Emergency Power Generator Connection Help Needed

[armylifer]

I need some help with connecting three portable generators up to my house for emergency power. I have one generator that is capable of producing 5000 Watts continuous power at 120/240 VAC. I also have two other generators that are capable of producing 2000 continuous Watts at 120 VAC each. The total available continuous wattage from all three generators is 9000 Watts at 120 VAC, or 75 continuous amps.

The help that I need is in a few areas.

1. Is it possible to hook all three generators up to an auxiliary power panel (connected to house main power panel) and feed that power to the house?

2. If it is possible to run all three generators to one auxiliary power panel and then from there to the house, is it possible to power both 120 VAC outlets as well as at lease one of the 240 appliances? I know that my portable generators only provide me a total of 75 amps if all three of them are running at the same time, but that should be sufficient power if I don't try to use all circuits at once. I know that means I will have to select which circuits to power and which ones to leave powered off.

3. The setup that I am envisioning will allow me to run all three generators at the same time, or selectively run only the number of generators that I need for the power load needed at any one time.

4. If what I want to do is possible, what equipment will I need to do this? I have attached a picture of my main power panel in case it helps to determine what I need to do this.

I want to say right now that I am not planning to do the hookups myself, I will hire an electrician to do the work. I am just trying to research if it is possible to do this and get an idea of costs involved. I also want to know enough to determine if I am getting a fair deal from an electrician. I also plan to buy all the components myself and save some money there.

Any help offered is greatly appreciated. Thanks for reading.

 

[Russell King]

I doubt you can hook all three up together into one circuit. There would be no easy way to get them into “phase” so the sinusoidal waves are all at high point at same time. You may be able to segregate your power needs into three separate systems and power each with one separate generator. That way you won’t care about them being in phase.


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[armylifer]

I doubt you can hook all three up together into one circuit. There would be no easy way to get them into ***8220;phase***8221; so the sinusoidal waves are all at high point at same time. You may be able to segregate your power needs into three separate systems and power each with one separate generator. That way you won***8217;t care about them being in phase.


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I understand what you are saying but I have to ask how the newer generators on the market can be daisy-chained to one load. I would think that there has to be some way to get all three generators in phase before being connected to an electrical load.

 

[mattwithcats]

You can run a manual transfer switch for the 4000 watt generator...

This is enough for two breakers, I would wire the kitchen outlets, and one bedroom...

This Old House did an episode on how to do this...

https://youtu.be/GLgtFCJlVFQ

 

[bcp]

From:
http://engineering.electrical-equip...n/paralleling-generators-synchronization.html

Incompatible generators

Paralleling generators with different characteristics is a bit complex. Apart from the compatibility issues, there are other system level problems the sizes.

If the sizes are the same, the system is capable of supporting a higher priority load in case of an emergency. However, if the sizes (in KW) are different, the maximum priority load is limited by the smallest generator; otherwise a higher load will overload the generator unless it is prevented from coming up. In such situations, the control is quite complex and might involve changing the sequence of operation. In addition, manual operation as well as dealing with failure modes becomes difficult.

The design should ensure that larger loads are dropped out first in the event of a failure of the bigger generator; this ensures that the smaller generator will be left with a load it can support.


For the generators to be paralleled and synchronized correctly, each of the sets should have the below characteristics

Frequency: the frequencies must be the same


Voltage: The generators should produce or be set to produce the same voltage


Phase number: The two systems should have the same number of phases, either three or single phase.


Phase rotation: For three phase systems, each of the three phases must be matched. This prevents excessive mechanical and electrical stresses as well as avoiding power surges.


Voltage Phase angle: The waveforms should be matched such that they rise and fall together. There should be no angle difference and the potential difference between the phases should be zero.

==========================
Another article (PDF)

www.netaworld.org/sites/default/files/public/neta-journals/Charleswtr04.pdf

===========================

With the modern parallel-capable generators that have connecting cables, all this stuff is taken care of by the internal computer systems.

