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Old 06-05-2021, 10:01 AM   #41
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Quote:
Originally Posted by Nalle View Post
Wildcard,

I have taken the liberty to slightly modify one of Rheine3's sketches and would appreciate your comments..


If there is some usable space between the 46515 and the engine, would it not improve airflow if one used a slightly curved cover of the original air return.
Rheine shows a straight blue line and I have indicated my thinking in red.
Even a one to two inch "bulge" should help. Yes???
Your picture isn't showing. Rheine3, the OP had the same problem. I can see the link when I quote you even though it doesn't show above. If you just post the link, the picture still won't show but clicking on it will show it:

https://drive.google.com/file/d/1wbd...ew?usp=sharing

I'm not sure how he fixed his photo posting problem.
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Old 06-05-2021, 10:50 AM   #42
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My replacement unit is Airxcell 46515-811
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Old 06-05-2021, 11:51 AM   #43
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Quote:
Originally Posted by Nalle View Post
Wildcard,

I have taken the liberty to slightly modify one of Rheine3's sketches and would appreciate your comments..


If there is some usable space between the 46515 and the engine, would it not improve airflow if one used a slightly curved cover of the original air return.
Rheine shows a straight blue line and I have indicated my thinking in red.
Even a one to two inch "bulge" should help. Yes???
Somehow the picture got lost......

https://drive.google.com/file/d/1wbd...ew?usp=sharing
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Old 06-05-2021, 07:26 PM   #44
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Update. Started the trip, coach was pretty warm. Split was 19 degrees and airflow was good. Maybe not as good as my high fan on the old unit. An hour later we are in camp on 50A. Split and airflow are decreasing. Couple hours later I suspect it's serious. Looked into the closet and sure enough ice all over the evaporator. So what;s going on here. I can't believe it's a Freon problem. I don't have a filter in place. I had good steady water coming out of the bottom. Must be airflow?
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Old 06-05-2021, 07:36 PM   #45
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Wildcard, I completely agree with rounding the intake IF I had the room. I had about an inch and used foil back duct board on that since it's close to the engine.
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Old 06-05-2021, 08:16 PM   #46
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Bummer. Recycling 30-50% of the air is creating two problems:

1) Not enough CFM... passing through the evaporator.

2) The evaporator coils are freezing over.

To solve both problems, what can be done to increase air flow?

Can you add an external booster fan to the cold air duct?

rheine3: How cold was it outside when you were running your AC? And what was the air temperature out of your roof vents?
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Old 06-05-2021, 08:24 PM   #47
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Bummer. Recycling 30-50% of the air is creating two problems:

1) Not enough CFM... passing through the evaporator.

2) The evaporator coils are freezing over.

To solve both problems, what can be done to increase air flow?

My first thought was to add a pre return fan over the hole in the floor.
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Old 06-05-2021, 08:35 PM   #48
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Bummer! And we had our fingers and toes crossed for you.
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Old 06-05-2021, 08:53 PM   #49
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Originally Posted by imnprsd View Post
Bummer. Recycling 30-50% of the air is creating two problems:

1) Not enough CFM... passing through the evaporator.

2) The evaporator coils are freezing over.

To solve both problems, what can be done to increase air flow?

Can you add an external booster fan to the cold air duct?

rheine3: How cold was it outside when you were running your AC? And what was the air temperature out of your roof vents?

85 outside 66-68 out of the vents
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Old 06-05-2021, 09:45 PM   #50
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Wildcard/Everyone: Short of taking some refrigerate out of the lines, which would de-rate the system, how can the OP move more air through those evaporator coils?

rheine3: Was it 85F and really humid where you were at... when the coils freeze over?

==> What about blocking 1/3 of the air passing through your condenser?

My concern is that any de-rate will produce poor cooling inside the cabin. Then again, we are dealing with recycled air flow though the evaporator, so maybe the CFM into the cabin ceiling vent is not a problem?

...And if CFM is not the problem, then the problem with rheines' modifications are that his system is too efficient.

What if:

==> You put a square floor fan in the bedroom that blows air into the intake vent? (Wouldn't that be great if it worked? ..And you would get more cold air out your ceiling vents.)

