Monday, October 5, 2015

Backup power: When the lights go out

I purchased the farm I'm on in 2013, and since then I've had quite a few power outages.  Some lasted for hours, some for days, and the most recent one was one of the longest:  5 days without power.

I have a small generator - a 7000 watt gasoline-powered generator.  I use it for construction that's away from power sources, and have used it for the house; but to power the bits of the house that need it means that I have extension cords all over the place, and I'm having the refill the generators fuel every 8 hours or so of operation.  That's fine in a pinch, but this last week-long outage pointed out the biggest problem:

The automtatic transfer switch

The pump and pressure system for the farm runs on 240 volts, and the little generator doesn't do that, which is unfortunate; and no other 240 volt appliances work, either.  So no stove, no clothes drier, no welder.  I'm lucky that I switched to a tankless propane-fired water heater, or I'd have to add no hot water, but with no water at all I hadn't reallyh noticed.

In the last two years I've gotten it down to a routine.  Power goes out, fill the tank on the generator and put it on a pallet.  Use the skidsteer to set it in the back yard, far enough away from the house that the noise isn't too distracting, and run extension cords.  One cord to the tv/sat dish, one to the computer, one to the microwave.  Two cords go to each set of freezers (we have 6 total) and one cord goes to the chicken egg incubators in the barn.  Crank the generator up, and then move around the farm plugging in each item to spread the load out, one freezer at a time, one plug at a time.

It's a bit of a hassle, but with the incubators I can't let them go cold, and so when the power goes out I drop everything I'm doing and go set up the generator.  Sometimes I'm halfway through and the power comes back on, sometimes it's days.  It's pretty annoying.
The wiring inside the switch

One of my neighbors solved the problem with a pretty nice system; a standby generator and automatic transfer switch.  The generator is big enough to run his entire house, and the switch notices when the utility power goes out, and automatically starts the genrator 10 seconds later; once started, the switch goes from utility to generator, and that's it.  no intervention required, no extension cords, and for the farm, water heat and light are all restored 10 seconds after being lost.

The way that it works is that you add the switch between your electric meter and your houses power panel, inline.  Doing it this way means that the house doesn't have to know where the power is coming from, and if you pick a generator big enough to run the house (say 20,000 watts or bigger) you don't have to select which circuits have power - everything is powered.

For this particular project I chose a propane-powered generator, 22,000 watts, with an aluminum case.  This type of generator is usually installed on a concrete slab poured on the ground, but the ground next to my house is actually flood plan, so I installed it on a wood platform above the flood level.  To meet code I had to put a layer of fireproof insulation (hardiboard) and then a sheet of metal on top of that.

Installation of the transfer switch was pretty straightforward.  I purchased 25 feet of the appropriate gauge wire.  I detached the wires from the base of the meter, ran the wires into the connections in teh transfer switch, ran the wires from the transfer switch into the existing breaker panel for the house, and then attached the wires from the generator.

Other than the power wires there are smaller wires that do the signaling between the generator and the transfer switch - the "sense" wires that allow the detection of utility power fail, and the relay power wires that flip the power from utility to generator.  you'll see those wires in the picture above as a small white wire.

In the picture above the utility wires enter the transfer switch at lower left, then loop around and connect to the switch in the upper right.  At the bottom right there are two sets of cables.  The cables that enter from the bottom of the box straight up are the input power from the generator.  The cables that run out the right side of the box go to the existing electrical panel replacing the cable that used to supply utility power.

Once installed the operation is automatic.  Power goes off, generator goes on.  Power goes on, generator goes off.  This particular transfer switch has a utility shutoff breaker -- if the uility power is browning out you can manually shut off the utility power, which the switch will interpret as a utility power failure and start the generator.  This makes it easy to test the operation of the unit, too.

The generator will start and run for 15 minutes every week; distributes the oil over the working parts, charges the batteries, makes sure things are in good shape.

While I was doing this work I lowered the main breaker panel for the house by 5'; this house was jacked up from the ground and a foundation put under it to raise it above the flood plain.  But they didn't move any of the panels, so the house breaker panel was 7' above the ground; every time a breaker flipped I h ad to go get a ladder to reset it.  With the main panel lowered to normal height it's both easier and safer.  If you're going to do something might as well do it right, and do it all.  No half measures.

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