Bruce

 

[Flienlow]

I am not an exert, but this is a very bad idea. Get generator sized for you load. Harbor freight sells very good inexpensive generators.

 

[mattwithcats]

6 circuit transfer switch...

https://www.homedepot.com/p/Reliance-Controls-30-Amp-6-Circuit-Manual-Transfer-Switch-306A/206499418

Going to be next to impossible to parallel two or more generators...

This is why I referenced only the 4000 watt one...

 

[armylifer]

Thanks to all for the expert advise. I appreciate the help. It looks like I will just have to use one generator for the barest essentials such as lights, toaster oven and well pump, not all at the same time of course.

 

[niteshiftfromkc]

You might consider getting one of the Generac units with the auto transfer switch. It switches on the generator about 20 seconds or so after losing power. Depending on the size of the home, you can run a lot of various circuits off of it. There is a 9KW unit with the transfer switch for around $2500 at Home Depot.

We had one of these at a previous home and it was great. My wife didn't have to worry about trying to drag the portable unit out of the garage, fill it up, hook it up and start it in the middle of the night while I was at work. It also came in handy when the neighborhood lost power for a couple of days while we were on vacation. We didn't have to worry about the sump pump or losing all the food in the freezer.

 

[coachgeo]

However you do it. If you wire the house to plug a generator into it.. GET AN ELECTRICIAN. Done wrong and one can back feed electricity into the grid and any emergency electrician working to restore power at a power line down the path from you can be electrocuted...

As to expensive manual transfer switches... luckily some communities codes now accept block off plate switches.. massively less expensive.

What these do is actually block off access to what must be blocked, but can only be put in place when correct circuits are turned off. When in place it opens a port on the fuse panel you can plug a generator into to power items based on size of gen set.

see....
. https://www.interlockkit.com/
. http://www.nooutage.com/interlock_kits.htm
. https://www.homedepot.com/p/Square-...r-Generator-Interlock-Kit-HOMRBGK2C/203030954

 

[coachgeo]

Wellll. I'll be damned... things have changed..... with this gizmo (well with a couple of them) you could use more than one generator.

Appears these are are simple (looking) manual transfer switches unlike the big ol' giant ones I am accustomed too. They automatically prevent feed back into the power lines that can harm an electrican restoring power to folk. Looking at prices.. three or more starts getting into how much it cost for a big ol' manual transfer switch.... but then again.... a big ol' switch require a matching big ol' massive whole house generator. If one already has some smaller generators.... then this ends up less costly.

http://ezgeneratorswitch.com/

 

[armylifer]

Thanks Coach. I'll have to check this out.

 

[armylifer]

Coach, after looking at those switches I see they are only 15 amps. I need 20 amps on each circuit. These will not work for me.

 

[CaveCreekRay]

Joe,

Sure you need 20 amps per circuit? Just because the circuit wiring can handle 20 amps doesn't mean a breaker panel that can only handle 15 can't supply power. If you overload the generator panel it will simply pop the breaker on the generator supply panel. As long as your 20 amp circuits don't need all 20 to run something on them, they will likely do fine on a 15 amp service during emergency. If you need a panel that can handle 20 amps across six circuits, that's 120 amps of load. No panel made for home use will handle that load! I don't know of many portable generators that can handle 60 amps. Even my panel is limited to 30 amps total across six circuits of 15 max each. If I max each out at 15 amps, that's 90 total amps and my generator is limited to 30 off the 220v tap which means 30 amps on each 110v phase, or 60 amps total (30 off two phases of 110v). In an energency, don't plan on running your heat pump!

I installed one in my garage. It will run six circuits IF you generator can handle them. My generator will not handle them all at once so I selectively run my fridge and freezer and then shut those circuits off and run my well to pressurize the tank, then I shut the well off and go back to powering the fridge/freezer. Its a minor pain but it gets the job done in emergencies. If I forget, my generator main breaker protects the generator from excessive loads.

