Buck & Boost for 120V Outdoor Circuit

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
Would a B&B transformer work ok to boost a 120V circuit for a electric gate opener?
I don't know what the voltage is but a customer wants to abandon (6) halogen spot lights and use the power for the gate. I don't know what or if anything else is on the circuit. I cautioned the guy that depending on the motor load there might not be enough power considering the length of the run and anything else on the circuit.
I just wanted to see IF there wasn't enough if a B&B would work.

Also, are there outdoor rated B&B maybe similar to a pool transformer?
 

iwire

Moderator
Staff member
Location
Massachusetts
You will have fluctuating voltage which may or may not be a problem

The open circuit voltage will be well above the loaded circuit voltage.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
You will have fluctuating voltage which may or may not be a problem

The open circuit voltage will be well above the loaded circuit voltage.
Just remembered he also wants some post lights on top of the column off the same circuit. So I would probably need to feed the lights straight line voltage and bypass the transformer for those.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
What is the voltage at the gates now ?
Is the voltage low due to long run of cable ?
Or too small gauge of wire ?
There isn't any power to the gates now, there isn't even a gate yet;). Customer is getting it installed and gate company said they needed 120V on each side of driveway.
Customer wants to use existing circuit for landscape spot lights and do away with the spot lights.

The circuit could be long the way it has to wind around to hit all the lights. He wants to run the power from the light that is closest to the gate. I have no idea where that light fits in as far as it's place along the circuit. Could be the first light, middle, or last.
This was a late appointment and it started raining so I don't have a lot of the details I need yet.
 

curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
Using a BB transformer for this application in not a good idea. The voltage to the controls for the gates will substantially elevated when the motors are not running.
 

iwire

Moderator
Staff member
Location
Massachusetts
Just remembered he also wants some post lights on top of the column off the same circuit. So I would probably need to feed the lights straight line voltage and bypass the transformer for those.
Well that would prevent over voltage to the post lights but they would still dim when the motor starts.
 

iwire

Moderator
Staff member
Location
Massachusetts
Using a BB transformer for this application in not a good idea. The voltage to the controls for the gates will substantially elevated when the motors are not running.
Yes, depending on the control circuit design the smoke might come out when the motor is off.
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
There isn't any power to the gates now, there isn't even a gate yet;). Customer is getting it installed and gate company said they needed 120V on each side of driveway.
Customer wants to use existing circuit for landscape spot lights and do away with the spot lights.

The circuit could be long the way it has to wind around to hit all the lights. He wants to run the power from the light that is closest to the gate. I have no idea where that light fits in as far as it's place along the circuit. Could be the first light, middle, or last.
This was a late appointment and it started raining so I don't have a lot of the details I need yet.
Find out more about the gate. I'm working on a project right now with about 1000' of circuit length. The gate motor is a 12V DC motor, so the 120V we are running is for a battery charger and a couple of lights. The whole thing could be run in 12AWG and be just fine.
 
So your worried about voltage drop on the long line for the lights ?

You can uprate your main feeder cables to minimise/compensate for loss

or you can use CFL'S or LED's which are much more tolerant of lower mains voltage,
due to the smps in the bases which will simply adjust to suit.
 

mike_kilroy

Senior Member
Location
United States
Would a B&B transformer work ok to boost a 120V circuit for a electric gate opener?
I don't know...
Asking if one can use a B&B for this makes about as much sense as asking if one can use a B&B for powering a candy machine across the block in your neighbor's home to make candy faster... Without SOME details, the answer is obviously NO.

Until you know:

- the length of the present 120vac run from its source to the gate location
- the gauge of that wire
- how many conductors
- the exact specs of the gate actuator
- the exact specs of the gate controller
- details for opening in loss of power in case of emergency
- etc.

You cannot possibly respond to the homeowner with ANY reply worth a darn, let alone begin picking some wild components...

You will likely be liable if their house burns down when they have a lightning strike fire that knocks off the electric and the gates will not open. Think this through very carefully before offering any solution. I do believe you will find you want a battery run low voltage gate as was previously mentioned for emergency situations. Then you can begin to put together a plan that takes all the details still missing into account to come up with the hardware required so you can quote the job.
 

growler

Senior Member
Location
Atlanta,GA
Find out more about the gate. I'm working on a project right now with about 1000' of circuit length. The gate motor is a 12V DC motor, so the 120V we are running is for a battery charger and a couple of lights. The whole thing could be run in 12AWG and be just fine.
I think most of the gate openers are DC powered. If you didn't have the battery you would have a problem when the power is off.

I think you are right and there is very little load on the circuit, just the charger.
 

mike_kilroy

Senior Member
Location
United States
I think most of the gate openers are DC powered. If you didn't have the battery you would have a problem when the power is off.

I think you are right and there is very little load on the circuit, just the charger.
Right on. I have 3,500' run from house to the street and use a 8pair 24gauge underground phone cable to power my stuff. I use 3 pair in parallel for 120vac then at street have 12v battery, 2amp charger, various sensors, and run 4-5 strings of LED Christmas lights too. Someday, if I ever get around to it, the 12' gate and yes, DC actuator, will be commissioned.
 

brantmacga

Senior Member
Location
Georgia
Occupation
Electrical contractor
Asking if one can use a B&B for this makes about as much sense as asking if one can use a B&B for powering a candy machine across the block in your neighbor's home to make candy faster... Without SOME details, the answer is obviously NO.
Its a response like this that makes me not want to participate here. The purpose is this forum is to ask questions and become more educated.


