Balancing load between phases

[m16ty]

I'm working on getting my MEP 003 up and going and will at some point have it hooked up to my house and/or shop. I know the TM says to keep the load balanced with no more than 5% difference from one phase to the other.

When you hook it up to your house panel, how to you keep the 120v loads balanced? Do you need to install some sort of ammeter on each phase to tell how much you are pulling off of each of them?

 

[Isaac-1]

I personally think this is the military being too picky in their manual, given most higher quality commercial generators in this size range are designed to tolerate 20-30% out of balance loads. Given the overall robust over built nature of these MEP generators, I suspect they would tolerate even more out of balanced loads than their commercial cousins. The big thing being that no single leg of the load exceeds capacity of that winding.

In other words I would not worry about a MEP-003a set for 120/240 single phase pulling 2,500 watts of 120V load off one leg and 5,000 watts off the other 120V leg, but I would worry about trying to pull 2,500 watts off one leg and 7,500 off the other

Ike

p.s. the 5% load balancing makes a lot more sense on BIG multi hundred KW generator than it does on anything any of us are likely to own.

 

[johnray13]

And, most or your large loads are 240v (oven/range, dryer, ac, well pump, etc) anyway so they are inherently balanced.

 

[rosco]

Its my understanding that the commercial meter on your house reads the leg that is pulling the most currant, so if your much out of balance on your house system, you might not be getting all that your paying for. In that sense, then it would be meaningful, to have your house as closely balanced as possible. That would be reflected to, back to your MEP. The easyest way to I know to do that is with a clamp-meter. Measure your incomming legs to your breaker box, and you can even note the draw on each breaker. If out of balance, switch the breakers around on the panel, till you get it as close to balanced as possible. Usually, every other breaker slot in a row, pulls from alternate legs w/130V. Once you have a clamp-meter, you will find it indespensible. My 375 Fluke also measures C currant.

 

[rosco]

"My 375 Fluke also measures DC currant." Good around MV's. It will even measure the draw of small DC lights.

 

[m16ty]

I've got some old factory equipment electrical cabinets (I was going to strip them and use them for storage cabinets). They have in them current meters. It appears the meter works like one of those clamp on multimeters, the pickup is what appears to be a coil and the wire it's reading passes through it. When I wire my house to hook up the generator, I may use these to mount on each leg to monitor current draw.

Rosco, That's interesting about the electric meter. I wired my house with no regard to load balance. If my wires are long enough in my panel I may change some breakers around to try and balance better.

That's also good to hear about the Fluke 375. I've got a Klein clamp on meter but it won't do DC current. I've actually never seen a clamp on meter that would do DC. I'll have to check out the Fluke.

 

[Isaac-1]

DC clamp meters are handy to have, but don't work very good on small DC currents. Mine is a Fluke 337a which is about 5 years old and is the predecessor to the new 370 series.