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A/C as exhaust fan?


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Gentle Readers, here's the Inquisitive Idiot* Question Of The Day:

Is it possible for a rooftop a/c to replace a powered rooftop exhaust vent?  That is, if you are not plugged into shore power or running a generator, will the fan part run on 12 volt dc from the house battery(s)?  If not, can you run just the fan part via an inverter, and if so, how big an inverter ?  If you CAN run it, is it a good idea to do so?  If you are running it while cooking, won't the smoke and grease build up in the a/c eventually?

 

* "There may not be any stupid questions, but there sure are a lot of inquisitive idiots!"

Regards

John

DON'T FEED THE VULTURES!

My Body is a Temple!  Ancient, Crumbling, Probably Cursed . . .

I Don't Like to Make Advanced Plans.  They Cause the Word "PREMEDITATED" to Get Thrown Around in Court!

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I think you are asking if the fan alone in a standard rooftop AC can be run off an inverter and will it act like a rooftop fan?

Yes you probably can run it without the compressor kicking in, at least the specific Dometic unit on our rig can be set to run that way. I have no idea what the fan would draw on it's own you could probably look it up on the manufacturers website. I think the fan in ours is 1/2 HP but what the start current might be I have no clue.

No it doesn't act like a rooftop fan because it doesn't exhaust to the outside, it recirculates the air inside the rig thru the cooling coil so any smoke etc would just recirculate inside the rig. And yes the grease will clog the filter and coat the cooling coil in the AC.

Brian

2009 Monaco Cayman DP 38'

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50 minutes ago, Optimistic Paranoid said:

That is, if you are not plugged into shore power or running a generator, will the fan part run on 12 volt dc from the house battery(s)?

No. The blower of the roof air conditioner gets power from the same supply as the compressor and all other parts. In addition, the blower uses an alternating current motor and those cannot be operated from direct current as the design of each is quite different.

52 minutes ago, Optimistic Paranoid said:

If not, can you run just the fan part via an inverter, and if so, how big an inverter ?

It could be run via an inverter if your a/c unit has a "fan only" selection, as most do. 

54 minutes ago, Optimistic Paranoid said:

If you CAN run it, is it a good idea to do so?  If you are running it while cooking, won't the smoke and grease build up in the a/c eventually?

In my opinion, it isn't practical to do this, but it is possible. As to the cooking grease issue, that would be no different than what happens when you use the a/c while cooking. The cooling coils do get a buildup of dirt and grime over time and should be cleaned occasionally. Most of them do not get cleaned until problems develop so the result is that the a/c becomes less efficient as it gets dirtier. 

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
Kirk & Pam's Great RV Adventure

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Even when you do operate the a/c on fan only, it doesn't exhaust any air but just moves the inside air through the unit. An exhaust fan is probably much better for what you want and those are typically powered by 12V-dc.

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
Kirk & Pam's Great RV Adventure

            images?q=tbn:ANd9GcQqFswi_bvvojaMvanTWAI

 

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Simple answer is yes you need to have both an AC unit and a fan that can exhaust air.

Two different jobs need two different approaches. One to cool and one to change out the air inside the RV.

 

Bill

Bill & Lynn Baxter

MCI102A3 Conversion, Detroit Diesel S50  

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Next question is doesn't your present rig already have at least one exhaust fan?   Most have two (one in kitchen area, one in bath) and often 3 (another for the bedroom).  Lots of evenings we will turn on the exhaust fan and open a window and let cooler air move through the rig.  Of course we also always have floor fans to more air around.

Barb & Dave O'Keeffe
2002 Alpine 36 MDDS (Figment II), 2018 Ford C-Max HYBRID
Blog: http://www.barbanddave.net
SPK# 90761 FMCA #F337834

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Don't currently have a rig.  I'm currently saving up to buy an Alaskan Truck Camper.  I already have the truck, a Ford F250.  The camper will only be 10 feet long.  I've been wondering if I can fit both an a/c and a power vent on the roof.  Hence my curiosity.

Regards

John

DON'T FEED THE VULTURES!

My Body is a Temple!  Ancient, Crumbling, Probably Cursed . . .

I Don't Like to Make Advanced Plans.  They Cause the Word "PREMEDITATED" to Get Thrown Around in Court!

MyMapS.jpg

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1 hour ago, Optimistic Paranoid said:

Don't currently have a rig.  I'm currently saving up to buy an Alaskan Truck Camper.  I already have the truck, a Ford F250.  The camper will only be 10 feet long.  I've been wondering if I can fit both an a/c and a power vent on the roof.  Hence my curiosity.

I have never seen a truck camper [have had 5] that did not have a power vent. Normally if you buy new, a roof ac will be extra. Many I have seen have both. For a well built camper, best to open at least one window to allow air flow when running vent.

Had a Lance that had ac and one vent over bed and one in bathroom.

Foretravel 40ft tag 500hp Cummins ISM  1455 watts on the roof, 600 a/h's lithium in the basement.

 

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Alaskans are unusual in that there are no dealers, and no stock on hand.  They custom build yours when you place the order, and you have to drive to their factory in OR, where the factory installs it on your truck as part of the deal.

It's $275 for the optional a/c wiring and support, and $1100 for the Polar Cub 9200 factory installed.

Regards

John

DON'T FEED THE VULTURES!

My Body is a Temple!  Ancient, Crumbling, Probably Cursed . . .

I Don't Like to Make Advanced Plans.  They Cause the Word "PREMEDITATED" to Get Thrown Around in Court!

MyMapS.jpg

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