Live in the sticks Generator switch?

[ArmyPair2]

:smiley_aafz:When I want to ask a rookie question I sometimes find the answer in the search box which is great but does this stop others from putting their input in on a topic without getting slammed by somebody say check search? I do have a questions and seek your knowledge that I could not find and it has to do with generators and switches .

We have two 30 amp generators at 7500 and 7600 outputs and are tired of running cables when there is a outage. I have been looking at what is called the interlock or the transfer switch to hook our house when there is a blackout. My main concern is that is there is no back feed in the lines that could harm a worker.

Which would you chose and why?

 

[aczlan]

This thread had some good info: http://www.tractorbynet.com/forums/...rator-transfer-switch-connection-choices.html
Here is what I would like to do at some point:

Howdy,
This was brought up in another thread which showed some products with good prices from local sources.
GE Power Mark Gold 200 Amp Main Breaker 4-Space 8-Circuit Meter Socket Load Center View attachment 283573 and the matching GE PowerMark Gold Generator Interlock Kit View attachment 283574 really is a nicely priced outdoor NEMA 3R meter base with generator interlock ability. With this being at the meter, you can control it with this service disconnect and then still have your main panel inside with service disconnect as well.

NOTE: always check with your Utility service to see if this is acceptable for service. They have the say so since it holds the meter.

See also: http://www.tractorbynet.com/forums/rural-living/259476-generator-install-plans.html

Aaron Z

 

[ideburger]

I have this one I bought on Amazon...

http:// http://www.amazon.com/Reliance-31410CRK-10-Circuit-Generator-Generators/dp/B000HS2L3O/ref=sr_1_1?ie=UTF8&qid=1387247260&sr=8-1&keywords=transfer+switch

I have been very happy with it and it was simple to install.

 

[buickanddeere]

Thank you for caring and wanting to do the right thing. There are so many dangerous cheap knowitalls out there that backfeed 120/240 into a three prong welding receptacle.
If your generator is setup with a floating neutral. A properly fitted external interlock on the main breaker panel is acceptable. The following links also provide a couple of other options.
I like the reliance as it mounts outdoors, allows all circuits to be fed. And has four breaker spaces for local loads or a place to tie in a distant shed, fish pond, yard lights etc.
The reliance will also allow future use of a larger generator. I remember one time standing at an auction sale wondering how I let a 15KW pto generator get past me for a couple of hundred bucks. A 15Kw is hopeless for a modern farm but will run most houses just fine.


GenerLink Downloads

TWB2012DR Panel/Link | Product Details | Reliance Controls Corporation

 

[dave1949]

I have a manual interlock in my main service panel--the one fed by the meter socket. I have to turn off the 200 amp main breaker, slide the interlock, then turn on the breaker that passes generator power to the service panel. All circuits receive generator power. It is impossible to have both the main breaker and generator feed breaker on at the same time. I like it better than a transfer switch that has dedicated, pre-determined circuits connected to the generator output. I manage my load as needed by turning off circuit breakers such as for the water heater that I can't control when it will decide to heat.

My generator connects to an "inlet" box using a power cord similar to the cord used to connect an RV to utility power. I'm not sure about two generators coupled to the same electrical system. I think some generators are not built to receive power, and they would be connected to each other electrically via the 120V busses in the service panel.

 

[dusty3030]

I have a 400 amp fused switch between the meter and my main panel. You totally disconnect from line power and when you throw the switch all the way down you run your whole panel off generator. You can choose what to power and what not.

 

[aczlan]

Thank you for caring and wanting to do the right thing. There are so many dangerous cheap knowitalls out there that backfeed 120/240 into a three prong welding receptacle.
If your generator is setup with a floating neutral. A properly fitted external interlock on the main breaker panel is acceptable. The following links also provide a couple of other options.
I like the reliance as it mounts outdoors, allows all circuits to be fed. And has four breaker spaces for local loads or a place to tie in a distant shed, fish pond, yard lights etc.
The reliance will also allow future use of a larger generator. I remember one time standing at an auction sale wondering how I let a 15KW pto generator get past me for a couple of hundred bucks. A 15Kw is hopeless for a modern farm but will run most houses just fine.


GenerLink Downloads

TWB2012DR Panel/Link | Product Details | Reliance Controls Corporation

IMO, the meter base/breaker panel I linked to (GE Powermark Gold, TSM420CSCU) is a better deal. It is $120 for the meter base/panel, $40 for the interlock and under $20 for the generator breaker. Less than half the $440 cost of the Reliance panel and if you replace your current meter base, you should be able to re-use the current wires running to it (rather than having to buy more wire).

