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Old 06-03-2021, 11:55 AM   #21
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Quote:
Originally Posted by Nalle View Post
Well, The duct on the side requires cutting and welding on the old frame/hanger. Your idea eliminates all that. My only concern is the air flow and heat exchange with your design, as sleek as it is. Did you discuss your design with Coleman?? Probably the company lawyer told them not to comment.
No Coleman is not going to help me break warranty. My airflow is strong. As for efficacy of the condenser coil in this scenario it needs to be field tested. We are headed out this weekend, camping in the 80s.



Consider the duct solution from top to back. I don't think the air climbing down over the back through a 2" opening is going to spread evenly across the height of the coil. There is probably a direct relationship between vertical entry point on the coil and the amount of airflow. In my case it's not a bright idea just the only idea I could think of.
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Old 06-03-2021, 12:05 PM   #22
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If you getting -20F out your vents and your evaporator is not freezing over, then your system is working like she should.

What is the model number of your new Coleman-Mach (2-Ton) and can you tell us what compressors it comes with?

I'm guessing these are 134a type compressors vs the old R22 type? ...So how many BTU did the literature spec in this new basement AC or did they leave this information out?

Here are some diagrams of my 6535-671 model I have collected from other forum members and edited for better/easier understanding.
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Old 06-03-2021, 03:05 PM   #23
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Mine looks just like that.
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Old 06-03-2021, 05:37 PM   #24
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I like your idea and I hope it works out for you.

My concerns are your bringing most if not all the airflow through the Evaporator coil the long/wrong way. This disrupts 2 theories.

1- the refrigeration theory where the at the entry point of the refrigerant the state is a low pressure low temp liquid. As it travels the tube it goes from low temp liquid to low temp saturated liquid/gas and as it exits the coil on its way back to the compressor its a low temp superheated gas. You interupted the flow of air per design across this coil and the only way to know is measure superheated at the compressor to make sure your not flooding back.

2nd being airflow. The coil was designed to draw air the thin way. Your blower performance can be tested via actual amperage vs nameplate RLA corrected for actual voltage vs RLA at rated voltage. More voltage than rating will naturally equal less amperage. You have to visit the ole electrical PIRE wheel. Restricted airflow will draw less amps...yet overheat the motor and cause refrigerant circuit problems.

Both issues could result in shortened compressor life, and the latter would kill the fan motor early.

Another issue that may arise is the airflow issue may allow some water/condensate to be sucked off the coil vs just running down the fins and dripping into the pan, drawn through fan and spit into ductwork. This can be verified by after some extended run time, shut it down and look at the blower wheel for wetness.

I would at a minimum once you get a load where both circuits are running and the RV is cool, near set point and humidity is undercontrol is to check the temp differences between the return at the filter and the closest supply vent in the bedroom. If its 20* or more you have an issue. 20*,21*,23* I wouldn't sweat it.

I say all this for educational purposes, I do Industrial HVAC for a living and I love re engineering what engineers design...most of the time in my case cause it doesn't work as designed to begin with. You re-engineered and engineered design and I hope it works. I can't sit here in my recliner and say yep er nep without data.

If you have any questions reach out to me in the "other forum", I don't come here much at all.
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Old 06-03-2021, 05:41 PM   #25
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Originally Posted by imnprsd View Post
If you getting -20F out your vents and your evaporator is not freezing over, then your system is working like she should.

What is the model number of your new Coleman-Mach (2-Ton) and can you tell us what compressors it comes with?

I'm guessing these are 134a type compressors vs the old R22 type? .
R-410a is what's in the new units not 134a.

