How to find if my 15 amp breaker has the wiring for a 20 amp breaker?
#1
04-06-15, 08:32 PM
How to find if my 15 amp breaker has the wiring for a 20 amp breaker?
Hi,
I had an over the range microwave and it stopped working. So, I replaced that with a vent hood and bought a countertop microwave. The microwave is plugged in a 15 amp circuit and it keeps tripping(atleast 2 times a week). A toaster is plugged in the same circuit. But, I have noticed the microwave trips when the toaster is not used, plugged or unplugged). All other outlets are unused.
So, I am thinking of changing the 15 amp circuit to 20 amp.(or is there any other option instead). How do I find out if the wiring needs to be changed or can I just change the breaker & the receptacles?
Thanks.
I had an over the range microwave and it stopped working. So, I replaced that with a vent hood and bought a countertop microwave. The microwave is plugged in a 15 amp circuit and it keeps tripping(atleast 2 times a week). A toaster is plugged in the same circuit. But, I have noticed the microwave trips when the toaster is not used, plugged or unplugged). All other outlets are unused.
So, I am thinking of changing the 15 amp circuit to 20 amp.(or is there any other option instead). How do I find out if the wiring needs to be changed or can I just change the breaker & the receptacles?
Thanks.
#2
04-06-15, 09:39 PM
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Hi. A microwave can really pull some juice. I have a 4k generator that will nearly bog out if I try to run our 1100 watt microwave off of it. So I would say 15 amps is definately not big enough. If possible I would recommend a dedicated circuit (meaning 12/2 wiring, 20 amp breaker with a single outlet on the end to power any microwave (if any outlets on this leg are close to the sink or possible water then you should CGFI too (If you place a cgfi outlet as the first outlet in the leg then all of the outlets after that are CGFI protected as well, as long as you use the lugs on the CGFI outlet and not isolate it with wirenuts and a separate wire extended from the main circuit (a branch?)). Tripping breakers with too much current can damage them as well, so sooner or later it will start to trip more frequently and then will need to be new after that (try to minimize use until you get a handle on whats going on or move to a known 20 amp curcuit and use only when other items on circuit are not in use)----
ALSO before you swap the 15 amp circuit you may want to verify that the wire supplying the circuit is 12/2 and not 14/2, since I don't recommend using a 20 amp breaker with 14/2 wiring... Its just a hunch but I don't think that a microwave should be run off of 14/2. If its a 15 amp breaker then theres a chance that the electrician has 14/2 wire running from it, since 20 amp breakers are the norm for 12/2 with outlets and 15 amp breakers with 14/2 wire is generally used for lighting.
PS Be sure to turn off the main breaker, before you pull the breaker in question and BE CAREFUL!
Mod Note: For a general purpose circuit #12 or larger needs to be used for a 20 amp circuit.
ALSO before you swap the 15 amp circuit you may want to verify that the wire supplying the circuit is 12/2 and not 14/2, since I don't recommend using a 20 amp breaker with 14/2 wiring... Its just a hunch but I don't think that a microwave should be run off of 14/2. If its a 15 amp breaker then theres a chance that the electrician has 14/2 wire running from it, since 20 amp breakers are the norm for 12/2 with outlets and 15 amp breakers with 14/2 wire is generally used for lighting.
PS Be sure to turn off the main breaker, before you pull the breaker in question and BE CAREFUL!
Mod Note: For a general purpose circuit #12 or larger needs to be used for a 20 amp circuit.
Last edited by pcboss; 04-07-15 at 06:07 AM. Reason: added mod note
#3
04-07-15, 02:59 AM
ALSO before you swap the 15 amp circuit you may want to verify that the wire supplying the circuit is 12/2 and not 14/2, since I don't recommend using a 20 amp breaker with 14/2 wiring
If new wiring needs to be done, I will call the electrician since I have no electrical knowledge. Just started to learn from here. But, if it is just changing the breaker, I will go for it. In any case, I want to be knowledgeable before calling the electrician.
