What Model Contractor Goes to Disconnect My Generator From Home Distr.Panel?

Ideally it needs to be a changeover arrangement with a feed from either the mains or the generator, and not both, with the common connection to the house supply. It must be rated to carry the maximum supply current from the mains supply.

There are other ways of doing it depending on the rating of the generator and the detail of the house wiring, which cannot be seen from here.

Is using 2 nos 4P contactors with electrical and mechanical interlocks acceptable by codes?.

Each jurisdiction has its own set of codes. Ask your local authority not someone half way around the world.

Acceptable to code? Must be.

The arrangement you stated works fine (from experience) and eliminates the risk of having both connected together.

After all some "proper" ATS have this very arrangement at their core.

Sometimes just 3 pole common neutral.

Some ATS have motor driven switch.

OP could even use a 100% manual changeover switch and forget the contactors altogether.

Really depends on what OP needs, wants, or is capable of.

I totally agree with#2.Do it right.

Do not be responsible for killing someone working on a HV line presumed to be "OFF".

The transformer on the pole works both ways;It steps the voltage down from 13.2Kv to 240volts, but it will also work in reverse, if voltage is applied to the secondary when the primary is disconnected.So even though your generator only generates 240 volts, it will put 13.2Kv on the feeder line if not properly isolated.

Most localities also require a licensed electrician to install the transfer switch.

Although you may be allowed to wire your own house, or shop,(in effect, you can jump with the parachute that you packed), when someone else is at risk, you must be licensed.

I have had different thoughts as to whether the neutral should also be isolated with the generator changeover switch, ie should a two pole switch be used to isolate the incoming neutral or is single pole switch sufficient. In NZ jurisdiction either approach can be used. Any thoughts?

Either way a suitable qualified electrician should do the job.

I recently came across a faulty changeover switch installation where not only could the genset back feed the 11kV distribution line, but the pins on the plug for the genset to plug into the mains board were live when the switch was on "mains" mode.

Scary.

The transfer switch should be double pole double throw type, so that both the phase and the neutral are isolated. There shouldn't be interconnection between the supply neutral and the generator neutral.

This is an inexpensive alternate way of doing the switchover: http://www.interlockkit.com/intro2.htm

It's an interlock kit for an existing panel that does not allow both breakers to be on simultaneously.

It's possible that the manufacturer of your panel has an interlock kit available for your panel.

Is there equipotential bonding on that metal interlock?

The best way to put a changeover switch in is to build the board with a changeover switch in mind so that loads that are out side of the capability of the gen-set are not included in the circuits that are being powered up.

If your gen-set is less than 5kW (and remember that the manufacturers of those little petrol gen-sets are usually quite overly optimistic about the performance of their equipment) it is really good to have fridges, freezers, lights, domestic water pressure pumps, septic tank pumps etc separated from hobs, ovens, air-con.

There are change over switches that need no intervention at all, they automatically isolate the mains coming in stat the Genny & switch to Genny,then when the power is restored it reverses the procedure. Its a long time since the last one I fitted so you need to trawl through some suppliers to find a switch, look under boat chandlers they supply a good range.

Bazzer

"When you cannot afford to lose, don't gamble."

Do not trust ad-hoc engineering in a life or death situation.

Opinions do not matter in this case,unless from a qualified individual, and a truly qualified individual will not offer advice to an unlicensed individual for fear of potential liability issues in the future.

Use only UL approved transfer switch.

Be safe, or be sorry.

I think the question is " What contactor not contractor", still who am I to stop you waxing lyrical on the subject.

Bazzer.

I think my answer(#10) gives a valid response to either question.

In reply to your interrogative:Nobody.

As for lyrics:

I'm a nobody,

Who are you?

Are you a nobody too?

Hush!

They'll banish us you know

Don't tell- they'll advertise

Oh how dreary to be somebody

So public, like a frog

To croak away the month of June

To an admiring bog.

(Emily Dickinson)

I have to totally agree with you HiTek, I took some time off and I see that things are still cruising along the same here. It's great to help someone out in a areas that won't kill themselves or some poor fool lineman trying to scratch out a living on a pole that should be by all accounts be off line.

When you come to a forum such as CR4 asking a remedial question about what contactor to use for switch gear, tells me that this individual is not qualified to perform what they want to do. And any info. gleamed here, could potentially kill someone

Sadly yet again the originator does not identify where s/he is from so while all advice is in the best interest of solving the issue, it may be completely wrong for the individuals situation. Unless we know what country you are in iaraktchiev no advice can be tailored specifically to suit the legislative requirements of your country rather we give advice based on our experience and/or home country.

While I could provide an exact solution to suit my home country I will not provide any advice to anyone without knowing where they are. All I will say is, with electricity, if you don't know then find someone qualified to do the job for you and avoid becoming yet another charred statistic.