Anyone here use "UndermountAC" ?

[Chronicpenguins]

I guess that depends on what your needs are.
If you are trying to maintain or get to a temperature in your van, then a system like ours has the greatest benefit, as we can get you there efficiently as our output vs input is higher than our competitors. Our system cycles based on needs and set temp point, its not a constant non-stop draw.

If you are looking at just directing a small stream of cold air constantly throughout the night so you need it to draw the least amount of wattage doing so, our system is not designed for you.

I’m interested in both use cases, like when I’m sleeping I don’t need the whole van to be ideal temp I’m sure I can just get by with a cold stream to save energy, especially if I am in a very warm environment that would make it difficult to maintain a low temp. I think the sleeping part is more important to me then day time usage.

the lowest wattage is 750W, while the highest for the malbru unit is like 610W for 12000 BTU. I just wish there was an eco mode for night time usage.

the other thing is that there isn’t a lot of a user feedback / experience out there, so I’d like to hear some reviews before spending 4k… the malbru unit is like 40% less expensive but roof mounted

 

[cobratom]

Take a look at the Transit forums. We have so many customers using our system on the transit forum that there is a thread dedicated to ESP home control of our UndermountAC. Also a dedicated unpaid youtube video by a van builder "Tim and Katie"

The Malbru unit has been proven to use deceiving numbers. It's a 9000btu unit that you can get on Alibaba for about $1000.00.

Hopefully some our sprinter customers see this thread and chime in with their experience here.

 

[Airtime]

The Malbru unit has been proven to use deceiving numbers.

I’d be interested in some more specifics on this

 

[cobratom]

I’d be interested in some more specifics on this

I will send you a PM. It's not the intention of the this thread and I don't want to derail it.

 

[Spicy Mushoon]

Take a look at the Transit forums. We have so many customers using our system on the transit forum that there is a thread dedicated to ESP home control of our UndermountAC. Also a dedicated unpaid youtube video by a van builder "Tim and Katie"

The Malbru unit has been proven to use deceiving numbers. It's a 9000btu unit that you can get on Alibaba for about $1000.00.

Hopefully some our sprinter customers see this thread and chime in with their experience here.

I would love to hear more about this ESP control. I'm looking forward to hooking up a rixens unit for heat and your unit for AC and it would be great to control both via home assistant. I tried searching the transit forums but didn't find what you are mentioning.

 

[Chronicpenguins]

I would love to hear more about this ESP control. I'm looking forward to hooking up a rixens unit for heat and your unit for AC and it would be great to control both via home assistant. I tried searching the transit forums but didn't find what you are mentioning.

Let me know if you find the thread too, but I also am considering rixens + under mounts. Do you have a good starting point for home assistant and van?

 

[cobratom]

Here is the start of the ESP Home control discussion along with a simple circuit to control it that is placed between the thermostat and relay board.

UndermountAC.com Install on 2021 Transit Ext

www.fordtransitusaforum.com

 

[dartboard]

I am in the process of installing the 48V version on my sprinter, so far the kit seems very nice and they’ve been really responsive to my questions.

It’ll be a bit before I get it up and running though, I have to finish removing the generator and propane tank underneath that my build came with. So far it seems like the only really “difficult” step will be the vacuuming/filling, but I guess we’ll see!

 

[mike2016]

Is it possible to mount the evaporator(new ducted version) vertically? there are drain tubes on either side, as long as one side is able to drain it should be fine?

 

[cobratom]

Is it possible to mount the evaporator(new ducted version) vertically? there are drain tubes on either side, as long as one side is able to drain it should be fine?

Unfortunately not. It must be horizontal for the drains to function. There is a seam midway up that would leak water otherwise.

 

[99sport]

What is the condensation like on the outside of the evaporator - specifically the copper lines (but also the case)? - The copper lines are insulated, but there are quite a few gaps with bare copper showing. I was planning on putting a plywood bottom on this cabinet - will the lines / case sweat and get the plywood wet?

Also what about insulation on the lines? I bet the condensate line temperature will be way below the dew point and the low side hose will be cold too. Do I need to insulate these lines to prevent dripping / water damage to nearby structures?

 

[cobratom]

What is the condensation like on the outside of the evaporator - specifically the copper lines (but also the case)? - The copper lines are insulated, but there are quite a few gaps with bare copper showing. I was planning on putting a plywood bottom on this cabinet - will the lines / case sweat and get the plywood wet?

Also what about insulation on the lines? I bet the condensate line temperature will be way below the dew point and the low side hose will be cold too. Do I need to insulate these lines to prevent dripping / water damage to nearby structures?

View attachment 271037

Check your parts bag, you would have been provided with insulating tar tape for this purpose.

 

[99sport]

I have the tar tape.

What do I need to insulate? The exposed copper? The crimp fittings? The condensate line? The low side hose?

If I need pipe insulation on the lines then they aren't going to fit in my wall and I'll need to figure out different routing. The hoses is the real question I have as I can't insulate them after I bury them in the wall. If needed, I can go back and apply tar tape to fittings after the install, but I can't insulate the lines.

My instructions make no mention of what gets cold enough to cause condensation / needs to be insulated prevent water damage.

