Go from 40amp breaker to 50amp?

[Andy_GTS]

I have a detached garage with a subpanel. I have 100amp service to my house with a 40amp breaker and 8-3 wire to the subpanel. The run is approximately 65ft. As I am adding additional circuits to the garage, I'm considering replacing the 40 amp breaker with a 50amp. Is this feasible, recommended, or even legal?

 

[lakeroadster]

Copper or Aluminum wire?

What type of wire:

• TW, UF
• RHW,THHW,THW,XHHW
• RHH, THHN, XHHH, XHHW

 

[Bert_]

If it is NM cable (aka romex) you are limited to 40A.
It sounds like that is what you have since you say 8-3. I am assuming it is copper as well.

 

[Andy_GTS]

Not great pictures, I know. Copper. THHN is printed on it. The sheathing says NM-B.

 

[sberry]

Why do you want to change it? Has it tripped?

 

[wyliesdiesels]

I have a detached garage with a subpanel. I have 100amp service to my house with a 40amp breaker and 8-3 wire to the subpanel. The run is approximately 65ft. As I am adding additional circuits to the garage, I'm considering replacing the 40 amp breaker with a 50amp. Is this feasible, recommended, or even legal?

8/3 NM-b is limited to 40a...

But NM-b is not permitted in wet locations which includes underground conduits.

Does this cable run underground?

Not great pictures, I know. Copper. THHN is printed on it. The sheathing says NM-B.

Thats strange. NM-b doesnt have individually labeled conductors.

Do those black and red wires come from the NM-b cable?

 

[Andy_GTS]

Why do you want to change it? Has it tripped?

It hasn't tripped but I was just looking to maximize my systems potential, especially since I have filled all the slots on my subpanel.

 

[Andy_GTS]

8/3 NM-b is limited to 40a...

But NM-b is not permitted in wet locations which includes underground conduits.

Does this cable run underground?



Thats strange. NM-b doesnt have individually labeled conductors.

Do those black and red wires come from the NM-b cable?

The NM-b runs from the house panel to a junction box by the riser. It is connected to wires labeled THHN I believe. Those run about 60ft underground in PVC conduit maybe a foot deep or so.

 

[Dagny]

If it's not giving any trouble leave it.

 

[AntonLargiader]

So you're saying the subpanel in the detached garage is full? What's on it? And what else are you planning to add?

 

[Andy_GTS]

So you're saying the subpanel in the detached garage is full? What's on it? And what else are you planning to add?

The subpanel has:
50 amp main
15 amp 110v (lights)
20 amp 110v (outlets)
20 amp 220v (compressor)
30 amp 220v (welder/lift)

Not looking to add anymore than that. Maybe I should remove some if 40 amps isn't enough???

 

[AntonLargiader]

I would just leave it, also, unless it is tripping.

Upgrading would mean new wire. If perchance the THWN is #6, then you could just replace the NM-B and get to 60A, but otherwise you'd be replacing everything (and it looks smaller than #6 to me). If the conduit is 3/4", you can keep it.

 

[sberry]

If it isn't tripping the breaker don't mess with it. It's not going to add power if it's not tripping.

 

[wyliesdiesels]

The NM-b runs from the house panel to a junction box by the riser. It is connected to wires labeled THHN I believe. Those run about 60ft underground in PVC conduit maybe a foot deep or so.

ok that makes more sense.

What gauge is the THWN??

The subpanel has:
50 amp main
15 amp 110v (lights)
20 amp 110v (outlets)
20 amp 220v (compressor)
30 amp 220v (welder/lift)

Not looking to add anymore than that. Maybe I should remove some if 40 amps isn't enough???

Whats the most u run at the same time?

 

[Andy_GTS]

It's all 8 gauge from what I can tell. The most I can imaging using is raising the lift and having the conpressor start at the same time. The lift is 23amps and the compressor is 17.5amps. And then whatever the lights are. This would be unlikely but the most possible I would think.

 

[wyliesdiesels]

It's all 8 gauge from what I can tell. The most I can imaging using is raising the lift and having the conpressor start at the same time. The lift is 23amps and the compressor is 17.5amps. And then whatever the lights are. This would be unlikely but the most possible I would think.

Well if u want 10 extra amps, u would need to replace the 8/3 NM-b with 6/3 NM-b or #8 THWN in pipe which is rated for 50a...

 

[forAK]

Well if u want 10 extra amps, u would need to replace the 8/3 NM-b with 6/3 NM-b or #8 THWN in pipe which is rated for 50a...

Why is that? #8 vs 6/3. Why can you get away with smaller THWN than running bigger NM-b and get the 50a rating?

 

[lakeroadster]

Why is that? #8 vs 6/3. Why can you get away with smaller THWN than running bigger NM-b and get the 50a rating?

Code Specification.. Different insulations types have different ampacity ratings.

 

[wyliesdiesels]

Why is that? #8 vs 6/3. Why can you get away with smaller THWN than running bigger NM-b and get the 50a rating?

Because NM wire is limited to 60* c ampacity in above chart...

 

[forAK]

Thanks guys

 

[sberry]

It's all 8 gauge from what I can tell. The most I can imaging using is raising the lift and having the conpressor start at the same time. The lift is 23amps and the compressor is 17.5amps. And then whatever the lights are. This would be unlikely but the most possible I would think.

Stop raising the lift if the comp starts, don't start the lift if its running. I really doubt it would trip anyway.

 

[theoldwizard1]

Stop raising the lift if the comp starts, don't start the lift if its running. I really doubt it would trip anyway.

Sometime the solution to a "problem" is SO EASY !