Outdoor Lighting Transformer 208-120V.

pf22

I have existing outdoor landscape lighting where 208V fixtures are mounted on black Arlington weatherproof posts. I have two hot legs and ground but no neutral. I also have many 120V LED Christmas lights I want to use. Running a neutral isn't feasible since the locations are up to 200' from the source and run under asphalt through many existing 208V fixtures.

I'm looking for a possible option of installing an adjoining enclosure for each 120V LED location which will have a GFCI to plug the 120V lights into. I'd like to utilize a small step down transformer fed from the existing 208V post. Each light string is rated at 4.8 watts 120V. They're rated to be joined end-to-end (series) up to a max. 210W. I figure the maximum string and load on each transformer will be 100W.

I'd rather just cut the prongs and hardwire the LED's but the prongs have a built-in 3 amp fuse and I also think the 120V LED's require GFCI protection. They will be on shrubs well within reach.

dmxtothemax

Do the led strings run directily off 120v?
or off a tranny ?
Could be important for the gfci !
Otherwise the idea of a tranny for 208 to 120 could work,
but you need to find out what the code allows!

AllanJ

A typical step down transformer "isolates" the load from the house current so that touching a (defective) exposed live part of the Christmas lights and ground will not cause electrocution. So a GFCI might not be that important. At any rate you can install a GFCI receptacle on the secondary circuit (120 volts) of the transformer. With the transformer set up as a cord and plug device you don't need any special treatment for the 208 volt line.

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(Only for those eavesdropping and with so many lights that a transformer would be very expensive) I am not saying you should do this but I would.

Start with the 208 volt line equipped with 240 volt only receptacles at each location.

Make up jigs each with a short cord leading to a 240 volt only plug. The other end goes into as small metal (for portability) box with a 120 volt duplex receptacle unit. Break the tab on the gold screw side and connect one hot lead to each of the gold screws.

What this does is put the two halves of the duplex receptacle in series and the lights plugged in each get 104 volts provided that the load is balanced, here, equal amounts of lights plugged into each receptacle using extension cords or power strips or whatever.

Make just one jig and test it to be sure that the lights actually work on 104 volts instead of 120. Incandescent lights definitely will work and will actually last longer at the reduced voltage.

__________________
The disadvantages of crab apple trees. In summer, the apples are too sour to pick and eat. In winter the birds come and leave dropping all over the place.

carmusic

it is illegal to leave a 120v circuit floating, bond the secondary of xfrm to ground, use proper fuse on primary of xfrm and use a regular gfci outlet.

pf22

The LED strings have 120V plugs that have a snap in fuse in them, no transformer. I'm looking at some transformers in Grangers. I figure I'll put it in a W.P. enclosure and use sealtite to connect to the 208 feed in the existing post.

pf22

What do you mean by xfrm? Do I have to put a fuse between the 208 feed and the step down transformer?

dmxtothemax

I think it is a abreaviation for "transformer"
And if you use a transformer as you propose,
Then a gfci on the primary side of the circuit
wont protect the LED string
because there is no ground reference,(floating)
You will have to ground one side, (bonding)

AllanJ

A GFCI on the secondary (output) of a transformer) compares the difference in power leaving one terminal of the transformer secondary and returning to the other terminal*. It does not need a ground.

It is a good idea to put a fuse a transformer, preferably on the primary side which requires some calculation to get the correct value in amperes given the maximum number of watts the transformer can deliver. Maximum secondary amperes times secondary voltage equals watts, divide the watts by primary volts to get primary amperes.

Nitpicking: It's xfmr. There is also xtal for crystal (radio-electronics). And everyone knows what Xmas stands for.

* And vice versa so many times per second for alternating current.

__________________
The disadvantages of crab apple trees. In summer, the apples are too sour to pick and eat. In winter the birds come and leave dropping all over the place.

pf22

The GFCI will have to go on the secondary side since I want a normal 120V receptacle location.

I'm curious if a GFCI will work fed from a small transformer, I thought there is a bit of electrical leakage in them. Also unlike regular 120V with just one hot, both primary legs have voltage in reference to ground but not exactly the same voltage. I assume they're 2 legs from a 3ph feed. (We have 120/208 3ph 4 wire main power)

Years ago I actually worked as an electrican. We would test a GFCI by putting our tester leads into the hot and ground which would trip the GFCI. It didn't work when we tested neutral to ground or hot to neutral.

