# Interlock switch vs Transfer switch



## PiscBc2 (May 6, 2020)

Had a rep. from Power Company by to examine my generator setup.

Suggested TS...since, have looked at several videos and believe IL switch will work better for me w/ a Power Inlet box mounted beside main breaker panel. (below the weather head)

As I understand, this will allow me to use only breakers from the inside panel I need in an outage.

Generator is a 4400 Diesel. Thanks


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## Browse Deweb (Jan 16, 2021)

Yes, a generator feeder breaker and interlock allows you to use any circuits controlled by the panel it is installed on. You choose what to power based on your required loads and available generator output. Connect the generator to the input box, turn on the generator, power off the main breaker and all circuits, lift the interlock and turn on the generator breaker, then begin to power each individual circuit you need by switching on the breakers one at a time. Don't overload the generator. If your generator doesn't have 240V output capability, don't turn on any 240V (double pole) breakers.


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## PiscBc2 (May 6, 2020)

Okay, thanks for the reply.


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## drmerdp (Apr 10, 2018)

There are perks for both options. 

Interlock is ease of installation and cost. Plus the whole panel is energized. But it’s less “idiot proof” as far as being selective with circuits That should not be powered On generator.

Transfer switch is a tad pricy and a bit more complicated to install and are very limited with powered circuits. But usually have wattage meters for reference, and are entirely “idiotproof” as far as operation. Also, this Route just like a sub panel frees up circuits from the main panel allowing for future expansion.


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## PiscBc2 (May 6, 2020)

I believe our electricians were thinking of the former route,"ease of installation and cost" with all of our home wiring.


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## PiscBc2 (May 6, 2020)

Which receptacle connector is used to connect generator to the Power Inlet box? Thanks


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## Browse Deweb (Jan 16, 2021)

PiscBc2 said:


> Which receptacle connector is used to connect generator to the Power Inlet box? Thanks


Looks like you have a NEMA L14-20 outlet for the 240V connection. You would need this connector to feed both sides of your panel.

Input box:








Reliance Power Inlet Box - 20 Amp, L14-20, Raintight, Metal


Power Inlet Box - 20 Amp, L14-20, Raintight, Metal (4) knockout holes Ample wiring space for easy connections The Raintight™ power inlet box is wired to your indoor load center and mounted to an exterior wall near where your gen




www.absolutegenerators.com





Cable:








Conntek 25 ft. 10/4 STW L14-20 20 Amp 125/250-Volt Generator Extension Cord 20591 - The Home Depot


This is a 4 prong 125/250-Volt NEMA L14-20 25 ft. generator power extension cord. The cord is fully molded for long lasting durability. The cable comes in a bright yellow color for easy visibility and



www.homedepot.com


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## drmerdp (Apr 10, 2018)

I would recommend a l14-30 inlet box. L14-20s receptacles are not common anymore on generators You can get an adapter to go from l14-20 to l14-30.


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## Browse Deweb (Jan 16, 2021)

drmerdp said:


> I would recommend a l14-30 inlet box. L14-20s receptacles are not common anymore on generators You can get an adapter to go from l14-20 to l14-30.


This makes sense. Your wiring would then all be for 30A, even though the generator won't be able to provide it. Then you can upgrade to a larger generator in the future and use the standard 30A outlet.

Something like this would work as an adapter:








AC WORKS Locking Adapter 20 Amp 4-Prong L14-20P Locking Plug To L14-30R 30 Amp 4-Prong Locking Female Connector ADL1420L1430 - The Home Depot


This AC WORKS brand locking adapter [ADL1420L1430], is very durable. This locking adapter is NEMA L14-20P to NEMA L14-30R. The NEMA L14-20P is a 20 Amp, 125/250 Volt, 4-prong male plug. The NEMA L14-30R



www.homedepot.com


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## iowagold (Jan 22, 2020)

we run 50 amp inlets for future expansion.
that way if you upgrade later it is super easy to do.


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## Browse Deweb (Jan 16, 2021)

iowagold said:


> we run 50 amp inlets for future expansion.
> that way if you upgrade later it is super easy to do.


Smart!


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## iowagold (Jan 22, 2020)

yup
always plan for more in the future...
and run the wires once!
it does cost a bit more for parts...
but the labor is the same.
and yes bigger is better! on wire size!


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## PiscBc2 (May 6, 2020)

Thanks everyone for the reply's and recommendations. Which Interlock brand should I use?


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## PiscBc2 (May 6, 2020)

iowagold said:


> yup
> always plan for more in the future...
> and run the wires once!
> it does cost a bit more for parts...
> ...


Paul, so buy a 50 Amp Power Inlet box.... if so, buy the female plug to fit it (50 amp) and which size plug to fit the generator receptacle...30 w/ adapter or 50 w/ adapter?

Also, did you suggest #4 gauge wire for generator to PI Box? Thanks


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## iowagold (Jan 22, 2020)

it depends on how long you need
i will pm a page with the info


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## PiscBc2 (May 6, 2020)

Okay


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## FlyFisher (Jun 30, 2018)

Note that with cable size there is a difference between copper and aluminum.

Copper clad aluminum also exists out there.

All copper is best, but is about 3x the price of aluminum.

If you go with aluminum wire you need to size up the gauge. There are different grades of aluminum cable and the temp rating varies on the different grades of cables. You want to make sure that the grade and gauge combination that you pick is capable of carrying the amps you are working with.

