Dimming lights in the shop..

[skeer]

So I think I know what the deal is but I'd like 3rd party verification

My shop building is roughly 150ft from the house where power is supplied from. The 12/2 romex run goes from 30amp breaker in the basement underground to the first shed ~100ft, thru a 30amp breaker to the shop at another ~50ft. It terminates to a panel I put in this last summer to a 20amp breaker. All my lighting in the shop is LED. Which then distributes to the 5 circuits. I was testing the 'new' miter saw which is rated at 120@13A and immediate kick on all teh lights visibly dimmed.

Now I know LED's are more susceptible to electric sags like that, and I know that 12/2 isn't the best feeder option but could that be my limitation in electron flow rates here? Would it help (or even be possible) to add say a big capacitor somewhere in my shop to help with overall surges?

Thanks!

 

[Almost Retired]

a buck boost transformer would be much more effective
you are making a big mistake putting 12-2G on a 30amp breaker
it should be on a 20amp breaker

 

[pattenp]

The #12 is the problem, plus #12 should be on a 20A feeding breaker not 30A breaker. Another problem is romex (nm) is not allowed underground. Or is the cable UF?

 

[aandpdan]

The feeder breaker should be a 20 amp. It shouldn't be Romex either.

 

[nadogail]

Skimping on your conductor size was a mistake.

 

[u2slow]

The 150' distance at 120V is the kicker. You really don't have more than a 15A circuit available... with a wire size bump (#12) to help the voltage drop.

The saw is an inductive load, so it pulls more than 13A to start; which drops the voltage further, which is why your lighting cuts/dims.

Get a proper size feeder out to the shop.

 

[PoorUB]

150 feet of run? You probably need #6 for that run to minimize the voltage drop.

That #12 wire is only good for a couple lights at that distance.

 

[skeer]

Skimping on your conductor size was a mistake.

Previous owner ran the feeder, I did interrupt it with a breaker at the shed and the panel at the shop though..

 

[skeer]

The feeder breaker should be a 20 amp. It shouldn't be Romex either.

Eh, Im old enough to call damn near everything that has solid core conductors Romex. My bad. I'd assume it's not the typical interior wiring but TBH I can't remember when I looked.

 

[skeer]

Thanks all, I knew my feeder was undersized but it's just another thing on the list to be done, its just near the bottom is all. I wanted to ask primarily to see if there was maybe something I could do to help out that I was unaware of.
I will rip out the 30 and replace it with a 20 though!

 

[skeer]

A follow-up question if I may folks: Say the feeder line is upgraded and Im able to get a real 30amp circuit out there. Would there be any benefit, with regards to lighting at least, to help negate that initial current jump like say a big capacitor? I know thats a thing in commercial/industrial setting but does it cross the line into residential at all?

 

[Innovate1]

I doubt a capacitor is going to help on an AC circuit. They are used for power factor correction in larger sites with inductive loads so you might get a slight improvement for the saw. You could make the circuit 240V (not 120/240 that would need another conductor for neutral) and step it down with a transformer at the far end or rewire the saw for 240 if it has that option. But that isn't a practical solution IMHO and you would need transformers for both the out buildings. The saw draws several times rated current at startup. That's why the lights dim. And it will limit the power of the saw. If you are going to be running saws and other tools then think about running a larger 4 wire circuit and put a sub panel there if you want to avoid issues like this.

 

[mike93lx]

If you are going through all the work to rerun the feeder (and I think you should), don't do 30a. Too much work for too little power.

#2mhf with a 60a breaker. The wire is probably cheaper than the right size copper for 30a

You also need 2 ground rods at both locations

 

[Innovate1]

This link indicates that during motor starting the power factor is very low in which case a capacitor can help. This is for very large motors but I expect the basic effects would be the same. It's possible a cap could help. Probably several caps to get enough capacitance for the optimum size but that's just a guess. The determination of the proper size is left as an exercise for the student. Maybe do some google searches. Still, if the shop is going to be used for more than this one saw a larger feed seems like a better solution.
https://site.ieee.org/repc-2018/fil...ts-using-fast-acting-capacitor-assistance.pdf

 

[skeer]

I doubt a capacitor is going to help on an AC circuit. They are used for power factor correction in larger sites with inductive loads so you might get a slight improvement for the saw. You could make the circuit 240V (not 120/240 that would need another conductor for neutral) and step it down with a transformer at the far end or rewire the saw for 240 if it has that option. But that isn't a practical solution IMHO and you would need transformers for both the out buildings. The saw draws several times rated current at startup. That's why the lights dim. And it will limit the power of the saw. If you are going to be running saws and other tools then think about running a larger 4 wire circuit and put a sub panel there if you want to avoid issues like this.