 

[Midwestdrifter]

Everything downstream of the expansion valve will be below ambient temperature (and the valve itself).

 

[99sport]

Everything downstream of the expansion valve will be below ambient temperature (and the valve itself).

How about the condensate line? Anyone know if automakers insulate those (or use special hose to prevent them from dropping below the dew point)?

And will the low side hose be cold all the way back to the compressor or does it warm up eventually? And is it cold enough to cause drips on to surrounding structure?

I need to go see if / where there is insulation on one of my car ACs, but a lot of the lines in question are buried under the dash and not accessible. I am hoping someone here knows best practice

 

[Midwestdrifter]

Yeah, I would do the condensate line as well. Its probably not going to get cold enough, better safe than sorry with hidden condensation sources.

The low side hose can be below ambient right up until the compressor. Though depending on system conditions it may be pretty close to ambient most of the time.

Auto systems don't use insulation for space saving and fire reasons. Home systems with the TXV at the indoor unit are a good example to follow.

For best efficiency you want the low side hose insulated wherever its not in the passenger compartment (so it won't pickup heat unnecessarily). For condensation you want to insulate when its inside the passenger compartment generally.

 

[99sport]

Yeah, I would do the condensate line as well. Its probably not going to get cold enough, better safe than sorry with hidden condensation sources.

The low side hose can be below ambient right up until the compressor. Though depending on system conditions it may be pretty close to ambient most of the time.

Auto systems don't use insulation for space saving and fire reasons. Home systems with the TXV at the indoor unit are a good example to follow.

For best efficiency you want the low side hose insulated wherever its not in the passenger compartment (so it won't pickup heat unnecessarily). For condensation you want to insulate when its inside the passenger compartment generally.

Interesting.

My 92 Civic has the low side insulated all the way back to the compressor - probably 6 feet of line. Strangely, the high side hose is also insulated from the compressor to the evap - might be a noise thing? The condensate drain line is plastic in the car and actually penetrates the firewall. A thick rubber hose connects on the engine side of the firewall - even though condensation after the firewall is probably irrelevant, that hose looks so thick it should be an excellent insulator.

Summary of other cars I checked:
1992 Civic and S2000 have low side line insulated from the firewall to the compressor.
T1N, Miata, and Camry have little / no insulation.

So it looks like insulating the cold side line all the way back the the compressor is best practice, but far from universal. Of note, the lines mentioned above are mostly aluminum tube and the lines in this kit are reduced diameter barrier (rubber) hose. So, I think I'll skip the low side insulation (I am going to try to fit the 3 AC lines, a 10/2, 18/2, cat 6, and rg coax cable in the pillar shown below). If I need / use pipe insulation, there is no way the AC lines will fit in there. Also below is a gratuitous shot of the S2000 AC lines / engine.

 

[cobratom]

You only need to insulate the entirety of the larger fitting all the way down to the exposed brass/copper.
The expansion valve does not need to be insulated as it generally runs well above ambient, but you should insulate the line leading up to it. (the little part exposed before the actual pressure chamber.

The rest of the of the line or the condensation line do not need to be insulated. It's pretty rare for rubber lines to sweat, the photo of the Honda show a hard aluminum line which is why it would sweat.

 

[99sport]

The general layout of my van is shown below. Note AC evaporator and bed position.

Option 1: I had originally planned to mount the evaporator like this (note that I need to cut off the part that extends past the cabinet frame):

I would draw air from below through an filter (probably a 1" household AC filter about 18"x11") with almost the entire bottom of the cabinet open. The problem with this is that there is a fairly sharp turn and a tortuous path to get into the coils. The area circled in green is the tightest location and is about 1/2 the area of the evap coils.


Option 2: It looks like I can turn the unit around and exhaust out the bottom. This would yield basically perfect airflow into and out of the unit. The problem is it blows down (half being on the galley countertop) and I'm not sure how well the air will mix. the other issue is that the condensate drain is 3" lower and it won't gravity drain inside the cabinet - I'll have to run it out the bottom of the cabinet where it will be exposed.


In summary.
Option 1:
Pros: Mounts the same way as a minisplit high-mounted wall unit - blows air across the bottom of the ceiling for good air mixing.
Condensate line hidden in cabinet / wall so clean looking install
Cons: Tortuous path for air into the unit
A good bit of sheet metal work required to reconfigure the evaporator

Option 2:
Pros: Trivial sheet metal work (just need to cut an opening in the bottom of the unit for the exhaust air)
Better airflow into and out of the unit
Cons: Ugly condensate line sticking out of bottom of cabinet for unprofessional look
Probably poorer air mixing / distribution

Feedback on pros and cons of each option? Am I missing something? Other thoughts? I don't think there is an issue cutting a hole in the bottom of unit (there is a sepreate condensate pan - and closed cell foam on the inside of the unit - so I don't THINK the inside will have condensate in it, but if there were that would be a real problem with a hole in the bottom).

 

[cobratom]

I can't advocate for modifying the evaporator in any way. The evaporators have a surprising amount of R+D into them and that 981 was 3 or 4 revisions in by the time we started ordering it. We inquired about placing the blower closer to the evaporator core to make for a tighter package but there would be low pressure areas on the core that end up freezing from not enough airflow. Can it be relocated to the floor? under the bed?