#4
04-07-15, 04:56 AM
Member
How old is this house? If it is Romex you may be able to read the wire size on the outside of the cable if any of it is exposed.
Geo
Geo
#5
04-07-15, 05:09 AM
Member
Unless you have 12-2 you should not be changing the breaker to a 20 amp.
If you did that the wire becomes the fuse and could burn up before the breaker tripped.
Also there's not need to change the outlet to a 20 amp. A 15 amp. is legal and save to use.
A modern home wired to code would have to have at least 2, circuits for over counter outlets, be 12-2 20 amp. wires, no more the 4' apart and be GFI protected.
Microwave would be on it's own dedicated circuit.
If you did that the wire becomes the fuse and could burn up before the breaker tripped.
Also there's not need to change the outlet to a 20 amp. A 15 amp. is legal and save to use.
A modern home wired to code would have to have at least 2, circuits for over counter outlets, be 12-2 20 amp. wires, no more the 4' apart and be GFI protected.
Microwave would be on it's own dedicated circuit.
#7
04-07-15, 09:46 AM
How old is this house? If it is Romex you may be able to read the wire size on the outside of the cable if any of it is exposed.
A modern home wired to code would have to have at least 2, circuits for over counter outlets, be 12-2 20 amp. wires, no more the 4' apart and be GFI protected.
Microwave would be on it's own dedicated circuit.
Microwave would be on it's own dedicated circuit.
Microwave was on a dedicated 20 amp circuit but, we replaced it with a venthood.
What is the best way to solve this problem?
Let me know if I understood it right.
Replace the 14/2 wiring in the 15 amp with 12/2 and change the breaker to 20 amp and use it for microwave along with other receptacles.
Or keep the 15 amp circuit for all the receptacles and just run a new 12/2 wiring for one of the receptacles in the current 15 amp circuit and have it converted to a 20 amp circuit and dedicate it to the microwave.
Also, in the future if I am adding some other small appliances, would I run into any problems with any of these methods or else should I go ahead and do both of them. I just want to get it right the first time.
Thanks everybody.
#8
04-07-15, 10:04 AM
Go to the hardware store and buy one foot of #12 and one foot #14 THHN solid wire. Strip back the insulation an inch or so and compare to the bare portion of the wire in the breaker.
#9
04-07-15, 10:37 AM
You mentioned your house was three years old, so two thoughts:
1.) all romex cable made in the last 10+ years has a color coded jacket: 14 ga is white, 12 ga is yellow, 10 ga is orange, larger is black. Code requires at least 1/4" of Romex jacket be visible in the wire clamps in the box (outlet box or circuit breaker panel). You should be able to peak in and spot the jacket color.
2.)
For a house that's three years old, the circuit you described as "a 15 amp for the remaining receptacles in the kitchen, island, formal dining and nook" should be a 20A circuit by code (NEC Article 210.52(b)). The fact that the lights are on a separate circuit (good) suggests your house should be close to the current code standard.
1.) all romex cable made in the last 10+ years has a color coded jacket: 14 ga is white, 12 ga is yellow, 10 ga is orange, larger is black. Code requires at least 1/4" of Romex jacket be visible in the wire clamps in the box (outlet box or circuit breaker panel). You should be able to peak in and spot the jacket color.
2.)
We have one 20 amp circuit for the Fridge and 2 receptacle, another 20 amp circuit for Vent Hood, another 20 amp for Dishwasher and Disposal, a 15 amp for the remaining receptacles in the kitchen, island, formal dining and nook and a 15 amp for Lights in the kitchen, dining and family.
#10
04-07-15, 11:13 AM
all romex cable made in the last 10+ years has a color coded jacket: 14 ga is white, 12 ga is yellow, 10 ga is orange, larger is black.
So, I can change just the 15 amp breaker to 20 amp right? But, if the wiring is for a 20 amp, why did the microwave kept tripping the breaker? Maybe because the breaker is 15 amp? Just curious.
Please let me know what to do next.
Thanks.