The installation is really simple: The box comes with two wires for each circuit. You simply select the breakers (circuits) you want to power and you pull those breakers out one at a time. You simply hook each CB to the generator panel wire and wire nut the other wire to the old circuit wire that was originally hooked to the CB. The LINE-OFF-GENERATOR switch on the generator panel isolates each circuit when powered by the generator. Without it, when line power returned, you would blow your generator in a second.

Simple and easy to wire. The only hassle is getting the generator panel flex containing the circuit wires into a knock-out on your CB panel. The Generator panel comes with a great DVD describing the installation.

Good luck!

(I agree with the previous comments on daisy chaining dissimilar generators: NOT POSSIBLE. The chainable generators auto synch. To do that, you need two generators of the same brand that have the same circuit installed to modify their engine speed to get the proper synchronization.)

Here is my installation. Having drywall meant I had to cut the drywall to get the feed cable into the circuit breaker panel but it worked. The generator plug in to the lower right is included with the generator panel.

 

[dandeman]

.... but I have to ask how the newer generators on the market can be daisy-chained to one load. I would think that there has to be some way to get all three generators in phase before being connected to an electrical load.

I'll go ahead and answer this question anyway as prior posts have pointed out how difficult this is with generators not designed with this capability.

In particular the small Honda generators are inverter type generators, meaning the engine driven generator (typically a small 3 phase generator whose output is converted to DC) does not directly produce the 60Hz AC power to the load as other non inverter generators do.

In the Honda inverter power units, the generator supplies power to an inverter which, describing it very simply, takes the engine developed output and "amplifies" a small 60 Hz master clock output up to the rated power of the generator. Further, this type generator has a "master clock" output that can be connected to another same type generator that assures all outputs of the generators will be precisely locked in phase, independent of engine rpm.

A major benefit of the inverter type generators is that the engine no longer has to run continuously at synchronous frequency (3600 rpm for 2 pole generators, 1800rpm for 4 pole generators), but instead can throttle up and down based solely on overall power demand.. The output frequency is precisely controlled by the master clock driving the inverter. This provides far more efficient ,quieter, precise frequency control with the downside being it's a more expensive unit.

One other comment about just how dramatic, two generators coming on line out of phase can be. When they are 180 degrees out of phase, that is a hard short circuit of the two generator outputs. In larger generators, the magnetic forces from an instanteous short circuit can be so strong to literally rip windings loose.

Multiple generators are paralleled in power generation plants, ships, and some large commercial, critical load make before break generator systems (the latter under strict licensing agreement with the power company with stringent technical requirements defining sophisticated control system to do this safely.

Honda site re: inverter generators.. https://powerequipment.honda.com/generators/inverter-generator-advantages

 

[D2Cat]

Ray, your pictures show a 3 in 1 switch doesn't it? Is this from the same company. 'cause the one they show is green and a single switch?

 

[CaveCreekRay]

I have six of those switches on my panel, one for each circuit. They are LINE-OFF-GENERATOR isolation switches.

My panel was made by Reliant and I got it from Homey 'Po.

 

[bcbull378]

The most " IMPORTANT " thing when hooking generators up to your home is to make sure you open your main breaker before energizing, if not your will be back feeding the electrical system. When you supply 120/240 volts to the low side of a transformer it will back feed to the high side what ever primary voltage the transformer is wound at. This can be deadly to linemen working on your system, just be careful. Dan 37 year journeyman lineman So Ca Edison.

 

[skeets]

Thats the idea of the inline disconnect switch,,, if a line man finds a genset running and only the main opened you might wind up with a healthy fine, and as far as I know no jurisdiction will except that as it is not in compliance with the NEC,,, just MHO

 

[CaveCreekRay]

A very real threat indeed and why nearly every solar package will not be of use in a power outage. They trip off when line voltage goes to zero.

As I explained to Len, there is NO WAY that the generator can feed line voltage because each circuit is isolated. Its ONE or the OTHER. This also allows you to run the generator for testing while power is still on. By flipping the isolation switch for each circuit, you can go OFF or to GENERATOR and back to LINE to test your circuits.