Aaron Z

 

[ArmyPair2]

Silly me I should have made sure to say one of the generators is just used for backup.

 

[4shorts]

I just installed a Honda 6500 watt 30amp back up generator and I installed this transfer switch. Works great and safe for everyone.

Transfer Switches Manual - SQUARE D by SQUARE D - Transfer Switches Manual by Zoro Tools Industrial Supplies

 

[techman]

Simple. Buy a connector to mount outside the house, like: Amazon.com: Reliance Controls PB30 L14-30 30 Amp Generator Power Cord Inlet Box For Up To 7,500 Watt Generators: Patio, Lawn & Garden

Then put a mechanical interlock on your existing panel, connected to a 30 amp 2 pole breaker. You can get one to fit any make box from:
Generator InterLock Kit Manual Transfer Switch

Just remember to switch off large loads, like hot water heaters, large AC etc when you switch over.

paul

 

[buickanddeere]

. I'm not sure about two generators coupled to the same electrical system. I think some generators are not built to receive power, and they would be connected to each other electrically via the 120V busses in the service panel.

Please elaborate about this two generator thing and generators not being built to receive power???

The Two links I provided both systems supply power to all circuits. I can't imagine why people install those little ding dong four or six circuit only transfer panels.

 

[dave1949]

Please elaborate about this two generator thing and generators not being built to receive power???

The Two links I provided both systems supply power to all circuits. I can't imagine why people install those little ding dong four or six circuit only transfer panels.

All I know is what I have been told. The installers of my grid-tied solar system said to disconnect the solar inverter from the service panel (open its breaker) before switching to generator power. They claimed the solar output could harm some generators by feeding them power. ????

 

[buickanddeere]

Ahhhhhhh makes much more sense now.
The solar system should be isolated when on generator power when using a single bi-directional power meter for net metering. I'm going to read up on that tomorrow in the latest code book.

 

[dave1949]

Ahhhhhhh makes much more sense now.
The solar system should be isolated when on generator power when using a single bi-directional power meter for net metering. I'm going to read up on that tomorrow in the latest code book.

I have two meters, and IN and an OUT. The solar system produces a maximum of 16.2 Amps, ~4200 watts.

I don't think the meter(s) was the issue, it was damage to the generator they were warning about. I don't know if that is a code issue, or if there would be anything regarding that in the code?

This generator was connected to the house without isolating it from the grid when the power was restored:
Beware of Backfeeding - How NOT to Connect a Portable Generator


I'm not sure synchronization (phase) would be an issue for a grid-tied solar system since it gets it 60 Hz clocking from the service panel power.
Do 2 5000 watt generators = 1 10000 watt generator - Straight Dope Message Board
You can't just chain generators together like batteries, they have to be running in phase or you'll get one "pushing" while the other is "pulling" in the AC cycle and the result would be interesting.

There is a Honda EU series unit made to run in parallel with another Honda, but they are designed for that.

 

[farmer2009]

400 amp automatic switch gear. Power company knows about the generator and if they get concerned or have a problem they will come pull my meter to stop back feeding then reinstall after the work is complete. But they also call and tell me if they must shut down power for scheduled service. Storm damage or line failures are no warning but they can't do anything about that.

 

[buickanddeere]

I have two meters, and IN and an OUT. The solar system produces a maximum of 16.2 Amps, ~4200 watts.

I don't think the meter(s) was the issue, it was damage to the generator they were warning about. I don't know if that is a code issue, or if there would be anything regarding that in the code?

This generator was connected to the house without isolating it from the grid when the power was restored:
Beware of Backfeeding - How NOT to Connect a Portable Generator


I'm not sure synchronization (phase) would be an issue for a grid-tied solar system since it gets it 60 Hz clocking from the service panel power.
Do 2 5000 watt generators = 1 10000 watt generator - Straight Dope Message Board
You can't just chain generators together like batteries, they have to be running in phase or you'll get one "pushing" while the other is "pulling" in the AC cycle and the result would be interesting.

There is a Honda EU series unit made to run in parallel with another Honda, but they are designed for that.

If there are two meters , with the solar panel's inverter connected direct to the grid. Then there are no concerns about backfeed or paralleling the standby generator and the solar inverter when a proper generator transfer switch is used.

 

[techman]

It is true that you could cause some issues running a generator with solar. If you have a large solar output and little load, the inverter wants to push power out onto the grid. If the "grid" is a generator, the inverter will raise the voltage it is supplying to drive to drive it's full power. This increase voltage will cause the voltage regulator (on a better generator design) to back off the output of the generator, since the voltage will be too high. This will all happen within a second or two and the likely outcome is the inverter will shut down due to overvoltage, and restart again. It is unlikely to damage the generator. If there is a reasonable load at the time, they may work well together.