134a does not work well in medium/high temp Evaporator of comfort cooling.
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Old 06-03-2021, 06:05 PM   #26
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Wildcard Thank you for that knowledgeable post on disrupts. In post #4 I show that I am forcing air through the flat side of the coil's upper half and then back through again for the bottom. I did not see another way to route air unless I moved the whole unit out a couple inches from the frame and use a top to side duct solution. With the new box being so deep I would never get the door closed.
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Old 06-03-2021, 06:39 PM   #27
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Wildcard Thank you for that knowledgeable post on disrupts. In post #4 I show that I am forcing air through the flat side of the coil's upper half and then back through again for the bottom. I did not see another way to route air unless I moved the whole unit out a couple inches from the frame and use a top to side duct solution. With the new box being so deep I would never get the door closed.

Like I said...or maybe I didn't. I like it. I actually like it enough that when I replace mine I may do the same vs a return air transition duct. I just like having the data for system health...it's just me, I do it for a living so it's 2nd nature.

I have the room...but it would eat into my access to that side of the engine.


I feel you will be perfectly fine.

Pretty work and great creativity to think of that baffle.
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Old 06-03-2021, 07:08 PM   #28
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Was it possible to reuse the old metal case?
Put the new inards in it?
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Old 06-03-2021, 09:24 PM   #29
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Was it possible to reuse the old metal case?
Put the new inards in it?

Might be possible but I am not versed in HVAC. The newer one is really fine engineering if you consider they shrunk the box by 30% but beefed up the condenser and evaporator coils. The condenser (hot side) coil is much longer pushing the coach fan back That's why there is no room to tilt the evaporator coil for top return air.,
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Old 06-04-2021, 01:21 AM   #30
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Since everyone is commenting...

First, I applaud your thinking and willingness to build a better mouse trap.

Second, I applaud you sharing your efforts with all of us.

Now to the meat and potatoes: If you say your new basement AC looks just like my old 2004 model, which is smaller, then is it redesigned or didn't you guest get a different model?

Again, what is the model number of your new basement AC and what BTU did they rate it at?

Next, could you have got that 90-degree air handler duct work from a RV salvage yard for cheap? (See part #2 in the drawing below.)


It looks like your new Basement AC would fit my 2004 Itasca Horizon, but I don't have eyes on it like you do.

I.e., the purpose of this "air handler" is to take the downdraft air from the bedroom (under the washing machine) and re-direct it to the side port.

Next, I think your idea of routing air in both directions is interesting. What are your runtime numbers?

1) OAT?
2) Compressor #1 running ==> ???? degrees out the air vent
3) Compressor #1 & #2 running==> ???? degrees out the air vent

Note: I don't see how routing the air like you did has any effect on the compressors.

Why?

Answer: The compressors are located on the "hot side" of the box and there is insulation between the "cold side" and the "hot side". So one side is supposed to be isolated and insulated from the other.

I'm not an HVAC expert so I hope WildCard set me straight on this subject. For example, I think the evaporator is only affected by the cold side and who cares which way the air passes through the evaporator coils as long as there is cooling taking place?

In fact, the 50/50 design may prove to be more efficient. ...OP: What to sort of cooling number are you getting?

===

Note: I once put a portable AC right in front of my basement AC bedroom intake and I got better efficiency (colder air) out the roof vents by tricking the basement AC into think the air temperature in my cabin was colder than it really was.

On the other hand, I think there is some efficiency gain when you start your AC at 80F vs. waiting until you get back from your day trip and find the inside temperature of your RV at 95F... and then try to cool down the inside of the coach.

Plus the efficiency gain was adding another 8,000 BTUs to my RV 2-ton basement AC system, so naturally there would be better cooling.

===

The Basement AC is only supposed to drop the OAT by -20F.

However, a portable AC will work to drop the inside RV room temperature by -20F and it will exhaust hot and dehumidified air in the process.

...And, let's not forget the power of a fan!

My point is that if you have both cold air and a fan working together you get the best of both worlds!

That's why I repositioned that portable AC from the bedroom to the the living room area, and then I hid it inside my RV living room area credenza.

