[Perry401]

There is a non profit thrift store in my area which sells most anything that someone might bring in. They usually test electrical appliances and plug connected things like refrigerators and washing machines before putting them out for sale. They would like to install 240 volt outlets for testing dryers and ranges. The manager has ask me for my opinion on doing this. I have some concerns about the volunteers and helpers hooking up and un hooking high-current, high voltage AC devices, even if all are cord connected. I know that a safety switch could be installed between the power source and outlet(s) but this alone would not insure that the switch would be used.

Please understand that some of the employees have low levels of education or are mentally challenged and should not be messing with this stuff, but there is no way to currently insure that "rules" will be properly followed. Also please understand that someone might drive up and donate a range or dryer which has a short or other defect.

For these reasons, I believe that the store should only sell these 240 volt items "as is" and without any warrentee. I don't think some employees should even be testing desk lamps or tv sets! I think that the outlets used to test 120 volt things should at least be upgraded to GFIC and perhaps have disconnect switches also. Perhaps the test outlets should be locked out at all times unless the manager unlocks them. This way the testing of electrical equipment would be limited to specific employees who are capable of following the proper procedures.

Any feedback would be appreciated!

 

[Jim Port]

With the concerns you voiced I think some method to limit the access would be a good idea.

You might want to consider adding both 3 and 4 wire receptacles in the 30 and 50 amp sizes for the dryers and stoves.

 

[gregzoll]

Also to have included, maybe find a retired electrician or one that is available on a schedule on call for lets say weekends that does these tests and certifies that the appliance is in good working order. The only draw back is waiving liability if the appliance breaks and who would be the one that the customer would call for repairs, vs placing the risk on the thrift shop.

 

[joed]

I don't the exact details of how accomplish it but some sort of cover over the receptacle that de-energizes it when opened. Open the cover, plug in device. Close cover and it is energized. Perhaps a low voltage switch and a contactor in another box?

 

[Perry401]

An industrial safety gate switch with internal solenoid lock mechanism would permit joed's idea to be accomplished. These devices are made by Allen Bradley, Square D, and others. They are used as a safety device on equipment which have enclosures or fences that must be closed before power can be applied. Once the access door is closed, an internal switch system closes, and this can be used to activate power. The solenoid latch is powered from the system to keep the access door from being opened until the power is turned off. Traditional safety gate circuits include redundant wiring to reduce the chances of a single failure or loose wire in the safety circuit from permitting the energy to be applied at the wrong time. Such a system would provide a higher level of protection to store employees than a simple safety switch.

Now I wonder if appropirate GFIC breakers are available in 30 and 50 amp sizes for 120/240 volt applications. This would hopefully help protect the stores employees if there was defective wiring to the grounded dryer or stove case.

 

[frenchelectrican]

For two pole 30 or 50 amp GFCI breaker they are not cheap and somehow limited numbers of them all it depending on what load centre you have them in there and I really suggest that have a electrician come in and assist you on this one due this is a commercal building.

For the dryer or range tester I know couple have good idea with safety poducure however I may go further is use the actual fuse than breaker because with fuse you may reduce the amout of damage from direct short circuited compard what breaker will do.

And also I am not sure if you are aware or not some commercal building you may NOT get a 240 volt circuit but 208 volt circuit if that the case I will suggest have a electrician to verify it to make sure.

And also if you actually have 208 volt supply keep in your mind the heating elments will take a bit longer to get heated up compared what the 240 volt supply will do.

Few poster did have few very good points on the issue you are bring up in here.

Merci,
Marc

 

[Perry401]

Frenchelectrician --

I am aware that GFIC's are expensive and would expect a 30 or 50 amp unit to be even more expensive. The building is wired 208 but we have secured a single phase, 208 to 240 volt transformer from a local commercial contractor who will be supporting the project with all materials. I think it is either 15 or 20 KVA -- more current than needed to test a single stove or dryer. I intend to specify fused disconnect switches on both the primary and secondary sides of the transformer. This is because of the higher fault clearing characteristics of fuses when compared to circuit breakers. The actual wiring will be done under the supervision of a liscensed electrician, but work will be done by electrical students from the local jobs training center. All work requires a building permit and inspection approval. The building manager and insurance companies require this, and must approve any planned changes to the wiring of the building.

