120/215/120 Do I need a transformer to get standard 208V??? No One Can Answer

[paulsonsmithfamily]

Good day brothers,

Issue: Pizza oven motor burns up. Needs to have a 240v plug changed to 208. <<<From client.

Stats:
Current outlet is 245v.
Service is 123/215/123v metered.

I, nor anyone I have spoken to can answer if & why I would need a transformer, rather than just landing L1 on 215v tap & L2 to Neutral.

I know (240v single phase) is actually (240v split phase), and I know why. Is (208 standard single phase) actually (208 split phase)? If so than I know why we need a transformer, but if not can people stop calling (split phase) (single phase) for the rookies

Look forward to your replies.

 

[petersonra]

Good day brothers,

Issue: Pizza oven motor burns up. Needs to have a 240v plug changed to 208. <<<From client.

Stats:
Current outlet is 245v.
Service is 123/215/123v metered. I don't know what this means. Are you saying you have 3 hots and these are the voltages to the grounded conductor.

I, nor anyone I have spoken to can answer if & why I would need a transformer, rather than just landing L1 on 215v tap & L2 to Neutral.

I know (240v single phase) is actually (240v split phase), and I know why. Is (208 standard single phase) actually (208 split phase)? If so than I know why we need a transformer, but if not can people stop calling (split phase) (single phase) for the rookies

Look forward to your replies.

208 is usually 3 phase. It seems possible what you have is 240V delta with a center tap in one winding, sometimes called high leg delta.

if your motor will work on single phase 208 there is no reason you cannot wire it from the high leg to the grounded conductor (it is not actually neutral in this case).

However it seems unlikely to me that the motor would burn up if it was a single phase 208V motor wired to single phase 240V.

 

[JFletcher]

208 volts is a three-phase service with 3 120 V legs 120 degrees out of phase with each other. You have a high leg Delta system running slightly higher than nominal voltage.


If there are only two connections for the motor then it is single phase. Most small single phase Motors can run on either 208 or 240 volts. Using the B phase and the neutral is not typically how anything is wired, 208 volt single phase will usually use two ungrounded conductors of a three-phase 208 system.

The two 120 volt lines in a high leg panel are 180 degrees apart and provide 240 volts. If the motor is only designed for 208 volts, then yes you could use the high leg and a neutral to power it.

That all said, I have worked at pizza places with conveyor ovens, I think it is far more likely you have a mechanical problem causing High amperage and subsequent motor burnouts. The oven conveyor belt, gears that drive them, and the shafts are very seldomly cleaned or lubricated.

Eta: I'm sure you know this already, however if you choose to use the B phase and neutral idea, you must use a full 240 V rated breaker not a 120 / 240.

Is this a new installation or an older existing one?

 

[infinity]

You have a 3Ø, 4W Delta system. Normal voltages are 120-208-120 to ground/neutral, 240 Ø to Ø. What does the nameplate on the pizza oven say?

 

[paulsonsmithfamily]

You have a 3Ø, 4W Delta system. Normal voltages are 120-208-120 to ground/neutral, 240 Ø to Ø. What does the nameplate on the pizza oven say?

Oven tag says 208v that's is for voltage.

 

[paulsonsmithfamily]

208 volts is a three-phase service with 3 120 V legs 120 degrees out of phase with each other. You have a high leg Delta system running slightly higher than nominal voltage.


If there are only two connections for the motor then it is single phase. Most small single phase Motors can run on either 208 or 240 volts. Using the B phase and the neutral is not typically how anything is wired, 208 volt single phase will usually use two ungrounded conductors of a three-phase 208 system.

The two 120 volt lines in a high leg panel are 180 degrees apart and provide 240 volts. If the motor is only designed for 208 volts, then yes you could use the high leg and a neutral to power it.

That all said, I have worked at pizza places with conveyor ovens, I think it is far more likely you have a mechanical problem causing High amperage and subsequent motor burnouts. The oven conveyor belt, gears that drive them, and the shafts are very seldomly cleaned or lubricated.

Eta: I'm sure you know this already, however if you choose to use the B phase and neutral idea, you must use a full 240 V rated breaker not a 120 / 240.

Is this a new installation or an older existing one?

Existing, very dirty oven I can tell you that.

 

[paulsonsmithfamily]

208 is usually 3 phase. It seems possible what you have is 240V delta with a center tap in one winding, sometimes called high leg delta.

if your motor will work on single phase 208 there is no reason you cannot wire it from the high leg to the grounded conductor (it is not actually neutral in this case).

However it seems unlikely to me that the motor would burn up if it was a single phase 208V motor wired to single phase 240V.

After further discussions with the client, they say "There's electrical smoke coming from it" so all talk of the motor is client troubleshooting

 

[paulsonsmithfamily]

SO....

208 single phase can be wired high leg (215v) to ground? It is not a split phase with an offset like common 240v, correct?

 

[paulsonsmithfamily]

208 is usually 3 phase. It seems possible what you have is 240V delta with a center tap in one winding, sometimes called high leg delta.

if your motor will work on single phase 208 there is no reason you cannot wire it from the high leg to the grounded conductor (it is not actually neutral in this case).

