Low voltage Air Conditioning [RE-wrenches]
Blair May
tump at hughes.net
Wed Apr 23 04:45:39 PDT 2008
I have done quite a bit of work on class 8 tractors. There are quite a
few APUs out there that despite what you say there are advantages for
your customer to think about. Weight versus anti idling fines, the
availability of service ON THE ROAD is a very important thing to
consider especially in TEXAS. I have investigated BB systems that are OK
for this northern climate but OO(owner operators) will usually find the
additional benefits of an APU in both summer & winter far outweigh the
additional cost compared to batteries & their weight. Road damage is
quite a problem most of these guys do at least 175-200K miles a year.
Contact me off list for info on both. tump
-----Original Message-----
From: Larry Crutcher, Starlight Solar [mailto:larry at starlightsolar.com]
Sent: Tuesday, April 22, 2008 8:20 PM
To: RE-wrenches
Subject: Re: Low voltage Air Conditioning [RE-wrenches]
Thank you all for the responses.
APU's are very costly. RV, camper rooftop AC units are 13,000 BTU, 120
VAC and very noisy. The DC compressor based systems I have found are
over priced. Peter, evaporative cooling would be great here in Yuma with
our 6% humidity. However, the trucker spends many days in Texas and the
central states; very high humidity so water removal is key to comfort.
It looks like I will have to install an inverter. I can use a mini split
AC that draws 700 watts. It provides 9000BTU of cooling, too much for
the sleeper space but it's the smallest I can find and it's very quiet.
8 hours of continuous operation is 5.6 kWhr. 80% on time is 4.5 kWhr.
Four 8D's are about 12 kWhr. A 1500 watt (Invertek) inverter efficiency
is 88% at 50% load. So, the batteries will average about 50% DOD in 8
hours. The truck will be started and run for 11 to 14 hours The
batteries will fit easily and the mini split bolts to the back wall of
the sleeper. If he buys, I'll let you all know how it works out.
Larry Crutcher
----- Original Message -----
From: Travis Creswell
To: RE-wrenches at topica.com
Sent: Monday, April 21, 2008 10:18 AM
Subject: RE: Low voltage Air Conditioning [RE-wrenches]
Hello Larry,
You mention a "small diesel generator". Are you talking about an
Auxiliary
Power Unit or a generator? APU's are becoming really popular on
trucks from
what I've seen. They are generators and air conditioners so they take
care
of two birds with one stone. Here is an example of one.
http://www.rigapu.com/index.php I have no affiliation with them, it's
just
the first hit on Google (who I also have no affiliation with). They
"comply
with strict idling laws" so I would assume they are allowed. I'm sure
it's
pricey but so are all those batteries. By the way, where are you
planning
to put 18kWh worth of batteries? That's ~8 L-16's or ~14 T105's by my
math.
Plus that weight results in that much less freight he can carry which
might
be a deal breaker all by itself.
According the specs; 20,000 BTU of cooling capacity, 6kW generator and
60
amps of DC output, .3 gallons per hour at full load. Hmnn...these
could be
a solution for off gridders that wanted/had to have air conditioning.
(No
comments needed from the efficiency peanut gallery, please)
Best,
Travis Creswell
Ozark Energy Services
-----Original Message-----
From: Larry Crutcher, Starlight Solar
[mailto:larry at starlightsolar.com]
Sent: Monday, April 21, 2008 11:27 AM
To: RE-wrenches at topica.com
Subject: Re: Low voltage Air Conditioning [RE-wrenches]
Wrenches,
I did not get a response to my post from last week. I know most of you
do
not work with battery based systems but is there anyone here that can
offer
some experiential advice about low voltage air conditioning?
Thanks again,
Larry Crutcher
----- Original Message -----
From: Larry Crutcher, Starlight Solar
To: RE-wrenches at topica.com
Sent: Thursday, April 17, 2008 11:30 AM
Subject: Low voltage Air Conditioning [RE-wrenches]
Does anyone have experience with DC air conditioning equipment? I
have a
customer with a semi truck and wants a roof air for the sleeper.
Many
truck stops now forbid engine idling for more than 5 minutes so they
can
not use the cab air.
A small diesel generator is one solution but the trucker is not sure
if
some truck stops may forbid that as well. Since the truck engine is
only
off for 10 hours or so, it looks like 18kWhr of battery @ 50% DOD
will
operate the A/C load until the engine starts again.
Some customers in Mexico are running mini-splits successfully but I
don't want to add the complexity of an inverter if there is a low
voltage DC solution.
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