240VAC vs 120VAC (Pros / Cons)

[AWinston]

I am working on a project where the client has a lot of loads that can be configured for 120VAC or 240VAC. Is there any benefits to going with either one? My only thought was they can save money on conductor sizing since current is lower on higher voltage systems.

 

[GoldDigger]

That is basically right as an underlying principle.
But you also need to take into account that a 240 branch circuit requires a 2 pole breaker and you might have to run three wires (red, black, white) plus EGC instead of two (red or black, white) plus EGC for each circuit. That depends on how the equipment actually looks configured for 240.
If your circuits are in the low current range (<15A) you might not gain on wire cost because of the minimum wire size.

 

[iwire]

I am working on a project where the client has a lot of loads that can be configured for 120VAC or 240VAC. Is there any benefits to going with either one? My only thought was they can save money on conductor sizing since current is lower on higher voltage systems.

The conductor sizing s pretty much the only savings. You would have to put that cost against the cost of two pole breakers vs single pole same with disconnecting means etc.

Are the circuit lengths reasonable or long?

 

[AWinston]

That is basically right as an underlying principle.
But you also need to take into account that a 240 branch circuit requires a 2 pole breaker and you might have to run three wires (red, black, white) plus EGC instead of two (red or black, white) plus EGC for each circuit. That depends on how the equipment actually looks configured for 240.
If your circuits are in the low current range (<15A) you might not gain on wire cost because of the minimum wire size.

Thanks for the insight.

 

[GoldDigger]

Thanks for the insight.

You are welcome. Are any of the loads going to be cord and plug connected? If so the code puts a *minimum* wattage on use of 240 to a receptacle.

 

[gar]

151209-1715 EST

AWinston:

I have a DeWalt radial arm saw. Single phase 120 or 240 and something over 1 HP possibly 1.5 HP. Installed was a 10 or 12 inch blade.

This was wired 120 V, and was in a location with about 120 ft of #12 copper Romex from a 20 A QO in the main panel. On startup it drew 80 A or so for a number of seconds, I believe about 5 seconds before reaching speed. A short time, a few seconds, possibly 10 or 15, if a restart was tried the QO would blow. To be expected.

If this same Romex had been supplied with 240 the motor would have started very quickly. It wasn't really Romex, but rather #12 in conduit, but Romex was a good way to indicate the wire length.

If the saw is much closer to the main panel with a shorter run of wire, then it starts with a second.

Why not rewire the saw for 240. Because the saw can be moved around and 120 is available almost anywhere.

.

 

[fmtjfw]

For fixed locations (non-portable loads) 240V will give you 1/4 the voltage drop and 1/2 the circuit losses. For total-cost-of-ownership this may save money in the long term especially if the only expense is a single 2-pole breaker versus two 1-pole breakers. Also motor loads will probably start faster due to 1/4 the percentage of voltage drop at 240V.

240 is the voltage of choice for most of the world.

 

[electrofelon]

151209-1715 EST

AWinston:

I have a DeWalt radial arm saw. Single phase 120 or 240 and something over 1 HP possibly 1.5 HP. Installed was a 10 or 12 inch blade.

This was wired 120 V, and was in a location with about 120 ft of #12 copper Romex from a 20 A QO in the main panel. On startup it drew 80 A or so for a number of seconds, I believe about 5 seconds before reaching speed. A short time, a few seconds, possibly 10 or 15, if a restart was tried the QO would blow. To be expected.

If this same Romex had been supplied with 240 the motor would have started very quickly. It wasn't really Romex, but rather #12 in conduit, but Romex was a good way to indicate the wire length.

If the saw is much closer to the main panel with a shorter run of wire, then it starts with a second.

Why not rewire the saw for 240. Because the saw can be moved around and 120 is available almost anywhere.

.

Ditto. Try doing some hard ripping with a table saw on 120 vs 240 and you will be amazed at the difference.

 

[iwire]

Ditto. Try doing some hard ripping with a table saw on 120 vs 240 and you will be amazed at the difference.

The performance will be the same if you oversize the wire as much for the 120 circuit as it would be for the 240 circuit.

 

[electrofelon]

The performance will be the same if you oversize the wire as much for the 120 circuit as it would be for the 240 circuit.

OF course, but in practice you cant upgrade the existing branch circuit/feeder/service entrance conductors/utility secondary conductors, and the motor windings

 

[JFletcher]

I'm curious as to what these loads are. Are they continuous? Long cable runs? Portable/fixed? Is there any difference in eqpt cost between 120V and 240V?

GoldDigger already mentioned my other thoughts.

 

[iwire]

OF course, but in practice you cant upgrade the existing branch circuit/feeder/service entrance conductors/utility secondary conductors, and the motor windings

Let's not get carried away, the OP is talking about a new installation so it's not an upgrade.

And back to the panel should be far enough unless that is one huge saw. :blink:

I think folks forget that the motor uses two 120 volt windings so to the motor 240 or 120 is irrelevant as it runs on 120 either way.

 

[ActionDave]

I think folks forget that the motor uses two 120 volt windings so to the motor 240 or 120 is irrelevant as it runs on 120 either way.

But only 240 lets you brag to your neighbours about your table saw or compressor.

 

[iwire]

But only 240 lets you brag to your neighbours about your table saw or compressor.

:thumbsup:

When I was about 19 I bought an air compressor and I chose 240 volt so my brother in laws would not ask to borrow it. That was effective.

 

[infinity]

One other consideration is that if you choose to use 240 volts you will need two breaker slots for each load. Since the OP said that he has lots of loads by utilizing the 120 volt operation it will give you double the amount of available breaker slots in the panel.

 

[kwired]

More information on application and conditions will be very helpful.

Work I have done in art 547 type of applications it is sometimes desirable to avoid usage of the grounded conductor as a circuit conductor as much as possible just to help minimize potential stray voltage problems.