NH Shooter
04-18-2023, 11:44 AM
With the recent threads on whole-house capable backup power supplies, I thought I'd share my now complete upgrade with all of the in-the-weeds technical detail. I hope you find this post useful.
Note: I was a licensed electrician (and master plumber) back in my trade days, which ended in the mid 90s.
Winter power outages are a common winter occurrence in NH. This past winter we lost power for 27 hours on Christmas eve (with out-of-state family visiting) and then again in January for 24 hours. The most memorable power outage was in December of 2008 when we lost power for seven days due to a massive ice storm that took down power lines all over the state.
We had been getting by (just barely) with a 4200/5000 watt generator we had when we moved to NH. It kept the lights on, the boiler (heat/hot water) running and two refrigerators cold, but sucked wind badly when the 3/4 HP well pump kicked on. We would jockey circuit breakers, turning the well breaker off until we needed to run water beyond what was in the well tank. It was a PITA, but it got us by. I wired the 240v outlet of the generator through a 240v breaker in the main panel, always being sure to turn off the 200 amp main breaker before doing so. This is NOT the way to tie in a generator, so I purchased a Pro/Tran 2 ten-circuit transfer panel to do it right. It sat on the shelf and never got installed.
After the two outages this past winter, I decided it was time to address this issue once and for all: purchase a generator capable of running the most important circuits without having to play musical chairs with circuit breakers, and install the transfer panel that had been gathering dust on a shelf.
For the generator, I settled on the Westinghouse Wgen 12000 (https://westinghouseoutdoorpower.com/products/wgen12000-generator) which has enough power to carry the anticipated loads with less than 5% THD. The generator has good reviews and so far it has met my expectations.
The Install
This work began before the new generator was delivered. The first step was to map out the circuits on the main panel and determine which ten would be tied into the transfer panel. With 21 circuits in the main panel, ten in the single transfer panel was not enough to cover all of the needed loads so I purchased a second 6-circuit panel to piggyback onto the ten circuit panel. These panels were installed in the garage, directly behind the main panel on the other side of the wall.
These panels allow each circuit to be transferred individually to the backup generator. In normal operation, power from the corresponding breaker in the main panel feeds through a single-pole/double-throw selector switch in the transfer panel. When power is needed from the generator, the switch disconnects from the main panel and takes power from the generator through a set of circuit breakers in the transfer panel. It is impossible to have power for any individual circuit from both the main and the generator at the same time, so the two power supplies never meet. Additionally (and unlike the main panel), I installed the circuits in the transfer panels to keep the load on the generator as balanced as possible.
Here is a photo of the two panels installed. Power comes in from the conduit on the right (6 AWG wiring) from the generator inlet box (240V/50A) and supplies the bus bars in both panels;
https://i.ibb.co/5GD851y/gen-1.jpg
The watt meters on the top are really handy for keeping an eye on the load. Below the meters are the switches to select power from the main or generator. The individual circuit wiring and the 6 AWG generator neutral and ground wires are routed through the bottom of the panels to the main panel through flexible metal conduit.
Here is a photo with the panel covers installed;
https://i.ibb.co/WsJ9tKG/gen-2.jpg
Notice the warning label, which I am required to use to pass inspection for this configuration.
In order to use these transfer panels (which do not switch the neutrals), the generator must have a floating neutral (htthttps://www.electronicshub.org/bonded-neutral-vs-floating-neutral/#:~:text=Floating%20neutral%20systems%20are%20comm only%20used%20in%20portable%20generators%2C%20espe cially,system%20through%20a%20transfer%20switch.p://) or be capable of being converted to a floating neutral. In layman's terms, a generator "floating neutral" means the neutral and ground wires do not "bond" (join together) until they reach the main panel, and share the same grounding point (grounding rod) as the main (service).
A "bonded neutral" which is common in portable generators means the neutral and ground are bonded on the generator. The NEC requires that there be only a single point in the electrical system where the neutral and ground bond, at the first disconnect from where the main enters the building. This is typically in the main breaker panel where neutrals and grounds are tied on the same bar. Connecting a generator with a bonded neutral requires that it be a separately derived system (https://iaeimagazine.org/2009/november2009/separately-derived-systems/) with its own grounding rod, and neutral from each circuit be switched to the generator only.
The Wgen 12000 comes set up as a bonded neutral, but the OM includes instruction on how to convert it to a floating neutral (which was very easy to do).
Here is another photo of the panels;
https://i.ibb.co/prz2pCj/gen-3.jpg
Photo of the generator inlet box on the outside of the garage (same warning label required);
https://i.ibb.co/ynkGJ7j/gen-4.jpg
And finally, the new generator connected and powering the house;
https://i.ibb.co/m5xgr4H/gen-5.jpg
What a massive improvement over what we had! Next up is the fabricating of a generator cover because in NH, power outages go hand-in-hand with wind and frozen precipitation.
