Neutral Wire Missing

If there is no neutral available then do NOT USE A 4 wire SPD! I repeat do not use a 4 wire SPD on a 3 wire system. A 4 wire is designed with the neutral in mind for any surge or spike. This is like having an arc fault and the current exceeds fault current rating on a electrical breaker. It will blow it's self up and cause more damage to the sytem. Get the right one, there is a reason they have a 3 wire SPD

-Woz-

10 Years Of Electrical Installation in Industrial setting

Electrical Eng. for 5 years

Thanks kwoznia 1 for the reply. However, let me clear that they do not have a 3-wire system (delta). I checked the voltages, they are for sure in wye (4-wire + ground, L-L is 470v, L-Ground is 271v). The problem is there is no neutral wire at the circuit breaker (or anywhere) where I have to install the SPD. Are you suggesting that I should not use an SPD designed for wye (and just have the neutral & ground lead wires of the SPD spliced together and connect them to the grounding system of the building) and instead use a 3-wire, delta-designed SPD? Please reply as soon as possible. Thanks again.

Rossmmac,

There are 2 different types of surges to consider: voltage & current.

The SPD should clamp line voltage and drain any excess through the ground terminal, not the neutral. The design is based upon the rated line voltage, so you should be fine there as long as the SPD nameplate agrees with the service design.

For current surge protection the answer is less certain, because a 4-wire device is designed with a neutral wire in mind to carry part of the total energy transfer. The current limiting circuitry may not have the capacity to drain all the energy through only 3 terminals. However, if the peak phase current and energy dissipation ratings are sufficient for anticipated faults, you may be okay.

All of this is with the caveat that I don't know the brand/model/design of the particular device you have, nor of your distribution system, so I'm making a few assumptions which may not apply in your situation. Depending on the type of SPD, your device may not even include current surge protection, which makes the analysis much easier. Most reputable SPD manufacturers have very good tech support, so you may be able to call them and get a clearer answer for your specific installation.

This is this an industrial setting? What are you trying to protect on this system?

Being a voltage of 277Vl-g.... I assume this is an industrial application. Once again they are designed for more sensitive equipemtn. I dont think the SPD will do much but sure go for it. Splce the bond/neutral together as the neutral turns into the groud back at the main service/tx anyways.

Good luck, and remember, turn the power off!!!!! I lost too many friends this way

It is a Radio Broadcasting Company. They have transmitter. Actually, they don't have any usage of the 277v. Just the 470v.