Backing Up the Back Up Generator


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Old 09-25-22, 06:36 PM
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Backing Up the Back Up Generator

My friend/neighbor's Generac genny (about 15 yrs. old) has seen a lot of use and parts wearing out. So rather than expense a new Generac, he was given a plan by a master electrician to wire in an immediate back up the Generac (for when it finally dies) with an 8.5k Honda gasoline unit.

Today I helped him implement the plan, which worked. Basically it involves switching the input to the house genny sub panel between the Generac genny and the Honda gasoline genny via a center off exterior cut off switch. (I don't know exactly what you call it, see pic.)

So here's the thing...my Generac is almost as old as his and I want to copy his back up method for when mine dies...so I know exactly what to do.

Getting hold of the electrician for answers is difficult so here are my questions.

--What is the precise term for this center off switch so I know what to ask for. (The GE pictured supposedly came from ebay.)

--Can you see any flaws with this plan? (My only thought was power draw limits with the gasoline unit.)

Thanks!


 
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Old 09-25-22, 08:11 PM
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That is just a GE 100 amp outdoor manual transfer switch (Example) https://www.homedepot.com/p/GE-100-A...323R/100171587
With a 30 amp outdoor inlet. (example) https://www.amazon.com/WELLUCK-Gener...s%2C202&sr=8-5

As long as to have another transfer switch inside to disconnect utility power I don't see any issues.
 
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Old 09-26-22, 06:05 AM
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Your house breaker panel needs a transfer interlock switch so poco power wires never connect to generator power wires. This transfer interlock switch eliminates need for generator select switch OFF position unless its there for some other reason. The transfer interlock switch and generator select switch should be placed in closed and select position respectively before generator is started to eliminate switch contact arcing.
 
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Old 10-05-22, 01:14 PM
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Personally, I wouldn't go to all that trouble. I'd just have the parts on hand to disconnect the Generac and connect a 30A male plug to the whip that was connected to the generator.

You'll have to plug in your new gas generator and manually transfer the switch (since the automatic switching will be expecting inputs from the generator that it won't have). But that's a simple switch over when/if the Generac fails.

Hopefully, the Generac will fail during a weekly test, so you'll have time to get it fixed or replaced - but you'll have a backup in case it doesn't.
 
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Old 10-05-22, 02:12 PM
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This method will work fine if you have manual transfer switch or automatic transfer switch that senses input voltage, but if you have automatic transfer switch with some sort of computer or load balancing it might cause issue.

Most modern automatic transfer switch will not switch until generator output has stabilized and this transfer is powered and signaled by your standby generator. If this is the case, automatic transfer switch will not transfer if your standby generator has failed.
Some automatic transfer switch has manual override, so you might be able to us that to switch transfer switch.
 
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Old 10-06-22, 05:53 AM
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I would appreciate if original poster responded with type of interlock he has to keep poco and generator electrical connections separated.
 
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Old 10-06-22, 07:55 PM
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The transfer switch is the original that came with he Generac. Nothing has been added or subtracted in that regard. I stressed to my friend to test the operation of the gas generator to be sure it comes online properly including the transfer switch.
 
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Old 10-07-22, 05:56 AM
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Have your friend test with standby generator turned off (There usually is a switch) and main breaker for power company feed.


I would appreciate if original poster responded with type of interlock he has to keep poco and generator electrical connections separated.
He has existing standby generator with transfer switch already. So, poco and generator feed is separated. He is trying to install another transfer switch to generator feed so he can choose between standby generator and portable generator.
Only trouble is automatic transfer switch is usually controlled by standby generator and automatic transfer switch will not switch in case of standby generator failure.

There are ones that actually senses input voltages instead of having standby generator signalling. In that case it will work fine.
 
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Old 10-07-22, 06:19 AM
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Transfer switches can be automatic or manual. The transfer switch may/may not switch the neutral. What is yours? Installation of either type requires rerouting/replacing of the 2 (two hot) or 3 (two hot + one neutral) conductors from the meter to breaker panel to from the meter to the transfer switch. The generator 2 or 3 output conductors also get wired to the transfer switch. New conductors are required from transfer switch to breaker panel.
 
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Old 10-07-22, 06:44 AM
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We're not trying to install another transfer switch. And it's out of my hands though at this point. I told my neighbor to test this out...what I would have done if it was my house. I won't hear from him unless there's a glitch.
 
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Old 10-07-22, 02:29 PM
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On all Generac generator controllers I have seen the controller's transfer signal to the automatic transfer switch is 12 vdc. How are the 2 transfer signals, one from each generator being handled since they are not connected to the manual generator select switch?
 
 

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