For example - I use a lot of 6 gauge aluminum SE/SER grade cable (Service Entrance cable). It is rated to 75deg C and will carry 50 amps - what the main breaker is on my big generator. Here is an example chart that compares copper and aluminum grades for reference:


https://www.cityelectricsupply.com/downloads/Ampacity%20Chart.pdf



Another tidbit with aluminum is you need to use an antioxidation compound on the joints for longevity - especially on dissimilar metals like the terminals in your connectors and circuit breaker connections.


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## Browse Deweb (Jan 16, 2021)

PiscBc2 said:


> Thanks everyone for the reply's and recommendations. Which Interlock brand should I use?


They make interlocks for each panel configuration. You need to find the one that matches your panel. Try looking here:





Generator Interlock Kits | Electrician Interlock Kits | GenInterlock


The GenInterlock.com generator interlock kit provides an economical and dependable way to meet your electrical needs.



www.geninterlock.com


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## PiscBc2 (May 6, 2020)

FlyFisher said:


> Note that with cable size there is a difference between copper and aluminum.
> 
> Copper clad aluminum also exists out there.
> 
> ...


Thanks Flyfisher for your reply....if memory serves me correctly, they used a lot of aluminum in the US during WWII for the housing market wiring. I wasn't even a thought then...F. Forward 30 years when I worked construction in the housing market, I remember when electricians would run across it during remodeling of houses and they would yank it out of the studs, ceiling/floor joists and toss it. Most recently, while the Power Company rep. was here inspecting my generator set-up, we were talking later out by his truck and I noticed one of the new style spot rotating lights on his hood. I asked him how he liked it and why was it mounted in the front position of his hood on the passenger side.
He said,"the hood is made of aluminum as well as the cab." I found that hard to believe but he lifted the hood and the light was mounted by bolts and nuts. It was a '19' F-550 Ford and he said all trucks were aluminum now.

Looking at the chart link you provided, it takes a 12 ga. aluminum wire to carry what a 14 ga. copper wire will handle.
Wealthiest nation on the planet and we have to use aluminum...makes me wonder what pennies are made of now days and why we stopped using products that were the best for an application but have resorted to inferior materials.

The anti-oxidation happens w/ copper also as w/ battery terminals and winch cable electrical wires but not so sure in Breaker panels as you were mentioning if using aluminum.

Thank you for the reply and the information.


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## PiscBc2 (May 6, 2020)

Browse Deweb said:


> They make interlocks for each panel configuration. You need to find the one that matches your panel. Try looking here:
> 
> 
> 
> ...


Deweb, Thanks for your reply...I read the type B Panel and breaker brands were a factor in the type IS used but wasn't sure if manufacturers provided their version to fit a variety of the market.

I'll look at mine today and see what the electricians used. Thanks again and for the link.


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## iowagold (Jan 22, 2020)

wow we had sticker shock again today!
8-3 with ground $380.00 usd for a 125 foot chunk!
WOW!
if you have upgrades planned get your wire now!
it is supposed to go up again on price in july and aug 2021!


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## PiscBc2 (May 6, 2020)

Is that aluminum wire?


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## iowagold (Jan 22, 2020)

100% copper


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## iowagold (Jan 22, 2020)

power for a 230 vac 15 amp rated freezer. (20 amp plug)


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## PiscBc2 (May 6, 2020)

That is what I want, copper...If you could provide the list of what I would need for what I've discussed:
PIBox 50 amp, IL switch, conduit to connect the two w/wires for connection, generator will be within 25' of meter base (wire for that and handle 50 amp service for later/future expansion), and connector to generator I'm presently using. 
Anything you can foresee I might be overlooking also and I'd buy it all from you than HB or some other big conglomerate.


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## FlyFisher (Jun 30, 2018)

PiscBc2 said:


> if memory serves me correctly, they used a lot of aluminum in the US during WWII for the housing market wiring. I wasn't even a thought then...F. Forward 30 years when I worked construction in the housing market, I remember when electricians would run across it during remodeling of houses and they would yank it out of the studs, ceiling/floor joists and toss it.


That is correct. Copper was in short supply in wartime so aluminum was commonplace back in that era. The big issue you have with the wire is the connections. If they aren't set up with antioxidation compound the connections can corrode. As that corrosion increases so, too, does the resistance. Pushing current through more and more resistance creates more and more heat. That era of construction with aluminum wire is a common cause for house fires.

If you can prevent the corrosion aluminum is a suitable conductor. 

Take a look at the service entrance cable from your meter to the circuit panel in your house. Chances are it is aluminum. We have 200 amp service here and it is aluminum. When we did additions on the house I grew up in many years ago we changed the overhead power cable to a buried cable. It, too, was aluminum. During the additions somehow the new electric line got nicked. About 2-3 years after the additions half the house's power would go off - usually triggered by the vacuum sweeper running. It started out as a bit of a nuisance in needing to reset breakers, but it got worse fast. The power company came out to test the feed and found a problem in the line. They dug it up and one leg of the feed looked like a loaded baked potato - the insulation on the cable was split, and if you can imagine a cook smushing up a potato to push it out of the slice - thats what the cable looked like. Somewhere I have that piece of cable as a souvenir.

In any event, heavy aluminum cable is more common place than you might think - and it can work well if done correctly. 



PiscBc2 said:


> Looking at the chart link you provided, it takes a 12 ga. aluminum wire to carry what a 14 ga. copper wire will handle.


That sounds about right - there is about a 1 step in gauge difference - so 14 to 12, 8 to 6, etc etc. 

Of course, long runs change the ballgame even further. You get more loss in voltage even if a particular gauge wire is suitable for the amperage. In that case size up to prevent the voltage drop.


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