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Author Topic: Efficiency of A/C on Itasca MH  (Read 9168 times)

sheltie

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Efficiency of A/C on Itasca MH
« on: January 17, 2009, 10:34:39 AM »
Last summer there were a few days that the basement a/c on my '04 Itasca Suncruiser 38R had a hard time keeping the temp anywhere near where I wanted (75 degrees).  It would take several hours of run time before it MIGHT reach the desired temp.  I called Coleman (the maker of the system) and they told me to check under the MH to insure that the vent system had not separated (it had not) as the system should be able to maintain the requested temp.  The outside temp was generally about 90-93 with very low humidity.  I've seen where others say they could "hang meat" in their MHs.  Any suggestions?  If I have a technician check it out, my inclination is that a "regular" a/c man would be as good, if not better than taking it to my MH dealer.  Any ideas about that?

geodrake

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Re: Efficiency of A/C on Itasca MH
« Reply #1 on: January 17, 2009, 11:19:12 AM »
My guess is thatyour A/C is just fine!

Motorhomes are not particularly well insulated.  The sun coming through the windshield can act like a blast furnace.  Reflective windshield inserts can make a big difference.  And keep in mind that it is much much easier to keep the MH cool than it is to cool it once it has already become hot.   The secret we have learned is to turn on the A/C in the morning, before it gets hot out.  Set the thermostat to the desired temperature and let it take care of it's self.   
George Drake

FrontrangeRVer

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Re: Efficiency of A/C on Itasca MH
« Reply #2 on: January 17, 2009, 11:27:38 AM »
Well, you came to the right place for this question.  ;D

There has been some concern with the basement air in the Winnebago class A's being large enough to handle the load of units that are longer than 35 feet with several slides.  For 2009, Winnebago has upped the capacity of the basement air for any unit that is longer than 35 feet.

Yours and mine fall into this "size" category with our basement air.  :'(

There are several problems I see with the cooling system as currently used by Winnebago.

1.  Lack of insulation in the "box" structure by Winnebago.  Where the roof is attached to the sidewalls are not insulated and the extruded aluminum joints the run the full length of the motorhome sides are not insulated.  Above the entertainment center along the front cap receives a small "blown on" foam coating which is very low R-value.

2.  In some 2004/2005 models, there have been some cases of separation of the rear "Y" rigid ducting that comes from the basement air, then "Y"s to both ceiling ducts UNDER the rear cap.  The way to check this is to get under your motorhome and reach up as far as you can and feel along the rigid duct that goes to the "Y" and see if you have cold air escaping.  Another way is to use a hand held pistol IR thermometer and see if you have much temperature change when you aim it at the "Y" area of the ductwork.  I have done both with mine, and I can't see anywhere where the cold air is escaping.  The only other way is to remove one of your tail lights and run your hand toward the duct to see if you feel cold air escaping/and use the IR Thermometer gun around that area.  Other owners have said that if you run your hand over the rear cap and feel cool temps where your rigid ductwork is, that you might have a leak....I didn't find that the case even though during hot days, I can run my hand on the outside of the rear cap where my duct runs, and it is noticiably cooler than the rest of the cap. 


What we have done about this, and what you can do:

1.  Cover up the OUTSIDE of your very large BTU loss Windshield with a Sunscreen.  Many of us have used these with VERY good results.  I use THIS type on my windshield and front side windows to block the very hot sun.  Also use and install Window Awnings....I did which is an EXCELLENT way to keep the hot aluminum  window frames COOL.  The key thing is to get into as MUCH SHADE as you possibly can so the sun can't make that glass and fiberglass sidewalls so hot!  Use your main awning if your curb sidewalls is in the sun....you would be amazed of the temperature differenct as you remove the sun from these sidewalls!

2.  Open up ALL your flow vents in your motorhome for good air flow....even the ones in the bathroom.

3.  Keep your inside filter clean.  I just got off the phone with RVProducts (manufacturer of the basement air), and they recommend the cheap blue fiberglass filters.  He told me that if you can't "see your hand" through the filter, don't use that particular filter.

