Generator Transfer Switch Installation

Today we take a step away from the garden to install a generator transfer switch in the house. In the three years that we have lived at Three Acre Paradise we have only lost power once for an extended period of time (around 18 ours) but in previous residences I’ve been without power for up to three weeks. We do have a grid tied solar power system here but if the grid goes down the solar system also shuts down as a safety measure. There is a way to back feed a generator to the house which works fine but it is more difficult to set up and has many other disadvantages.

A generator manual transfer switch is an less expensive alternative to a whole house generator. In the future I plan on adding a battery backup to the solar system so it can run off grid so in the meantime I don’t want to spend the money on a whole house generator. The transfer switch allows me to quickly switch selected circuits over to alternative power (portable generator or battery bank & inverter) while the rest of the house is still tied to the grid. On nice thing about this is that when grid power does come back on it will be obvious (other circuits will power on) and I can switch back very easily.

Here is the panel I bought:

Relaince Pro/Tran2 panel

After a bit of research I found that Reliance panels are rated very well and for my purposes a 10 circuit 30 amp panel is needed. When sizing a panel you have to add up all the loads you would like to run (amps) and figure out how many circuit breakers these are spread across. I could actually get by with a 20 amp panel but I needed at least 9 circuits to cover all wants. All lights in the house are LED (make this your first step – it’s cheaper to conserve) so the lighting draw is very low but spread out throughout the house and a lot of circuits.

In addition to the panel, I got a flush mount kit to make the installation look clean. Here’s Amazon links to both items:

I wanted to mount the transfer switch next to the main circuit breaker panel for ease of access. Here’s a lifepro tip: if you build a home take a TON of pictures during construction. The most important ones are when all the wall framing is up, wiring is in, but insulation has not been put in yet. This gives you an x-ray view into your walls, and as you can see here it came in very handy.

Xray view of wall

This is the view behind my main breaker panel. I can’t put the transfer switch to the left of the panel due to a doorway. To the right, I can see there is a cross brace (blue) and some studs backing an interior wall (red). I’ll have to put the panel low and deal with the wall backing when I get the hole cut.

The first thing I did was cut a large hole in an area I know is clear, from here I can reach my hand in and determine where that horizontal cross brace is (blue from above).

First hole cut in wall

With that in mind, I traced an outline for the box making sure it was far enough away from the circuit panel so that I could get the flush mount kit flange installed as well.

Box outline and hole cut

Here’s the wall after the hole was cut. This picture is actually from a few steps later where I made notches around the outside corners for the flush mount kit as you will see in the next few steps. The studs for the inside bracing can be seen here running right down the middle.

Wall interior

I still wasn’t sure how good the fit would be so this is the moment of truth:

Test fit of Reliance Pro/Tran2

Pretty good! The knockout for the wires can be seen here and it lined up between the drywall and studs. The mounting tabs for the flush mount kit stand out just a little bit due to the boards on the back, but the studs will provide a secure place to screw the box to.

Here’s a closer look at the mounting tabs, they are out just about a quarter of an inch. I need them flush with the drywall for the best fit.

Closeup of bracket ears

The mounting tabs are not part of the main box, rather they are an “L” bracket screwed onto the side. To move the tabs back I simply extended the holes on the brackets to allow them to slide back a little further. This was nice as it did not require any modifications to the main box.

At this point I got tired of dealing with all the wires dangling in the way so I took out the switch assembly.

Reliance Pro/Tran2 gutted

To get the transfer switch wiring to the main breaker panel I had to cut through a wall stud. I got lucky as the breaker panel had a knockout in the right place, if it hadn’t then I would have had to cut a hole in the metal.

Conduit path cut

Once the hole was cut I did a test fit of the conduit and cut it to length. This flex conduit was included in the Reliance Pro/Tran2 310C kit.

Conduit test fit

The transfer switch box is now ready for mounting, I screwed it directly to the studs behind the box. It is VERY secure.

Reliance Pro/Tran2 cabinet mounted

Since I moved the bracket for the flush mount kit back, the trim panel now bumps into a couple of screws on the main box. A metal nibbler took care of this.

Reliance Pro/Tran2 flush mount kit K2F10 notched

Next step is to put the switches back in and run the wiring. Easy to say, not so easy to do.

Reliance Pro/Tran2 mounted with K2F10 flush mount kit

There was no way that was going to work. I’ve run plenty of wires through conduit and I tried all the tricks. I used wire lube, tried running them one at a time, tried pulling through as a bunch. That ninety degree bend is a challenge so there’s only one way I could think of to get it done:

Running wires for Reliance Pro/Tran2 310C

Yup, I took everything back apart and ran the wires before putting the whole assembly back in the wall. The ninety degree bend (elbow) on the conduit could be taken apart so I ran the wires first, then bent them and assembled all the conduit pieces. A bit of a pain in the neck but in the end this was the most difficult part of the whole process.

Reliance Pro/Tran2 310C mounted

Now the switch is back in place and all the wires are run to the breaker panel.

Here you can see a closeup of how tight the wires are coming through the conduit. One rule when working with conduit and wiring, whatever conduit you think you need go ahead and bump it up one size. Unfortunately this one came this way so I just used what they provided.

Generator panel conduit detail

At this point I’ve got the transfer switch mount completed and I’m ready to wire the breaker panel. I had to wait until I could shut the power off at the main breaker outside the house and I had to remember to shut down the solar inverters as they also provide power to the panel.

Reliance Pro/Tran2 ready to wire

Here’s the start of the wiring, I did the only 240v circuit first and tested it before doing the others. This circuit powers the water pump for our well. This transfer switch allows for up to two 240v circuits but I only needed one. Each 240v requires two switches, this left me with eight switches for the rest of the house.

Reliance Pro/Tran2 wiring started

I tried to balance the remaining circuits across the legs equally (each 120v branch is a leg, combined they make a 240v circuit). This helps get maximum use from the generator. For example, we have two refrigerators so I put each on a different leg. The rest of the circuits are pretty light draw (mostly lighting) so they were just balanced across.

List of circuits

Here is a picture of the panel all wired up, I took the opportunity to move a few breakers around as part of this process.

Reliance Pro/Tran2 wiring complete

The final product all buttoned up.

gen-panel-23

I chose to put the power inlet right on the panel rather than run a power inlet box outside. My reasoning is that during a storm I can use a battery bank (a couple of deep cycle batteries or golf cart batteries) with an inverter to keep some lights, tv, and refrigerator running. Once the storm passes I just run a cord outside to a generator.

Anything I would do different? No, I’m happy with how this turned out. I run an annual test of my generators (at the start of hurricane season) and this will make that easier and more accurate as I can easily put the real load in place. If battery prices come down in the next few years than maybe a triplet of Tesla Powerwalls will make this unnecessary but it will still be there for backup in case they fail.

 

Installing a transfer switch is not hard but unless you are a serious DIY’er like myself then I would just hire an electrician to do it. Buy the parts yourself and it shouldn’t take them more than a couple of hours.

Until next time, stay warm and lighted!

 

 

 

 

 

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