This place appears to be the fount (font?) of all knowledge, so as I need help and advice in another area, am again requesting help from the resident 'spurts.

I volunteer at a place that has a few large walk in fridges, plus an assortment of water pumps. That area is plagued with sudden extended voltage drops which has resulted in a few quite expensive motor burnouts. There are three 220 volt feeds to a variety of buildings. This 220v in turn is cut to 115v as required. Very often only one leg of the 220 drops in voltage, like to about 70 volts or even less.

Is there some sort of cheap device that can be installed to sense a voltage drop below a set voltage and automatically cut everything to protect the motors? Then once the correct voltage is restored, switch everything back on again? What is this device called and where would I buy it? Can I build one up myself? Are they expensive?

Thanks in advance for the help.

 

I'm sure there is such a device. If motors are properly protected, low voltage overcurrent would trip the protector long before the motor was damaged. Secret is in protecting each motor seperately and carefully sizing the protector. (circuit breaker) A combination of a auto reset breaker and a compressor saver (time delay device) would automatically protect the equipment and allow it to run when possible.

 

Stan, since you are in Mexico we have to ask, do you mean you have 3, 220 volt legs as in 3 phase power or 3 separate 220V single phase feeds? ( 2 legs of 115V )

There are phase leg protectors to do what you want for 3 phase, I am not sure if there is such a thing for single phase.

 

Pat, on rereading what I wrote, can see how you could be confused. Will try to now unconfuse the issue.

At that location, which is quite extensive with many buildings, they have their own dedicated transformer. It feeds a central distribution center with normal 220 volts. It could be 240 volts, but have never measured it at the source. At the distribution center, it is fed to what we could call 3 zones for this conversation. Each zone has it's own main breaker. Each zone then branches out to various buildings where it is broken down to 115 / 220 volts as required. It is the motors at each building that have on occasion fried because of the brownouts. Some motors are 115 volt and others 220. It is the 220 volt motors that have given the most problems because when the power drops in voltage, it is normally only one leg of the 220.

Clearer now?

 

Stan,

I did not go searching the web for this, but I know there are in-line protection devices used in the RV industry that do exactly what you ask. You can get both 240 or 120v units. Not cheap, but one motor would pretty well pay for it. The different units use different protocol for how they protect. Some are just surge protectors. Others are both surge and low voltage protection. I have an inverter on mine that monitors both the source for proper configuration, will drop out for surges and re-engage after a delay if all is well. It will also swing over to the inverter on the batteries to provide 120v at whatever voltage I have preset. All this to say there are several varieties - - check out some RV sites for something that would handle what you want.

Bob

 

Stan, take a look at this, might be just what you are looking for.

 

Pat, thank you. That sure looks like it would do the job, but I cannot see any amperage rating for it.
Some of the comments do not appear to like this item due to a high failure rate.

 

It's rated at 5 amps, so it would handle a small air conditioner or refrigerator unaided. Add a solid state relay, and it can handle anything.

This item would be the combination under voltage cutout and time delay compressor saver I first wrote of.

There's several more models of these. The ICM493 has a 40 amp relay built in.

Single Phase Monitor | Phase Monitor | ICM Controls

 

Just sent someone to go and check the largest fridge and it is rated at 208/230 volts and 14.4 amps. The other walk in fridges are a little bit smaller, but will need to go and check each motor for size.

 

That's what I was looking for !

 

Stan, I noticed you made a comment of "walk-in" coolers. Remember when the cooler is operating you have a condenser (outside with compressor and condenser fan) and an evaporator (inside with just a fan). When you size your protection device you need to accommodate both loads when figuring your device size and install it in the circuit before both loads are connected.

Gary

 

Thanks everyone for the info. Will put it to good use.

Gary, excellent thought. Would probably have overlooked those items. So far none of those motors have burned up from brownouts.

 

No help from the the local utilities correct?

This is where I get a lot of my HVAC equipmqnt, check "line monitors"


Johnstone Supply 206 catalog - page Cover

These look to be for single device only, like compressors or motors

Johnstone Supply 206 catalog - page 1207

Johnstone Supply 206 catalog - page 1208.

I checked our shop and found everytime their air compressor next door would start our computers would crash after enough complaints to the utility company they found the transformer feeding the block was undersized not enough current, they replaced the transformer.

If it is consistantly low you could install a buck/boost transformer, I carried one for construction sites where erybodys tools were running.

 

HA!!! The local utility is the cause of the problem! I occasionally have the same problem at home. When this happens at home and I hear the fridge complaining, I just run an extension cord from the other room which is on the other leg of the 220 and plug the fridge into that until the power comes back. When power goes down on one leg or vanishes totally, it can last for just a few minutes, or 24 hours.

Thanks for Johnson info.

 

This is Mexico. If he complains the power company will come out and put 10 amp fuses in.