4.  Start your cooling process EARLY in the morning...it's ALOT easier to keep a cool motorhome cool, than a hot motorhome cool.  Trying to cool off all the interior hot couches, tables, chairs takes a long time.

5.  We have pulled in our kitchen slide (we have opposing living and kitchen slides) during the hottest part of the day, and that helped the cooling as the slideouts are not insulated very well.

I have owned several other brands of motorhomes, all having roof airs, and they all could keep down the temperature inside.  My current Winnie with the basement air will keep the inside temps similar to yours with similar outside temps, so we do the above steps to help it as best we can.  ;)


« Last Edit: January 17, 2009, 01:28:54 PM by FrontrangeRVer »
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John Canfield

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Re: Efficiency of A/C on Itasca MH
« Reply #3 on: January 17, 2009, 12:29:10 PM »
Mark - very well put!  I wasn't aware RVP wanted us to use a thin (aka-cheap) filter, but it makes sense (not to mention it will save money!)  I learn something all the time!

In addition to Mark's excellent analysis and tips, be aware a properly operating AC will exhibit a temperature differential of 20-30 degrees from the inlet air to outlet air.  If your air is 85 degrees going into the inlet, it will be 65-55 degrees out at the first outlet.

Having a non-contact thermometer available on your rig would be a big benefit - use it to check your AC , use it to check tire temps, wheel bearing temps, etc.  Every time we stop, I always 'shoot' the tires on the coach and toad to look for a tire that is significantly hotter than the others.  Heat is a good indicator of potential trouble for tires and bearings.
--John
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sheltie

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Re: Efficiency of A/C on Itasca MH
« Reply #4 on: January 17, 2009, 01:44:44 PM »
What we have done about this, and what you can do:

1.  Cover up the OUTSIDE of your very large BTU loss Windshield with a Sunscreen.  Many of us have used these with VERY good results.  I use THIS type on my windshield and front side windows to block the very hot sun.  Also use and install Window Awnings....I did which is an EXCELLENT way to keep the hot aluminum  window frames COOL.  The key thing is to get into as MUCH SHADE as you possibly can so the sun can't make that glass and fiberglass sidewalls so hot!  Use your main awning if your curb sidewalls is in the sun....you would be amazed of the temperature differenct as you remove the sun from these sidewalls!

2.  Open up ALL your flow vents in your motorhome for good air flow....even the ones in the bathroom.

3.  Keep your inside filter clean.  I just got off the phone with RVProducts (manufacturer of the basement air), and they recommend the cheap blue fiberglass filters.  He told me that if you can't "see your hand" through the filter, don't use that particular filter.

4.  Start your cooling process EARLY in the morning...it's ALOT easier to keep a cool motorhome cool, than a hot motorhome cool.  Trying to cool off all the interior hot couches, tables, chairs takes a long time.

5.  We have pulled in our kitchen slide (we have opposing living and kitchen slides) during the hottest part of the day, and that helped the cooling as the slideouts are not insulated very well.

I have owned several other brands of motorhomes, all having roof airs, and they all could keep down the temperature inside.  My current Winnie with the basement air will keep the inside temps similar to yours with similar outside temps, so we do the above steps to help it as best we can. 

Thanks for the advice.  I'm pleased that we do all you have suggested except open the vents and close the slides (we have dogs and want them to have room to roam.  Wouldn't opening the vents allow the cool air to excape to the outside?

FrontrangeRVer

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Re: Efficiency of A/C on Itasca MH
« Reply #5 on: January 17, 2009, 02:04:44 PM »
I'm talking about the airconditioner ceiling ducted vents....not the roof vents to the outside.  ;)
« Last Edit: January 17, 2009, 02:12:57 PM by FrontrangeRVer »
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seilerbird

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Re: Efficiency of A/C on Itasca MH
« Reply #6 on: January 17, 2009, 02:06:36 PM »
My opinion of basement A/Cs is that they probably wouldn't do as good a job of cooling as a roof A/C would. Hot air rises and cool air sinks. So putting the A/C on the roof and allowing the air to come out of the ceiling and sink just makes more sense to me.

