The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
breaker meltdown
by sparky
09/27/16 07:30 PM
230 or 345 kV transmission lines?
by Vlado
09/24/16 09:33 AM
Electrical mast flashing product
by ThomasWinfrey
09/22/16 12:14 AM
What estimating software do you recommend?
by sparky
09/21/16 07:20 PM
"Dry Run" Inspection goes awry
by HotLine1
09/20/16 07:39 PM
New in the Gallery:
12.5A through 0.75mm▓ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
HotLine1 14
sparky 10
gfretwell 8
sparky66wv 8
Vlado 6
Who's Online
0 registered (), 247 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#166537 - 07/23/07 07:59 AM low volt transformers
falcondfb Offline
Member

Registered: 09/28/02
Posts: 37
Loc: Jersey, USA
I do a lot of dedicated lines for landscape lighting for another company. We have been having problems with inrush tripping breakers.
We have used 1200 watt trans from multiple manufactures but have had trouble anyway. Breaker style or manufacture doesn't seem to matter, although SqD work best.
On the last project that was on a pool panel where the line was 5' long I buried a 50' run of 12/2 UF under ground to provide a cushion and it works well. Anybody have similar problems or solutions besides extending the run?

Top
Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#166547 - 07/23/07 12:50 PM Re: low volt transformers [Re: falcondfb]
RODALCO Offline
Member

Registered: 12/08/05
Posts: 862
Loc: Titirangi, Akld, New Zealand
The TX inrush can be up to 20 times the nominal current hence tripping of the MCB.

A way around it is to have a timing device controlling a relay, which at switch on, first put a high power resistor ( ┬▒ 4.7 Ohm 50 watts ) in series for about 1 to 2 seconds, than the relay will short the resistor and the TX has normal power applied.

The resistor can be built from five 10 watt 20 ohms ceramic wirewound resistors in parallel in a safe enclosure.

Because of the short interval time the resistors are on for hardly any heat is generated.
Similar systems have been used on high powered amps with large capacitors, when the TX at switch on is feeding basically a dead short at the output for a couple of cycles.
_________________________
The product of rotation, excitation and flux produces electricty.

Top
#166580 - 07/23/07 06:25 PM Re: low volt transformers [Re: RODALCO]
falcondfb Offline
Member

Registered: 09/28/02
Posts: 37
Loc: Jersey, USA
That sounds great but I am not sure I understand how exactly it works, I have forgotten the parts of "Electricity 1-7" that I don't use often and I am kind of looking for a less involved solution. I was wondering about maybe using a hard start kit for a a/c condenser. Although that might be backward of what I want to accomplish.

Top



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals