MEP 805B wired to split 400amp panels

[Tommytone]

I have an 805B we are working to get running and are planning out the connections to the house.

We have a split 400 amp set up with (2) 200 amp panels.

To use the 805B to the fullest it made sense to install a three phase 100 amp panel and feed the 200 amp panels from there. That would allow use of all 3 legs with one being used twice. The panels have manual lockouts preventing the main and generator breakers from being on at the same time.

My question is what, if any issues, could there be here. My only thought is that, since the panels are tied in the meter box, if ever the main and generator feed were both on you would have a short. The lockouts should prevent this.

Any thought?

 

[Evvy Fesler]

I have an 805B we are working to get running and are planning out the connections to the house.

We have a split 400 amp set up with (2) 200 amp panels.

To use the 805B to the fullest it made sense to install a three phase 100 amp panel and feed the 200 amp panels from there. That would allow use of all 3 legs with one being used twice. The panels have manual lockouts preventing the main and generator breakers from being on at the same time.

My question is what, if any issues, could there be here. My only thought is that, since the panels are tied in the meter box, if ever the main and generator feed were both on you would have a short. The lockouts should prevent this.

Any thought?

Feeding panels with large capacity from a panel with smaller capacity is a red flag for me. Can you sketch a diagram or take a couple of pictures? Both would be great. You can pencil the sketch and take a picture of it to make it easier.

 

[Scoobyshep]

If you are isolating the main breaker for each panel with an interlock there should be no problem. What can get you into some trouble is if the grounding and bonding is not done correctly, especially if for some reason you run 1 panel on generator and the other on utility.

You also need to be very careful with your loads since one phase will be shared between both panels.

and yes, Pictures or a sketch would be helpful.

 

[Tommytone]

If you are isolating the main breaker for each panel with an interlock there should be no problem. What can get you into some trouble is if the grounding and bonding is not done correctly, especially if for some reason you run 1 panel on generator and the other on utility.

You also need to be very careful with your loads since one phase will be shared between both panels.

and yes, Pictures or a sketch would be helpful.

I will draw one up.
The panels would need to be all utility or all generator no mix loading.
My other thought was on grounding, neutral and bonding. My plan was to use 5 pin pin and sleeve style cable to feed the fused outside disconnect which would allow the generator to be grounded/neutral through the house panel.

So the hots are switched but the grounds an neutral are not switched.

I will work on a drawing today.

 

[MDdeuce]

I'm planning on doing the same thing with a MEP-804B I got from GP in July. Super interested in community suggestions and details from your install.

 

[Tommytone]

Feeding panels with large capacity from a panel with smaller capacity is a red flag for me. Can you sketch a diagram or take a couple of pictures? Both would be great. You can pencil the sketch and take a picture of it to make it easier.

Here is a crude drawing. The mains are fed from the same meter can.

I am assuming the generator would not be bonded as the generator would pick up the bonding in the main panel. The panels are both bonded and I would assume you would run ground and neutral to/from each panel to the 3phase 100 amp panel.

The reason the 100 amp panel is smaller is that is what I understand the 805b can produce so no larger panel is needed to distribute the .
Both main panels have lockout manual generator connection so we would manage the load before turning on the generator. That would be accomplished by switching between two heat pumps, well, water heater and other large loads as needed.

 

[Evvy Fesler]

Here is a crude drawing. The mains are fed from the same meter can.

I am assuming the generator would not be bonded as the generator would pick up the bonding in the main panel. The panels are both bonded and I would assume you would run ground and neutral to/from each panel to the 3phase 100 amp panel.

The reason the 100 amp panel is smaller is that is what I understand the 805b can produce so no larger panel is needed to distribute the .
Both main panels have lockout manual generator connection so we would manage the load before turning on the generator. That would be accomplished by switching between two heat pumps, well, water heater and other large loads as needed.
View attachment 885035

Picture's worth 1,000 words! I'm happy with this. To make this better would you please mark it up with wire gauge and material (al or cu)? You should be using the 75-C column in the ampacity chart for NEC

 

[Tommytone]

Picture's worth 1,000 words! I'm happy with this. To make this better would you please mark it up with wire gauge and material (al or cu)? You should be using the 75-C column in the ampacity chart for NEC

Here is the markup with wire/cable specs.

 

[Evvy Fesler]

Here is the markup with wire/cable specs.View attachment 885048

Looking good! You've created a non-separately derived system because your neutral is not switched. In this situation you do not bond neutral to ground at the generator. To make your diagram perfect you might draw your grounding electrode, but this is a not on my part because I understand them to be at the 400-amp disconnect (not shown), right?

With all that's been said, please understand that none of us, especially me, is representing a qualified electrical opinion. A qualified electrical contractor should be engaged to verify compliance to local and national electrical code (NEC).

 

[Tommytone]

Looking good! You've created a non-separately derived system because your neutral is not switched. In this situation you do not bond neutral to ground at the generator. To make your diagram perfect you might draw your grounding electrode, but this is a not on my part because I understand them to be at the 400-amp disconnect (not shown), right?

