live, by code, both the refrigerator and the microwave require a separate circuit. The refrigerator outlet is 'allowed' to have a clock, of all thngs share the circuit. Mind you I'm talking 15 amp circuits here, not 20, but those two devices potentially use a lot of power and adding more load is asking for trouble.
 
I should look into the code for my area because they put the Microwave the Refrig and my entire dining room all on the same 20amp circuit.
 
Mike,

It just depends on when the house was wired and what year's NEC the jurisdiction had adopted. You are not required to updated the wiring to meet each new code.
 
The new circuits will have to conform to the current code, but you still (in most cases) would not be required to update the grandfathered circuits :)
 
My house is only 3-years old, so I doubt any codes have changed since then, but I don't know for sure. So after the work is done do I have to have an inspector come out?
 
<a href=showthread.php?s=&postid=13891859#post13891859 target=_blank>Originally posted</a> by BeanAnimal
They both use the same amount of electricity :) You are billed in WATTS, not AMPS.

Watts measure POWER, AMPS simply measure current. You buy water buy the gallon, not by the pressure and rate of delivery.
Click to expand...

Hi BeanAnimal

Doesn't voltage x amps = watts
 
yes, Voltage x Amps = Watts

You PAY for Watts, measured in Watt/hours.

So the 250W ballast comes in 120V and 240V version.

250W / 120V = 2.08A
250W / 240V = 1.04A

So twice the voltage = half the current. So why do commercial properties use 240V or 480V ballasts? Simple, wire SIZE is dictated by CURRENT not Voltage. Therefore if you up the voltage you can place more ballasts on the same feeder wire.

Lets take a real work example with a 20A circuit.

We will ignore the 20% safety factor needed on a circuit for ease of math.

SO according to Ohm's Law
A 120V, 20A breaker can handle 2400Watts of load.
A 240V, 20A breaker can handle 4800Watts of load.
A 480V, 20A breaker can handle 9600Watts of load.

All three circuit will run over the SAME size wire (#12). Remember wire GAUGE is a function of current. Wire insulation dictates the voltage capacity.

You are wiring up highbay lighting in a warehouse with 250W halides. You can only get (9) 120V ballasts on the 20A circuit, but you can get (19) 240V ballasts on the same 20A circuit, or 38 ballasts on the 480V circuit.

No apply the same logic to the power lines outside of your home and you understand part of the reason that they run at 7,200V - 72,000V (depending on the area and purpose) and the wires are not much thicker than your finger. If the transmission voltage was say 240V, then the wires would have to be thicker than your thigh to carry the current.
 
Nothing more to add, my husband has electronic warfare background in the Air Force and says Mr Bean has covered it all in very good detail, He also says your welcome Bean as hes a disabled vet.
 
Have to add a small bit t hough, I know Virginia code that dining rooms must be on there own breakers as well as kitchen seperate, there resoning is that a dining room could have a hot plate therefore must be on a dedicated circuit, stupid yes but we failed our electrical inspection while building our last house because my husband wired it wrong, also make sure the compressor is running when your running them both together to do your smoke checks, opening the door is not enough to pull anything , the actual compressor has to be running at the same time you have everything else running
 
<a href=showthread.php?s=&postid=13937570#post13937570 target=_blank>Originally posted</a> by beachbumva
Nothing more to add, my husband has electronic warfare background in the Air Force and says Mr Bean has covered it all in very good detail, He also says your welcome Bean as hes a disabled vet.
Click to expand...

Your husband has my deepest gratitude, as do you and your family.
 
You must log in or register to reply here.

Similar threads

FishMann
Electrical Upgrades
Replies
2
Views
134
wvned
wvned
M
Can I use 2 bubble magus qq2 in my tank?
Replies
3
Views
174
Guygettnby
Guygettnby
R
How is my chemistry looking?
Replies
2
Views
237
ReefKG
ReefKG
S
Help with Overflow Design Issue
Replies
0
Views
153
SFMAquariums
S
T
Alternative Lighting for Biocube 29
Replies
0
Views
119
thommyboy12183
T
Back
Top