Note: I was a licensed electrician (and master plumber) back in my trade days, which ended in the mid 90s.
Winter power outages are a common winter occurrence in NH. This past winter we lost power for 27 hours on Christmas eve (with out-of-state family visiting) and then again in January for 24 hours. The most memorable power outage was in December of 2008 when we lost power for seven days due to a massive ice storm that took down power lines all over the state.
We had been getting by (just barely) with a 4200/5000 watt generator we had when we moved to NH. It kept the lights on, the boiler (heat/hot water) running and two refrigerators cold, but sucked wind badly when the 3/4 HP well pump kicked on. We would jockey circuit breakers, turning the well breaker off until we needed to run water beyond what was in the well tank. It was a PITA, but it got us by. I wired the 240v outlet of the generator through a 240v breaker in the main panel, always being sure to turn off the 200 amp main breaker before doing so. This is NOT the way to tie in a generator, so I purchased a Pro/Tran 2 ten-circuit transfer panel to do it right. It sat on the shelf and never got installed.
After the two outages this past winter, I decided it was time to address this issue once and for all: purchase a generator capable of running the most important circuits without having to play musical chairs with circuit breakers, and install the transfer panel that had been gathering dust on a shelf.
For the generator, I settled on the Westinghouse Wgen 12000 (https://westinghouseoutdoorpower.com/products/wgen12000-generator) which has enough power to carry the anticipated loads with less than 5% THD. The generator has good reviews and so far it has met my expectations.
The Install
This work began before the new generator was delivered. The first step was to map out the circuits on the main panel and determine which ten would be tied into the transfer panel. With 21 circuits in the main panel, ten in the single transfer panel was not enough to cover all of the needed loads so I purchased a second 6-circuit panel to piggyback onto the ten circuit panel. These panels were installed in the garage, directly behind the main panel on the other side of the wall.
These panels allow each circuit to be transferred individually to the backup generator. In normal operation, power from the corresponding breaker in the main panel feeds through a single-pole/double-throw selector switch in the transfer panel. When power is needed from the generator, the switch disconnects from the main panel and takes power from the generator through a set of circuit breakers in the transfer panel. It is impossible to have power for any individual circuit from both the main and the generator at the same time, so the two power supplies never meet. Additionally (and unlike the main panel), I installed the circuits in the transfer panels to keep the load on the generator as balanced as possible.
Here is a photo of the two panels installed. Power comes in from the conduit on the right (6 AWG wiring) from the generator inlet box (240V/50A) and supplies the bus bars in both panels;
https://i.ibb.co/5GD851y/gen-1.jpg
The watt meters on the top are really handy for keeping an eye on the load. Below the meters are the switches to select power from the main or generator. The individual circuit wiring and the 6 AWG generator neutral and ground wires are routed through the bottom of the panels to the main panel through flexible metal conduit.
Here is a photo with the panel covers installed;
https://i.ibb.co/WsJ9tKG/gen-2.jpg
Notice the warning label, which I am required to use to pass inspection for this configuration.
In order to use these transfer panels (which do not switch the neutrals), the generator must have a floating neutral (htthttps://www.electronicshub.org/bonded-neutral-vs-floating-neutral/#:~:text=Floating%20neutral%20systems%20are%20comm only%20used%20in%20portable%20generators%2C%20espe cially,system%20through%20a%20transfer%20switch.p://) or be capable of being converted to a floating neutral. In layman's terms, a generator "floating neutral" means the neutral and ground wires do not "bond" (join together) until they reach the main panel, and share the same grounding point (grounding rod) as the main (service).
A "bonded neutral" which is common in portable generators means the neutral and ground are bonded on the generator. The NEC requires that there be only a single point in the electrical system where the neutral and ground bond, at the first disconnect from where the main enters the building. This is typically in the main breaker panel where neutrals and grounds are tied on the same bar. Connecting a generator with a bonded neutral requires that it be a separately derived system (https://iaeimagazine.org/2009/november2009/separately-derived-systems/) with its own grounding rod, and neutral from each circuit be switched to the generator only.
The Wgen 12000 comes set up as a bonded neutral, but the OM includes instruction on how to convert it to a floating neutral (which was very easy to do).
Here is another photo of the panels;
https://i.ibb.co/prz2pCj/gen-3.jpg
Photo of the generator inlet box on the outside of the garage (same warning label required);
https://i.ibb.co/ynkGJ7j/gen-4.jpg
And finally, the new generator connected and powering the house;
https://i.ibb.co/m5xgr4H/gen-5.jpg
What a massive improvement over what we had! Next up is the fabricating of a generator cover because in NH, power outages go hand-in-hand with wind and frozen precipitation.