You will likely be liable if their house burns down when they have a lightning strike fire that knocks off the electric and the gates will not open..
Acts of God typically exclude you from any liability. If that is a concern of the homeowner, they can purchase a fail-to-open battery backup.


Sent from my iPhone using Tapatalk
 

brantmacga

Senior Member
Location
Georgia
Occupation
Electrical contractor
I think most of the gate openers are DC powered. If you didn't have the battery you would have a problem when the power is off.

I think you are right and there is very little load on the circuit, just the charger.
I've seen a lot of it both ways.

Some are straight 120v motors and some 120v with 12v batteries connected to an inverter, and I've worked on gates that have both 120v & 12v motors, although that I've only seen in commercial applications.


Sent from my iPhone using Tapatalk
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
Asking if one can use a B&B for this makes about as much sense as asking if one can use a B&B for powering a candy machine across the block in your neighbor's home to make candy faster... Without SOME details, the answer is obviously NO.

Until you know:

- the length of the present 120vac run from its source to the gate location
- the gauge of that wire
- how many conductors
- the exact specs of the gate actuator
- the exact specs of the gate controller
- details for opening in loss of power in case of emergency
- etc.

You cannot possibly respond to the homeowner with ANY reply worth a darn, let alone begin picking some wild components...

You will likely be liable if their house burns down when they have a lightning strike fire that knocks off the electric and the gates will not open. Think this through very carefully before offering any solution. I do believe you will find you want a battery run low voltage gate as was previously mentioned for emergency situations. Then you can begin to put together a plan that takes all the details still missing into account to come up with the hardware required so you can quote the job.
I never said I was going to connect a B&B nor did I say I told the customer I could.

I only ask, in general, if a B&B would work if the voltage is too low.
The customer is getting me the info from the gate installer so I know what I'm up against.
The question from me was just to give me ideas of what I might could do and I am gathering info before quoting him anything.
 

templdl

Senior Member
Location
Wisconsin
I never said I was going to connect a B&B nor did I say I told the customer I could.

I only ask, in general, if a B&B would work if the voltage is too low.
The customer is getting me the info from the gate installer so I know what I'm up against.
The question from me was just to give me ideas of what I might could do and I am gathering info before quoting him anything.
Yes, yu ou could use a B-B to boost the voltage but as one of the others I believe said when you apply the transformer is the boosted voltage based upon the circuit when loaded? If so the voltage may end up being higher than you would like without a load.
Going with a B-B is more economical if you go that route as the transformer's KVA only needs to be large enough to change he voltage.
You may consider a step up step down combination, more expensive but you can use 480 from one transformer to the other reducing the current by 25% which may result in a lower voltage The transformers. If the transformers have HV taps the voltage can befurther corrected. Unlike the B-B transformer where you need only one you need 2 to step up and back down and must be sized to carry the load. .
 

mike_kilroy

Senior Member
Location
United States
I never said I was going to connect a B&B nor did I say I told the customer I could.

I only ask, in general, if a B&B would work if the voltage is too low.
The customer is getting me the info from the gate installer so I know what I'm up against.
The question from me was just to give me ideas of what I might could do and I am gathering info before quoting him anything.
Rereading my reply it seems very harsh; sorry, it was not meant to come out harsh.

After you get the data, if it turns out you would have a voltage drop issue, rather than a buck boost transformer, consider a CVS transformer (Constant Voltage). They will accept typically around 80vac to 140vac input and turn it into solid 120vac output - does the work of boosting only when required. Sola is the big name in these.

Example from google: http://www.solahevidutysales.com/cvs_hardwired_series_power_conditioner.htm

Another potential is a properly sized UPS like you normally use on your computer; it too will normalize the output ac irregardless of the input.
 

iwire

Moderator
Staff member
Location
Massachusetts
Another potential is a properly sized UPS like you normally use on your computer; it too will normalize the output ac irregardless of the input.
The typical UPS used for a PC does not regulate voltage. It sits there doing nothing until the supply goes out if perimeter than the unit switches to battery.

To do what you are suggesting would require a full or dual conversion UPS.
 

mike_kilroy

Senior Member
Location
United States
The typical UPS used for a PC does not regulate voltage. It sits there doing nothing until the supply goes out if perimeter than the unit switches to battery.

To do what you are suggesting would require a full or dual conversion UPS.
Not necessarily... depends on the objective...

Sure, if +/-1% regulation is required, then the more expensive regulating kind of UPS would be required.

But here, the object seems to be simply to keep voltage from going way too high or way too low for non critical equipment like lights and gate motors. I just verified a 3kva UPS I have here on an old 6 switch setting isolation transformer; it of course fed straight through 108 to 135vac, but went to UPS 118vac output when I went down to 98vac input and above 138vac input. So for this use, like our computers, I think a cheap UPS probably would be sufficient. Of course the proof is in the details; once data is obtained on the exact components to be powered, their specs can be checked to verify this type of range is still acceptable.
anci C84.jpg
 
Top