However it seems unlikely to me that the motor would burn up if it was a single phase 208V motor wired to single phase 240V.

Motor windings burning up was the initial complaint from client. However, after a later discussion (there's just electrical smoke coming from the oven)... Not sure who said they have to go to 208v at the moment, although the oven tag says 208v.

Yes, 240 high leg delta.

 

[infinity]

If you connect a 208 volt oven to a 240 volt system you will get a much higher heat output and possible burnout. Since it rated for 208 volts you need to connect it to a 208 volt source not 240 volts. Sounds like you need a transformer.

 

[paulsonsmithfamily]

If you connect a 208 volt oven to a 240 volt system you will get a much higher heat output and possible burnout. Since it rated for 208 volts you need to connect it to a 208 volt source not 240 volts. Sounds like you need a transformer.

but again, why do I need a transformer to get single phase 208 is I have 215v high leg?

 

[infinity]

but again, why do I need a transformer to get single phase 208 is I have 215v high leg?

What kind of single pole circuit breaker can you buy that will give you a 1Ø, 208 volt circuit from the a 3Ø, 4W Delta system? Practically speaking the 1Ø, 208 volt circuit from the a 3Ø, 4W Delta system is unusable.

 

[paulsonsmithfamily]

What kind of single pole circuit breaker can you buy that will give you a 1Ø, 208 volt circuit from the a 3Ø, 4W Delta system? Practically speaking the 1Ø, 208 volt circuit from the a 3Ø, 4W Delta system is unusable.

Initial thought is a single pole 40a breaker on the high leg to ground. Also: Seeing you are a mod, I have an unanswered post on the free practice tests "currently unavailable" if you could see... http://forums.mikeholt.com/showthread.php?t=190421

 

[JFletcher]

If you connect a 208 volt oven to a 240 volt system you will get a much higher heat output and possible burnout. Since it rated for 208 volts you need to connect it to a 208 volt source not 240 volts. Sounds like you need a transformer.

Possible if the heating elements are also electric, we don't know. I would think they would just cycle faster than on 208 to reach the oven set point,

It will probably be very difficult to impossible to find a 1 pole breaker that is not / rated. Would more than likely need a 3 Pole

Again you can use the high leg to get 208 single phase, however you're limited on most older transformers to 5% of its capacity doing so. I think newer transformers allow up to 35% but still not commonly done.

 

[kwired]

I suspect you might have other issues. Assuming this is a single phase unit based on some of what has been already mentioned. A 208 volt rated motor will run fine on 240 volts nominal. May have a shorter life but will still be a fairly long life. If you just connected this and it started smoking almost immediately, I doubt it is from being connected to 240 volts.

To answer your question in thread title - yes you need a transformer to change voltage. A buck-boost transformer is the lesser expensive way to go - it won't need to be as large as a full isolation transformer.

 

[paulsonsmithfamily]

Possible if the heating elements are also electric, we don't know. I would think they would just cycle faster than on 208 to reach the oven set point,

It will probably be very difficult to impossible to find a 1 pole breaker that is not / rated. Would more than likely need a 3 Pole

Again you can use the high leg to get 208 single phase, however you're limited on most older transformers to 5% of its capacity doing so. I think newer transformers allow up to 35% but still not commonly done.

I suspect you might have other issues. Assuming this is a single phase unit based on some of what has been already mentioned. A 208 volt rated motor will run fine on 240 volts nominal. May have a shorter life but will still be a fairly long life. If you just connected this and it started smoking almost immediately, I doubt it is from being connected to 240 volts.

To answer your question in thread title - yes you need a transformer to change voltage. A buck-boost transformer is the lesser expensive way to go - it won't need to be as large as a full isolation transformer.

You can both see my confusion here; I have several senior members saying I do & do not need a buck boost.... a 12% buck boost at 40A is listed at $2800!!!

 

[ptonsparky]

You can both see my confusion here; I have several senior members saying I do & do not need a buck boost.... a 12% buck boost at 40A is listed at $2800!!!

I’ll sell at that price! Maybe even installed.

i don’t buy at list price. Have a competent salesperson at your wholesaler size and price.

 

[infinity]

You can both see my confusion here; I have several senior members saying I do & do not need a buck boost.... a 12% buck boost at 40A is listed at $2800!!!

The problem is that someone bought an oven that didn't match the building system voltage. Just install the transformer and bill accordingly.
Not sure where you got that price but it's way off.

http://catalog.larsonelectronics.com/bestsellers/240-To-208-Transformer

 

[ptonsparky]

BB transformers are very reasonably priced and the easiest way to deal with your problem. Google buck boost, find a manual and read.

 

[kwired]

You can both see my confusion here; I have several senior members saying I do & do not need a buck boost.... a 12% buck boost at 40A is listed at $2800!!!

You either have selected the wrong one, have the "list price", or need to look for it someplace else. You should be able to find one that size around $150-200.