How much is too little?

[Wishlist]

I hooked up my Mep003a to the house the other day and ran the AC, lights (most house lights are LED's), oven, and well on and off my son was playing with the hose and I was running at about 25% give or take. With the AC and oven off I was only at 1-5% load. My question is what is considered to little of a load to keep the Mep003a running? I see you are not supposed to run at an idle, but will a small load on the generator hurt the unit as well?

 

[Isaac-1]

You may run into an issue of carbon build up and perhaps some wet stacking if this is constant for days on end, and it never gets up to rated load, but the truth is these small air cooled diesel can tolerate light loads much better than larger water cooled diesel can.

Ike

 

[Chainbreaker]

I think there are 3 things to be concerned with:

1. Low RPM's - Keeping the unit running at or slightly above 60 Hz (1800 RPM) (61.5 Hz warmed up with no load to allow for full load droop)
2. Load Balancing - Keeping the loads balanced as much as possible when running hard. You don't want to end up with lets say a 5% load on one leg and 90% load on another leg of the 120V output. My understanding is that you can overheat the generator head windings when loads are severely unbalanced. Hopefully your electrical panel has the loads distributed fairly well for emergency generator power. If not, you need to manage by using breaker management.
3. Potential wet stacking - long runs with low to no load could lead to wet stacking and possibly fouled injectors. Less of an issue with air cooled MEP-002/003 but you should exercise it fairly hard during periodic test cycles and run it long enough to ensure the oil is hot enough to burn off any moisture.

For my periodic test runs I run a 240V 5600 Watt clothes dryer for an hour which gives me a nice balanced load, a fully heat cycled engine plus dry clothes to boot!

 

[ke5eua]

We never ran our generators below 25% to prevent wet stacking. In the event we did run a light load on them I would crank on the 4 400 Hz generators, 2 christie power units for about 30 mins. Talk about cleaning out the system.

 

[rustystud]

We never ran our generators below 25% to prevent wet stacking. In the event we did run a light load on them I would crank on the 4 400 Hz generators, 2 christie power units for about 30 mins. Talk about cleaning out the system.

I agree, don't run under 25%. I had my MEP-003A running for 2 days last year. The second day it was under 25% and it started to wetstack ! You can see the fuel dripping out of the exhaust ! I had to turn on all the appliances and lights and the well pumps to help burn it out.

 

[Wishlist]

I think there are 3 things to be concerned with:

1. Low RPM's - Keeping the unit running at or slightly above 60 Hz (1800 RPM) (61.5 Hz warmed up with no load to allow for full load droop)
2. Load Balancing - Keeping the loads balanced as much as possible when running hard. You don't want to end up with lets say a 5% load on one leg and 90% load on another leg of the 120V output. My understanding is that you can overheat the generator head windings when loads are severely unbalanced. Hopefully your electrical panel has the loads distributed fairly well for emergency generator power. If not, you need to manage by using breaker management.
3. Potential wet stacking - long runs with low to no load could lead to wet stacking and possibly fouled injectors. Less of an issue with air cooled MEP-002/003 but you should exercise it fairly hard during periodic test cycles and run it long enough to ensure the oil is hot enough to burn off any moisture.

For my periodic test runs I run a 240V 5600 Watt clothes dryer for an hour which gives me a nice balanced load, a fully heat cycled engine plus dry clothes to boot!

Great advice, I did not notice any wet stacking, but on the other hand I only ran the generator for one hour. The next time I run the unit i want to try and increase the load on the generator, I guess it will be laundry time. Thanks for all the advice from everyone, I just wanted to make sure I was not hurting the unit by running at such a minimal load.

 

[rustystud]

Great advice, I did not notice any wet stacking, but on the other hand I only ran the generator for one hour. The next time I run the unit i want to try and increase the load on the generator, I guess it will be laundry time. Thanks for all the advice from everyone, I just wanted to make sure I was not hurting the unit by running at such a minimal load.

At one hour you won't hurt anything, unless your not at 60HZ (up to speed, remember the Voltage Regulator doesn't like that !)) . It takes awhile to wet-stack .

 

[steelypip]

This is one reason I always tell people to get the smallest generator they think they can get by with, instead of one you're 'sure' is big enough. This is especially true of military gensets, which are hugely underrated. Another way to think about it is to size the genset to your largest single load in the house that you know you will want to run, and then shed load to keep the generator in its happy range of output.

