Improving 2014 Parkliner air conditioner

[trasko]

Forgive all the posts and data, but I found something useful. See the attachment. It is a table showing the "Net Free Area" calculations for certain vent types. This is generally used for attic venting calculations but seems relevant here.

To use the chart you can look at the vent & mesh type and then run calculations. For example: the exhaust vent on my Parkliner has 2 holes 6x7" which adds up to 84 in^2 of area. However, they are covered with 1/8" hardware cloth and aluminum louvers. That means the NFA drops to 40% of the otherwise un-obstructed area. So now we're talking 33.6 in^2.

The "intake" vents are 6 holes w/ 1/8" hardware cloth and no louvers. This calculates out to 40 in^2.

I'll be basing my calculations on these numbers. I need to triple these numbers at least because 1) it was insufficient before; and 2) the higher BTU unit needs more air.

[Eddie Longest]

Just a thought. Scamp glasses in a support maybe 1/4" thick inside in the trolly top to support the A/C. On the older Escapes they glassed on the separate A/C support cap over top of the trolly top. The Parkliner has a reverse (sunken) trolly top. You could glass in a support on the outside and it not really be visible and not need to have a perfect finish. Then you could go with a standard RV A/C. Maybe get pictures of the support on newer trailers with A/C. Before cutting up your trailer.
Eddie

[trasko]

Been awhile since I updated. Project got slowed down due to home life. I'm not going to write a bunch this time. Hopefully the pictures explain everything.

I made a bunch of committing cuts to the trailer so hopefully this proves successful. Initial testing I've done is unclear since the weather is so mild right now. The A/C works fine but that doesn't really matter when the temp is 74F. This Sunday is calling for mid/high 80s so that will be temperatures similar to when I gathered as my "before" dataset.

If everything works as I hope it does I'll assemble it more permanently and be done.

[daleeb]

Originally Posted by trasko

Been awhile since I updated. Project got slowed down due to home life. I'm not going to write a bunch this time. Hopefully the pictures explain everything.

I made a bunch of committing cuts to the trailer so hopefully this proves successful. Initial testing I've done is unclear since the weather is so mild right now. The A/C works fine but that doesn't really matter when the temp is 74F. This Sunday is calling for mid/high 80s so that will be temperatures similar to when I gathered as my "before" dataset.

If everything works as I hope it does I'll assemble it more permanently and be done.

Looking better for both in and out. Will the large exhaust be problematic for road splash water? Going to be following this for sure.

[trasko]

Originally Posted by daleeb

Looking better for both in and out. Will the large exhaust be problematic for road splash water? Going to be following this for sure.

Who knows regarding the splash, but I would think not. I had the original holes open to the elements for about 2 weeks and during that time there were at least 5 heavy downpours during the afternoon thunderstorms we get this time of year. I didn't notice any water inside.

On the plus side the original ACU had a hole drilled in it's bottom and it would just drip into the bulkhead below where the vents are and then drain out of another hole near the wheel well. So any water that does get in the vent will follow the same path. There is some electrical in there (12V and 120V) as well as the shower drain line but nothing I expect to be problematic. I used a "weather rated" electrical box to do the 120V extension joint since I saw one at the store and figured there is a chance of water in there.

[trasko]

In separate news I've been working on the fridge. It's a little 1.8 ft^3 Dometic 3-way (I think it is Dometic). During our big summer trip the performance was disappointing but from what I've heard not entirely out of the ordinary. It can do 35-40F below ambient. But we were regularly hitting 95-100F and so regularly having food at 50-55F for long periods.

The fridge in the Parkliner is held in only at the front panel by 6 rivets. During this A/C project I have pulled out the fridge, cleaned it up real good (inside the box but also the burner/chimney/fins/etc), tweaked the metal baffles and replaced the rivets with rivnuts so I can more easily service it. I ended up testing it and still not getting great performance.

I have a stick on thermometer I put at the top part of the door. It reads ~40F when it's 80F outside. However the floor of the fridge with a couple bottles of water reads 33F. So... Perhaps that's okay and I've been reading a maximum temp. of the fridge vs. something more typical on the inside.

Yesterday I pulled the fridge out again (thanks rivnuts!) and "burped" it per some threads I've seen on the RV forums. Short version is: flip it upside down, on it's side, on it's back, etc for a few minutes per turn and then reinstall. Don't start for 1 hr after the "burp." I'll go check on it later today to see if that had any effect. If not I'll likely leave it alone for the next 3 seasons and look to get a compressor unit next summer.

[trasko]

This project is done. It was more work than I thought it would be and I would have done things differently had I known.

First: I think it was a success.
I'm not sure as I'll need a 90F+ day to prove to myself that the A/C can cool to a comfortable level in that situation. Given the forecast for the next 10 days I expect that will have to wait until next summer. I will explain WHY I think it will work, though.

1) I've proven that an extra fan circulating air takes care of the "A/C on the floor" problem.
2) I've increased the capacity of the ACU from 5000btu to 8000btu.
3) Most importantly, I've significantly increased the "venting" (intake & exhaust for the "hot" side). From 40/33 in^2 up to 140/110 in^2 "Net Free Area."
4) I've greatly improved the sealing between the 3 zones of the ACU.

Lastly, I have one more trick up my sleeve: if the tripled vent area is still insufficient on very hot days I can remove some of vents (I used rivnuts) and can double the NFA of them. That means I can go as high as 240/220 in^2 NFA which is 6X more than from the factory.


What would I do different next time?
I think almost all of the problems with the factory A/C are due to venting. 1) not enough NFA both for the hot exhaust air and for the replacement air. 2) Mixing between "replacement air" that should be sucked into the exhaust and "cold side" air which should NOT be sucked out of the conditioned space (but was).

I think the small capacity of the ACU (5000btu) is actually sufficient for the space. And given the very tight space constraints one should avoid trying to fit something bigger like I did. I believe that was a mistake. Although the unit was not super expensive (~$300) it was by far the single largest expenditure of the project. The rest of the components were likely around $100 (screws, rivnuts, vents, caulk, special blades for jigsaw, etc).

So next time I would:
1) pull out the ACU to give me room to work w/o removing the cubby
2) cut some holes like I did in my project.
2a) increase size of exhaust holes (and use rivnuts w/ new vents)
2b) add additional "intake" space (also using rivnuts)
2c) cut holes in fore side of ACU cubby and shower floor cubby to allow replacement air a path to the ACU (this is scary!)
2d) I would not cut a hole for the "scoop" like I did unless I felt strongly I needed the small extra NFA (~30 in^2). I think it is helpful but too much effort and risky beacuse any imperfections are very visible.
3) Take great pains to seal the 3 "zones" from each other (hot exhaust, hot replacement air, cold). Using incense or smoke pen to track down any leakage from one to the other.
4) re-install ACU like from the factory

This plan would avoid the expenditure of a new ACU and all the mess and headache of removing the cubby from the trailer (scraping old caulk, exposing rivet holes, pulling back carpet, etc). My gut says for 1/4 of the work and 1/4 of the cost you would get 3/4 of the improvement I will get. And if you're still not satisfied you can copy my plan and none of the work you have done would have been wasted.


For now I have put everything back together, caulked it and put all the trim back in place. Vacuumed everything and wipes all the fiberglass/wood dust out. I'm done and likely won't know the true verdict on this project until next June/July.