Power transfer switch for homes.

[MPrewitt]

I have one that runs my 20 KW Briggs and Stratton Generator.

It is installed between the meter and the main breaker box in the house.

When the power goes off, 30 seconds later it switches over automatically, eliminating back feed to the line and the generator fires up.

Once it senses power has been re-established it allows the generator to run 15 minutes to verify line power is stable then it switches over to line power killing the generator.

 

[tsteahr]

Total Isolation is a bit more complicated than that. I think you will find there remains an electrical path through the grounding system and likely the neutral, in your transfer switch. Don't get me wrong, it is a nice set up, but the only way to develop total isloation is completely separated circuits. The aux. or generator circuits would only operate off the gen set and have totally separate wiring including a different ground. This is the only way to be completely isolated from the utility.

If you use a three pole switch you break the neutral along with the two hots and you are totally isolated (because the utility only consists of three conductors). As to the ground, in my area there is no utility ground. The ground is just that, a wire connected to copper rods driven into the ground outside the house. I used three ground rods although only two are required by code here. The genset ground is connected to the same ground as the main panel ground. All grounds in the house must be tied together. It would be against code to have multiple ground paths in my area.

A three pole switch does nothing to help with lightning strikes that travel through the earth, from say a nearby strike. But a three pole switch will fully isolate you from the utility, at least in my area where the incoming utility consists of three conductors, two hots and a neutral.

Unless I'm not understanding your point about the grounds...

EDIT: I did not read rkjobbeman's reply before I typed this. He said it much better than I...:thumbsup:

 

[Diamondpilot]

A lot of utility companies won't allow you to install the above product. The most commonly items I've seen used come from the following company. There are a variety of options to pick from, and many are sold on eBay.

Reliance Controls Corporation The World's Leading Manufacturer of Transfer Switches for Portable Generators

Big issue with them is you have to decide what you want to run. Also they only handle x amps. What happens if you later get a 200 amp generator?

I just have a 200 amp transfer switch between the panel and the meter. Right next to it is a large 50 amp 4 prong twist lock plug.

Chris

 

[Diamondpilot]

I mounted the switch on the wall, installed the generator outlet and ran the wire and conduit from the generator outlet to the switch myself. The meter needed to be pulled (which requires a permit and informing the utility company) to complete the installation so I hired an electrician to do all the work with the heavy 0000 wire that goes from the meter to the switch and from the switch to the main breaker panel. That aluminum wire is difficult to get through conduit. I needed a longer run of wire coming from the meter box. This meant working in the meter box in close proximity to the live feeds coming from the utility pole. I was not comfortable working with the heavy wire and wrenches only inches from a nearly unlimited current source. One slip of the wrench and toast :shocked:.

In total I probably spent $1300-1400 for all the materials and 5 hours electrician labor. But time and material required will be different for every install. Mine was a little more involved that average because of switch placement issues. I probably saved 4 hours labor installing the generator plug, conduit, wire and mounting the switch myself.

We did this for about $400. My neighbor is a electrician and I got the switch, Cuttler Hammer, for $300 on sale back then and a 20% off coupon.

200 Amp Generator Manual Transfer Switch

The rest I got at Lowes, some wire, a box, plug, ect.

I do not like the idea of only have 6 circuits energized like some of the small panels do. I have been out of power 8 days at a time and a few 4 day stints and the last thing you want is not having what you need.

By the way I have a Troy Built 8550 Watt Genny and it will run 24 hours on 9 gallons of gas. I keep 3 days fuel on hand and use my 100 gallon boat tank as a backup. Learned that the hard way when I had to drive 100 miles for fuel.

Chris

 

[tsteahr]

We did this for about $400. My neighbor is a electrician and I got the switch, Cuttler Hammer, for $300 on sale back then and a 20% off coupon.

200 Amp Generator Manual Transfer Switch

The rest I got at Lowes, some wire, a box, plug, ect.

I do not like the idea of only have 6 circuits energized like some of the small panels do. I have been out of power 8 days at a time and a few 4 day stints and the last thing you want is not having what you need.

By the way I have a Troy Built 8550 Watt Genny and it will run 24 hours on 9 gallons of gas. I keep 3 days fuel on hand and use my 100 gallon boat tank as a backup. Learned that the hard way when I had to drive 100 miles for fuel.

Chris

Good Deal! I agree it's nice to be able to pick and choose whatever circuits you want to be energized. I spent more than $400 just on wire and an outlet. 100' of 6 gage (or was it 4?) and another 50' of 0000. I think the 20' drop cord from the generator to the outlet was over $100... Oh Well, whenever I get into electrical it costs me a bundle.