FrontrangeRVer

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Re: Efficiency of A/C on Itasca MH
« Reply #7 on: January 17, 2009, 02:08:02 PM »
Tom, the Winnebago basement air comes out of ducts in the ceiling, not the floor furnace vents.
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John Canfield

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Re: Efficiency of A/C on Itasca MH
« Reply #8 on: January 17, 2009, 09:54:42 PM »
My opinion of basement A/Cs is that they probably wouldn't do as good a job of cooling as a roof A/C would. Hot air rises and cool air sinks. So putting the A/C on the roof and allowing the air to come out of the ceiling and sink just makes more sense to me.

Tom - I think the significant issue is the cooling ability in BTU or tons and not if they are roof or basement mounted.  Like Mark stated - the air comes out the top ducts in any case.

Basement vs. roof air was not a deal-maker or deal-breaker when we shopped for a coach.  After over three years experience with our basement air, I'm liking it because 1) the weight is low 2) relatively easy to service being at ground level and 3) less stuff on the roof.
--John
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seilerbird

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Re: Efficiency of A/C on Itasca MH
« Reply #9 on: January 18, 2009, 09:40:58 AM »
Tom, the Winnebago basement air comes out of ducts in the ceiling, not the floor furnace vents.

Then I am wrong. I looked at one RV with a basement air and I saw duct covers on the floor and I assumed it was the A/C ducts. However if the A/C is in the basement and the ducts are in the ceiling then the temperature loss would be even worse. Sending the cold air through 15 to 20 feet of duct work in the walls of an rv would only raise the temperature by quite a bit.

sheltie

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Re: Efficiency of A/C on Itasca MH
« Reply #10 on: January 18, 2009, 04:41:57 PM »
Then I am wrong. I looked at one RV with a basement air and I saw duct covers on the floor and I assumed it was the A/C ducts. However if the A/C is in the basement and the ducts are in the ceiling then the temperature loss would be even worse. Sending the cold air through 15 to 20 feet of duct work in the walls of an rv would only raise the temperature by quite a bit.

While what you say makes sense, my house (and most every one that has a/c) has VERY long runs to get to different vents.  When it arrives at the destination, it is still cold.  I guess it depends largely upon the insulation (and obviously the unit).  My guess is that the insulation in my RV isn't nearly as good as at home, but the principle should be the same.  It should still be cold when it arrives at the vent.  Considering that the temp during the summer in my attic frequently gets above 130, your thesis would lead me to believe that my house would never cool off, but it does the job quite nicely.  Again, we may be comparing a little apples to oranges in the different types of units, but not much.

Denny

John Canfield

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Re: Efficiency of A/C on Itasca MH
« Reply #11 on: January 18, 2009, 05:38:08 PM »
Tom is correct in that there is some BTU loss due to the rear duct in the back cap, but like you Denny, I believe the issue is the overall design of the system and not a simple roof vs. basement air judgment.  The designer can easily make up for any BTU loss in the duct runs by specifying out a little larger cooling capacity in the case of basement air.

One system is not inherently better than the other - there are advantages and disadvantages of both.  Like I said in an earlier post - I could have lived with either system.  Whatever Winnie put on my Horizon would have been okay.
--John
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seilerbird

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Re: Efficiency of A/C on Itasca MH
« Reply #12 on: January 18, 2009, 09:34:23 PM »
Since there is very few interior walls in most RVs I am guessing that the ducts would have to go through the exterior walls and unless there was a tremendous amount of insulation then the temperature increase would be significant. I think that since over 95% of the RVs I see have roof a/c there must be some very good reasons.

kevin

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Re: Efficiency of A/C on Itasca MH
« Reply #13 on: January 18, 2009, 09:51:36 PM »
I prefer the basement air over the roof air for these reasons.
gives more cabin height because roof can be higher without the huge airs on the roof
less things to have draged off the roof when in low clearence campgrounds(trees)
less weight on the roof
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Ron

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Re: Efficiency of A/C on Itasca MH
« Reply #14 on: January 18, 2009, 09:57:32 PM »
Since there is very few interior walls in most RVs I am guessing that the ducts would have to go through the exterior walls and unless there was a tremendous amount of insulation then the temperature increase would be significant. I think that since over 95% of the RVs I see have roof a/c there must be some very good reasons.

