MEP-804B Single Phase Use Questions

[CallMeColt]

Everyone,

I thought I had it figured out, but I am second guessing myself and I am supposed to go pick the generator up tomorrow.

My goal is to use this for backup power at the two houses on my property. They are on separate panels of 240v but on the same meter.

I understand that the MEP-804B is ONLY 3 phase, but it can be run in 3 legs of 240v single phase is set correctly. That way, I can spread those loads out unlike some others that only have a single 240v lead going into their house. For example, using the attached chart from the TM below, using L1 and L0 (N) is single phase 240v.



Where I am a bit confused is I have read people are using these for home backup, but at reduced output due to not being able to utilize all the phases. But, maybe it's because I have been looking for hours on my phone, then a few more hours on the computer and my brain is fried, but, if using my L1 and L0 (N) example above, wouldn't this be a single wire with 240v when usually you have 2 wires of 120v making 240v to make power coming into a residential home panel.

Or am I just thinking to literally, and you would wire as you would with regular 240v single phase, say with L1 and L2, then L0 (N) is your neutral? All the legs in this setting are 120v, become 240v single phase when put together with a ground, and then 416v 3 phase when all 3 are hooked up to a 3 phase motor for example? And the TM is assuming you have the basic knowledge of this as it does when it comes to other things in TM's?

Here is a picture of the MEP-804B output lugs just for reference as well that I pulled from another members post.

 

[DieselAddict]

Yea, you would set it up at 208v then use any 2 load phases such as L1 and L2 along with L0 for neutral plus GROUND to your backup power input. That will get you ~10kw.

The remaining L3 terminal can be used with L0 for some ancillary 120v loads. Stuff like garage fridges/freezers and such.

 

[CallMeColt]

Yea, you would set it up at 208v then use any 2 load phases such as L1 and L2 along with L0 for neutral plus GROUND to your backup power input. That will get you ~10kw.

The remaining L3 terminal can be used with L0 for some ancillary 120v loads. Stuff like garage fridges/freezers and such.

I didn't mention ground for simplicity but of course, yes, grounding wires are a MUST. I do sound a but dumb with these question but I promise I'm not that dumb, haha.

So, I would NOT use it in 240/416 mode, I would use it in 120/208v mode? But then I may have the issue of running 208v to motors that I'm not sure will like it. I have no data on my well motor because it is old. I should have mentioned this was a worry of mine as well.

 

[nextalcupfan]

The problem is those modes are fundamentally different.
First of all it's a problem with what we call 240v here in north America. We call it single phase when it's technically split phase.
240v is actually 2 single 120v phases either 120 or 180 degrees out of phase with each other.
Setting the unit in 240/416 mode and hooking up one phase to a house will NOT work.

After all your house needs 2 120v phases. If you hook 1 240 to one side then you'll have all your 120v circuits on one side of the panel getting 240v and everything on the other side getting nothing.

You may want to look into a 3 phase to single phase transformer. That way you can use pretty much all the output of the generator and probably have a less complicated wiring setup.

 

[CallMeColt]

The problem is those modes are fundamentally different.
First of all it's a problem with what we call 240v here in north America. We call it single phase when it's technically split phase.
240v is actually 2 single 120v phases either 120 or 180 degrees out of phase with each other.
Setting the unit in 240/416 mode and hooking up one phase to a house will NOT work.

After all your house needs 2 120v phases. If you hook 1 240 to one side then you'll have all your 120v circuits on one side of the panel getting 240v and everything on the other side getting nothing.

You may want to look into a 3 phase to single phase transformer. That way you can use pretty much all the output of the generator and probably have a less complicated wiring setup.

This was the simple explanation I needed. I learned something important today, thank you! This makes TOTAL sense to me now. Never fully understood by 240v had 2 wires in some cases but not in others.

A transformer would be nice but I'm on a budget.