And now I'm more comfortable in hotter weather; and I don't even run my basement AC when the OAT is 80F or less. This hopefully will extend the life of my current basement AC too now that this little 8,000 BTU portable AC is my primary AC and I only use the Coleman when I want some super cooling.

Any way, for more information on adding and hiding a portable AC in your RV, you can go to this thread:

https://www.winnieowners.com/forums/...ad-360836.html

OP: I think your basement AC conversion is a "homerun" if the numbers check out. So please get yourself a digital cooking thermometer on Amazon and take some measurement to share with us!

...And what are you going to do with your old basement AC?
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Old 06-04-2021, 06:32 AM   #31
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Like I said...or maybe I didn't. I like it. I actually like it enough that when I replace mine I may do the same vs a return air transition duct. I just like having the data for system health...it's just me, I do it for a living so it's 2nd nature.

I have the room...but it would eat into my access to that side of the engine.


I feel you will be perfectly fine.

Pretty work and great creativity to think of that baffle.
Wildcard,
I have the same situation. I have the space behind, but, like you, it limits engine access.
It seems to me that the only reason this can work, is that the coil fins are vertical. Since I could probably steal 1-2 inches on the back side, without interfering with engine access, would it improve airflow if the rear return was covered with a curved piece, sticking out a couple of inches, rather than just a flat sheet??
I have made all the measurements and drawings for a rear return duct. However, if this works, it is so much simpler and provides the needed engine access.
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Old 06-04-2021, 08:20 AM   #32
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Since everyone is commenting...


Note: I don't see how routing the air like you did has any effect on the compressors.

Why?

Answer: The compressors are located on the "hot side" of the box and there is insulation between the "cold side" and the "hot side". So one side is supposed to be isolated and insulated from the other.

I'm not an HVAC expert so I hope WildCard set me straight on this subject. For example, I think the evaporator is only affected by the cold side and who cares which way the air passes through the evaporator coils as long as there is cooling taking place?

[/B]
Why it matters? I have added in this quote a refrigeration system operating chart that you posted.

Now it matters not the location of the compressors as they are refrigerant cooled. If you follow the chart (and I would like to add that chart is not law,, temps etc vary. For example it could be designed for a 45* evaporator coil) refrigerant line temps back (suction, low side refrigerant pressure) and follow the temps. They show 40* through the coil as the refrigerant state changes. Then as the refrigerant exits the coil and back to the compressor the temp of the refrigerant rises. This is called superheat. Now a compressor requires a certain design of superheated gas to cool. If the superheat is low the compressor is seeing liquid. The compressor is a gas pump not liquid. Liquid washes the bearings of oil and is hard to compress vs a gas and will eventually destroy the scroll, valves or veins depending on design.

If airflow is low across that evaporator we will start to have low superheat = liquid entering suction of compressor.

Again it matters not where the compressor is located...you can put it on the roof or under the seat.

And your correct it does not matter which way airflow across the coil...just as long as it does at rated air flow.

Again, I am not saying it won't work, doesn't work or the sky is blue only data can confirm. I would love for the OP to take a vacation to the OBX and let me get some readings.
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Old 06-04-2021, 10:18 AM   #33
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Do you have any idea how much room one would need behind the new unit to modify the return air ducting to the back. I have a 2002 Suncruiser 35U so I may have more room than you have.
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Old 06-04-2021, 11:35 AM   #34
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Bob,
These are the max dimensions for my 04 Itasca Meridian. Additionally, it need a new/modified base and a relocated inside hanger rod. I.e. cutting and welding

https://drive.google.com/file/d/1hX_...ew?usp=sharing
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Old 06-04-2021, 11:54 AM   #35
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Bob,
These are the max dimensions for my 04 Itasca Meridian. Additionally, it need a new/modified base and a relocated inside hanger rod. I.e. cutting and welding

https://drive.google.com/file/d/1hX_...ew?usp=sharing
Thanks, this is helpful. Is the modified ductwork something you fabricated or is it available from somewhere?
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Old 06-04-2021, 01:59 PM   #36
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Wildcard: Your HVAC experience is much appreciated.

