buck-boost

Status
Not open for further replies.
P

puckman

Senior Member
Location
ridgewood, n.j.
does anyone know how to size a buck-boost transformer to get 3 phase 220 to 230 volt from 3phase 240 volt . the load is 75 amps. 240volt is to much voltage.
 
if i had my ugly's book handy i could tell you but i'm home and my books in the office.If you can get your hands on one you will soon wonder how you ever did without one.With my calculations you will need a 5% boost
 
Last edited:
puckman said:
does anyone know how to size a buck-boost transformer to get 3 phase 220 to 230 volt from 3phase 240 volt . the load is 75 amps. 240volt is to much voltage.
Click to expand...
r u talking about going from 208 to 240 3 phase :-? am i missing something or ?
 
puckman said:
240volt is to much voltage.
Click to expand...
Are you sure? 230v is the normal rating for equipment designed to operate on 240v.

In fact, most motors run better and cooler at the high end of the voltage rating range.
 
chris, no it is a roof top ac unit about 15 ton paper work says 208 - 230 volt. it also saids operating range 187 - 253 volts. unit was ordered before any contractors were hired. thanks to all
 
puckman said:
3phase 208 - 230 at 70amp.
Click to expand...
in that case go with a 30 kva 240v to 208v x 120v xfmer if u can get one in 30 kva our price cat. only gives 45, 75 112.5 and 150 kva call ur supplier he may be able to get a 30kva in these voltages. and what larry said i can't chew gum and type and think that fast.
 
Last edited:
puckman said:
chris, no it is a roof top ac unit about 15 ton paper work says 208 - 230 volt. it also saids operating range 187 - 253 volts. unit was ordered before any contractors were hired. thanks to all
Click to expand...
i think what u have is a unit that run on either 208 or 240 u would probly need to change some taps in the unit itself depending on the voltage avaliable also i belive the 187-253 is what the unit will run on before it is going to suffer as votltages vary Ex. 120v meter will somtimes read 123, 115 etc.
 
puckman said:
chris, no it is a roof top ac unit about 15 ton paper work says 208 - 230 volt. it also saids operating range 187 - 253 volts. unit was ordered before any contractors were hired. thanks to all
Click to expand...

Then its 2 motors. Your set. No transformer needed.(IMO)
 
I know that most of the better tanning beds say 230 volts MAX, so having to buck from 240 down closer to 230 is very commong for connecting a tanning bed. They're not 3?, however.
 
puckman said:
chris, no it is a roof top ac unit about 15 ton paper work says 208 - 230 volt. it also saids operating range 187 - 253 volts.
Click to expand...
You're good to go. No transformers needed, and there should be no taps to configure.
 
208 to 230 plus or minus 10% is 187 to 253. No problem. No buck-boost needed. Just make sure the tap on the 24 volt control transformer in the RTU is properly set.
 
mdshunk said:
Just make sure the tap on the 24 volt control transformer in the RTU is properly set.
Click to expand...

I do change this tap but I feel that is the mechanical contractors responsibility on start up. You don't make up the Tstat terminations do you?
 
chris kennedy said:
I do change this tap but I feel that is the mechanical contractors responsibility on start up. You don't make up the Tstat terminations do you?
Click to expand...
That really depends. Yes, about 50% of the time I do have to terminate the stat connections, set the control transformer taps, and comfirm the rotation of the RTU. Other than that, it's the tin-knocker's baby. I only run the unit for a matter of seconds. I fully realize that in most areas, the electrician just gets power to the unit and never has to lay eyes on it again. I think I operate in an area where the HVAC guys are a little spoiled, but it's okay with me.
 
Status
Not open for further replies.
Top