Sorry I should have been more granular, I didn’t mean a cap for the saw alone but just for overall power usage. I was reading about the bucks in industrials settings. Which I am not.. I got curious about the idea really is what it boils down to.

 

[skeer]

If you are going through all the work to rerun the feeder (and I think you should), don't do 30a. Too much work for too little power.

#2mhf with a 60a breaker. The wire is probably cheaper than the right size copper for 30a

You also need 2 ground rods at both locations

Thanks for this, and you are right. I would love to have 220 out there but the wire cost and needing to throw a sub panel in the basement to accommodate the extra two circuits. The extra costs for that has been prohibitive

 

[mike93lx]

Thanks for this, and you are right. I would love to have 220 out there but the wire cost and needing to throw a sub panel in the basement to accommodate the extra two circuits. The extra costs for that has been prohibitive

It would only be one additional circuit since you have one in use now. No space for that? Using a tandem would free up a spot if the panel allows them.

I hear you, it's not a simple or cheap project either way. Trenching *****

 

[ez-duzit]

If you are going through all the work to rerun the feeder (and I think you should), don't do 30a. Too much work for too little power.

#2mhf with a 60a breaker...

This. Do the job correctly.

 

[skeer]

This. Do the job correctly.

I'd love to! First place I looked, #2mhf was $4 per ft! Second was $3.99, I know AL and metal in general is up a lot in the past year or two. Can ya'll suggest better places to shop for wire at?

 

[ez-duzit]

Get a job.

 

[Innovate1]

I'd love to! First place I looked, #2mhf was $4 per ft! Second was $3.99, I know AL and metal in general is up a lot in the past year or two. Can ya'll suggest better places to shop for wire at?

A lot of us here, myself included, got wire from wireandcableyourway.com

 

[skeer]

I certainly will never need 60 amps, so anything I do out there. Looks like 4-4-4URD would give me 40A @ 155ft or 50A @ 120ft.

 

[skeer]

Get a job.

Thanks for this.

 

[skeer]

A lot of us here, myself included, got wire from wireandcableyourway.com

Actually they were my first stop earlier, lol!

 

[mike93lx]

I certainly will never need 60 amps, so anything I do out there. Looks like 4-4-4URD would give me 40A @ 155ft or 50A @ 120ft.

URD can't go inside a building at all, so it means outside junction boxes.

You also need a 4 wire feed

 

[skeer]

URD can't go inside a building at all, so it means outside junction boxes.

You also need a 4 wire feed

Interesting, I assume it has to do with fire code maybe? Poisonous fumes from burning urd sheathing? Good to know but that ***** because the exit distance from the basement panel is @2'. Yeah if I wanted 220 for sure

 

[skeer]

It would only be one additional circuit since you have one in use now. No space for that? Using a tandem would free up a spot if the panel allows them.

I hear you, it's not a simple or cheap project either way. Trenching *****

Nope, I've used the remaining spots for other things. However if the biggest blocker project bears fruit, I'll be adding a sub panel anyway for a Heat pump water heater.

 

[skeer]

You guys have provided a ton of good info, I hope no one thinks that I'm knocking any of it. I def appreciate it!

 

[Shiftless]

If you only really NEED 20 amps and one circuit, just change the breakers to 20A for safety and then just tolerate momentary dimming of the lights. You can still see fine during that initial 2 seconds of saw motor start up, right?

 

[Shiftless]

If you only really NEED 20 amps and one circuit, just change the breakers to 20A for safety and then just tolerate momentary dimming of the lights. You can still see fine during that initial 2 seconds of saw motor start up, right?

edit: If you’re adding another sub panel for the heat pump water heater, it sounds like you’re committed to some serious upgrades. Are you sure you want a heat pump water heater?

 

[skeer]

If you only really NEED 20 amps and one circuit, just change the breakers to 20A for safety and then just tolerate momentary dimming of the lights. You can still see fine during that initial 2 seconds of saw motor start up, right?

Oh for sure! And I am going to throw a 20 back in there for the reason you mentioned. IDK, I've got one of those brains that wants to make everything better. Even if some/most of the ideas are not cost effective nor common. Like asking about throwing a capacitor on my shop feed. That sounds like a neat thing to try to me even if the result is 100% limited to stopping an LED from flickering, lol.

 

[skeer]

edit: If you’re adding another sub panel for the heat pump water heater, it sounds like you’re committed to some serious upgrades. Are you sure you want a heat pump water heater?

I love the idea of one along with the intrinsic efficiency. A bonus to one of those is I can pipe the colder exhaust air into the room above me during the summer months. As a lot of Miciganders we don't have central AC and that room as no windows for a window unit.
Also we're on propane out here so it's the $3.50-$4 a gallon propane or electric, my only choices for hot water.

