Dan
The AC start up load should be in the specs. If not, double the running
current draw if its a bleed down unit, triple the running load if its not.
In the 90's I built and operated several shelterized instrumentation radars for
use in deserts on generator power. Generators had to package in the shelters
for deployment. Inverter generators did not exist back then.
AC was a pain. Large random current draws and voltage drops on start up
followed by voltage surges on shut down. This wreaks havok on sensitive
equipment. To lesser extent resistance heaters and blowers did the same thing.
Much of the start up problem is due to commercial AC units not having a bleed
down capability so they try to start up against a HEAVY compressor load. Lots
of insulation, white paint on the roof and a silver side up tarp over the roof
for shade and an air gap minimized short cycling of the AC. But the huge start
up load was still there.
AC units with compressor bleed down and interlocks to prevent a loaded start up
were special order, militarized mobile units back then. This helped A LOT. It
may be a more common item on RV units today, check for this capabity. A home
window unit probably wont have it.
Even with all of this I had to size the generator for twice the max current
draw of the AC unit on start up stay over 100 volts so the electronics were not
too unhappy. Straight generators depend on rpm for gross voltage stability.
Inverters will still surge as the throttle opens under a big load spike, but to
a much lesser extent.
The AC load will far and away be the biggest load on your system. Once running
I found that the AC generated an unacceptable level of noise on the power
lines. This led to a lot of filtering for the radar electronics.
Taken all together this resulted in an acceptable but far from ideal solution.
Ultimately I ended up with TWO 10kw generators. One for electronics and one
for support functions. The shelters were rewired to isolate them from each
other but the were still minor disturbances through the shared a.c. grounds.
When the radar was in standby the load was so low on the electonics generator I
had to add a resistor bank to force the generator off idle to a stable 3600rpm
level. I could have used a smaller electronics generator but one is none and
two is one, plus I would have to double up on spares.
Here is what I suggest:
An inverter generator for the electronics on its own circuit.
An AC unit with compressor bleed down.
A second generator (inverter or conventional) for the AC which is oversized by
at least 50% for the start up load, 100% if the AC doesnt have bleed down, you
dont care about voltage spikes on this generator as long as the AC can handle
it. Conventional generators are much cheaper at higher power levels.
Keep the grounds seperated.
With the second generator you can bring a coffee maker, small fridge, a
microwave, lights, floods for set up and have all the comforts of home.
73
John
KM4KMU
Sent from AOL Mobile Mail
On Saturday, March 10, 2018 Dan Evans via VHFcontesting
<vhfcontesting@contesting.com> wrote:
Hello group, I'm putting together a small (12') pull behind trailer for grid
hopping / portable operations. It's actually a 1967 Winnabago that I'm
restoring / remodeling. Anyway, I would like to add a small window unit air
conditioner to make summer operating bearable. The original AC unit is long
dead, so I was planning to install a 5000 BTU. This is the smallest unit I've
been able to find. My question is how much generator am I going to need for
this setup? I know one of the small inverter types should be plenty to run my
radio equipment, but will it handle the AC? I know there are plenty of guys on
the list that have been down this road before, so I would appreciate your
input! 73Dan -- K9ZF Vice President, Clark County Amateur Radio Club,Amateur
Radio Emergency Service, Clark County Indiana. EM78el The once and future K9ZF
/R no budget Rover ***QRP-l #1269 Check out the Rover Resource Page at: List
Administrator for: InHam+grid-loc+ham-books Ask me how to join the Indiana Ham
Mailing list! On Saturday, March 10, 2018, 12:31:28 PM EST, Mike & Becca
Krzystyniak <k9mk@flash.net> wrote: Greetings All, James, AF5EH is selling
his pair of HP 8753C (3 GHz) & HP 8753D (6GHz) model network analyzers.
Both have their respective S parameter sets and fresh CRT's. Anyone
interested? If yes, please contact James off list at james at jwarden dot com
Thanks for reading this. 73's Mike K9MK
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