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After thinking about it for a moment, I definitely want to fuse the transformer. If someone plugs a power tool into the outdoor receptacle it could easily cook a small transformer. I was also thinking of a 300 VA xfmr instead of 100 VA. I prefer fusing the primary side. I'd like a fuse mechanism which can be reset. Any recommendations of what type or make would be best?

My calculations;

primary: (208 Volts) X (Amps) = 300VA
300VA/208V = 1.44A.

or secondary: (120V) X (Amps) = 300VA
300VA/120V = 2.5A

carmusic

you can use a double pole 2A breaker curve C or D on primary and you'll be ok wihout secondary protection
like this one
http://www.automationdirect.com/adc/...xx%29/WMZS2D02

pf22

After thinking about it again, I feel protecting the secondary side is more important to protect the trans. but I then don't have a ready means to disconnect it.

The Square D type TF transformer 9070TF300D3 seems to fit my needs. It has two primary and one secondary fuse block mounted on it. I can install it in a WP enclosure that's mounted to some sort of stake or pole. The support will have to be fairly strong since the trans.and box will weigh over 10 lb.

What would be proper fusing for that particular unit? It's rated at 300VA 208 primary 120 secondary, 80 degree. It will only be used for lighting. The load will be continous.

Since I'll only have total of 2.5 Amps 120V available, I'd like to use some type of locking plug in cover so others don't plug in something else and blow the fuse. If I do that then will code require me to install some type of alternate disconnect? I'll still have an extension cord from each recptacle to each light string that I can simply unplug on it's female or load side end.

pf22

That's an interesting option. I didn't know about those low amperage breakers. It brings up an alternative that doesn't appear to be too expensive. I can get a cheaper (non-fused) transformer, the breaker is much more convienient than fuses and I have a convenient disconnect on the line side.

If I were to get a WP breaker panel, can I install the transformer in it and stay within code? The appropriate transformers are much larger than the ones you usually see attatched to panels so that option may not be feasable.

CoolestKidKaito

Safer outdoor lights have an approved transformer that converts 240 volts to an extra-low voltage supply. You'll find four types of extra low-voltage lighting systems available: light sculptures, rope, fairy and bud lighting. Also have approved outdoor 240-volt lights, including festoon lights, and exterior power points for lighting transformers installed by a licensed electrician if they are to become a permanent or long-term festive lighting system.

Check bulbs and tubing
Before dangling lights, lay them on the ground to examine for damaged and loose or missing bulbs. Switch off the electricity and unplug the power cord before replacing bulbs with new ones of the same type and wattage. To prevent the danger of overheating, never switch on lamps which are still packaged or stored in a box.

Setting up oudoor lighting
Keep electrical cords above the ground to avoid damage or a trip hazard. Attach cords and lighting strings or sets to existing fixtures with appropriate tape, electrical cable ties, clips or clamps. Never use nails. Cords should be suspended at 2.5 metres higher than the ground. Cord lengths in excess of 10 metres ought to be avoided. Use approved plugs and cord extension sockets. Don't pass cords through door openings.

Avoid danger
Ensure individual power points are not overloaded. For more than 2 cord plugs use a suitable adaptor board instead of a double adapter. Keep all electrical connections away from areas that could become wet due to watering or extreme weather conditions. In which there isn't a permanently installed safety switch, use a portable type from the power point.

To avoid a power shock
Never modify lighting outlets, plugs or cords. Never work with an extension cord which has a 3-pin or piggy-back plug at each end. Never replace fuse wire or plug-in circuit breakers with larger sizes. Keep combustible material for example paper, plastic and structural metalwork 150mm far away from bulbs.

pf22

Those lights turned out to be a headache to maintain at first. The helpers who strung them up didn't protect the plugs properly. After a few rains some of the plugs shorted and blew a fuse. The problem is they're wired in series and a chain is only as strong as it's weakest link. (fuse) One shorted out section can blow any fuse in the entire string that's pluged to it. I had to unplug all of them and test each one. I now wrap each plug with rubber tape covered with high quality electrical tape.


I ended up buying the Eaton 1077 breakers and fuseable transformers from them. I'm sure glad I fused the load side. Without them all the transformers probably would have been cooked by now. In addition to the shorts, people looking for power see a gfci outlet and plug right into it, as I expected.

This part has worked flawlessly. Thanks

biggles

change the exsisting post bulbs to 120V bulbs.then take one hot leg off that 208V and make it a neutral inside the panel then you have 120VHOT,Neutral and ground running out breaker will havwe to be changed going from 208V to 120V wattage/amps jump