Buck - Boost Transformer Connection

Reply

  #1  
Old 12-14-12, 09:35 PM
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 7
Buck - Boost Transformer Connection

I have an Acme T-1-81052 120/240v buck-boost transformer for a tanning bed (230v-1ph). The problem is there are three input wires to the transformer (two black 'hots' and a green ground), but there are four wires at the junction box (a red 'hot' and a black 'hot', a green and a bare copper). What should I do with the bare copper?
 
Sponsored Links
  #2  
Old 12-14-12, 09:38 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,285
Normally a bare copper is a ground. Not sure why there are two grounds (green and bare) so you might want to find a wiring diagram.
 
  #3  
Old 12-14-12, 09:46 PM
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 7
Tolyn,
thanks for the quick reply. I should have been a little more specific. The green input on the transformer is bonded to the metal case.
The power feed to the junction box is from a sub-panel and that may explain the green (neutral?) and bare copper (ground?) that are not bonded in the sub-panel.
Does that help?
 
  #4  
Old 12-14-12, 10:19 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,058
green (neutral?)
No, green is never neutral. It may be the green is the isolated ground and the bare is the shared ground. Is this a commercial environment?
 
  #5  
Old 12-14-12, 11:22 PM
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 7
Not commercial. Did some more checking. The junction box has a red, black, white (not green) and a bare copper. I think they just ran a 10-3 w/ gnd. Therefore believe I just need to connect the 'hots' and the green from the transformer to the bare copper. This sound correct?
 
  #6  
Old 12-14-12, 11:54 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 46,228
What are you actually doing to the voltage ? From what to what ?
 
  #7  
Old 12-14-12, 11:56 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,058
Yes that sounds correct but is the breaker sized for the transformer load? Why aren't you running a 240 volt circuit to the tanning bed?
 
  #8  
Old 12-15-12, 07:48 AM
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 7
My line voltage is about 248vac, the bed manual recommends no more than 230vac to the unit. The transformer is a 0.75kVA rated and allows a drop / increase of 12 or 24 vac (depending on how it is field wired). The bed requires a 30amp two-pole breaker, which is whats installed.
 
  #9  
Old 12-15-12, 08:30 AM
Member
Join Date: Jun 2012
Location: USA
Posts: 1,036
Tanning beds are special in that you want to keep the input voltage between 220 and 230. Commercial 208 needs to be boosted and residential 240 needs to be "bucked." The bulbs are expensive enough that you don't want to risk it with the wrong voltage.

tanningbeds.org Blog Buckboost transformers – Myths and Facts
 
  #10  
Old 12-15-12, 08:31 AM
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 7
Thank you for your advice and help!
 
  #11  
Old 12-15-12, 08:49 AM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,058
Astuff thank you for your input and link. I am deleting my previous response but I have to say I would not purchase equipment from a manufacture that didn't make sure it worked on normally available voltage but then I would not pay to increase my risk of skin cancer just for vanity.
 
  #12  
Old 12-15-12, 09:22 AM
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 7
Thank you Astuff on the voltage concurrence.

Regarding vanity, personally couldn't agree with you more, but I have to stay married to her
 
  #13  
Old 12-15-12, 12:03 PM
Member
Join Date: Jun 2012
Location: USA
Posts: 1,036
To confirm for safety's sake: The white coming from the panel is not used - gets capped with a wire nut. The black and red from the panel go to to the transformer's input taps according to directions supplied with device. The bare copper from the panel gets bonded (attached) to the chassis of the transformer where you see the green wire. That green should also get connected to the cable leaving the transformer so that the tanning bed itself is grounded.

Also - use a multimeter to measure the output voltage of the transformer before trying it with the bed. You don't want to accidentally feed it with the wrong voltage.
 
  #14  
Old 12-15-12, 03:10 PM
Member
Thread Starter
Join Date: Dec 2012
Location: USA
Posts: 7
Astuff,
Thank you for the info. Did as you suggested. Voltage between the two hot legs is 231, close enough to the 230, otherwise i am going to be around 219-220 if I change the transformer taps.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes