Wiring MEP-004A to two houses

[1800 Diesel]

Looking into a setup at my brother's house on the gulf coast where we could install one generator to power two houses. Both houses are 100% natural gas for stove, HW heater & clothes dryer. As for electrical loads, both have central AC & the larger of the homes has multiple window units on the 2nd story. After Katrina we wired to the larger home with an MEP-003A for over two weeks and it ran at less than 75% load (though the central AC unit was not in service since it had been flooded with sea water).

The above details are provided for general information reasons. I would like the focus of this thread to be on the concept of simultaneously "driving" two houses with the same generator and any issues/concerns of electrically connecting both load cables from each house to the output terminals on the generator.

My first-look at the setup: 1. Both houses would have a transfer switch installed to isolate from the grid. 2. The load cables for each house would be connected together at L0, L1 & L3 output terminals. 3. At the loss of grid power, heavy load breakers in each house would be shut off & one transfer switch at a time would be turned on & then loads would be added as circuits were needed. 4. The generator will be re-wired for single-phase output, hopefully passing an 18 KW load test. 5. No ABT/PLC setup will be installed; this will be a manual operation following suitable training of the homeowners. 6. Generator load would be monitored closely during initial light-off to confirm suitability of the generator capacity, though I believe the MEP4 will handle the task with ease.

In my electrically-limited brain, it would seem that the two different loads combined at the output terminals would not cause any problems, but I would like some feedback from those with more knowledge & experience than me. I still need to sort out the concept of the proper arrangement for handling the generator earth ground & the neutral line L0. I believe there is already much discussion on the relationship between the neutral & the earth ground--this subject I need to get smarter on.

So, if anyone has any concerns/comments, additional safety recommendations, etc, please weigh in. If this it totally dumb for reasons I don't know, please educate me--I will not be offended....

Thanks,

Kevin

 

[Munchies]

While not typical it will work fine. We had separate buildings all running off one genset many times.
Should be good on the load too, since the stoves are gas. that's the biggest load in a house really.
My 002 starts my 2.5 ton ac and everything else in the house just dandy. Just cant cook with anything else going, as the stove could pull up to like 13K on its own.
The 004a with a much larger/heavier rotating mass will be great.



Disconnect the neutral from the back of the ground stud. I stick a piece of heatshrink tube over the terminal and zip tie it up to the other main leads.

If you have a cabin or some such with no power service to it you leave it on. On a regular dwelling with commercial power, the neutral is already bonded.

 

[Isaac-1]

You will likely need to use a switched neutral transfer switch for at least one house

 

[Harleyd315]

I have 0ne MEP 003 set up to run my house and my garage. Both bldgs have an interlok kit installed and are hard wired to an outside plug to hook up the cords. Always worked fine and only had one hiccup, the automatic garage door opener remote won't work on generator power. Once the grid was back up after Sandy it worked again, not sure of the reason. Before I had the 003 I had an 004 hooked up the same way, just a little big for the load. My cousin in Florida has an 005 hooked up to his house uses 2 legs for his house and lets the neighbor use the 3rd leg to keep his 110 appliances running. Never had a problem and they were without power for almost 2 weeks for one of the hurricanes that hit them a few years back.

 

[Triple Jim]

HD, are the capacitors still on your fuel pumps?

 

[1800 Diesel]

Ike,

Would that be something unique to buy? Both houses will need their meter boxes replaced with one that can accept a transfer switch between the meter & the 240v main panel. Are most transfer switches set up for switching L0 & both 120v lines or just the two 120v lines? Also, I have found conflicting direction as to the proper method for connecting (or not) the generator earth ground to the house ground, which I believe is common to the neutral cable? I will be hiring a licensed electrician to do the installation but I would like to better understand the safety & code requirements.

Thanks,

Kevin

 

[1800 Diesel]

HD, are the capacitors still on your fuel pumps?

Jim,

I never removed the capacitors from the fuel pumps--if you're referring to the unit (our designation is unit #1 of the MEP-004A models being worked) that had the pumps running when they weren't supposed to....today's question is related to a machine we haven't started working, but do know it'll have to be an ASK model. Have one in the wings but haven't started the basic maintenance & testing work.

Thanks,

Kevin

 

[1800 Diesel]

Thanks Harleyd325--at least I know I wasn't in left field or something...

 

[1800 Diesel]

....Disconnect the neutral from the back of the ground stud. I stick a piece of heatshrink tube over the terminal and zip tie it up to the other main leads.....

Can you elaborate on exactly what/why you're doing here? Are you saying you don't use the generator ground lug (not L0 but the frame ground lug)?

Thanks,

Kevin

 

[Harleyd315]

The radio suppression capacitors were removed on my 003 but not sure on the other units I had running during Sandy. My engine broke the oil shaft on my 003 and after that I was using an 005 and the FD's 003 which I'm not sure if the capacitors are still hooked up. Thinking maybe thats what interfered with the garage remote?

 

[Munchies]

Can you elaborate on exactly what/why you're doing here? Are you saying you don't use the generator ground lug (not L0 but the frame ground lug)?

