View Full Version : Keep blowing fuse

06-01-2005, 01:57 PM
Any help would be appreciated. I installed a 600w transformer (2-300W circuits). On first circuit I have ~200w of lights, 6-20w spots, 3-17w path lights on a run of around 200 ft. On the second circuit I have 1-20w spot and 2-15w path lights on a run of about 100 ft. I have it set to go on at dusk. About 3-4 times a week when the lights kick on the breaker goes (25 amp breaker). It runs fine once I kick it back on. It just seems to be the initial switching on that causes a problem. I'm plugged into a ground fault switch and have the transformer mounted indoors. If I calculated correctly I should only be drawing about 2 amps. Any ideas? This installation is at my home and I'm not a lighting contractor, hopefully I posted in the right area. Thanks

NY Landscape Lighting
06-01-2005, 03:16 PM
A 25 amp breaker is good. however are you sure nothing else in house is on the same breaker ie: garage or basement lights or outlets.You may have something else running on that breaker and when the outdoor lights come on it then trips. Days when it doesn't trip, perhaps the other items on that breaker aren't turned on.

06-01-2005, 03:20 PM
I also have my water softner on the same circuit. It should not be drawing electricity at dusk but I can try and reinstall the transformer so it is on its own circuit to rule this out. Thanks for the reply.

NY Landscape Lighting
06-01-2005, 03:45 PM
we have our elecrician run the GFI outlet on its own breaker to avoid any problems like this. Hope this works for you.

06-01-2005, 07:44 PM
check to see if that same circut is not tied into the bathroom circut, etc...

also............ sounds to me like you're pushing about 18 amps

235/13=18.07 amps

06-02-2005, 10:02 AM
Thanks - it looks like I need to put this on its own circuit. You are also correct about the amps. Thanks for all the help. I'll let you know how things work out.

Mike & Lucia
06-04-2005, 07:03 AM
There a plenty of reasons why this may be happening, and I agree that the problem is most likely on the line voltage side of the transformer. However, the amperage calculation offered that indicates 18a is wrong.

Each 300 watt circuit on the low voltage side is good for 25 amps, as measured on the secondary leads, which run from the transformer to the lights. If the power box is equipped with secondary breakers, you don't mention the manufacturer, they would trip first if you were pulling too much power on one of the runs. Even with voltage drop in the wires, you are not even close to overload.

Run #1 is 171w/12v=14.25A
Run #2 is 50w/12v=4.17A
Total on the primary side is 221w/120v=1.84A

When actual readings are taken with an amperage tester you will read a bit higher due to the wire. Assuming you are using at least a 12 guage wire, your problem is not here.

Check your water softener, again. Check the breaker itself. Is the wiring from the breaker to the outlet capable of a 25a breaker? Investigate further, and I'm sure you'll find the problem on the high-side of the transformer.

06-04-2005, 01:53 PM
When a transformer is first energized you get what is called "in rush". Basically its reverse current. It will spike the amperage on the circuit and may trip the breaker. Once the transformer is energized, then shutoff for a second or two and then re-energized, in rush is not a factor, as the transformer will hold some energy in its coils. Put an amp clamp on the breaker and see what is actually being drawn during start up.

06-05-2005, 10:41 PM
210 watts of lights pulls around 18 amps? that just doesnt seem right.. am i missing something?

Eddie B
06-06-2005, 12:33 AM
Try switching the breakers or replace the one that keeps tripping. It could simply be a bad breaker.

Electricity can do funny things, we once had a problem where our garage door opener would trip whenever we used the microwave, and they were on completely different circuits. A breaker swap did the trick.

06-06-2005, 10:33 AM
My transformer is a Hampton Bay from HD. I did not want to spend $300 on a transformer if I did not like the lighting of my house. I do like the lighting, it looks great so I think I need to upgrade to a better transformer. The area around my house got struck by lightning Saturday and the transformer does not work anymore, reset GFI and breakers on panel. No voltage coming out of transformer. Seems a typical problem for these cheap transformers. Anyway - I installed a dedicated GFI for the system. I'm also looking into getting a breaker that is made to help with the 'in-rush' mentioned earlier. All of this should eliminate the blowing of the fuse. Thanks for the help. If I'm missing something please let me know. Thanks.

06-07-2005, 12:31 AM
210 watts of lights pulls around 18 amps? that just doesnt seem right.. am i missing something?

210 Watts is 17.5 amps at 12 volts
17.5 amps it the transformer out put. The draw off the AC line going into the transformer is 210 watts/120 vlots or 1.75 amps.

Now is AMPS is all you want to talk about it take more AMPS to start your car than if you turned on everything in your house at once. Your house has a 200 AMP sevice if it is like most and it can take up to 300 AMPS to start a car.