 

[nextalcupfan]

This was the simple explanation I needed. I learned something important today, thank you! This makes TOTAL sense to me now. Never fully understood by 240v had 2 wires in some cases but not in others.

A transformer would be nice but I'm on a budget.

No problem, the same thing happened to me 4 years ago when I got into this.
I ended up in a 3 hour conversation over Discord with an electrician from New Zealand trying to figure out how "single phase" 240 works.

And I totally understand the budget thing, I hear a transformer could be pretty pricey to handle 30kw.
Though whenever I tried to look one up they never seem to list the price.
I guess it's the old saying "If you have to ask you can't afford it".

 

[DieselAddict]

I didn't mention ground for simplicity but of course, yes, grounding wires are a MUST. I do sound a but dumb with these question but I promise I'm not that dumb, haha.

So, I would NOT use it in 240/416 mode, I would use it in 120/208v mode? But then I may have the issue of running 208v to motors that I'm not sure will like it. I have no data on my well motor because it is old. I should have mentioned this was a worry of mine as well.

For sure not 416v mode. That would be bad.

208v isn't normally an issue for residential 240v appliances. Take a look at the nameplate for the stuff and it will likely list 208v as one of the options.

 

[nextalcupfan]

But then I may have the issue of running 208v to motors that I'm not sure will like it. I have no data on my well motor because it is old. I should have mentioned this was a worry of mine as well.

I don't think this will actually matter too much. People in the forum mention this all the time but I don't recall it ever actually being a problem.
The vast majority of motors will be rated for 208/240v.

Personally I would very slightly bump the voltage until one of the legs was as 124v or so. That should put your 208 around 210.

What you DON'T want to do is bump it up until your 208 is at 240. While your motors may be happier now all of your 120v stuff is screaming at you because it's probably at 145v.
Also the if you get a slight hiccup in your voltage the unit will trip on over voltage protection because you're basically running on the redline.


P.S. I just thought of something, I'm pretty sure the voltage regulator only monitors one leg for droop/surge so you probably want to include that one in your hook up.
Unless you don't want the voltage regulator to compensate for load droop.
On the 802/803 series it monitors L3 if I'm not mistaken.

 

[CallMeColt]

No problem, the same thing happened to me 4 years ago when I got into this.
I ended up in a 3 hour conversation over Discord with an electrician from New Zealand trying to figure out how "single phase" 240 works.

And I totally understand the budget thing, I hear a transformer could be pretty pricey to handle 30kw.
Though whenever I tried to look one up they never seem to list the price.
I guess it's the old saying "If you have to ask you can't afford it".

I just went and looked up some transformers. It isn't as bad as I expected for a 50 amp rated one. I'd need to do two of them as I'd split the load across all three legs.

Here is a 50 amp;
https://www.larsonelectronics.com/p...v-primary-240v-secondary-at-46-8-amps-50-60hz

Basically, before my transfer switch, put the electrical to each houses panel going through one of these. This brings the power to 240v from 208v on each leg. If the power flutters at all from the generator, I think these clean it up as well.

Hmmm, this adds some cost to make it what I will need but it will be correct.

 

[CallMeColt]

For sure not 416v mode. That would be bad.

208v isn't normally an issue for residential 240v appliances. Take a look at the nameplate for the stuff and it will likely list 208v as one of the options.

I would, but I have no data on my well motor. I have the original make/model, but the company was purchased 5 times and the data has since been lost. I do water/wastewater and usually can track that stuff down. Company that took over ultimately only kept old data for 5 years. So I don't know for sure and it is working great now. And don't want to pull a 400ft deep well motor. Especially with the cost of replacements right now... IF you can get them.

 

[DieselAddict]

+1 on not adjusting the voltage up to get closer to 240v.

Correct that L3 is the feedback for the VR on the 802/803.

 

[DieselAddict]

I would, but I have no data on my well motor. I have the original make/model, but the company was purchased 5 times and the data has since been lost. I do water/wastewater and usually can track that stuff down. Company that took over ultimately only kept old data for 5 years. So I don't know for sure and it is working great now. And don't want to pull a 400ft deep well motor. Especially with the cost of replacements right now... IF you can get them.

