From: John De Armond
Subject: Re: We have a trailer! Now a generator?
Date: Tue, 20 Nov 2001 12:11:55 -0500
Dee Crabtree wrote:
> Dan, I tried a single EU2000I on a brand new 5er with a single 15K AC
> unit just to see if it would run it. The AC compressor kicked in, and
> the fan started blowing. I let it run until I felt cold air. The
> generator never faltered. While the AC was running, I switched on the
> 120v overhead fan & light and the EU2000i overloaded and popped its
> breaker. I had to shut off the AC to reset the breaker, otherwise it
> immediately popped the breaker when I pressed the reset.
The power the AC draws varies directly with the outside
temperature. When it is the hottest and you need the AC the most,
it draws the most power. I know that with my 3kw generator (that is
significantly worn), I can run both the 13,500 btu AC and the
microwave when the outside is 75 while at 95 the genny barely pulls
the AC by itself. Important to keep this in mind when evaluating a
given genny and AC together.
> It is my understanding that constantly running the EU2000i over its
> rated load will cause it to run hotter and probably shorten the life of
> the unit. My 5er dealer service tech commented that running a genset
> that is too small may damage the appliance circuitry (?) and appliance
> life may be impacted. So, from that point of view, it does not appear
> to be good idea. But I'm not an electrical engineer, so I have to take
> their word for it. Maybe someone else on here can explain that.
With a conventional generator, overloading causes the engine to slow
which drops both the voltage and the frequency. The lower frequency
in particular is very hard on electric motors already running (near)
fully loaded. With the EU series of generators, neither the
frequency nor the output voltage is determined by the engine speed.
Both voltage and frequency are electronically regulated. Both will
remain relatively constant during overload until the inverter's
protective circuit shuts itself down or the breaker trips. so what
your service tech said does not apply in the case of the EU gennys.
But in contrast to a conventional genny which will slow a bit but
keep running when overloaded, the EU will simply shut down. It is
an all or nothing situation.
I very seriously doubt that one EU2000 would carry a single 13,500
BTU AC in very hot weather. That's just shaving things too close.
From: John De Armond
Subject: Generator experiments
Date: Sat, 30 Dec 2006 17:12:28 -0500
I had some time to kill here at the cabin so I decided to do some
experimenting. I'm looking for a cheap and easy way to air condition
my truck come summer without having to idle.
In my straight truck that I own, on long trips I've carried my
QuietPack generator in the box and placed a 10,500 BTU portable GE air
conditioner in the passenger floorboard. This unit is one of those
that you roll up to a window, stick the hot air hose out and get spot
cooling for a room. I made up an adapter for the truck window to fit
the hose. It works great. It's very quiet and is more than enough to
cool the small cab.
I'm thinking along the same lines for my semi except that I can't
carry such a large generator. This little $100 2-stroke 1KW generator
came to mind. Time for an experiment.
I first tried the generator with my medium-sized GE dehumidifier.
Cranked that sucker off just fine with barely a bobble in line
voltage. Next the AC.
I hooked it up. It tried to start for about half a second and cut
off. After a little poking around I discovered that the electronic
control board under-volts and drops out the compressor relay. Damned
I have one of these ACs with a burned out control transformer (combine
a knucklehead dishwasher, a plug adapter for a light bulb socket and a
metal-halide fixture and the blue smoke leaks out. But that's another
story.) I already had the thing open to replace the transformer so
instead, I installed a fan switch, a compressor switch and a
I hooked this unit up to the generator and flipped the compressor
switch on. The generator groaned for a full second before the
compressor kicked off but kick off it did! Flipping the fan on
completed the load. L'il booger just loafed along. The throttle
looked to be between 1/2 and 3/4 open. I blocked the condenser air
inlet until the outlet air temperature was 140 degs, simulating a hot
summer day. The generator loaded a bit more but stayed within the
control band of the governor.
Further experimenting showed that the system had to be allowed to
completely equalize (cool down) before the compressor could
subsequently be started. I think that a hard start kit will do
wonders but I don't have one up here. At worst I might have to
install an equalization solenoid in the refrigerant circuit. A simple
mechanical time delay relay will let the compressor start before
turning the fan on.
There is more power to be had out of that little 2-stroke. I'm going
to fall back on some of my old 2-stroke race tuning techniques and see
what I can get out of it. I think I can get this combo to reliably
start every time. If I can then I have the truck problem licked. I'll
weld up a little steel cage that'll clamp to the truck frame and hold
the generator and a gallon or two of gas. Sure beats the heck out of
a $7000 APU!
Perhaps just spinning the engine a little faster will do the trick. It
will also provide the advantage of getting a bit more cooling and air
flow out of the AC, since the AC motors will spin faster on the higher
I don't have a scope up here yet but I did get some good indication of
the crappy waveform out of this generator. The fan motor in the AC
buzzes just like it does when connected to my big inverter. I bet the
waveforms look quite alike.
BTW, my 1500 watt inverter strapped to the battery pack with 4-0 cable
won't start this AC. Shows the power of a little mechanical inertia
:-) Take THAT, you EU-1000s.......
I went ahead and paid the $9 for the service plan from Northern. Given
that this engine probably has a rated life of under 1000 hours, I
suspect that they'll be giving me at least one replacement and maybe
two during that warranty period. 1000 hours is just 100 10 hour
mandatory breaks - about a summer's worth. I suspect that this will
be $9 well spent.