With all that's been said, please understand that none of us, especially me, is representing a qualified electoral opinion. A qualified electrical contractor should be engaged to verify compliance to local and national electrical code (NEC).

Good point on finishing the drawing.
The ground is tied into the panels there is no 400 amp switch just a meter box. In the meter box (2) 4/0 200 amp services are run into one meter and tied together in front of the meter. On the output side/load of the meter they are split back into (2) sets of 4/0 aluminum service runs each terminating in its own panel. This is how our electric company engineers approve these most often I gather. So the only disconnect is a meter pull I guess.

Here is a modification showing the meter and feeds. The ground is via 1 ground wire attached to two grounding rods in series. I think they are 10 feet apart but that is from memory.

 

[Evvy Fesler]

Good point on finishing the drawing.
The ground is tied into the panels there is no 400 amp switch just a meter box. In the meter box (2) 4/0 200 amp services are run into one meter and tied together in front of the meter. On the output side/load of the meter they are split back into (2) sets of 4/0 aluminum service runs each terminating in its own panel. This is how our electric company engineers approve these most often I gather. So the only disconnect is a meter pull I guess.

Here is a modification showing the meter and feeds. The ground is via 1 ground wire attached to two grounding rods in series. I think they are 10 feet apart but that is from memory.View attachment 885063

Nice! Yes, there are a couple of ways that 400-amp services are divided up into 200-amp services. A 400-amp disconnect is used in some parts of the country. They often resemble Frankenstein switches! A meter pull is a valid way to service a system as long as there's a way to disconnect the load completely.

Grounding electrodes are supposed to be a minimum of 6' apart. Ten is better! The idea is to assume that soil resistivity is subpar and have a second electrode. It's safer and worth the $8-12 that they cost.

You did an excellent job laying it out from what I can see. Drawings are worth the effort. It'll serve you well.

 

[Tommytone]

I'm planning on doing the same thing with a MEP-804B I got from GP in July. Super interested in community suggestions and details from your install.

Are you going to hard wire it or have it portable? I am leaning heavily toward portable.

 

[MDdeuce]

Yes, I'm planning on going portable also. Mine came on a LTT and I can't see taking the trouble to unmount it, plus having the ability to take it places seems useful.

I'm going to run a length of type w cable to it and use pin and sleeve connectors on it. I'm going to use 5 conductor type w to pull earth ground from the service entry so I don't need to worry about grounding at the gen set. Non-separately derived source similar to how you are planning. Makes it a bit more expensive on cable and connectors but a more convenient hookup each time.

I'll also need to get an extra connector to make a harness to connect to the A427A.

I'll post the diagram I made up a few months ago when I get some time.

 

[MDdeuce]

Attached is the diagram I plan on using form my hookup.

When I load tested my MEP-804B I ran it to 120% with the clamp meter showing 55A per leg. I couldn't run it any higher without really dropping a 140% load on it since my A427A load bank's variable 3kw load does not work on the top end of its range (shorted windings it seems). I didn't want to do this as I thought dropping that high a load would be unkind to the gen set. Given this I'm not fully sure of the true max output current of the gen set. Without spending a ton of money the pin and sleeve convectors I could find were rated for 415V/63A, so I decided to fuse the output to 60A at the gen set. With this decision I selected lowest cost cable that exceeded a 60A rating. Went with 6/5 type W for the outdoor feeder rated at 2000V/69A, and 6AWG THHN for all the indoor wiring rated at 600V/75A. All cable is Cu.

The only really unconventional part is the house junction/breakout box where I need to separate from the 3P legs to "1P." I'm going to make a special purpose enclosure and use quad mechanical lug connectors rated for 2-14AWG Al/Cu wires to split the legs to the appropriate transfer switches.

Since I'm running ground in the type W, I'm going to unbond the N and GND at the generator (which I believe is accomplished via the bonding bar in the at the male service terminals?), this way I only have a single N-GND bound at the panels and don't need to worry about grounding at the gen set itself. However when I load test, I will need to re-connect the gen set N-GND bond and run a ground rod.

Currently all that is installed are the transfer switches (installed by electrician during construction). I ran this plan past my electrician while we were building the house, he said 'unconventional, but will work'.

 

[Evvy Fesler]

Attached is the diagram I plan on using form my hookup.

When I load tested my MEP-804B I ran it to 120% with the clamp meter showing 55A per leg. I couldn't run it any higher without really dropping a 140% load on it since my A427A load bank's variable 3kw load does not work on the top end of its range (shorted windings it seems). I didn't want to do this as I thought dropping that high a load would be unkind to the gen set. Given this I'm not fully sure of the true max output current of the gen set. Without spending a ton of money the pin and sleeve convectors I could find were rated for 415V/63A, so I decided to fuse the output to 60A at the gen set. With this decision I selected lowest cost cable that exceeded a 60A rating. Went with 6/5 type W for the outdoor feeder rated at 2000V/69A, and 6AWG THHN for all the indoor wiring rated at 600V/75A. All cable is Cu.