If its a Grundfos pump then its fine.

 

[G744]

240/416 is an old designation. It should be adjustable to 277/480V via the regulator knob. Why Uncle Sam stuck with that I just can't understand.

Kinda like 110/220V stuff...It doesn't exist in any US distribution system today. Well, maybe where Deliverance was filmed...

Going from 3ph to 1ph via either Scott or le Blanc connected transformers will work, but the overall efficiency will suffer.

If you are going to commit to a permanent 3ph generator install, I'd investigate a good switching system allowing load balancing using all 3 legs. L to L 240V demands will be fine on 208V, and L to N will be 120 already.

This way you use the power your genset makes with good efficiency.

Of course, having most all motors as 3ph units is the best deal: wells, pumps, HVAC units, eTc.

DG

 

[Scoobyshep]

240/416 is an old designation. It should be adjustable to 277/480V via the regulator knob. Why Uncle Sam stuck with that I just can't understand.

Kinda like 110/220V stuff...It doesn't exist in any US distribution system today. Well, maybe where Deliverance was filmed...

Going from 3ph to 1ph via either Scott or le Blanc connected transformers will work, but the overall efficiency will suffer.

If you are going to commit to a permanent 3ph generator install, I'd investigate a good switching system allowing load balancing using all 3 legs. L to L 240V demands will be fine on 208V, and L to N will be 120 already.

This way you use the power your genset makes with good efficiency.

Of course, having most all motors as 3ph units is the best deal: wells, pumps, HVAC units, eTc.

DG

416 is more of an overseas thing. As to why the Mil stuck with them, I cant give a solid answer

 

[Scoobyshep]

Another thing is how you hook this up. depending on your connection changes how your bond (connection between ground and neutral) must be setup.

Before I go into a huge post about the differences and rules of grounding and bonding, How are you hooking up to your service?



And yes typically appliances work fine on 208 (though heating takes longer)

 

[CallMeColt]

Another thing is how you hook this up. depending on your connection changes how your bond (connection between ground and neutral) must be setup.

Before I go into a huge post about the differences and rules of grounding and bonding, How are you hooking up to your service?



And yes typically appliances work fine on 208 (though heating takes longer)

I understand all about the neutral bonding and how it needs to only be in one place. I'd be hooking up through my two houses main panels, so the neutral bond and grounding will be taken care of already at the panel.

Side note; on my MEP-802A, I put a protected switch to quickly make the bond on the generator depending how you are running it.

 

[CallMeColt]

Everyone,

Thank you for the input everyone. I decided to not go get it, even though it was a REALLY good deal. I don't want to take the chance with 208v. It would probably be okay, but at times I run for a day or so on generator power to put a good load on and keep load off the grid on peak days, while running my watering system to irrigate everything. Don't want to risk heat buildup in my pumps when it's easily over 100 deg daily here. I'm probably being over picky but that is what I do!

I'm going to just keep a look out for an MEP-803A as I already have a lot of experience with the MEP-802A, spare parts, filters, and all that. Or, since they seem to be way more abundant, maybe I will just run multiple MEP-802A around the property. Seems simpler for a simple guy. That way I can just keep them on trailers as well.

As always, I learned a lot here. I hope this thread down the road helps others as well!

 

[peapvp]

416 is more of an overseas thing. As to why the Mil stuck with them, I cant give a solid answer

NATO 3 Phase 380VAC 50Hz

 

[Scoobyshep]

NATO 3 Phase 380VAC 50Hz

Yes.

not to mention all the other "standard" voltages of the world. Kinda makes you wonder why they picked their areas power back in the day.

 

[G744]

Years ago in North America, 4160 was a popular distribution voltage, easily divided by a 10:1 ratio to 416.

It sees use only in non-upgraded facilities here.