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Mep803a wiring to home panel questions?

HDJ81MAX

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Homestead, Florida
Hello Everyone. I just got my first mep803a and want to hook it up to my panel. Right now i have a 200amp main panel for my house and have a 50amp that i use to back feed when the power goes out i turn off the main breakers and turn on the 50amp to power my house. Soon i will be hooking up the mep803a to my house panel it will be about 120' away. I would be running the whole house withba 5ton A/C unit with a soft start. Wanted to ask a few questions. Before i start this project

1. Should i switch the 50amp breakers to a 60amp?

2. Should i add a manual transfer switch outside?

3. What size wire should i run? And what kind? Approximately 120' run
 
Last edited:

jcollings

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I ran #6 wire 115' run. Run single phase 120/240 . Only running Necessary equipment for storm condition, rated nameplate of generator. Also disconnecting the bar ground in generator and running ground of house connection.
That's what l did.

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dougco1

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Cooperstown NY
Hello Everyone. I just got my first mep803a and want to hook it up to my panel. Right now i have a 200amp main panel for my house and have a 50amp that i use to back feed when the power goes out i turn off the main breakers and turn on the 50amp to power my house. Soon i will be hooking up the mep803a to my house panel it will be about 120' away. Wanted to ask a few questions. Before i start this project

1. Should i switch the 50amp breakers to a 60amp?

2. Should i add a manual transfer switch outside?

3. What size wire should i run? And what kind? Approximately 120' run
Don't be messing with your project if your not experienced or qualified to do the install.

All it will take is a faulty installation with the potential of back-feeding your service entrance to the grid. Without the proper disconnect, you can end up killing a lineman working on the powerline that's trying to repair it.

You have to "contact your power grid supplier" for the install and it "must be inspected" before they will let it be hooked up to your house.
 

HDJ81MAX

New member
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7
3
Location
Homestead, Florida
Don't be messing with your project if your not experienced or qualified to do the install.

All it will take is a faulty installation with the potential of back-feeding your service entrance to the grid. Without the proper disconnect, you can end up killing a lineman working on the powerline that's trying to repair it.

You have to "contact your power grid supplier" for the install and it "must be inspected" before they will let it be hooked up to your house.

How would i have power going back to the powerlines if my main 200amp breaker would be off?
 

loosegravel

Just a retired mechanic who's having fun!
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A simple interlock on your main panel will prevent the possibility of back-feeding the main line power as was suggested. There are a few of them out there. I'm using a MEP-803A as a whole house back-up power supply. I have an all electric 2600 sq. ft. home with a heat pump. Some load managing is necessary in my case. I turn off the power to my hot tub. I turn off the power to my water heater. And I turn off the power to the 20kw back-up heat strip on the indoor air handler for my heat pump. I also installed a soft start on the outdoor unit for my heat pump. It makes a huge difference.
 

dougco1

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Cooperstown NY
How would i have power going back to the powerlines if my main 200amp breaker would be off?
If you don't have an automictic transfer switch you must have an interlock of some sort in place. If not, there is a chance of a back-feed if you forget the process of shutting the main off and starting your generator. Or worse yet, someone else that is not familiar with the proper operational sequence of your system tries to do the transfer.
 

fb40dash5

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I would say +1 on just using an interlock, unless you were going to get fancy with an automatic transfer switch. I looked at several options for manual switches, and didn't like the setup. I actually ended up installing a subpanel (my main panel is so old it was hard to find an interlock, plus despite being huge it was only a 20-slot & was quite full) and putting the interlock on that, with all the loads I wanted to power in it, and the stuff I wouldn't be using in the old panel.

You want the generator breaker sized for the lowest rated component in your inlet wiring- i.e. if you used a 30A plug, you'd want a 30A breaker, if you used a 60A plug but cable only good to 40A, you'd want a 40A breaker.

If you're iffy on whether you know what you're doing... call someone who isn't iffy. If you're not an electrician & you're not nervous when working inside your panel, you should probably call someone, because that means you don't know what you're messing with. I'm not an electrician but I'm pretty good, and running the feed cables to my subpanel past the 200A hot lugs that have no disconnect besides pulling the meter took me about 40 minutes with my heart in my throat.
 