 

[Shiftless]

If that heat pump WH is in the basement, it will definitely cool the basement. Is that living space? Nice in the summer but it will make your basement extra cold in the winter. I see you live in MI so whats the temp in your basement in the winter? Is there a furnace duct in the basement?
My house here in the SF Bay Area has a walk out basement with one furnace register and a cold air return. I have a gas water heater and a gas furnace and an electric stove.

 

[skeer]

If that heat pump WH is in the basement, it will definitely cool the basement. Is that living space? Nice in the summer but it will make your basement extra cold in the winter. I see you live in MI so whats the temp in your basement in the winter? Is there a furnace duct in the basement?
My house here in the SF Bay Area has a walk out basement with one furnace register and a cold air return. I have a gas water heater and a gas furnace and an electric stove.

Yup yup, Im aware of how they work. The coolness of the basement in winter is a slight unknown right now. Currently the two vents from the supply run are blocked because I also use the basement as an office and with the wood furnace I personally get enough radiant heat. However if there's not enough heat down here for a HPWH, that's easily remedied. If a vent or two down here isn't quite enough there's an older vent from basement to the first floor I can make use of for intake air.

 

[Shiftless]

At the risk of sidetracking your thread, I bet I’m not the only guy who wonders about the details of running a wood burning furnace. Do you cut your own firewood or buy it? How often do you have to go out and add wood to the fire box?

 

[skeer]

At the risk of sidetracking your thread, I bet I’m not the only guy who wonders about the details of running a wood burning furnace. Do you cut your own firewood or buy it? How often do you have to go out and add wood to the fire box?

I can totally start a thread about the wood furnace if it'd help anyone. I've actually had some questions lately with regards to ducting and blowers that any HVAC pro online seems to develop amnesia if I let the words 'wood furnace' slip.

 

[Chilliwack Murray]

I don't know the code requirements regarding voltage applied on the wire type installed etc in your area however there is a practical solution to dramatically improve the the amount of available power and reduce voltage drop.

If you can connect the existing feeder to 240V (two pole breaker instead of one pole breaker and neutral) and install a 240:120/240V transformer (like this https://canadatransformers.com/5-kva-isolation-transformer-sc5c-k.html) to supply your panel you will cut the amperage on the feeder in half. The transformer would make your shop panel a new source and require the transformer neutral to be grounded at the shop panel as there is no longer a neutral connected back to the house. Others familiar with US electrical code would need to add their 2 cents regarding legality but electrically this is fine assuming the feeder cable is suitable for 240V. You would also have 4800W available instead of 2400W that you currently have with the 120V supply.

At a minimum, you would need to ensure any other breakers between the shop and main panel are also 2 pole and there are no other 120V loads fed from this circuit between the main panel and the shop.

Power factor correction capacitors will reduce the current required to run that motor slightly but likely won't be a noticeable improvement and it does nothing for inrush on an AC system.

 

[u2slow]

If the lights cutting-out bother you, could put them on a ups until you get a larger feeder installed. The ups will just cut-in when you create a 'brown out' from running a hungry power tool.

 

[mike93lx]

If the lights cutting-out bother you, could put them on a ups until you get a larger feeder installed. The ups will just cut-in when you create a 'brown out' from running a hungry power tool.

I don't think a cheap ups will respond fast enough. It would have to be a pretty nice unit

 

[Almost Retired]

I don't know the code requirements regarding voltage applied on the wire type installed etc in your area however there is a practical solution to dramatically improve the the amount of available power and reduce voltage drop.

If you can connect the existing feeder to 240V (two pole breaker instead of one pole breaker and neutral) and install a 240:120/240V transformer (like this https://canadatransformers.com/5-kva-isolation-transformer-sc5c-k.html) to supply your panel you will cut the amperage on the feeder in half. The transformer would make your shop panel a new source and require the transformer neutral to be grounded at the shop panel as there is no longer a neutral connected back to the house. Others familiar with US electrical code would need to add their 2 cents regarding legality but electrically this is fine assuming the feeder cable is suitable for 240V. You would also have 4800W available instead of 2400W that you currently have with the 120V supply.

At a minimum, you would need to ensure any other breakers between the shop and main panel are also 2 pole and there are no other 120V loads fed from this circuit between the main panel and the shop.

Power factor correction capacitors will reduce the current required to run that motor slightly but likely won't be a noticeable improvement and it does nothing for inrush on an AC system.

NEC requires a 4 wire feed, meaning a separate neutral and ground for all subpanels

what you suggest is done all the time, feeding a subpanel with 3 wires and it works well enough, but .....
and you dont need a transformer at the subpanel, you simply wire the subpanel as 240V because it was originally mfg that way