The only really unconventional part is the house junction/breakout box where I need to separate from the 3P legs to "1P." I'm going to make a special purpose enclosure and use quad mechanical lug connectors rated for 2-14AWG Al/Cu wires to split the legs to the appropriate transfer switches.

Since I'm running ground in the type W, I'm going to unbond the N and GND at the generator (which I believe is accomplished via the bonding bar in the at the male service terminals?), this way I only have a single N-GND bound at the panels and don't need to worry about grounding at the gen set itself. However when I load test, I will need to re-connect the gen set N-GND bond and run a ground rod.

Currently all that is installed are the transfer switches (installed by electrician during construction). I ran this plan past my electrician while we were building the house, he said 'unconventional, but will work'.

I can’t comment on connectors.

Yes, the bonding strap is the one that you describe. Bond means to connect.

You both need to ground your trailers. There’s a bolt on it somewhere for this purpose. Also, there should be a wire that runs from the bolt to the GND terminal. I believe it’s behind the terminal board. The notion here is that the electrical grounding connection from the generator cabinet/skid to trailer frame can’t be guaranteed. Probably because of the paint. Who knows? It’s a length of wire, right? Cheap money traded for safety. Inspect it to make sure it’s not broken.

You two are doing a good job. Very happy to see those diagrams. Thinking on paper is way cheaper than an awe crap. Oops! Forum rules????

🫢

 

[Evvy Fesler]

As always, electrical work for much less complexity requires permits and implementation by a qualified electrical contractor. Some levels of complexity requires that a licensed engineer provide oversight. I’m neither electrician nor licensed engineer. Proceed at your own risk.

 

[MDdeuce]

I'll have to verify the trailer ground. I figured this was accomplished through the trailer/skid bolts. But I guess the thick CARC paint will inhibit that since both were painted and then assembled. I'll have to check the TM diagrams on where the wire should be located.

 

[loosegravel]

Cool conversation. I was wondering though. Since your supplying power to (2) different 200-amp service panels with this MEP-804A, you have the "potential" to overload one or more of the L1, L2 or L3 legs of the generator. Sure, the generator is "supposed" to protect itself by shutting down for over-current, but do we really want to test this? Assuming here that you'll be relying on the "manual" selection of the circuits on each of the (2) 200-amp service panels that you'll be feeding by turning off the circuits not being used. I'm not an electrician, but I believe that they look very closely at the "potential" for something to go wrong when they inspect.

 

[Tommytone]

Yes, I'm planning on going portable also. Mine came on a LTT and I can't see taking the trouble to unmount it, plus having the ability to take it places seems useful.

I'm going to run a length of type w cable to it and use pin and sleeve connectors on it. I'm going to use 5 conductor type w to pull earth ground from the service entry so I don't need to worry about grounding at the gen set. Non-separately derived source similar to how you are planning. Makes it a bit more expensive on cable and connectors but a more convenient hookup each time.

I'll also need to get an extra connector to make a harness to connect to the A427A.

I'll post the diagram I made up a few months ago when I get some time.

We are on the same page. Mine is trailer mounted and keeping it mobile was my thought. I have ordered 5100p9w for the cord and 5100r9w for the generator and house plus one for the barn to do monthly’s and run 3ph equipment at times. Is that in line with your approach?

 

[Tommytone]

Attached is the diagram I plan on using form my hookup.

When I load tested my MEP-804B I ran it to 120% with the clamp meter showing 55A per leg. I couldn't run it any higher without really dropping a 140% load on it since my A427A load bank's variable 3kw load does not work on the top end of its range (shorted windings it seems). I didn't want to do this as I thought dropping that high a load would be unkind to the gen set. Given this I'm not fully sure of the true max output current of the gen set. Without spending a ton of money the pin and sleeve convectors I could find were rated for 415V/63A, so I decided to fuse the output to 60A at the gen set. With this decision I selected lowest cost cable that exceeded a 60A rating. Went with 6/5 type W for the outdoor feeder rated at 2000V/69A, and 6AWG THHN for all the indoor wiring rated at 600V/75A. All cable is Cu.

The only really unconventional part is the house junction/breakout box where I need to separate from the 3P legs to "1P." I'm going to make a special purpose enclosure and use quad mechanical lug connectors rated for 2-14AWG Al/Cu wires to split the legs to the appropriate transfer switches.

Since I'm running ground in the type W, I'm going to unbond the N and GND at the generator (which I believe is accomplished via the bonding bar in the at the male service terminals?), this way I only have a single N-GND bound at the panels and don't need to worry about grounding at the gen set itself. However when I load test, I will need to re-connect the gen set N-GND bond and run a ground rod.

Currently all that is installed are the transfer switches (installed by electrician during construction). I ran this plan past my electrician while we were building the house, he said 'unconventional, but will work'.

On breaking out the 3ph into two 1ph I was planning on using a 100 amp 3ph panel with a main 100 amp disconnect and 1ph breaker to feed each panel. Placed side by side in the panel that should pull L1 and L2 for one breaker and L3 and L1 for the second.

Does anyone know if any leg on these generators is “weaker”. I seem to recall someone saying when you increase power the voltage you watch the hottest leg but I could be remembering that wrong.