#12
04-07-15, 11:23 AM
How big of a microwave are we talking about? I mean how many watts? A 15A circuit can handle 1800 Watts max, 20A can handle 2400 Watts max. I'm assuming you're not leaving the microwave on for spells longer than 3 hours (NEC definition of continuous load, which imposes an 80% wattage restriction).
It also takes time for the breaker to heat up enough and trip.
I'm still curious as to why a 15A breaker was placed on a circuit that is required by code to be 20A and has 20A wiring.
It also takes time for the breaker to heat up enough and trip.
I'm still curious as to why a 15A breaker was placed on a circuit that is required by code to be 20A and has 20A wiring.
#13
04-07-15, 11:35 AM
Best guess someone replaced the breaker with what they had not what was needed.
How big of a microwave are we talking about? I mean how many watts? A 15A circuit can handle 1800 Watts max, 20A can handle 2400 Watts max. I'm assuming you're not leaving the microwave on for spells longer than 3 hours
Should I try changing the 15 amp breaker to 20 amp?
#14
04-07-15, 11:42 AM
What else is on that circuit, appliance wise? My house is from 1935 so doesn't comply with current codes. One 15A breaker runs all of my countertop outlets, a dining room outlet, and all of the lighting in front of my house. It can handle my 1100W microwave, until someone also tries to use the toaster 
I'm thinking the problem may be more than the sizing of the breaker.
I'm thinking the problem may be more than the sizing of the breaker.
#16
04-07-15, 12:20 PM
Possibilities:
a.) the microwave is somehow defective. Doubtful but easily ruled out, move it temporarily and plug it in on another circuit. Maybe turn the fridge off if you choose that circuit.
b.) the toaster is defective and drawing extra amps when off that overload the circuit when the load of the microwave is added. Doubtful, easy to check, unplug it! Although if this were the case the toaster or cord would be rather warm.
c.) high resistance "short" in the circuit that the electrician didn't find. Not enough to trip the breaker, until additional load added. Harder to troubleshoot without specialized equipment. If you have a clamp-type ammeter ($$), I'd measure the current on the hot wire coming out of the breaker. It should be zero when everything's unplugged.
d.) a long shot: a high resistance connection that lowers the available voltage at the microwave. If the microwave has a switching power supply, it can draw more current to make up for the loss in power from dropped voltage. Power (watts) equals volts times amps, for a resistive load like a toaster, less volts means less amps 9and thus less power), for a computer, its power supply can adjust to draw more amps on a lower voltage to sustain its power demand.
I'm not an electrician, I'm an engineer and this is all based on conjecture and theory. Theory tells you why the circuit works, not why it doesn't
a.) the microwave is somehow defective. Doubtful but easily ruled out, move it temporarily and plug it in on another circuit. Maybe turn the fridge off if you choose that circuit.
b.) the toaster is defective and drawing extra amps when off that overload the circuit when the load of the microwave is added. Doubtful, easy to check, unplug it! Although if this were the case the toaster or cord would be rather warm.
c.) high resistance "short" in the circuit that the electrician didn't find. Not enough to trip the breaker, until additional load added. Harder to troubleshoot without specialized equipment. If you have a clamp-type ammeter ($$), I'd measure the current on the hot wire coming out of the breaker. It should be zero when everything's unplugged.
d.) a long shot: a high resistance connection that lowers the available voltage at the microwave. If the microwave has a switching power supply, it can draw more current to make up for the loss in power from dropped voltage. Power (watts) equals volts times amps, for a resistive load like a toaster, less volts means less amps 9and thus less power), for a computer, its power supply can adjust to draw more amps on a lower voltage to sustain its power demand.
I'm not an electrician, I'm an engineer and this is all based on conjecture and theory. Theory tells you why the circuit works, not why it doesn't
#17
04-09-15, 08:06 AM
I moved the microwave to a different outlet in the same circuit since this one has an in-built breaker in this compared to the other one which is the plain normal one.
I don't think the toaster is defective since I had this even before I put the microwave. It uses 900 Watts. I will keep an eye and check if it becomes warm.
