Getting back to the poster who restarted this older thread: If I had a natural gas line, I would have gone with natural gas but since I am in a rural areas served only by propane I went with diesel. I have a large house with two central heating systems and the propane supplier felt that the existing 500 gallon tank would need to be upgraded to 1,000 gallons OR a separate tank could be added for the generator. The concern was that in very cold weather there may not be enough tank surface area to support sufficient vaporization for the heaters, water heaters, and generator.
Because of this, I went with diesel. My generator is installed in the semi-basement section of the barn and I treat the diesel with anti-gel but it probably isn't necessary given the lowest ambient temperature it sees. A 30 KW would have been sufficient but I went with a 40 KW unit because I preferred the direct injection/turbocharged engine used for the 40 KW system.
For safety and convenience, I went with a commercial grade ASCO auto transfer switch. It is more versatile than the typical consumer grade units and allows programming of delay to start time after failure along with time to transfer after start and time to transfer to main after main power return is sensed. I have mine set to allow a 4 minute warmup after the switch senses proper voltage/frequency before transferring the load. This allows the engine to warm up a bit and also allows the compressors in the refrigerators, deep freeze, and humidifiers to equalize before restart. It waits until the main power has been up for 2 minutes before transferring back and starting its 5 minute cool down cycle. It does a seamless synchronized transfer back to main power after power failures and during monthly test runs.
It was a bit pricier than the basic auto transfer switches but worth it to me for the quality and capability as a one time purchase.
Rodger
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