Wet stacking, RPM, I wonder aloud too much

[rustystud]

Wet stacking occurs because an engine which has a constant RPM (like a generator) runs at less then about 50% load for an extended time period. Since the engine injection system puts out the same amount of fuel into the cylinder at the given RPM if it is not run near capacity you will have excessive fuel to deal with. Since a good percentage of the fuel will not get burned it instead goes down the cylinder walls washing away all the oil. This is a simplistic explanation but pretty much explains what is going on.
This is also one of the reasons generator manufacturers went to an inverter style generation system. The engine can vary it's RPM as load demands.

 

[Lmtv772]

Wet stacking occurs because an engine which has a constant RPM (like a generator) runs at less then about 50% load for an extended time period. Since the engine injection system puts out the same amount of fuel into the cylinder at the given RPM if it is not run near capacity you will have excessive fuel to deal with. Since a good percentage of the fuel will not get burned it instead goes down the cylinder walls washing away all the oil. This is a simplistic explanation but pretty much explains what is going on.
This is also one of the reasons generator manufacturers went to an inverter style generation system. The engine can vary it's RPM as load demands.

Now here is a question then...
my FDECU 5 needs to have power to it for at least 3 hours before I can think of turning on the compressor. Even if i have the fan running it will only be at 20% capacity. So how do I deal with that dilemma?

 

[OverkillTASF]

So based on your last sentence, you can prevent wet stacking by putting the engine under heavy load relative to the peak power output at the presently running RPM, with no need to ramp up the RPM to the point of max power output and then load it to that power output.

An engine capable of 10 hp but running at a reduced RPM to conserve fuel, where the max power output is say 8 hp, can be run at 7 hp as a "heavy load" for that RPM?

 

[OverkillTASF]

Now here is a question then...
my FDECU 5 needs to have power to it for at least 3 hours before I can think of turning on the compressor. Even if i have the fan running it will only be at 20% capacity. So how do I deal with that dilemma?

3 hours? What the heck is happening during that 3 hours? Operating temp shouldn't take that long... but I have no idea what a fdecu is. Sounds like like a bank.

 

[Lmtv772]

3 hours? What the heck is happening during that 3 hours? Operating temp shouldn't take that long... but I have no idea what a fdecu is. Sounds like like a bank.

its a Field Deployable Environmental Control Unit.
From the TM
.4.6.3 Connect input power cable assembly (7) to a source of 208 Volts AC, 50/60 Hertz, 3-phase, 4-wire plus ground, 16 kilowatt (60 amp). (FDECU-2 ONLY) A compressor crankcase temperature lockout will prevent the compressor from
operating immediately. If the compressor is to operate, power must be connected to the unit for approximately three hours. This is to raise the compressor temperature above the surrounding ambient air temperature.

 

[gimpyrobb]

Now here is a question then...
my FDECU 5 needs to have power to it for at least 3 hours before I can think of turning on the compressor. Even if i have the fan running it will only be at 20% capacity. So how do I deal with that dilemma?

Plug something else in with it till your ready to "drop the hammer".

In my case that might be a kegerator or a disco ball for the stripper pole. Once you turn on the AC, you can tell if it works by the girls T.H.O.

Pretty simple if you ask me...

 

[rustystud]

So based on your last sentence, you can prevent wet stacking by putting the engine under heavy load relative to the peak power output at the presently running RPM, with no need to ramp up the RPM to the point of max power output and then load it to that power output.

An engine capable of 10 hp but running at a reduced RPM to conserve fuel, where the max power output is say 8 hp, can be run at 7 hp as a "heavy load" for that RPM?

We are talking extended runs times here. If you have a 5KW generator but only use 2KW for a couple of hours it will not be a problem. If you run this for 10 hours you will start getting "wet stacking" . All the manuals say to run the generators as close to 80% or higher for best performance. If you look at all the MEP generators they have a "percentage" gauge. On that gauge is the preferred area that generator should be running in. Remember that the generators injection pump can vary the fuel output a bit, but not a whole lot. This is not like a gas engines carburetor, or even a vehicle diesel engine which can vary the amount of fuel injected into the cylinders. It must keep the 1800 RPM or 3600 RPM depending on the MEP unit. So basically load the little pig as hard as you can.

 

[Poccur]

LMTV772 - Check where in the manual you read that about the 3 hours...that is in regards to the crank case heater on the FDECU-2 only...if it is too cold the lockout will stop the compressor until the heater has warmed it...which could be upto 3 hours...
And I thought yours was as FDECU-5...are you sure it even has the crankcase heater on the compressor?

 

[JRM]

I think a lot of these units come wet stacked. my 2hp well pump kicked on while my water heater had the top element on and I had chunks of carbon all over the top of my 803a

 

[rustystud]

I think a lot of these units come wet stacked. my 2hp well pump kicked on while my water heater had the top element on and I had chunks of carbon all over the top of my 803a

A build up of carbon is not always an indicator of a wet stacking condition.