Dimming lights in the shop..

[mike93lx]

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

The NEC doesn't require a 4 wire feed for all subpanels. 120v only and 240v only are fine with 3 wire. You are required to do 4 wire if you want 130 and 240v though

 

[Innovate1]

On 3 wire vs 4 wire - Probably want some lights out there. I suppose you could find 240v lights but that's pretty limiting. And that would mean no 120V recepticles. Seems crazy to only wire 240V to a building you will be working in.

 

[wyliesdiesels]

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?

yeah that stuff has gone way up. like 300%... i remember a few years ago when it was about $1.5/ft

 

[wyliesdiesels]

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

yeah have you seen the price for MHF on there lately?

$4.37/ft yikes

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[mike93lx]

On 3 wire vs 4 wire - Probably want some lights out there. I suppose you could find 240v lights but that's pretty limiting. And that would mean no 120V recepticles. Seems crazy to only wire 240V to a building you will be working in.

Completely agree

 

[wyliesdiesels]

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.

yes that would be a code permissible solution

 

[wyliesdiesels]

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.

thats a good way to burn up a UPS battery on short order and unless the UPS has AVR or is a double conversion model ($$$$), you will still have flickering of the lights... plus if the lights are hardwired, you would have to coble something together to be able to plug the lights into the UPS.... not a sensible solution

 

[wyliesdiesels]

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

it does? where is that code requirement?

 

[Innovate1]

yeah have you seen the price for MHF on there lately?

$4.37/ft yikes

Mobile Home Feeder Cable | WireAndCableYourWay.com

We stock Mobile Home Feeder Cable in a variety of gauge sizes. Most of our SKUs are sold by the foot and in bulk. Order today for fast shipping!

www.wireandcableyourway.com

I am glad I got the shop done just before prices went crazy!