Sam rejected a coach that she really like till the salesman pointed out the AC in the basement.  She told him no way since that was a waste of space.  Our A/Cs ore on the roof.
Ron & Sam-home is where we park it. Currently located   HERE

seilerbird

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Re: Efficiency of A/C on Itasca MH
« Reply #15 on: January 18, 2009, 10:12:17 PM »
I wouldn't want the A/C on the roof either. They don't stick up any higher than my satellite dish so overhead clearance isn't a problem. And putting them in the basement dramatically reduces the available storage space in the basement. And since we are full timers basement space is a serious issue.

John Canfield

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Re: Efficiency of A/C on Itasca MH
« Reply #16 on: January 19, 2009, 09:15:15 AM »
Basement vs. roof air is one of those perennial discussions that surface every few months with basically the same collection of evaluations and opinions.  I have no idea why the topic is so polarizing, but we can always count on it to keep the forum busy for a while  8)

I have one more comment, and then I think I'll move on...  Concerning using up valuable basement storage space - we also fulltimed in our Horizon and I can honestly say we never had an issue with volume of available storage space.  Our particular chassis and model has lots of room - I was always having to monitor our weight as we were always bumping up against our 32K limit.  Winnie fixed that for the next model year by going to a 14.4K rated front suspension.

Potato or patato... Cummins vs. Cat  ;)
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2dalake

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Re: Efficiency of A/C on Itasca MH
« Reply #17 on: January 19, 2009, 01:30:28 PM »
Any of us who have hung around RV forums have heard this discussion before and, as John says, the location of the AC would not be a deal breaker for me (not planning on making any deals anytime soon).  However, based on similar discussions, I had concerns about keeping me, the DW and the pooch cool at a rally 2 years ago in Branson, MO in mid July.   So, I did the following:

1.  cleaned the outside coil well with diluted simple green and fresh water.  It was pretty amazing how dirty it had become.

2. checked the rear cap area for any leaks in the main duct.  There was a small leak which was carefully re-taped with good foil duct tape.

3. when we got to Branson, we were parked in full sun.  Deployed all awnings and installed the exterior sun shield on windshield, the drivers window, and the entry door window.  Closed the interior windshield curtain/shade.

4.  put some of the foil deflecta-shield stuff we got at Camping World inside all of the roof vents and inside the shower sunlight opening.   

5.  kept the AC fan running continuously

We stayed pretty cool in spite of daytime temps in the mid to upper 90's (inside temp never exceeded 74).   John was there so he knows how hot it got. 

I would agree the basement AC (at least in our rig) may not be beefy enough to cool well in every circumstance.  However, we found that being proactive really made the difference.  We do love the heat pump feature...it really keeps the rig toasty until outside temps cycle it off and mandate using the LP furnace.   
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kevin

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Re: Efficiency of A/C on Itasca MH
« Reply #18 on: January 19, 2009, 05:25:07 PM »
where do you and wifey stay at in Branson?? Wifey and I stay at the KOA atleast once a month..well seems that way. our basement air did fine until last yeat augest in OKC, they wanted us to park out in the direct sun, no shade what so ever. I asked about the 5other empty spots in the shade, and they said ok, after that everything was fine.
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John Canfield

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Re: Efficiency of A/C on Itasca MH
« Reply #19 on: January 19, 2009, 06:00:26 PM »
John was there so he knows how hot it got.

Oh boy!

Kevin - we were at America's Best in Branson along with Gary (2dalake).  Gary's routine for keeping as cool as possible is pretty much ours.  Last summer (early in the summer I might add) we were in Gila Bend, AZ and the temps got up to about 110-112.  The best we could do in the coach was about 90 *but* we didn't have the bubble insulating thingy in the windshield (wasn't on our radar at that point.)

I used my non-contact thermometer to check the inside of the sidewall temps in the sun and it was in the high 80s or low 90s as I recall.

Amazingly, we weren't miserable.  We weren't exactly in our comfort zone  :D, but it was tolerable for a day.  If we had a Travel Supreme with optional insulation, my guess is we would have been ten degrees cooler (for another $50-100K.)
--John
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