Surge Protector

[tubesornothing]

I want to build a surge protector for my RV.  Comercial ones cost from $200-400.  I figure I can do it for a little less than that.  I figure I will have three MOVs one between hot and neutral, one between hot and ground, and then ground and neutral.  So what rating would I use?  This would be for a 120V 30A.

I will probably combine it with a neon lamp plug checker, to also check for neutral/hot/ground miswire.

The icing on the cake would be something that just switched it all off if the power was greater than 140VAC, in the case of someone wiring 220V instead of 120V (and yes, it does happen).

Any suggestions appreciated.

[tubesornothing]

OK, the surge protection is easy - a few MOVs.

The shorts to ground etc is also easy - just disect one of those neon plug in thingies.

All I need is an overvoltage/undervoltage circuit for AC.  I have hunted down a couple schematics and they are based on voltage comparators - I was wonder - is there something simpler?

[Ritchie200]

Hey TON,

How about a Zener rated at 140v connected to a relay with your line V connected to the normally closed side so that it would interrupt if your line voltage was over?  You could also rig a 100v Zener to another relay with line V connected to the normally open side that would drop out for under-voltage to keep current under control.  Although I'm not sure if reaction time would be an issue on the over-voltage to protect your unit.  How about a master switch after the relays with go-nogo lights hooked to the relays to let you know whats up before you flipped the switch.  Or am I missing something....sounds too easy!

Jim

[tubesornothing]

No, it is that easy.  I am liking that idea way better than a voltage comparison circuit.  There is a circuit called a AC Zener Clamp that will work well.

[tubesornothing]

One other thinkg that would be nice is an autotransformer circuit that would boost the voltage if required.  I might be able to to that with a zener clamp array.