My idea is the use of GFIC's to protect the personnel from relatively small ground faults and not major short-circuits. A bad or damaged heating element, for example, might cause a ground fault condition without causing the breaker to trip. I actually had this happen with my dryer at home a few years ago. Somehow the slug that should have been removed from the back of the dryer, the one where the exhaust port leaves the dryer, was not ejected properly when the panel was stamped. When the dryer was assembled, this 4 inch diameter "knockout" was left loose inside the dryer. Eventually it worked it's way down to the heating element, where it created a short between the heating element, an exposed wire coil, and a grounded surface. Because the dryers timer controls only interupt one side of the 230 volt wiring, there still was a path for current to flow on, and a section of the heater ran, with 115 volts on it all the time. (This isn't exactly true since the dryer door switch interupts the other side of the 230 volt line. But any time the door was closed, the heater would be on at a reduced capacity.) My wife once commented that the dryer was warm all the time, and I soon found the problem. Had the dryer been 4-wire and on a GFIC, the short to ground through the heating element would have tripped the breaker, avoiding a potentially dangerous condition. This issue did provide me with some income for several years when I addressed the problem with the Whirlpool engineers, and installed sensors on the progressive dies used to make the dryer parts to insure that every punched out hole actually falls out of the stamping press as part of the punching process before the sheet metal can advance. They also made procedural changes and added an inspection step to the manufacturing process in an attempt to correct the problem. They did not, however switch to what they call the "Chicago" wiring system, which breaks both sides of the circuit from both the door opened AND timer circuits.

 

[frenchelectrican]

15/20 Kva transformer that is one decent size tranny as long you can get 120/240 on secondary you are fine with it but instering twist most modern dryer and stoves will work on 208 volts supply without major issue due the dryers are useally have 120 volt motour in there { the dryer manufacters keep the motour voltage to 120 due have either gaz or electrique verison }

I understand the situation are at and I am glad you have the electrician to come out and help you on this one that is a very wise move on that.

I may suggest a " master " key which it means a key switch will interconnect to the mircoswitch for contractor to engerized the receptale when you do the testing them and when you are not testing you can remove the key and no one can able get this plug engerized up without have the key to turn the contractor on.

That one of few idea you may want to use I know a Thrift store near my area in Paris France that store have key lock out due we have 400Y240 system in here( in France ).

Merci.
Marc

 

[AllanJ]

YOu would need different receptacles for the different kinds of 240 volt plugs (30 amp, 40 amp, etc.) For a test-only circuit you can hang all of them off of a 240 volt circuit breakered for the lowest ampere receptacle. You canot test 120/240 volt equpment on a 120/208 volt system; here you may install 240 volt only receptacles but not 120/240 volt receptacles.

A more elaborate setup would have a subpanel with a separate breaker for each receptacle (separate breaker pair for 240 volt receptacles). This may permit supplying each receptacle with the maximum amperes it takes.

In most cities, electrical work in commercial buildings can be done only by a licensed electrician.

 

[Perry401]

AllenJ -- With regards to who can wire things in a commercial establishment, you are correct ... in most juristictions the wiring must be done by liscensed electricians. This would be true in the vast majority of communities in the USA.

... The actual wiring will be done under the supervision of a liscensed electrician, but work will be done by electrical students from the local jobs training center. All work requires a building permit and inspection approval. The building manager and insurance companies require this, and must approve any planned changes to the wiring of the building...

The use of electrical students in training provides a level of real-world expertise which they would not get only in the classroom. Work under this program is limited to non - profit organizations such as charitable organizations, churches, and similar circumstances. The students are paid one dollar each day, or portion of a day they work at the job site for their labor. The licensed electrician who supervises the work must be on-site when all work is done, but is paid for his or her services. He or she must remove students from the building even if he just runs across the street to get a donut or use a restroom.

In order to use this system, in addition to the work being done for non - profit organizations, the scope of work must be approved in advance by inspectional services to insure it is not beyond the capabilities of the class. For example, rewiring the elevators in a high rise structure would probably not be approved for this program, while upgrading lighting fixtures to more energy efficient units and work of this nature are usually accepted.

The non - profit organization must sign on to the program and the use of students, the building owner must sign on to the program and the use of students, and the building's insurance carrier must sign on to the program and the use of students. An errors and ommissions insurance policy must be in force at the time the work is performed. This is a far more stringent approval process than most communities require for such work done strictly by a licensed electrician.