There is a bigger issue. Most grid tie inverters have a very narrow range of frequencies that they will operate with to supply power. On my Fronius 10KW, the range of allowable frequency is 59.3-60.5 Hz Outside that frequency window, it will not sync and connect. Since the generator is quite a bit less accurate in terms of absolute frequency control, it is unlikely to be an issue. I have had several day long runs of outage with my genset running (9.8 KW diesel) and I have left the solar enabled (9.2 KW). First I always have some base load, and I saw that when the solar would connect (when the genset frequency was within the window) it would only last a few up to about 10 minutes, and then go off line again. I saw times when the solar was feeding and a fridge or well would kick on, and the motor starting would cause a momentary dip in frequency and trip the solar off. All in all, on a day where I would normally see 30-40 KWh of solar, I saw maybe 2 KWh of solar supply, supplied a few minutes at a time.

One is certainly safer disconnecting the solar from supplying during genset operation, but with all of the frequency and voltage interlocks on a modern grid tie inverter, it is likely that it may not connect at all, and if it does it will be only for a few minutes when conditions of the gen power and load are just right.

paul

 

[dave1949]

It is true that you could cause some issues running a generator with solar. If you have a large solar output and little load, the inverter wants to push power out onto the grid. If the "grid" is a generator, the inverter will raise the voltage it is supplying to drive to drive it's full power. This increase voltage will cause the voltage regulator (on a better generator design) to back off the output of the generator, since the voltage will be too high. This will all happen within a second or two and the likely outcome is the inverter will shut down due to overvoltage, and restart again. It is unlikely to damage the generator. If there is a reasonable load at the time, they may work well together.

There is a bigger issue. Most grid tie inverters have a very narrow range of frequencies that they will operate with to supply power. On my Fronius 10KW, the range of allowable frequency is 59.3-60.5 Hz Outside that frequency window, it will not sync and connect. Since the generator is quite a bit less accurate in terms of absolute frequency control, it is unlikely to be an issue. I have had several day long runs of outage with my genset running (9.8 KW diesel) and I have left the solar enabled (9.2 KW). First I always have some base load, and I saw that when the solar would connect (when the genset frequency was within the window) it would only last a few up to about 10 minutes, and then go off line again. I saw times when the solar was feeding and a fridge or well would kick on, and the motor starting would cause a momentary dip in frequency and trip the solar off. All in all, on a day where I would normally see 30-40 KWh of solar, I saw maybe 2 KWh of solar supply, supplied a few minutes at a time.

One is certainly safer disconnecting the solar from supplying during genset operation, but with all of the frequency and voltage interlocks on a modern grid tie inverter, it is likely that it may not connect at all, and if it does it will be only for a few minutes when conditions of the gen power and load are just right.

paul

That all sounds logical, thanks. I don't intend to test it, but maybe someday I will due to forgetfulness. I didn't look up my inverter's frequency tolerance but I recall it is a narrow range.

I typically don't have that much to gain even if it did work. Power outages here usually come with bad weather, or slippery winter roads, when sunshine is lacking. The last two were overnighters from late afternoon to early the next morning.

 

[buickanddeere]

With two power meters. The solar system could be connected parallel to the utility side of the transfer switch. In that case back feeding form solar is not an issue. If the solar system meter is in series with the main utility power meter, then yes. The solar unit could back feed. As previously stated it would however sync, then un-sync with the generator.

 

[Coyote machine]

:smiley_aafz:When I want to ask a rookie question I sometimes find the answer in the search box which is great but does this stop others from putting their input in on a topic without getting slammed by somebody say check search? I do have a questions and seek your knowledge that I could not find and it has to do with generators and switches .

We have two 30 amp generators at 7500 and 7600 outputs and are tired of running cables when there is a outage. I have been looking at what is called the interlock or the transfer switch to hook our house when there is a blackout. My main concern is that is there is no back feed in the lines that could harm a worker.

Which would you chose and why?

Simply put; a transfer switch or an interlock, correctly sized and properly installed, will each work as intended and NEITHER will allow for backfeed to your utility line. As has been pointed out, each serves a different purpose/function; the interlock allows all or select main panel breakers to be in use while on generator supplied power, the transfer switch can be limited to # of circuits in the transfer switch, so may offer less functionality/ choices if only a few circuits are switchable at the transfer switch. Either will work, and is safe, so long as the generator does not exceed the switch's rated capacity.