Transfer Switch

MEXICOWANDERER wrote:


To try and atone for my screwup may I suggest...?

http://www.ebay.com/itm/YC-GP-DPDT-2-YuCo-Power-Relay-110-120V-AC-Coil-30Amp-2-Pole-DPDT-Heavy-Duty-U-/282382602316?hash=item41bf50904c:g:G8cAAOSwXYtYukSS

I KNOW this style of relay can carry 30 amps of 240 vac either NO or NC. Matter of fact I like THIS relay even better. Transparent. Can view action and can view contact point.

Oh shoot I screwed myself. Now, I have GOT to order some of these...

Last year I got the NTE version of that switch, without the transparent case, for US$43 (C$57), on Amazon. But after buying a plastic electrical box to mount it in, and the wire strain reliefs for the box, and wiring it all in, I found it makes an insistent hummmmm when the coil is engaged and generates a fair amount of heat. It works fine though.

So am beginning to wish I had just bought a premade DC coil version like the 30A Prog Dynamics PD5110010 which I can get for C$88 on amazon.ca

Prog Dyn 30A Transfer Switch


And ok, I'm convinced. It's a good idea to switch BOTH hot and neutral!

Additional post different subject...

You shouldn't just switch between L1 and L2 leaving a common neutral

Why? You ask?

Connect to an improperly wired receptacle with L and N reversed

Guess what's gonna happen to the coil? NYAATTTT ZOOT

To try and atone for my screwup may I suggest...?

http://www.ebay.com/itm/YC-GP-DPDT-2-YuCo-Power-Relay-110-120V-AC-Coil-30Amp-2-Pole-DPDT-Heavy-Duty-U-/282382602316?hash=item41bf50904c:g:G8cAAOSwXYtYukSS

I KNOW this style of relay can carry 30 amps of 240 vac either NO or NC. Matter of fact I like THIS relay even better. Transparent. Can view action and can view contact point.

Oh shoot I screwed myself. Now, I have GOT to order some of these...

WHOA! I MISSED THAT! Thanks Brulaz!

School of hard knocks. Vendor says image is "Generic" actual unit is 120 vac. But no matter - I goofed up and was corrected. Three Amps NC wotta hoot!

time2roll wrote:
And the coil is 240 vac, where will that come from?

That is confusing. The written spec says 120v.

Considering the prices of the ones I've seen, I doubt I'd be trusting an $11 unit. Buy several.

brulaz wrote:
But that's only 3A rated on the NC contacts.

And the coil is 240 vac, where will that come from?

Yes, the neutral must be on the same switch.

Depending on the inverter or generator the neutral may carry 60 volts to ground that can be painful if not worse. If both sources are providing power they are not truly isolated if the neutral stays bonded.

The neutral should be switched because of neutral/ground bonding concerns and the possibility of reverse polarity power sources and so forth. If the transfer is between a built-in generator and shore power, the generator will have neutral and ground bonded, but the RV should not have them bonded for the shore power connection, hence the need to switch the neutral. With some inverters, grounding either of the output terminals (to the negative DC input, which is generally also the chassis ground) will let out the magic smoke, so it's necessary to switch the neutral there as well. That leaves precious few cases where it's not necessary or at least highly advisable.

That being said, transferring power does not require switching the neutral in the most general case; there's no way to backfeed power (or feed power) through an open circuit, such as there would be if the hot were disconnected. There's an analogous situation to a common neutral shared by two different power sources in the two 12V systems of motorhomes: the chassis ground is the neutral for both the house and the chassis systems, and they don't interact with each other unless otherwise interconnected.

As a practical matter, switch the neutral; it's neither particularly hard nor particularly expensive to do so, and never incorrect.

the Neutral has too be switched
your choosing between (2) power sources
a common neutral would burn something up, tripp breakers, maybe burn down the RV

NEUTRAL is Part Of the Power circuit
neutral CARRIES POWER

the ground does not carry power

brulaz wrote:
Is a double pole switch necessary?
My current switch is, so both hot and neutral are switched.

But have wondered whether neutral couldn't just be passed thru, like ground currently is.

Absolutely the neutral needs to be switched! Otherwise, the normal RV circuits will backfeed current on the neutral line!

That is a very bad thing.