Change 208 circuit to 240

[kwired]

I might....I'm not 100% sure, but I trust you. Keep in mind I never went to school for electrical, I backed into it one day pouring concrete at an electrician?s house and stayed longer than the rest of the crew.

In the case of the OP he wanted to use 240V elements on a 208V system.....that ain't gonna do what he wanted, that much I do know.

When it comes to motors (ballasts too) everybody says, "More voltage, less amps". But they leave out the part that you reconfigure the windings from parallel to series...kw is the same.

Same kW, yes, but less amps also means less copper expense is needed to supply it. But on a installation with light load to begin with - you also need to consider that the higher voltage switchgear, panelboard, etc. may also cost more.

 

[ActionDave]

Actually the important, and counter intuitive for some, thing about motors is that if you stay within the allowed range for a given wiring configuration (which might include both 208 and 240) the current will still increase as you drop the voltage as long as the load on the motor is constant.

That did not confuse me so much as the current going up when the voltage gets too high.

 

[GoldDigger]

That did not confuse me so much as the current going up when the voltage gets too high.

A very good point! For any iron core inductor the inductance falls off drastically when the core reaches saturation. That is extremely likely for a transformer, which is tightly designed, or for a motor without a VFD.

 

[jeremysterling]

I want to change it to 240v because I'll get higher output with the same amperage breaker and wire size.

As several members have pointed out, higher output will not occur, in fact the opposite will happen. This is because for a given fixed resistance (of the heater element), the power output (hot water) is directly proportional to the applied voltage (208V). You will receive only a percentage of the nameplate wattage.

In essence, you will have the same amperage breaker and wire size, but not the same amps.

 

[kwired]

I have a point of use water heater that is rated for 208 and want to replace it with one rated for 240. Can anyone explain how this would be accomplished? My limited license does not cover this work, but I need to explain to the customer in general terms what needs to be done and how involved it would be.

Thanks.

The discussion has strayed away a little from the OP, but still contained information that may be usable to the OP.

The first question is what are you trying to accomplish? If you want more heat, putting in 240 volt heater of same kW rating will actually put out less heat if still connected to the existing 208 supply.

If you put in a higher kW rated 240 unit but still connect to the 208 volt supply then you will not see the full kW output because you are not supplying it with full rated voltage. You will see about 75% of 240 rated kW if only supplying with 208 volts.

If you supply a 208 volt rated element with 240 volts you will get more heat out of it, but you very well will shorten it's useful life, you will get about 133% of rated kW rating out of 208 volt element connected to 240 volts.