Sandtrap wrote: ↑Tue Mar 06, 2018 3:45 pm
I'd have to have an electrician properly size the unit to our home. I've done initial requirements but it would be good to have a double check. Our home is 3 stories and about 5000 sf. Plus barn, well, 3 separate HVAC systems, etc, so perhaps it needs a higher capacity generator system.
Did your electrician do the size wattage requirements?
j
We had our HVAC folks (the one's who installed our original/replacement HVAC system/duct-work when we had our home built) do the sizing for the genset. They have folks on the design side that are responsible for ensuring that the system matches requirements in case of an outage. I've heard stories of electricians that install gensets without the design background. I'm sure they can do it with less expense, however I would be concerned if they were not certified brand dealers/installers, especially when it comes time for possible warranty work and they don't have a "relationship" with the genset vendors. For instance, "my guys" (and girl) in service have attended both Generac & Kohler vendor "schools" and are certified in their maintenance and design work, and are willing to go to bat for you if a manufacturing problem arises (I had none, but I've read of others who had a problem when installed by a non-affiliated electrician/installer).
BTW, the "brains" of the system is the switch, not the genset. The switch is what recognizes the utility failure, tells the genset to start, and manages the load via "load shedding" to reduce high amperage circuit usage according to your specified priorities. While our (Honeywell) switch has two HVAC (heat pump or air conditioner) controls, it also controls four other high amp (240v) circuits - our microwave/stove combo (priority 1), our island cook-top (priority 2), our hot water heater (priority 3) and our clothes dryer (priority 4). As usage exceeds the 83 amps generated by our genset (in a home that has 200 amp service) it automatically controls those high amp circuits by "cutting out" (temporarily) by priority those lower requirement circuits, thus keeping the genset running rather than popping the generator circuit breaker and shutdown of the entire system. As spare amps become available, those loads that have been "shed" come back on-line automatically. Load sheding also allows you to install a smaller, lower amperage genset and save some money by not over-engineering and putting in a much larger system that costs more to buy and maintain. While we have 200 amp service, we certainly don't use 200 amps 24 hours a day. If we would have installed a much larger (4 cyl, water cooled) system, we would have been spending much more money on the unit, along with using more fuel to generate amps we didn't necessarily need. Sure, I "only" have 83.3 amps to work with, but it supplies what I need during an emergency situation.
The order of sequence during a power failure is as follows:
- The transfer switch "waits" for 10 seconds. That time is given to allow the utility to reroute and restore power to the home. At around 11 seconds, the next step happens.
- The transfer switch/genset controller requests the genset to start up. This usually takes about 5 seconds, then continue to next step.
- The genset "smooths out" the electric generation, and the switch (automatically) transfers the feed from the utility to the genset. Your lights (all 110 circuits have priority) come on and you're no longer in the dark
... All this happens in 20 seconds.
The transfer switch is also responsible for genset disconnect when power is restored, telling the genset to go into cool-down mode (run for a few minutes without a load)
I've read about current generation transfer switches that can control (shed) up to eight different high amp circuits, if you want to take it further and make your priority list more finite.
BTW, our 20 kWh genset is for our 2400 sq. ft (all electric) home with 200 amp service. Your system must be designed for what you need, even up to a 300 amp, 3 phase system.
Good luck on your decision, whatever it may be.
- Ron