MEP 804B 805B Unbalanced Load

[Louis9113]

Hi!
First post! Is it necessary to balance these gensets if only running it for 1-3 days at a time for home backup? If so, what can you run to try and balance the L2 on them? A couple high wattage halogen 120v bulbs? I could move some household 120v things around to draw some of the L2 if I had to.

what do others use to balance their 804/805 when using it for a standby home generator?

How much generator do I need to run a 2.5 and 3 ton AC units? All electric home. I’m in Louisiana and hurricane season last year was brutal! Thanks in advance!

 

[Scoobyshep]

Balanced, not so much (other than efficiency) no load on 1 leg, can cause damage over time. A few heaters or lamps can make a difference. Sometimes people use the third leg for a work shop.

For your loads you would need to take amp readings and inrush is a thing. Another thing to keep in mind is voltage. These units put out 120/208 volt. Most residential is 120/240. Do not adjust voltage up as the line to ground would get too high. Most home appliances that require 240 are useable at 208. Be sure to consult the nameplates.

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[nextalcupfan]

Taking pictures of your big electric consumer nameplates and posting them would allow us to help you the most.
But an 803a should be able to handle your whole house, unless you have a tankless hot water heater. (Those things can be monsters)
Electric strip heat would also be pretty brutal.

 

[Louis9113]

Outside/inside panels and plates on the outside AC condenser units(2.5 and 3 ton).

 

[nextalcupfan]

So your AC's total running power draw is 28.45 Amps, or 6,828 watts.
That's roughly 54.7% of the output of an 803a.

If possible could you get pictures of your water heater and furnace data plates?
You'll probably have 2 furnaces if you have 2 AC's.

 

[Louis9113]

I honestly don’t know how to read this from the units in the attic. I didn’t see a simple plate like the outside condenser. I am only concerned with the AC portion of the unit and NOT the heating elements. I can call my AC guy tomorrow and maybe he can help.

 

[nextalcupfan]

I also needed those for the blower motor amp draw, which in your case is 2.5 amps each. Problem is I can't quite tell if the motor is 240v or 120v.
For now let's assume the worst and it's 2.5a at 240v times 2 units - that's 1200 watts for your indoor blower motors.
We are up to 33.45A or 8,028 watts so far.

I'm curious why you're not worried about the strip heat? Depending on which heating kit is installed just one of those could max an 803a.
Your pictures are a bit blurry but I think I see 12kw heaters as an option.

All I really need now is the hot water heater, maybe the stove/oven if you want to be extra through.

We're only at 64% of an 803a so far, and please keep in mind I'm calculating the AC's at the absolute worst case scenario.
I have a 3 ton AC, it's tag said 15.2A total unit power draw.
This year after maintenance I actually measured it with an Amp clamp and got 8.1A power draw.
Though please keep in mind my unit has a slight size issue so the compressor is under less load than it should be.

 

[Scoobyshep]

The air handler is vague because it depends on the heat kit installed. The installer is supposed to mark one.

Dont forget, Inrush is a thing.

 

[nextalcupfan]

The air handler is vague because it depends on the heat kit installed. The installer is supposed to mark one.

Dont forget, Inrush is a thing.

As long as they both don't start at EXACTLY the same time inrush shouldn't be a problem.
Mine will start the AC just fine even if its already at 40% load.

 

[Scoobyshep]

As long as they both don't start at EXACTLY the same time inrush shouldn't be a problem.
Mine will start the AC just fine even if its already at 40% load.

Which commonly happens when power has been out all day and then the generator is started, at that point it falls under load management.

 

[DieselAddict]

Don't forget that unless you are below the balance point for your heatpump the heat strips aren't needed. They will come on during a defrost cycle to maintain comfort but that is all. The reason I mention this is its an easy thing to install an emergency power interrupt for the heat strips to prevent them from coming on when you are on generator power. That can be a lot simpler and better option instead of buying a lot bigger generator to accommodate a load yo may rarely have to support.

 

[Louis9113]

Anyone ever ran wire from generator through attic to their transfer switch? That legal?

Any data anywhere on time/hrs on running these before the unbalanced load becomes a problem? Thanks!