* My concern is that if you RECIRCULATE more air thru the Evaportator it's just going to increase the efficiency, but maybe not? These HVAC "gotchyas" are bassackwards sometimes. So you just have to try it and see what happens?

==> The only other thing I can think of at this point is to install a 3" vent tube (like a dash AC vent tube) that runs into the bedroom? ...One which you can adjust like the AC vent on your dash to allow cold air to escape out of the cold box side and into the bedroom. And thereby allowing some of the cold air to escape from the cold side so it does not freeze-over inside.
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Old 06-06-2021, 06:20 AM   #51
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Quote:
Originally Posted by rheine3 View Post
85 outside 66-68 out of the vents
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Rheine3, this is a big bummer. Is there any way you can move the unit out an inch?? How close are you to the side door??. You also said that you have an inch on the inside. In my sketches attached, I have a 2" bump on the inside, hoping that that would be enough.
We need someone good with air flow here. Maybe a sheetmetal baffle, halfway down on the 2" bump, could direct more flow to the lower part of the bottom half. Did you have ice all over the bottom half, or just way down???
How come you only have one inch to the engine?? Is it a V12 in there?? Most of us just have a narrow straight six
There is a lot of people out here rooting for you on this. Hopefully we can come up with a working solution.
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Old 06-06-2021, 06:33 AM   #52
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Quote:
Originally Posted by rheine3 View Post
85 outside 66-68 out of the vents
Attachment 179337

Attachment 179338

Attachment 179339

Rheine3, this is a big bummer. Is there any way you can move the unit out an inch?? How close are you to the side door??. You also said that you have an inch on the inside. In my sketches attached, I have a 2" bump on the inside, hoping that that would be enough.
We need someone good with air flow here. Maybe a sheetmetal baffle, halfway down on the 2" bump, could direct more flow to the lower part of the bottom half. Did you have ice all over the bottom half, or just way down???
How come you only have one inch to the engine?? Is it a V12 in there?? Most of us just have a narrow straight six
There is a lot of people out here rooting for you on this. Hopefully we can come up with a working solution.
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Old 06-06-2021, 06:36 AM   #53
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Originally Posted by Nalle View Post
Attachment 179337

Attachment 179338

Attachment 179339

Rheine3, this is a big bummer. Is there any way you can move the unit out an inch?? How close are you to the side door??. You also said that you have an inch on the inside. In my sketches attached, I have a 2" bump on the inside, hoping that that would be enough.
We need someone good with air flow here. Maybe a sheetmetal baffle, halfway down on the 2" bump, could direct more flow to the lower part of the bottom half. Did you have ice all over the bottom half, or just way down???
How come you only have one inch to the engine?? Is it a V12 in there?? Most of us just have a narrow straight six
There is a lot of people out here rooting for you on this. Hopefully we can come up with a working solution.
I am thinking a baffle plate as shown in yellow on the attached image
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Old 06-06-2021, 07:20 AM   #54
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Worst fears are confirmed. To get by you can only run 1 circuit (just kill breaker). You basically only have 1/2 the rated airflow or less.

What you feel out your vents is velocity not actual cfm.

That baffle plate takes the rated 600cfm that is designed to go across the coil that is 15x20 (figuratively speaking) and now your taking it through 7x20 (again figuratively speaking) section of the coil. Forget the rest of the air travel after that as you've already lost flow. Everything past that is just further exaggerating the problem.

I am going to digest some of the pictures etc in this thread. I also have the manual for the OPs new unit and see what I can come up with.

OP, kill the 2nd stage breaker so you have some AC after you thaw the coil.

And if possible get me a picture of the space behind that is stopping you from using a transition return duct.
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Old 06-06-2021, 09:27 AM   #55
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Did put a fan in front of the intake hole this morning. Several hours now and no ice. Humidity at 74% but not quite 80 outside. I like the ideas and I think a combination of some are worth trying. A nice squirrel cage would fit in that hole. When my HVAC unit is all the way in and touches the back framework the door barely closes. I will home Monday afternoon ready to rethink this.



Quote:
And if possible get me a picture of the space behind that is stopping you from using a transition return duct.
Will try to get this today.
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Old 06-06-2021, 10:16 AM   #56
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Below is a picture I kept from one of "Fireup's" postings, which may not be relevant unless all Winnebago Class-A DPs have the same basement AC frame and rails? Also, you really don't see the area of greatest concern, which is where the "Air Handler" would go.