In my case, the largest single load was the downstairs heat pump (1300 sq ft floor, 5 year old pump). My MEP-002A will start it with a noticeable grunt and brief sag, and it runs at about 60% indicated load. I'm rather strict with my family about only running lights, computers and the refrigerators and freezers while the downstairs AC is on, and a lot of breakers just get left off in the panel. The result is that the set is in the 70-75% indicated load range when doing its heaviest work. That leaves us enough head room for start surges and running a single small stove burner or the microwave.

It's not a big deal to walk over to the thermostat and turn the heat pump off while doing something power intensive like making dinner. We're usually not preparing a three course banquet during a power outage anyway, so it's not a big deal. I do sometimes overcool the house by a few degrees so that I can turn the downstairs pump off for a while and use a majority of genset output for some other purpose.

The genset is completely happy with this workload, has a modest fuel consumption at this output, and wet stacking isn't an issue. If I had an MEP-003A, I'd have to run the upstairs AC as well to get anything like the same load, and I'd be scrounging load to keep it happy during mild days or winter days when we're heating with wood during an outage. I'd also be feeding it twice as much diesel fuel for the privilege which, in a crisis when there might not be diesel fuel available for purchase within half an hour's drive time (if I can drive at all), is not a trivial concern.

As for test/wet stack prevention loads, consider running a load of laundry. American style dryers are utter power suckers.

 

[rustystud]

I agree with you steelypip. I first bought the MEP-003A and it was great, but I only used 25% to 50% of it's capacity. I would also get wet stacking. So I got the MEP-002A. Yes there are times when it could use a little more power, but on average it is a perfect fit for our home.

 

[Wishlist]

The MEP-002a would be the perfect size for my house as well, but I like MEP-003a it is a powerhouse. I guess, I could just run some cable to the neighbors houses during power outages.

 

[Keith_J]

Consider an electric water heater as a load bank. You can trip the breaker off when you need power for the HVAC, then turn the water heater on when load is light. 4500 watts is a good load on a 003 (typical water heater).

On wet stacking, my step son was restoring a M1009 for about a year...well, he wanted to restore it but computer games got in the way of him getting his license so he just ran it every other day at idle in or at the shop. Well, when he finally got around to getting his license, the first month he was fumigated by the worst smoke/soot/smell I had ever experienced from the 6.2 liter J code Detroit Diesel. Yes, wet stacking.

 

[steelypip]

I've never heard of a 6.2 wet stacking before. Maybe an MP truck that idled a lot and had a bad thermostat? Yes, the water heaters make a pretty good load sink, except that they tend to turn off too quick. I've generally resorted to boiling four pots of water on the stove during load tests.

 

[cuad4u]

I am not fortunate to have access to a "real" load bank to load test the generators I restore. My "load bank" consists of an assortment of water heater elements (5500W, 4500W, 3500W etc). By wiring the corresponding elements in parallel to get the wattage I want to load the generator to and submerging them in a 55 gallon plastic drum filled with water, I can load test any generator up to 15,000 watts (MEP 003A) for as long as necessary. If the water gets too hot after a long load test, I just put a garden hose in the bottom of the barrel and let fresh cool water fill the barrel from the bottom while the hot water over flows from the top. I submerge the elements and the wires carrying the current about 2/3 down the barrel. And contrary to popular opinion, fresh water DOES NOT conduct electricity.

 

[Keith_J]

I am not fortunate to have access to a "real" load bank to load test the generators I restore. My "load bank" consists of an assortment of water heater elements (5500W, 4500W, 3500W etc). By wiring the corresponding elements in parallel to get the wattage I want to load the generator to and submerging them in a 55 gallon plastic drum filled with water, I can load test any generator up to 15,000 watts (MEP 003A) for as long as necessary. If the water gets too hot after a long load test, I just put a garden hose in the bottom of the barrel and let fresh cool water fill the barrel from the bottom while the hot water over flows from the top. I submerge the elements and the wires carrying the current about 2/3 down the barrel. And contrary to popular opinion, fresh water DOES NOT conduct electricity.

I doubt the electrical connections are potted so there will be some leakage current through the legs. AC in water just causes heat, electrolysis cannot happen. But you could have a potentially LETHAL combination there if the generator is grounded and there is a fault in the breakers. You would be much better suited by hanging the elements from a steel plate so everything but the last 1/2" of the element (closest to the bung) is submerged. This is what I do.

Or you could get an old water heater.

 

[Isaac-1]

For a portable small load bank I find cheap hair dryers hard to beat, 1,500 or so watts for about $6 each online

 

[rustystud]

The MEP-002a would be the perfect size for my house as well, but I like MEP-003a it is a powerhouse. I guess, I could just run some cable to the neighbors houses during power outages.

Your also using twice the fuel too ! When the power goes out here for days on end that difference in fuel usage can really be felt in the pocketbook !