DC A/C

[CLC379]

9000 BTU on less than 1hp

seems to be super efficient compared to a belt driven sanden compressor that requires about 4.4kw?

http://www.dcairco.com/products.html

[CLC379]

sorry if i am bringing up something that dont belong on the forumn, i am new to generation and cogeneration

but this is something that confuses me

http://www.sanden.com/index.php?id=U5H0AMX7Q

if you click on the power curve most of the compressors alone require over 4kw to turn. how is it that a complete 12/24/48 dc electric unit can run on less than 1hp?

sanden also lists this dc drive compressor but dont show specs  http://www.sanden.com/index.php?id=TSPM4GG46

[mobile_bob]

CLC:

welcome to the forum, and you are doing just fine asking about this in my opinion

not sure how to answer your question, but it appears to me that there are certainly those
that don't require 4kwatts input to work

http://www.sanden.com/images/SD7H15_Performance.pdf

it looks like this example produces about 3kwatt or cooling with an input of about 1.75 kwatts?

it might be that the dc units are variable displacement units and produce perhaps 1500watts of cooling for about a hp of input
give or take a bit.

bob g

[mobile_bob]

Give it a couple more days, WGB is still on the road home, he is our resident refrigeration guru
if he don't know, i bet he knows where to find out what you want to know

bob g

[CLC379]

Thanks Bob

im sure this is not complicated to most here. but im lost

1hp=746watts=.746kw

what i had done earlier was look up a 8-9k btu auto a/c, the size the compressor they used on sandens site, it require's about 4kw to run at peak efficiency. that is the compressor alone! on top of that it would also require both condensor and evaporator fans.

the reason i am asking is because i hope to build a auxillary power unit for my peterbilt. after reading about less than 1hp a/c im thinking maybe a better option would be to use there 12v a/c unit then mount a large alternator on the extra engine. plus replace the three group 31 batteries already on the truck with trojan deep cycle?

my plans are leaning towards finding a lightweight diesel around 10hp (perkins,kubota,yanmar) that will just drive a a/c compressor and a alternator. the a/c system would be seperate from the trucks a/c.,,,but then i noticed pony pack ties into the trucks existing a/c with its own compressor. this would be a nice option because it would save installing all the extra's. how it works or is tied in i dont know?

i have a webasto so heat will not be needed. i originaly liked the idea of using agm batteries when the truck is shut down but after reading the risk of ruining a set of batteries due to improper discharge recharge i at least know i want some type of engine driven system.

hope i havnt confused you all as much as i am, the more i search the more options and confused i get. plans are open for any suggestions ideas etc. and or a link to someone who has built a similar unit would be nice.

Thanks

[mobile_bob]

most of the sanden compressor do not take 4kwatts to turn, most take well under 2kwatt and go up to maybe 4kwatt at peak cooling capacity
at higher speeds.

there are several unit that work in the 2kwatt range and produce over 3kwatts of cooling, according to the charts.

which compressor are you looking at?

bob g

[CLC379]

i was looking at the sd7h15 154.7 cc

and thought that whatever compressor i used would probably need to be run at peek efficiency,


i think what your post meant is the compressor will work fine at the lower rpms requiring less hp?

[WGB]

Hi CLC,
Welcome to the forum.
It looks like both are doing close to the same thing.
12,000 btu to a ton usually runs close to a horse, 746 watts.
The DC unit is only 9000 BTU that would be well under the 746 watts (using a hermetic direct drive compressor I'm sure)
The Sanden unit is down in that range on their curve with belt loss and all.
Not sure if that helped, I'll look at it some more later, to see if I'm missing something.
Also it looks like you're comparing a wobble plate piston Sanden to what I'm sure would be a rotary vane.
All the truck issues and application questions, Bob would be the man!
Looks like you will be getting into some cost and time no matter what way you go.
Then there is this option.

Sorry I couldn't help myself!

[elnav]

Have you looked carefully at the A/C unit? Looking carefully you can see through the louvres and see that the shell is empty.