Safest way to uses a MEP 804b as a backup generator

jarmagno · Jan 21, 2018

This is my first post on a forum....
What is the safest way to use a MEP 804b as a whole house generator? I have seen the Generlink transfer switches, which allow the main panel to remain as is, but they don't work with 3 phase generators. What are people using?
Joe

DieselAddict · Jan 21, 2018

The safest way is to use a double ended transfer switch. That makes sure you can't export power to the grid while you are on generator power.

Since the 804 is a 3 phase only generator you'll be limited to 2/3rds capacity max.

Light in the Dark · Jan 22, 2018

How do you think over time the machine will take an unbalanced load like that?

DieselAddict · Jan 22, 2018

That has been discussed a number of times. The short version is - If you are doing backup emergency power don't worry about it. You aren't going to run the unit long enough to matter.

BUT - If you are off grid its not the right generator for the job. BUT BUT if you are off grid why not wire your setup for 3 phase, then its the right generator.

kloppk · Jan 22, 2018

You'll only get 208 volts instead of 240 volts across the two phases used.
Not sure if any of your 240 loads will care.

DieselAddict · Jan 22, 2018

kloppk said:
Also you'll only get 208 volts instead of 240 volts across the two phases used.

True and this also will not matter for virtually any modern appliance.

Guyfang · Jan 22, 2018

Chris, could not have said it better. The world will NOT end if you run an unbalanced load for a week or two, or even longer. All year long? then get the house set up for 3 phase power and be done with it.

Light in the Dark · Jan 22, 2018

Good point on the duration of run. I have stayed away from the 804s because I didn't see much value to the homeowner/small business segment (all single phase requirement). Maybe I should reconsider, with the caveat known.

Suprman · Jan 22, 2018

I have seen it done and it does work. But you only have around 2/3 capacity of the generator. So you are back to running a 10k basically, just with a higher fuel draw.

Chainbreaker · Jan 22, 2018

deleted: oops, wrong model answer.

Guyfang · Jan 22, 2018

Suprman said:
I have seen it done and it does work. But you only have around 2/3 capacity of the generator. So you are back to running a 10k basically, just with a higher fuel draw.

It would be interesting, when you have a 3 phase setup. Or a house, barn, shop and that kind of thing.

Triple Jim · Jan 22, 2018

It's possible to use one or more transformers to convert from three phase to single phase. You can find a lot of information about it with a search for "three phase to single phase transformer" or something similar.

But I would think that the 804 would be more than adequate for a whole house when using only 2/3 of it, unless you have a lot of electric heating requirements.

98G · Jan 22, 2018

Triple Jim said:
It's possible to use one or more transformers to convert from three phase to single phase. You can find a lot of information about it with a search for "three phase to single phase transformer" or something similar.

But I would think that the 804 would be more than adequate for a whole house when using only 2/3 of it, unless you have a lot of electric heating requirements.

The phase converters cost almost as much as the generator.

Agreed that 2/3 of an MEP804 is plenty for a house. The difference in fuel consumption compared to an 803 is the issue. For occasional use, I don't think it is a big deal.

CMPPhil · Jan 22, 2018

Hi

Question, will 220 volt motors be happy running on 2 legs of 3 phase? I'm thinking of well pumps.

Cheers Phil

155mm · Jan 22, 2018

DieselAddict said:
The safest way is to use a double ended transfer switch. That makes sure you can't export power to the grid while you are on generator power.

Since the 804 is a 3 phase only generator you'll be limited to 2/3rds capacity max.

This is the switch Chris was refering to, you can see the load (house) is the center poles, the bottom post (power company), top posts (generator). With this switch there is no way to get power from the genny to line, unless there is major ground issues.

If you have not read this thread, would be good reading.

https://www.steelsoldiers.com/showthread.php?167498-Wife-is-now-a-green-iron-believer/page2

Also grounding grounding grounding, proper grounding is something that I have seen alot of times overlooked, dont know, or just lazy. Grounding is the safety that keeps the angry pixies from going thru you to the ground if something goes wrong.

155mm · Jan 22, 2018

CMPPhil said:
Hi

Question, will 220 volt motors be happy running on 2 legs of 3 phase? I'm thinking of well pumps.

Cheers Phil

I have had no issues running 208 to a 240v water well, BUT it is a gamble. Our water well repair shop says the well motors are rated 240 +/- 10% for warranty issues, so 208 is outside the 10% but just a little bit for warranty. How would warranty know the difference between a brown out and 208 from a genny? unknown, except for honesty.

Light in the Dark · Jan 22, 2018

Yeah most devices unless specifically listing auto switching voltage (100-240 (50/60hz) are only good for a +/-10% swing.

Triple Jim · Jan 22, 2018

You can check with the well pump manufacturer. My guess is that most pumps are rated for 208-240 volts.

LEOK · Jan 29, 2019

Since this is turbo unit It will be interesting to see, let's say the average load works out at 7k will there really be a big difference?

98G said:
The phase converters cost almost as much as the generator.

Agreed that 2/3 of an MEP804 is plenty for a house. The difference in fuel consumption compared to an 803 is the issue. For occasional use, I don't think it is a big deal.

Safest way to uses a MEP 804b as a backup generator

More options

jarmagno

New member

DieselAddict

Well-known member

Light in the Dark

Well-known member

DieselAddict

Well-known member

kloppk

Well-known member

DieselAddict

Well-known member

Guyfang

Moderator

Light in the Dark

Well-known member

Suprman

Well-known member

Chainbreaker

Well-known member

Guyfang

Moderator

Triple Jim

Well-known member

98G

Former SSG

CMPPhil

Well-known member

155mm

Chief and Indian

155mm

Chief and Indian

Light in the Dark

Well-known member

Triple Jim

Well-known member

LEOK

Active member