Thanks,
Kevin

I use the ground lug , with a piece of solid copper ground wire, bent into shape, and up towards the output terminals. Neutral to L0 and either 120v leg to l1 and l3. I connect the ground I pull from the house via 6/4 SO cable to the solid copper ground which is ran to the ground lug with no neutral bond attached to the back of the lug. The point of this is that the neutral is already bonded in the panel on the house. In the "mep 003 hookup' thread the NEC code is mentioned and the terminology used is "seperatley derived system" ie the power coming in is seperate from the grid.
I am doing this because I am not breaking the neutral from the utility. I am backfeeding through a large breaker and shutting my main breaker off.
MOST transfer switches do not break neutral and it is the same story.

Gimmie a call. I can talk better than I can type.

"Separately Derived Systems. Separately derived systems, which are required to be grounded by 250.20(A) or (B), must be grounded in accordance with the requirements of 250.30.
Author’s Comment: A separately derived system is a premises wiring system that derives its power from a generator, and that has no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system. See Article 100 definition for separately derived system.
FPN 1: A generator is not a separately derived system if the neutral is solidly interconnected to the service neutral (transfer switch does not open the neutral). Under this condition, a neutral-to-ground connection must not be made at the generator or at the generator disconnect.
"

 

[Munchies]

In addendum to that...

Isaac brings up a good point.

Would it be a problem if both homes neutrals were not broken? I am not sure. Might be best to set one up so that it does break neutral and that it is more of a 'dumb load' added on

 

[Triple Jim]

Thinking maybe thats what interfered with the garage remote?

Exactly. It's possible the fuel pump contacts made enough RF noise to drown out the remote's signal.

 

[1800 Diesel]

In addendum to that...

Isaac brings up a good point.

Would it be a problem if both homes neutrals were not broken? I am not sure. Might be best to set one up so that it does break neutral and that it is more of a 'dumb load' added on

I just pulled the transfer switch I plan to use on my MEP-004A at our home in the panhandle and noticed it only breaks the the two load lines, not the neutral. It's a 100 amp Ronk Meter-Rite. Is that going to be a problem?

 

[Munchies]

No. Thats perfectly normal. For a large.. a very large percentage of installs that is how it will be.

The military sets are made to be setup as a separately derived system.

Ie. Hook into a distribution box, and run it to various tents and buildings as the sole source of power. You are setting up yours as a backup generator, NOT as the sole source of power and the neutral bonding is already done. Disco the neutral, tape it and zip tie it up, pull your ground all the way to the set and tie it into the main ground lug down below.

 

[Munchies]

As far as the two neutral ties to the grid on your BIL's situation. I bet sewerzuk can answer that. Wheres the bat signal?

 

[1800 Diesel]

No. Thats perfectly normal. For a large.. a very large percentage of installs that is how it will be.

The military sets are made to be setup as a separately derived system.

Ie. Hook into a distribution box, and run it to various tents and buildings as the sole source of power. You are setting up yours as a backup generator, NOT as the sole source of power and the neutral bonding is already done. Disco the neutral, tape it and zip tie it up, pull your ground all the way to the set and tie it into the main ground lug down below.

So you're saying we shouldn't even use L0 and only connect the generator frame ground to the house earth ground & then run L1 & L3 from generator to transfer switch? Why wouldn't L0 still run to the house circuit's neutral? Or am I mis-interpreting what you're saying? Without L0 it seems like there would be no return path. BTW, tried to call earlier.

Edit--We had planned to wire things up similar to the 2nd image on this site: http://www.imsasafety.org/journal/ma03/ma5.htm

Only difference is we won't have the disconnect switch between the generator & the transfer switch...(unless you call the main load contactor a "disconnect"...

 

[Munchies]

No no ..

Neutral still runs to L0. Thats a must. You run 4 lines from the house. Two lines of 120 on L1 and L3. Neutral on L0. Ground To the ground stud. Remove 1/2'' nut from backside of ground stud. Should be 3 wires there.(thats for an 002/003. on a 004-007 it will be the same but the lead goes up and over towards the re connection board) The smallest there should be the lead going into the re connection box. Remove this, insulate it and tie it up. That is the bond between neutral and ground. You are not breaking neutral in your transfer switch so you are good to go. Thats how a backup generator on a typical transfer switch is wired.

 

[1800 Diesel]

No no ..

Neutral still runs to L0. Thats a must. You run 4 lines from the house. Two lines of 120 on L1 and L3. Neutral on L0. Ground To the ground stud. Remove 1/2'' nut from backside of ground stud. Should be 3 wires there.(thats for an 002/003. on a 004-007 it will be the same but the lead goes up and over towards the re connection board) The smallest there should be the lead going into the re connection box. Remove this, insulate it and tie it up. That is the bond between neutral and ground. You are not breaking neutral in your transfer switch so you are good to go. Thats how a backup generator on a typical transfer switch is wired.

Got it...we're not ready to do the hook-up yet but just trying to get things straight in my mind. Still working on an MEP-003A for a friend at work & an MEP-004A for my brother and an MEP-002A for a another fellow....and then I can start working on the MEP-004AAS for my other brother. So it'll be a few months before we'll be doing the actual installations...thanks for the clarification....

 

[Isaac-1]

Sorry about being slow getting back to this thread, but my day started in Seattle today, and now I am back home in Louisiana, not really awake enough to type anything at the moment though, will try to post back after I have slept some.

Ike