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-   -   Question about QO interlock kit / breaker. (http://www.diychatroom.com/f18/question-about-qo-interlock-kit-breaker-94190/)

speedster1 02-01-2011 09:14 AM

Question about QO interlock kit / breaker.
 
I've been considering replacing my aging load center. I was debating between GE and Square D QO. I've heard that QO is the best but a GE system is quite a bit cheaper but still offers good quality. My intensions all long was to install an interlock switch for my portable generator.

Long story short I sqored a SquareD QO interlock kit (QOCGK2C) at Lowes on clearance for $1.00 Not bad considering they retail for about $80. Anyway, This has swayed me into buying the Square D load center. The square D interlock kit does not come with the breaker included. Since my generator (5000w) has a 30A RV style plug would it be appropriate to use a QO235 as my backfeed breaker? The instructions stated that several were compatable including the QO240. Seeing my gen has a 30A output wouldn't the QO235 be more appropriate?

Jim Port 02-01-2011 09:35 AM

You would match the breaker size to the output of the genset. This would be a QO230.

wirenut1110 02-01-2011 04:02 PM

The "breaker" used for a generator interlock is a means of disconnect, not for over current protection. The over current protection is on the generator.

The wire size and inlet box you use to feed this "breaker" should be based on the generator you intend to use.

If you change the size of your generator, you'll need to change the inlet and wire size.

Given this, you can put a QO260 in there since the price of breakers usually doesn't change until over 60 amps.

LyonsElecSupply 02-01-2011 09:00 PM

Quote:

Originally Posted by wirenut1110 (Post 582565)
The "breaker" used for a generator interlock is a means of disconnect, not for over current protection. The over current protection is on the generator.

The wire size and inlet box you use to feed this "breaker" should be based on the generator you intend to use.

If you change the size of your generator, you'll need to change the inlet and wire size.

Given this, you can put a QO260 in there since the price of breakers usually doesn't change until over 60 amps.



Your breaker in the panel is a means of disconnect AND as a means of overcurrent protection for the wire SERVING the breaker. Also should the breaker on the unit fail, what is protecting the GenSet, Outdoor cord and building wire????? I understand what you are saying, but what would clarify for the OP is this:

"Size the breaker and incoming wire to 60 amps to leave room for expansion"

Honestly tho, I would not mess with a generator hook up with anything larger than 8 AWG, a 40 Amp generator is about as big as you are going to get for portable.

I would recommend nothing bigger than 30 amps however due to the fact that 8/4 SO cord is pricey along with 8/3 romex, the inlet and there arent many 40amp portables on the market.

Get yourself a 30 amps breaker, 10/3 Romex, and a Nema L14-30 inlet and 10/4 SO cord.

All you have to do if you upgrade a generator is replace the male plug on the end to match the genset. Theres no need to replace the breaker, box AND cord each time.

You can ALWAYS oversize your setup as long as the wire is accepted for the connector.

speedster1 02-02-2011 06:23 AM

Interesting to see varying opinions here. I don't believe I'd ever envision myself getting a generator any larger than what I have. The one I have seems to supply me with enough power for emergencies just fine. The run from my electrical box to an outside box would be about 8ft. I'd prefer to position the generator a little further from my house under a carport so that run would be about 25-30 feet.

I still have a few questions about wiring and connections. My genset has 3 types of connections:
One standard 20amp electrical outlet
One 30-amp 120-volt twist-lock (which I believe is an L5-30)
One 30-amp 120/240-volt RV receptacle which is shaped like NEMA TT-30 with 3 prongs 2 of which are canted at 45 degrees and the other being round. It's definately not L14-30. Not sure what it's called.

I would assume the 30-amp 120/240volt RV connection would be the best choice for me to use. With that in mind what type of inlet, wire, and receptical do you recommend? Would I still wire 10/3 from the breaker to the inlet?

speedster1 02-02-2011 10:46 AM

After talking this over with a buddy of mine I'm beginning to wonder if I'm going to be SOL. The discription of the generator is "30-amp 120/240-volt RV receptacle" which led me to believe it output to 240V. But after seeing the output being a 3 prong TT-30 style outlet I don't believe that can output 240v can it? If this is indeed only 120v output then it wouldn't do me any good backfeeding it into my breaker box will it?

LyonsElecSupply 02-02-2011 11:25 AM

It looks like your generator might be supposed to power an RV only. It may only allow 120 volts. You need to get a multimeter and test between each line.

from what I have read, you have a 30a 120v generator. Your prongs will probably end up being 120 volts, of which you will have a hot, neutral and ground.......

Most residential generators have a 4 wire 120/240 L14-30 connector........unless they are only 120 of course (normally your inverter gensets)

The TT-30 IS NOT 120/240, it is 120, 30 amp......

wirenut1110 02-03-2011 09:53 AM

1 Attachment(s)
Quote:

Your breaker in the panel is a means of disconnect AND as a means of overcurrent protection for the wire SERVING the breaker. Also should the breaker on the unit fail, what is protecting the GenSet, Outdoor cord and building wire?????
The generator breaker in the panel is not for over current protection. Over current protection needs to be at the source which is the generator. If the genset, outdoor cord and building wire should fail this breaker is not going to de-energize those components, only remove the load on the generator. You can leave this breaker off all day and if the generator is running and connected, those components will be energized.

This is a 60 amp QO manual transfer switch, by what your saying is, the generator connections on this switch would need to be 60 amps and you'll have to use a 60 amp generator. Which is not the case.

The code is not based on "what if" situations. We can sit here for ages and say what if this, what if that.

speedster1 02-04-2011 07:19 AM

I've talked to the manufacturer of the generator and here is what I've found out......

Quote:

The model you received operates in parallel. What this means is we take the 2 -120 volt windings and stack them so you get the high amperage at 120 volt. Separating the windings will give you 2-120 volt hot legs (2x120=240 volt) can the generator be re-wired by someone who’s handy absolutely. Is it something you want to consider? An additional breaker would need to be installed and also the L14-30 receptacle. Most important question is does the generator have enough power to operate your 240 item? At 240 you’ll have 16.6 amps at start up and 14.6 amps running.
True be told I don't have any need for a 240V circuit (my stove and dryer are both gas). The reason I need 240V is so I can backfeed a double pole breaker and send 120V to each rail in my box. I guess theoretically I could backfeed a single pole breaker and just energize a single rail couldn't I? Of course that would limit me tremendously on what I could and could not use.

Would it be worth rewiring the genset and replacing the RV plug with a L14-30 outputting around 15A? My main concern in all this is being able to power the blower on my Heil Gas Furnace. I believe it draws around 500-600 watts. The next thing I would be concerned about would be the fridge. It's an LG Energy Star fridge that states that it uses 465kWh estimated yearly electric use. I don't know exactly what that means but I've been told most refrigerators generally use less than 600watts of power. Aside from that maybe a few 13w compact flourecents. I'm not afraid to rough it a little if the power goes off for a few days. I can live without TV's and computers and things like that. However in the winter I prefer to have some type of heat.

I could always do the ghetto style male-male backfeed through an outlet with the mains turned off but I prefer to do it in a way thats legal and follows codes.


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