For my next test we'll see if it'll pull a 1500 watt ceramic disc
heater. I believe it will. Especially if I choke off some of the air
flow so the power thermister will heat up enough to drop the power a
couple hundred watts. That trick has worked with the inverter in my
Seems like an odd architecture - running the diesel engine to send 12
volt power to the inverter to power a heater. But given that it takes
that big ole engine over a half hour to warm up enough to make any
heat from the bunk heater and I only need heat in the AM for maybe 15
minutes, it makes a lot of sense. Just crank the engine, flip the
heater on, dress and fix breakfast, then turn the heat off.
You know, if this combo turns out to be reliable then it might just be
the ticket for very small trailers and pop-ups. The GE takes up very
little floor space and the hot air discharge requires no permanent
holes. For about $400 one could be in the camper AC biz...
More experiments to come.
From: John De Armond
Subject: Re: Generator experiments
Date: Sun, 31 Dec 2006 06:56:21 -0500
On Sun, 31 Dec 2006 01:07:41 -0500, email@example.com wrote:
>On Sat, 30 Dec 2006 17:12:28 -0500, Neon John <firstname.lastname@example.org> wrote:
>>For my next test we'll see if it'll pull a 1500 watt ceramic disc
>>heater. I believe it will.
>Short conclusions: 1200 watts? In your dreams. This unit appears to
>top out at less than 900 watts with very poor regulation in that
>range. Maybe using Nitro would up the wattage, but with the small
>engine, 200 to 700 watts seems like where it wants to live.
>The Isobar didn't bat an eyelash, much less overheat, which was kind
>of a surprise. I wonder how much the filtering dropped the wattage
>when the unit dropped down to 52 Hz. That could be part of the poor
>performance, but I wasn't going to risk my KAW testing output without
Couple of thoughts. I'm tired right now and can't recall - is the KAW
true RMS responding? If not then the crappy waveform might be one
cause of the apparent under-capacity.
I bet the isobar is filtering out significant power.
I bought a bunch of KAWs when I caught 'em on sale for $20 so I don't
mind risking sacrificing one. I'll get mine out tomorrow and give it
a run. I found one of my ceramic disc heaters in a box (moving is
such a bitch!) so I'll give that a run too. I have a true RMS
wattmeter around here somewhere so if I can find it I'll compare the
>Re using a 10,000 btu AC. I suspect you'll find this unsatisfactory.
>I tried using a 6,000 btu household unit in my van and during the day
>it _almost_ kept the interior at exterior temperatures. That was with
>the hot side ducted both in and out. Your single duct unit will have
>to pull air from somewhere in your cooled space, and the makeup air
>from the outside will reduce your cooling to less than what I had.
This particular unit does a good job air conditioning the cab of my
medium duty truck which has practically no insulation. The
cab/sleeper of my semi is surprisingly well insulated. With the
blackout drapes pulled around the windows, it takes pretty much all
night for the thing to cool off enough to be uncomfortable (probably
50s) with it in the high 20s outside so I'd expect heat influx to be
similarly miserly. In any event, both the genny and the AC are
already bought and paid for so I've lost nothing but time if it
From: John De Armond
Subject: Re: 5th Wheel & Generator
Date: Wed, 02 May 2007 02:19:36 -0400
On Tue, 01 May 2007 20:40:16 -0700, altar nospam <email@example.com>
>On Tue, 01 May 2007 17:24:35 -0400, Hunter
>>It can run a 13,500 a/c if you run nothing much else. Put the fridge
>>on gas for example.
>>No microwave of course.
>Uh.... not all of them.
>Ask me how I know.
Probably won't run her's either in hot weather. Power draw rises
fairly linearly with condensing temperature until about 120-130 degs
F. Then the pressure spikes upward toward R22's critical temperature
of 205 deg. Above the critical temperature, R22 won't condense back
into a liquid regardless of the pressure. As the critical temperature
is approached, the condensing pressure rises higher and higher and so
does the power consumption.
Two hundred degrees at the condenser isn't hard to reach. A good hot
sunny south Texas or Arizona day, sun shining directly on the
condenser, maybe a little breeze opposing the condenser fan.
Usually/hopefully the compressor will trip the thermal overload when
running on shore or unlimited genny power. "Hopefully" because the
compressor's exhaust valves and oil are taking a severe beating.
An AC that will run on an EU2000 just fine in 80 deg weather in the
shade will simply trip the genny under hotter conditions. On my last
July trip to visit a friend in Texas, with the ambient over 100 deg
and high humidity my 13.5Kbtu Coleman was loading my Impact inverter
genny (3800 watts nom) almost fully. At least between the AC's
thermal overloads. I had to pay close attention to which direction I
parked so that the sun would not be on the condenser.
That same unit will run fine on an EU2000 in shady 80 deg weather.
My test for evaluating generators for my rig is to throw a large
appliance box over my roof AC and stick a thermometer through the
side. I let it run until the temperature in the box is in the 140 deg
range. Then I cut some holes to allow enough air to flow to stabilize
the temperature. If the candidate generator can run it under those
conditions then it's a satisfactory generator. The EU2000 doesn't
even come close. An EU3000 that I tested was chugging with all its
might. I'm sure that if a nightlight had come on inside the rig the
unit would have tripped.
It's these extreme conditions where our ACs simply MUST run. When
it's merely warm, we CAN muddle through without AC if we have to. But
on one of those 110 deg, 98% RH days like, say, Houston is known for,
working AC is a matter of survival. Or at least not being forced to
find a motel!
One final note. None of the R22 candidate replacement refrigerants
work as well at the extremes. None have as high a critical
temperature. That means that if/when the econazies and the feds force
R22 off the market, our roof-top ACs are going to perform much worse
under severe conditions. I think I'm going to replace mine this
summer even though it's running just fine so that I can still get an