 

[DieselAddict]

Anyone ever ran wire from generator through attic to their transfer switch? That legal?

Any data anywhere on time/hrs on running these before the unbalanced load becomes a problem? Thanks!

Sure, it should be no problem to run the wiring in the attic assuming its rated properly and run correctly per code.

People make more out of unbalanced loads than is necessary sometimes. Like most things there are not hard and fast rules here that make the decisions for us. The best thing to do is balance loads the best you can and run. You aren't going to hurt the generator so long as you are under the "per phase" power limits.

Think about this too - a 803 is a 10kw generator running 120/240v loads. The 804 is a 10kw generator running 120/240v loads assuming you can't find some load to put on the unused phase. There is no real benefit to going with a 804 versus an 803 if you are going to use only 2 of the 3 phases of the 804.

This is my personal opinion - If you need more than 10-12kw of 120/240v power you will be better served with a single phase generator. Don't try to shoehorn a 3 phase generator into single phase service if you are looking to get nameplate out of the generator.

One wrinkle here is if you can find an older MEP004. Those CAN be converted to single phase.

 

[Coug]

Sure, it should be no problem to run the wiring in the attic assuming its rated properly and run correctly per code.

People make more out of unbalanced loads than is necessary sometimes. Like most things there are not hard and fast rules here that make the decisions for us. The best thing to do is balance loads the best you can and run. You aren't going to hurt the generator so long as you are under the "per phase" power limits.

Think about this too - a 803 is a 10kw generator running 120/240v loads. The 804 is a 10kw generator running 120/240v loads assuming you can't find some load to put on the unused phase. There is no real benefit to going with a 804 versus an 803 if you are going to use only 2 of the 3 phases of the 804.

This is my personal opinion - If you need more than 10-12kw of 120/240v power you will be better served with a single phase generator. Don't try to shoehorn a 3 phase generator into single phase service if you are looking to get nameplate out of the generator.

One wrinkle here is if you can find an older MEP004. Those CAN be converted to single phase.

The only reason I can see for buying the 804 over the 803 is because, being 3 phase only, the 804 usually has a cheaper price compared to the 803. That's the only reason I've ever really seen for people buying it over the 803 (provided they knew what they were doing)

 

[Scoobyshep]

Yes, my feed runs through my attic. As long as it is properly rated for the current and there is overcurrent protection rated for the wire at the generator side.


You can run unbalanced, it reduces fuel efficiency, its best to have some load on the unused leg (couple of flood lights or a heater would work)

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[SCSG-G4]

Anyone ever ran wire from generator through attic to their transfer switch? That legal?

Any data anywhere on time/hrs on running these before the unbalanced load becomes a problem? Thanks!

That is a long run, go to the next larger gauge wire to cut line loss. I got a great deal on some 1 ga. for the 35 foot run betweeen the MEP-003A and the main panel - cheaper than buying the correct size (4 ga.) and I have almost 20 feet of 'scrap'.

 

[Abrant23]

That is a long run, go to the next larger gauge wire to cut line loss. I got a great deal on some 1 ga. for the 35 foot run betweeen the MEP-003A and the main panel - cheaper than buying the correct size (4 ga.) and I have almost 20 feet of 'scrap'.

Aluminum 1ga? Cause 35’ isn’t a very long run at all, and 1 ga copper would be serious overkill for a 10kw genny!

 

[SCSG-G4]

1 ga copper! And at current scrap prices for copper I'll probably recoup what I paid by selling the excess 20 feet of black, red, blue and white (80 feet total). Overkill, yes, but not over budget!

 

[Abrant23]

1 ga copper! And at current scrap prices for copper I'll probably recoup what I paid by selling the excess 20 feet of black, red, blue and white (80 feet total). Overkill, yes, but not over budget!

Yeah, prices are outrageous for wire these days. I was going to locate my 10kw unit next to the new barn I’m building but it being a 330’ run I’m thinking of just putting it next to the house!

 

[Louis9113]

First, I want to thank everyone for being so helpful!

Is anyone running two central AC units on one 803A, if so what are their size/amps drawn, soft start kit needed, etc.? AC only, no heat, I’m in Louisiana. Thanks!