Tanning beds need buck/boost transformers?

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Mr. Serious

Mr. Serious

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Location
Oklahoma, USA
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Electrical Contractor
I have a new customer, a tanning salon. Current tanning beds have 40A and 50A circuits (3-phase 208 volt, no neutral), the owner wants both upgraded to 60A for new tanning beds. She said something about the buck/boosts needing to be upgraded too. I took a look behind one tanning bed and sure enough, there are two little transformers behind it.

It makes little sense to me to have both a buck transformer and a boost transformer, unless they have automatic tap changing or something to compensate for voltage variations. They didn't look that fancy. I have a picture, but haven't taken the time yet to look at model numbers or anything. Anyone have experience with this and know what it needs? I'll take a close look at the picture and see if I can figure it out, from the existing installation.
 
OK, I took a look at the picture. Jefferson Electric Buck-Boost, cat no. 416-1241-000. It's a single-phase transformer. So, with two of them, you can convert 3-phase 208 volts to 3-phase 240 volts? That is my guess.
 
You can but you better do some research. If I read the chart correctly that transformer configuration is only good for about 26 amps, 240 to 208.
You need to know the exact load (kw) and the actual input voltage to select the correct buck n boost. There are several possibilities.
 
Yup. The beds are supposed to get 240V.

With two transformers you can boost 208 to 240 using an 'open delta' configuration. Based on the specs of those transformers they are probably putting out 236V, although with a non-standard connection you could get the full 240. You get about 25 or 30A of capacity at '240V'.

With three of those same transformers and the neutral, you can boost 208V to 236V in a 'wye' configuration; this gives you 46A of capacity at 236V. Depending upon the actual loads this may be sufficient for your '60A' circuit. (Is it 60A at 208V or 60A at 240V, and is the load only 80% of the circuit rating...)

-Jon
 
It is definitely a 208/120 system feeding the building, because it's a mixed-use shopping center, and the tanning salon owner says her power usage is by far the highest, but the shops all feed off the same service.

I will have to ask the owner for power input specifications of the new tanning beds. But, if I wanted to use a wye configuration with three of those same transformers, I'd need a line-side neutral, right? But the neutral could be under-sized compared to the ungrounded conductors?
 
LarryFine said:
Is there a point where it's better to use a single 208-to-240 transformer to supply a panel for all of the beds?
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Maybe if it had been planned that way from the start. They have two 200-amp 3-phase services, with 2 air conditioners and 4 tanning beds fed from one panel, and 1 air conditioner and 5 tanning beds from the other. The tanning beds are all different kinds, two of them are only single-phase. One is a bigger fancy one that has a 70-amp 3-phase breaker.
 
To use three transformers in wye you would need the neutral. You would need to size it by the neutral load.

But you might consider putting the transformers in the electrical room at the feed end of the circuits.

-Jon
 
If they are buying new tanning beds, make sure they are ordered at the correct voltage and you can get rid of the buck/boost transformers.
 
winnie said:
To use three transformers in wye you would need the neutral. You would need to size it by the neutral load.

But you might consider putting the transformers in the electrical room at the feed end of the circuits.

-Jon
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I have some old Square D literature that says the neutral conductor would only be required if you need a line - neutral voltage.
 
A lot of tanning beds are 220V, I would inquire about the allowable voltage range allowed by the manufacturer, a lot of times the buck/boosts are used because normal 240V is higher then allowed, with 208V they might not be needed.
 
Mr. Serious said:
Maybe if it had been planned that way from the start. They have two 200-amp 3-phase services, with 2 air conditioners and 4 tanning beds fed from one panel, and 1 air conditioner and 5 tanning beds from the other. The tanning beds are all different kinds, two of them are only single-phase. One is a bigger fancy one that has a 70-amp 3-phase breaker.
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Be careful that they do not use a neutral, especially the big fancy one. I hooked up one made in Germany, the Germans used the ground as a neutral for the controls. When using an open delta buck boost, only one leg will be 120 volts to ground.
 
Mr. Serious said:
It makes little sense to me to have both a buck transformer and a boost transformer, u
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Since no one else has pointed this out, a buck/boost transformer is a term, not two transformers, A Buck/boost transformer can be configured, for example to boost 208v to the 220v that Wolff tanning beds need, or from 240v to the same 220. Same transformer, different wiring configuration.
 
augie47 said:
Just lay in the sun = eliminate the "middle man", no panels needed :)
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There are many workers who enjoyed the show when a neighbor decided to sunbathe in the buff, but if someone is working on the roof next door, she must of not cared unless they were quite dense.
 
Salons use a lot of '220' equipment, we have done a few.
If you have to order new service for the salon ask for a 3 phase hi-leg delta.
It actually made it easier for me one time as that is a 'different system' per article 230 than the 208 wye.
 
tortuga said:
Salons use a lot of '220' equipment, we have done a few.
If you have to order new service for the salon ask for a 3 phase hi-leg delta.
It actually made it easier for me one time as that is a 'different system' per article 230 than the 208 wye.
Click to expand...
Didn't you still have to buck 240 to 220?
 
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