I don't have an ammeter but, I have a digital multimeter from Harbor Freight (I know it is cheap stuff) but, I don't know how to use it. Maybe I should learn.
Btw, the breaker didn't trip for the last two days. But, it was the case before too. It would trip 2-3 times in a week. I have to wait and see.
Meanwhile, can i go ahead and change the breaker to 20 amps? Maybe the breaker is bad and it is time to change. Since it is time to change, I thought of going from 15 amp to 20 amp since the wiring is for a 20 amp circuit (Yellow cable). I am thinking of buying this. What do you suggest?
Square D QO 20 Amp Single-Pole Circuit Breaker-QO120CP - The Home Depot
[ATTACH=CONFIG]49114[/ATTACH]
Thanks for taking the time to reply. I really appreciate you all.
I don't think the toaster is defective since I had this even before I put the microwave. It uses 900 Watts. I will keep an eye and check if it becomes warm.
I don't have an ammeter but, I have a digital multimeter from Harbor Freight (I know it is cheap stuff) but, I don't know how to use it. Maybe I should learn.
Btw, the breaker didn't trip for the last two days. But, it was the case before too. It would trip 2-3 times in a week. I have to wait and see.
Meanwhile, can i go ahead and change the breaker to 20 amps? Maybe the breaker is bad and it is time to change. Since it is time to change, I thought of going from 15 amp to 20 amp since the wiring is for a 20 amp circuit (Yellow cable). I am thinking of buying this. What do you suggest?
Square D QO 20 Amp Single-Pole Circuit Breaker-QO120CP - The Home Depot
[ATTACH=CONFIG]49114[/ATTACH]
Thanks for taking the time to reply. I really appreciate you all.
#18
04-09-15, 08:41 AM
Member
I plugged my toaster in one of the outlets. But, every time the microwave tripped the breaker, the toaster was just plugged in the receptacle but, not used.
#19
04-09-15, 09:31 AM
I moved the microwave to a different outlet in the same circuit since this one has an in-built breaker in this compared to the other one which is the plain normal one.
*Receptacle is a place where you insert a plug. Outlet is anywhere you tap power, for example a light or a receptacle.
#20
04-09-15, 09:59 AM
Sorry for the confusion.
I moved the microwave from this outlet
to this outlet.
It is the breaker that is tripping.
CasualJoe, I didn't explain clearly I think. The breaker doesn't trip as soon as I plug the toaster. I had been using the toaster for 2 years. Now I added the microwave. Every time the breaker trips, the toaster remains plugged in the outlet but, it is not used at the same time when the microwave is running. It is a 3 year old home. So, I hope there are no code issues.
I moved the microwave from this outlet
to this outlet.
It is the breaker that is tripping.
CasualJoe, I didn't explain clearly I think. The breaker doesn't trip as soon as I plug the toaster. I had been using the toaster for 2 years. Now I added the microwave. Every time the breaker trips, the toaster remains plugged in the outlet but, it is not used at the same time when the microwave is running. It is a 3 year old home. So, I hope there are no code issues.
#21
04-10-15, 07:06 AM
Member
It is the breaker that is tripping.
CasualJoe, I didn't explain clearly I think. The breaker doesn't trip as soon as I plug the toaster. I had been using the toaster for 2 years. Now I added the microwave. Every time the breaker trips, the toaster remains plugged in the outlet but, it is not used at the same time when the microwave is running. It is a 3 year old home. So, I hope there are no code issues.
CasualJoe, I didn't explain clearly I think. The breaker doesn't trip as soon as I plug the toaster. I had been using the toaster for 2 years. Now I added the microwave. Every time the breaker trips, the toaster remains plugged in the outlet but, it is not used at the same time when the microwave is running. It is a 3 year old home. So, I hope there are no code issues.
#22
04-11-15, 06:35 PM
IN the beginning, I thought it was a 15 amp circuit because it had a 15 amp breaker. But, EEsparks helped me identify the wiring color which is yellow which states that it is a 20 amp circuit. So, now I have to try changing the breaker from 15 amp to 20 amp.