In any event, here's a picture that will give you some idea of what the OP is working with until he can send you more accurate photos of his 2009 Ellipse frame and rails.
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Old 06-06-2021, 10:50 AM   #57
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That's what I am working with.
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Old 06-06-2021, 01:25 PM   #58
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I hope adding a floor fan works. And maybe you will have even more cold air blowing through your roof vents than you did before your modifications.

===

If you find adding a floor fan works, I suppose a better solution may be to add (and hide) a blower motor to your system.

However, you might want to wait until other HVAC experienced persons weigh in on that. I think you want just the right air flow for optimum use, and maybe adding a blower will be too strong?

Alternatively, maybe adding a "register fan" you plug into a wall socket above your washer/dryer is a better bet... and when you plug in a cord to a wall socket, you have a circuit breaker (protection) in your inverter panel (aka Sub-Main-Panel).

==

On the other hand, a blower may work even better? Again, it's one of those things you just have to experiment with.

However, if you go the blower route, then I suggest you wire it to your basement AC thermostat connector/plug so it will turn on with your thermostat calls.

Note: You might also install another relay #T92P7D22-12 to isolate the load from the Basement AC circuit board and use a 20A reset fuse. Or you can install a wall switch in you closet and tap into the wall socket near your washer dryer where I thing your bedroom TV plugs into.

See Thermostate wire diagram below.

=== TO MODIFY OR NOT MODIFY? ===

* rheine3's old Coleman-Mach is model #6537-A871.

* rheine3 bought a new Airxcell 46515-811, which I think has the same footprint as my 2004 model Colman-Mach #6535-471.

So this is why rheine3 had to modify is Airxcell 46515-811... but aren't we still talking about building the same "Air Hander" I use in my 2004 that has a side port to the evaporator?

If so, and I'm not saying this is the case, it sounds like you other RV owners who use a 6537-xxxx and are looking at buying a new Airxcell 46515-811...

...I suggesting you check with some salvage yards to pick up one of the Air Handlers used in Horizons and Vectra models, and report back to us if it works or not?

On the other hand, maybe rhenie3 modifications, to include a fan/blower, will prove to be even more efficient and this would be the better route if you can duplicate rhenie3 work. (TBD)

First we need to wait a while and get a "green light" from rhenie3 that adding a fan will cure his icing-over problems in high humidity and relatively low temperature (sub 80F) situations.

That said, in 90F-105F and in dryer climates, may his modifications may be a home run! TBD. It's amazing what just a couple degrees difference can make! ...And don't forget about the humidity factors too?

Wildcard: For a given temperature, like 80F in this case, where we know rheine3's evaporator coils are freezing over in 74% humidity... is it more likely or less likely this condition would have occurred in higher heat (like 85F+) when the humidity is less than 50%?
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Old 06-06-2021, 01:41 PM   #59
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You probably investigated all of these but I thought I'd ask:

1. Is there any way you can install the new "guts" in the old carcass?

2. Also, I noticed in one of your prior photos that there was a shaft protruding from the fan. Is it necessary that it be so long and, if it can be shortened, would that allow you to move your coil unit enough for the top vent to work?

Do you have a top view photo of your old unit with the cover off? I'm curious as to what the layout is like.
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Old 06-07-2021, 08:34 PM   #60
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At home. Fired her up. It was 85 degrees and 60% humidity. Coach sitting mostly in the sun. 89 inside. I stuck my HF 8" tin can fan in the hole. My airflow is better. My split dropped now to 12 degrees. It took fifteen minutes to get that first one degree drop in the coach. I am not sure if my choke point is the coil itself or the routing. Based on the temp I don't think I have air flowing over a big chunk of coil. I am ready to pull the unit to see if I can get any ducting to the back even if it's half or 3/4 of the coil width,



If you notice in post 57 ( scroll up a couple) there is a vertical support bar roughly in the middle. See wires wrapped around it. That is the very left end of the unit's hanger. To the left of that there is nothing near the unit when in place except the bottom front rail. The whole box sticks out free from that bar toward the rear. That may be what I was missing. I will make a few marks before I pull the darned thing out again.



There is a heat shield to contend with but I see a couple inches at least.
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