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Author Topic: Voltmeter ? (grid Voltage)  (Read 5465 times)

Offline curiousB

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Re: Voltmeter ? (grid Voltage)
« Reply #15 on: May 22, 2014, 12:36:38 pm »

sorry for the confusion..

i have all my routers, switches accesspoints vera and whatnot connected to power via a Computer power suply, which is served via a 500watt UPS .. so the vera stays on if the power is out.

on the Generator i installed a 1/4" Magnetic solenoid valve on the gasoline line which is also controlled by the same power source. the Rasperry PiFace board relais does control the Solenoid ... (small pyton app make sure the vera knows the status and can control it (i do control the same type solenoids (just larger ones) to water the plants outside in the same fashion .. so this is pretty much failsafe)

i also use a 220 Volt Relais to actually start the Generator (integrated the same way as the solenoids)

the generator output is hardwired to the Breaker box .. i put a large Industry Relais (120 Amps) before the Main Breaker (of course there is another "main" before that now)
which simply switch between the Grid and the Generator Power ..
the large relais is powered by the power coming from the generator .. so if everything is in idle .. the relais has no power and the Grid serves everything. very straight forward.

all this works great so far. (its not really rocket sience) ;)

the problem is that i have no way on "automatically" start the generator,
the vera does right now open the gasoline valve and actually start the generator .. (so i can do this while sitting on the sofa)
since the switching is hardwired there is no room for misstakes.

but i have to trigger it by myself.

How do you currently tell that grid power is back?  ...

i dont ! and that is the problem !

on daytime: what i do now is connect a Digital voltmeter .. to see the power is back up (since many times the grid voltage remains at 80 volts or so for hours)
in the night i just check the house across the street which is served by the same phase .. if the TV running there .. i switch back.

so there is currently NO way to safely assume the power has been restored, and i would really like to have this more automated, as i just can't expect my wife or the in-laws to do this kind of verifications.

with the vera controlling the gasoline pipe and the Starting of the generator itself .. my wife can just start the backup power process via the touchscreen on the wall ...
but there is just no way for anyone other than than me to get the grid back online.

while doing this aproach, having the right parts in place, automating this completly is just a few little steps away.

by simply monitor the Grid Voltage and make the values avaiable to the vera.
so a simple scene could start the generator (or at least send me a message that the power is out)
and if the grid voltage is stable for some given time the vera could just shut down the generator and everything would get back to normal.

well thats the idea so far ;)

This sounds interesting but you should be aware the NEC has strict rules regarding cross connecting generators to panels with all sorts of fail safe aspects to it. A home brew set up like this isn't likely to satisfy all the requirements. Also if you are feeding the entire panel then the generator needs to be able to supply the entire load base served. It doesn't sound like a 400W honda generator would deliver much compared to 100A (12,000W x2 ) service feed. As a minimum you should read what a break before make relay is and be sure you are using that...

I wonder if connecting in at the 100A side of the utility is the best place to do MacGyver experiments like this?

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Offline nullx8

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Re: Voltmeter ? (grid Voltage)
« Reply #16 on: May 23, 2014, 12:16:10 am »
This sounds interesting but you should be aware the NEC has strict rules regarding cross connecting generators to panels with all sorts of fail safe aspects to it.
thats is one of the advantages of living in Thailand ;) as there is no such thing.
for my own safety the switching mechanism's are hardwired and can't be tempered with. (very old fashioned) but it guarantees some sort of security.
i not have 100Amps anyway (the main's clip at 40 already) i just use a 120 Amp 3 Phase relay to ensure some safety. as they have a very large gap between the contact plates.

i use a 12 HP Gasoline Generator currently (delivers somewhat 6k5 watts).
its not exaclty made to serve the whole house. but well as long the fridge and the coffeemaker is working .. iam happy,
and in the night the tiny airconditoner in the bedroom can be served trough that as well.

the only thing i do not take care of, is the switch-over current, but i not run a Datacenter ..
so the initial peak in the switch over Moment is very little (about 3-4 Amperes)
this does pretty much solve itself (by accident) .. because in the moment the generator starts it does accelerate shortly (probably auto-choke)
about 2 secounds later the Generator turns on the Current, the Relais move and "it's ON" ;)

the acceleration before is enough to not make the engine stuck or drop the current. and the inverter keep the voltage on level .. so everything is pretty much taken care of .. even i'm sure the original engineers had sure other things in mind by making this behaviour ;)
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