Saturday, August 6, 2011

How I Connect My Generator to the House

Original Article

We had yet another power outage today. I waited about 20 minutes to see if it would come back on, then started the generator. That seemed like a good opportunity to do a short video and writeup about how I connect the genny to the wiring in my home, so here it is.
Note that I said how I do it, not how you should do it. This information is presented for its entertainment value and should not be construed as practical advice. This can be dangerous and may even be illegal where you live.
With that out of the way, here are the particulars:
The generator is the same Changfa I have featured in some other videos. I have had the basic generator for years, but the original Changchai S1100 needs an overhaul (after which it will probably become a boat motor) so I replaced it with a Changfa S195 engine that I bought new for that purpose in 2007, and have only recently gotten around to installing. Both engines are of the same design, and as far as I have been able to determine, all of these engines use the same stroke of 115mm. The bore or piston diameter is what varies, and the "1" refers to number of cylinders. Thus, S195 is a single cylinder with 95mm bore and 115mm stroke for 815cc; S1100 is a single cylinder with 110mm bore and 115mm stroke, and S1115 is a single with 115mm bore and 115mm stroke. They all make maximum power at around 2000-2200 RPM, and most generator applications (this one included) direct-drive a 4-pole generator head at 1800 RPM for 60 cycles. This is a good RPM at which to operate these engines. 1500 RPM works well too, and is the proper speed to turn a 4-pole generator to produce 50 cycles for our British cousins.
Both of my engines came equipped with a radiator mounted atop the cylinder, with a belt-driven fan to force air through the radiator. This is a really poor excuse for a cooling system, especially if you run antifreeze in it. For one thing, it absolutely relies upon that fan belt doing its job, as it does not hold enough coolant to work for very long without it. For another, in cooler temperatures it can over-cool the engine, resulting in poor efficiency, carbon buildup in the combustion chamber, and increased engine wear. With antifreeze in the mix, the temperature can go far above optimal operating temperatures on a hot day, even if it did have enough coolant in it. Early in the life of the S1100, the belt got loose, started slipping and eventually broke while it was running unattended while loaded. The radiator boiled over and then melted down, and the piston skirt expanded enough to greatly increase friction in the cylinder walls and shut down the engine. The engine survived and ran fine after this event, but I had learned my lesson.
I set that engine up with a thermosiphon tank-cooling system. I spent a lot of money on 25 gallons of antifreeze to achieve 50 gallons of 50-50 coolant for my 55 gallon drum cooling tank. That was still not a good way to go; the 50-50 mix still allowed the temperature to rise too high on a hot day. If I had used pure distilled water or rainwater, I could have used much less water for cooling and let the boiling point of pure water set the operating temperature.
I have since figured out that hopper-cooling with pure water is a brilliant, deceptively simple means of cooling an engine. The millions of engines like this that are used for all kinds of chores all over the world mostly use hopper cooling because it is simple, cheap and works well, but the fact of the matter is that it doesn't just work well; it works better than anything else you can come up with. It happens that the boiling point of pure water is a nearly ideal temperature to run an internal combustion engine. In the winter, just drain the water out of the engine and hopper when it is not in use. Store your cooling water in the house in jugs. In fact, set the jugs near the woodstove or whatever, and pour warm water into the hopper to pre-warm the engine when you are ready to start it.
The hopper on this engine is the one I was welding up in a previous video about welding with an automotive alternator.

Ok, on to the description of how I connected the generator to the wiring in the house. I needed electricity in my shop to power lights, power tools and welders. I can get by with only 30 amps at 120/240 volts, because the largest welding electrodes I use are 1/8-inch so I never need over about 140 amps of welding current, and 30 amps at 240 volts can supply that. I just have to be sure to turn off the air compressor before I weld. I had a scrounged breaker box from a house I helped to rewire, so I mounted that in the shop and spliced into the dryer circuit of the house to feed it. That means I can't weld while the dryer is running, either. No biggie; I used to live offgrid so I understand power management.
I also scrounged some 8 gauge aluminum power cable from the dryer circuit of the same house I helped rewire, so I used that to connect the generator to a 30 amp 2-pole breaker in the shop panel (the same one the cable was connected to in its previous life, to power the dryer). Now I can turn on the "dryer" breaker and turn off the main breaker in the shop to power the shop from the generator; or I can switch off the "dryer" breaker and switch on the main breaker to power the shop from the house. But let's pretend I don't have that added complication, and just consider how to connect the house to the generator. What I could do is scavenge a connection plug from a discarded dryer at the scrapyard, and connect it to a cable running through the wall (or a window) from the laundry room out to the generator. My generator has a circuit breaker on it too, so I would keep it switched off when not in use. So here is what I would do when the power goes off:
  1. Go to the service panel and switch off the main breaker. This is of utmost importance; never allow the main breaker to be on when the generator is connected.
  2. Switch off the breaker that controls the dryer.
  3. Go to the dryer. Unplug it and plug the generator connector into the dryer outlet.
  4. Go outside and ready the generator for starting. Make sure the breaker is switched off. Check the oil, fuel and cooling water. Add fluids as necessary.
  5. Start the generator and let it warm up.
  6. Go back in the house and double-check all connections and especially make sure the main breaker is off, while the generator is warming up.
  7. Practice power management: switch off the breakers to any non-critical loads and heavy loads that I do not want starting all at once. Also switch off loads that are too large for the generator, such as a central HVAC system if I had one and my generator wasn't large enough to handle it. Switch off the breaker to the electric stove and water heater. The water heater stores hot water for a long time, and I can always switch it on to run for a cycle later, if necessary.
  8. Go outside, bring the now-warm generator up to full speed, and switch on its breaker.
  9. Go inside, check that the main breaker is still off, and switch the dryer breaker on to power up the house through its circuit.
And that's it; I am running on generator power. When I am ready to switch back to public utilities, I use the following order of operations: switch off the dryer breaker, go outside and switch off the generator breaker, shut down the generator, unplug the generator cable from the dryer outlet, plug the dryer back in, and switch the main breaker back on.

1 comment:

  1. I have a friend who installed his system about 30 years ago. It is a small Pinto motor (1600 cc). He got the engine for free from a wrecked Pinto and mounted it on skids beside his garage. He has two alternators on it to charge two battery banks. He runs the water through the engine to two large water heaters. He runs a 200 GPM water pump off the clutch plate to fill his water tank set up on a hill. He only needs to run it for a couple of hours at about 1400 RPM or so (about twice as fast as idle). Suprisingly it uses less then a gallon to charge his batteries, heat a four day supply of water and pump a weeks worth of water into his elevated tanks. The little engine has a very small gas consumption even when compared with a two cylinder motor. It's been running for 30 years with no problems.