FarmingSmallKubota

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On my interlock, the breaker for the generator needed to be installed in the upper left position. This required a little rearranging of the existing breakers on that side of the panel. The main power breaker can now only be turned on if the generator power is turned off, and vise versa.
For my Interlock it was the upper right corner of the panel so i had to move a couple things, but gives me a piece of mind know it is safe and need be i can swap generators outside in less than 5 minutes with the 50 amp generator plug on the outside of the house.
 

Scoobyshep

Well-known member
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You absolutely need at minimum an interlock so that only one source may be active at one time.

The generator breaker in the panel is typically sized in a way to protect the wire. The generator breaker protects the generator from overload.

The other big thing to look at is grounding and bonding. At the first means of disconnect (typically the meter, but sometimes the panel containing the main breaker) the neutral and ground are connected (bond) When switching to generator from utility with a backfeed breaker (the neutral isnt switching) the bond at the generator needs to be opened. (look up separately derived systems) This might be a thing where its best to hire a professional, There is alot of chance for wrong turns.
 

WWRD99

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York Pa
Hello Everyone. I just got my first mep803a and want to hook it up to my panel. Right now i have a 200amp main panel for my house and have a 50amp that i use to back feed when the power goes out i turn off the main breakers and turn on the 50amp to power my house. Soon i will be hooking up the mep803a to my house panel it will be about 120' away. I would be running the whole house withba 5ton A/C unit with a soft start. Wanted to ask a few questions. Before i start this project

1. Should i switch the 50amp breakers to a 60amp?

2. Should i add a manual transfer switch outside?

3. What size wire should i run? And what kind? Approximately 120' run
I did 4 gauge aluminum for mine. I was about the same distance if I remember right. I ditch witched it 2 feet deep inside a 3-inch pipe. Worked really good. As far as switching, I went a little overboard, but it's code safe where I am. I could have done the interlock very easily since my 200 amp fuse is right there. My main reason was that I didn't want to rely on a fuse to click on and off. In my mind, they aren't meant to be flipped on and off a bunch, so I went with the ronks switch. I like that it has 3 ways to work, whether it be genset, line power, or off for everything. So I can have no power at all going to the main breaker and service that if I need to. The bonding is an issue you'll need to figure out plus at the genset as well since it has a bonding bar at the connection inside. I did months of research then hired an electrician to hook everything up correctly just so it was right. He had a helper and was here for about 8 hours total. Added 2 grounding rods. Was a good bit of work. I did do a soft start on my ac since it's start amps was more than what the 803 could make...it's at 23amps now so it works everything in my house.


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robert248

Member
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Location
Texas
If you don't have an automictic transfer switch you must have an interlock of some sort in place. If not, there is a chance of a back-feed if you forget the process of shutting the main off and starting your generator. Or worse yet, someone else that is not familiar with the proper operational sequence of your system tries to do the transfer.
What are some sources to get an automatic transfer switch? If I'm reading correctly the Ronk is still a manual switch of some kind. Please correct me if that's wrong.
 

dougco1

Well-known member
Steel Soldiers Supporter
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Location
Cooperstown NY
What are some sources to get an automatic transfer switch? If I'm reading correctly the Ronk is still a manual switch of some kind. Please correct me if that's wrong.
Depends if your trying to hook up a portable generator or installing a whole house standby generator system. My install was a 20 K Cummins standby with a 200 amp auto transfer switch. Expect to spend $900.00-$1,500.00 on the switch or $6,000.00 + on a complete system + installation extra.
Check out Norwall for prices https://norwall.com/

I lucked out and got my system just before prices jumped for just over $5,000.00. I installed the unit myself and hired an electrician to do the final wiring and hookup. Total investment about 7-K.
 

Scoobyshep

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I did an ats. It was made by generac. The generator and switch controls are all custom made

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robert248

Member
37
23
8
Location
Texas
Depends if your trying to hook up a portable generator or installing a whole house standby generator system. My install was a 20 K Cummins standby with a 200 amp auto transfer switch. Expect to spend $900.00-$1,500.00 on the switch or $6,000.00 + on a complete system + installation extra.
Check out Norwall for prices https://norwall.com/

I lucked out and got my system just before prices jumped for just over $5,000.00. I installed the unit myself and hired an electrician to do the final wiring and hookup. Total investment about 7-K.
Its going to be a stand alone MEP-802A that is the whole house standby generator.
 
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