Speaking for myself, I can follow a chart, but I don't really have a feel for the HVAC system like you.

I was aware the compressor would not survive if liquid coolant entered it. However, I can't imagine a system that would not have a check valve installed to prevent this from happening?

I.e., don't all HVAC systems go "out of balance" from time-to-time? So again, I wouldn't know, but I would hope there are some safeguards built in. Are there?

OTHER QUESTIONS

If my Matsushita/Panasonic R22 compressors go bad, where can I buy new ones? ...Or can a compressor be repaired? ...Or is there a kit to upgrade to R???

This basement AC is built quite well IMO. And I think when people complain about it's efficiency they wrongly blame the Coleman-Mach Basement AC, when they really should be blaming Winnebago for using cheap duct sealing tape and not doing more to deliver the cold air to the cabin more efficiently. This is especially true when you see all the bare sheet metal duct work running up the back cap of the RV.

COMPLAINTS:

* Coleman should have used sealed ball bearings on the blower motor shaft.

* I think a 5-2-1 Hard Start Kit design would have been better than using a PTCR.

* If you have trouble restarting your compressors in 105F+ heat, then I think you might be better off with a electronic 120V SPP4E to use in place of your OEM Hard Start Kit that uses a WSX5 or WSX7 "motor starter" which is just PTCR wrapped in ceramic material that resists melting. (Wildcard, what is your opinion on this subject: Is the SPP4E a good upgrade for our Coleman Basement ACs that normally call for a 88-108uF start capacitor & motor starter?

TIP: Use electrical parts cleaner on your thermostat slide switch and don't force the basement AC to come on. I.e., I like to set the thermostat above the inside temperature and then turn "on" or put in "Auto" mode... and then lower the thermostat temperature to turn on the compressors.
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Old 06-04-2021, 02:22 PM   #37
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Wildcard:

Speaking for myself, I can follow a chart, but I don't really have a feel for the HVAC system like you.

I was aware the compressor would not survive if liquid coolant entered it. However, I can't imagine a system that would not have a check valve installed to prevent this from happening?

No, there is no check valve

I.e., don't all HVAC systems go "out of balance" from time-to-time? So again, I wouldn't know, but I would hope there are some safeguards built in. Are there?

No, they don't go out of balance unless there is an issue

OTHER QUESTIONS

If my Matsushita/Panasonic R22 compressors go bad, where can I buy new ones? ...Or can a compressor be repaired? ...Or is there a kit to upgrade to R???

Panasonic is out of business. Mine has Tecumseh compressors and they can still be obtained.
No you can't convert to R-410

* I think a 5-2-1 Hard Start Kit design would have been better than using a PTCR.

I do agree
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Old 06-04-2021, 03:00 PM   #38
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It has to be fabricated. I have not done his yet as the old heatpump is still hanging in there. Made some strange bearing noises last night, so it is getting close.
I am leaning toward a fiberglass/epoxy duct, made on a sacrificial styrofoam mould.
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Old 06-04-2021, 03:58 PM   #39
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It has to be fabricated. I have not done his yet as the old heatpump is still hanging in there. Made some strange bearing noises last night, so it is getting close.
I am leaning toward a fiberglass/epoxy duct, made on a sacrificial styrofoam mould.
I really like the idea of molding it.

I'm pretty much in the same boat, mine has had some issues but I haven't given up yet.
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Old 06-05-2021, 09:39 AM   #40
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Like I said...or maybe I didn't. I like it. I actually like it enough that when I replace mine I may do the same vs a return air transition duct. I just like having the data for system health...it's just me, I do it for a living so it's 2nd nature.

I have the room...but it would eat into my access to that side of the engine.


I feel you will be perfectly fine.

Pretty work and great creativity to think of that baffle.
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???
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