Never installed a auto-transformer before. Help please.

[zappy]

Dental office has a 11.6amp single phase 208-230V motor. 208V. coming into it. Lasted about 5 years. On 8hrs. a day.

Abeint temp. in the room is 100 degrees plus. Manufact. says 208V. is on the low side, and should

be bumped up to 230V. So my questions are: 1. Can the breaker serve as a disconnect for the line

side of the tranny? 2. I also will need a disconnect for the load side of the tranny, before the motor?

3. Sizing the tranny. Is it as simple as anything bigger then 11.6amps? Or is there more to it?

Any other things you can point out would be very much appreciated. Thank you for your help.

 

[Strathead]

Dental office has a 11.6amp single phase 208-230V motor. 208V. coming into it. Lasted about 5 years. On 8hrs. a day.

Abeint temp. in the room is 100 degrees plus. Manufact. says 208V. is on the low side, and should

be bumped up to 230V. So my questions are: 1. Can the breaker serve as a disconnect for the line

side of the tranny? 2. I also will need a disconnect for the load side of the tranny, before the motor?

3. Sizing the tranny. Is it as simple as anything bigger then 11.6amps? Or is there more to it?

Any other things you can point out would be very much appreciated. Thank you for your help.

What you need to install is an auto transformer, but I refer to it as a buck boost transformer. for this application. It is installed in series with the load, and as such does not need a disconnect. The size needed, is equal to the Voltage difference times the amperage of the load. So 230-208=22Volts * 11.6 amps is 256va and the nominal tranformer size I think is .5KVA When you get the transformer, don't freak out, because it will be labelled as a 120/240V to 12/24 volt transformer, (or at least they used to be). There are wiring diagrams for how to hook up for each voltage selection.

 

[templdl]

Also, since a buck/boost transformer provides no isolation, that it is essentially in series witrh the load the branch breaker will serve as both the OCPD and the disconnect and you don't need an additional disconnect at the motor.

 

[stew]

if you have an Uglys there are connection diagrams that will help you understand how a boost/buck operates.

 

[kwired]

Buck boost supplier/manufacturer should have selection guide to help you determine what unit you need based on existing voltage, desired voltage, and amount of load.

link to Square D product selector click on the "product selector" tab within the page. Fill in data and it will give you which model you need for your application.

http://products.schneider-electric....ansformers/buck-and-boost-transformers/#tab=1

For some reason I messed up the link hopefully second one here works.

 

[barclayd]

Is it totally out of the question to get the proper motor?
db

 

[kwired]

Is it totally out of the question to get the proper motor?
db

May be the less costly route if it is a NEMA motor. If specialty motor you have what you have in most cases.

 

[ActionDave]

Since the OP stated the motor is 208-230V I am doubtful that the voltage is a problem unless the measused voltage is lower than 200V.

 

[templdl]

As I recall NEMA motors are supposed to be capable of being applied at +-10% of their NP voltage. Motors run at the lower end of the allowance will draw more current in order to provide the rater HP which translates to a motor which will run warmer.
I one concludes that increasing the voltage will help a B/B transformer is the answer. A specific B/B transformer will often be supplies with numerous wiring options dependent up us as a buck or boost and voltage applications. Caution should be used when installing this transformer.