Not that I think about it, when ever I get into anything it costs me a bundle :confused2:

 

[firedog]

[

QUOTE=tsteahr;2165948]If you use a three pole switch you break the neutral along with the two hots and you are totally isolated (because the utility only consists of three conductors). As to the ground, in my area there is no utility ground. The ground is just that, a wire connected to copper rods driven into the ground outside the house. I used three ground rods although only two are required by code here. The genset ground is connected to the same ground as the main panel ground. All grounds in the house must be tied together. It would be against code to have multiple ground paths in my area

There should be a utility ground at each power pole (distribution). This provides a ground grid for the entire system. Not quite sure how your's is set up, but if you connect to the same ground as your main panel which is in turn connected to the incoming ground/neutral from the power co. then you are still connected to their ground.

My incoming line run to a 200A main disconnect then to a 200A transfer switch. The ground/neutral from the meter is connected to a ground rod on the "incomer" side of the transfer switch. There is also a ground rod connection on the generator side of the transfer switch. This totally isolates the load and generator from the power co. system.

 

[67PLY]

We have 2000 watt Winco belt driven generator mounted to the front on our JD110 garden tractor. It's sole purpose it run the furnace (oil/hot water) in the case of a power outage. We ran a 110 volt dedicated line to a three position toggle switch and then to the furnace. I have a volt meter hooked up to adjust the engine/belt pto speed to around 125 VAC. The 3 position switch is left side Electric Company, middle position is 'no power' and the right side is marked John Deere. Having the middle position 'dead' avoids any possibiliy of feedback.

 

[tsteahr]

[
There should be a utility ground at each power pole (distribution). This provides a ground grid for the entire system. Not quite sure how your's is set up, but if you connect to the same ground as your main panel which is in turn connected to the incoming ground/neutral from the power co. then you are still connected to their ground.

My incoming line run to a 200A main disconnect then to a 200A transfer switch. The ground/neutral from the meter is connected to a ground rod on the "incomer" side of the transfer switch. There is also a ground rod connection on the generator side of the transfer switch. This totally isolates the load and generator from the power co. system.

Interesting. Around here the neutral is separate from the ground. All the neutrals are electrically separated from the ground. The wood utility poles do not have ground wires. The high tension metal towers are grounded, but that is for emf drain, not part of the electrical circuit. Since there is no ground provided by the utility, the main panel ties all the grounds from the house together and leads them to the ground rods. No current should be carried by the ground (unless something is wrong). It would be against the code here to tie the ground to the neutral. I'm not sure what would happen if you tried, but I don't want to find out. I'm thinking GFCIs would probably trip, since they compare hot to neutral current. I'm thinking if they were tied, some current could flow to the house ground rods, depending on the absolute potential of the local ground compared to the absolute potential of the neutral. I don't think the code wants current in the ground wire, and that's why they are electrically separated.

I'm not sure if around here the neutral is always at exactly ground potential. The neutral may "float" a bit. I also have this vague idea that the absolute potential of ground can vary from place to place as well. This was a reason for the floating neutral, to maintain a consistent balance point between the two hot legs. Even if the absolute potential of the hot legs varies, so long as the difference between the two remains 220 and the neutral is in the middle, all is well. This way the utility does not need to reference everything off the ground. They can control their neutral reference. For example, that way one hot leg could be +122, the other could be -118 and neutral be at +2 all relative to the local ground. 100 miles away the neutral could be at +1 relative to local ground, but that does not matter since having the neutral separate from ground creates a "closed" system for the utility. But electrical is not my thing so I'm really out of my realm, and I don't know if that's true.

 

[firedog]

Agree there should be no current in the ground conductor within a building or residence.
Generally, the ground and neutral conductors are only connected at the primary main panel, which is where the connection to earth ground (grounding rod) is also made. From there on out, including sub-panels no connection between the two should exist.
I'm not a lineman. but all our power line poles have grounds as well. The lines down my road consist of three 12,470V lines and one neutral line. Each transformer on the pole connects between a phase line and the neutral on the primary side. The secondary is the 240v with middle tapped ground also connected to the system ground/neutral.
The three (240V line to line, 120V to ground) provide service to the house.
Assuming loads are equally balanced, there would be no current on the neutral back to the system. But if you were drawing 50A on one line and 45A on the other the remaining imbalance (5A) would be returned to the system on the neutral.

 

[tommu56]

It would be against the code here to tie the ground to the neutral.

this is wrong

The ground and neutral has to be tied together at the service disconnect.

The service disconnect can be the main panel if it is the first place the main can be opened.
If there is a disconnect prior to the panel this that is were it has to be bonded.

From the bond point you have to run 4 wires. to the next device (assuming 120/240 single phase).

here is a picture