Mini-split Coolant Line Question

[HRTKD]

I am a heating and air guy. I would not install a conduit. It sounds good but won’t work down the road unless you make it straight and have a large access panel at the top end to form the lines as they exit the top of the chase. I would forget the conduit and install the lines and drain and wire now. The Best would be to install the mini split now. It is the perfect time to do so and you will love it. I have never heard someone say “Boy I sure don’t like that mini split.” Or “Man that thing is noisy.” Or “It sure cost a lot to operate.” I am a cash and carry guy but I would put it on a credit card if I had to while the wall is open.

Thanks for that advice. The rebuild of the front of my trailer is complete and I did not run anything for a future install of a mini-split. The wall is slightly less than 1.5" thick. Running conduit that would easily fit lines for a mini-split didn't seem like it would fit within the wall. The ~90° bend toward the top would have been challenging for the conduit (to fit in the wall) and would probably have been too sharp for the coolant lines.

If I decide to put in a mini-split, I'll run the lines outside the wall.

 

[DerpsyDoodler]

Thanks for that advice. The rebuild of the front of my trailer is complete and I did not run anything for a future install of a mini-split. The wall is slightly less than 1.5" thick. Running conduit that would easily fit lines for a mini-split didn't seem like it would fit within the wall. The ~90° bend toward the top would have been challenging for the conduit (to fit in the wall) and would probably have been too sharp for the coolant lines.

If I decide to put in a mini-split, I'll run the lines outside the wall.

View attachment 63328

If you haven't already made the purchase, and if you have room on the roof or in the underbelly, they do make horizontal mount mini split units. Couldnt tell you anything more about them than they exist.

 

[HRTKD]

If you haven't already made the purchase, and if you have room on the roof or in the underbelly, they do make horizontal mount mini split units. Couldnt tell you anything more about them than they exist.

I recently saw the underbody mount version. That would be handy.

 

[TKB4]

The lines are pretty flexible, but you still have to be carefull not to kink them. But if you carefully make a turn it's no problem.

just prevent applying too much pressure on a single point. When installing mine, I did apply pressure to make the bend and for each 'push' I moved 1 inch each side, so basicly forcing it into a curve, instead of bending on a single point and hoping for a curve.

I also noticed the insulation on the lines does help preventing applying too much force on a single point (thus causing a kink)

I do recommend evacuating the lines, even with the DIY sets. That always does a better job than just releasing the gas and assuming the majority of the air will be pushed out.
Remember, evacuating is not only to remove air from the lines, but more importantly also remove moisture in the air. By evacuating the lines, you're lowering the pressure, so any moisture will evaporate and be sucked out of the line (Lower pressure = lower boiling point - thus water becomes vapour)

Do you already have a mini split? Make sure you're getting an inverter one. The regular on-off ones are not regulated. Not as comfortable (its either fan blow or cold air, where as an inverter one can provide any temperature), but more important: an inverter one doesn't have the high inrush currents compared to a regular on-off one.
Does make a lot of sense when it comes to inverter sizing.

(But to be honest, I don't have any experiencing with the mini splits available in the US. They are very common here in NL (Europe in general) but it might be different in US)
The big ones you're using (with ducts) are here only installed in offices and big buildings, residential generally uses the mini split (or bigger versions with multiple inside units)

The DIY ones here mainly MR COOL brand should NOT BE VACUMED AT ALL ! They have FREON SEALED IN THE LINESET. The ones that people just choose to do as DIY install (almost all others) come with generally enough freon in unit for up to 25 foot linset. Its possible if you use a 15 foot linset you might get by with just flushing some of the extra freon through the lines to purge it but a vacuum would be much preferable .

 

[TKB4]

I recently saw the underbody mount version. That would be handy.

I have seen some mounted on the rear of RV which seems a likely place for a vertical mount unit.

 

[TKB4]

Not sure where to post this as it's about mini-splits in general. It doesn't matter what you mount it to (RV, building, etc).

How flexible are the coolant lines between the inside and outside units of the mini-split?

The reason I'm asking is that I'm getting ready to rebuild the entire front wall on my RV trailer due to delamination. I'm thinking of running conduit from the bottom of the wall to a point near where the ceiling would be on the inside. I'm hoping that if I want to put a mini-split on my RV in the future, I can just run the coolant lines through the conduit instead of having to drill a hole through the wall. Any idea if that would work?

I've never seen a mini-split in person, just in pictures. So I'm not sure what I would be working with. The lines look flexible in the pictures. They're in coils, so how bad could it be?

How large would the conduit need to be to run the lines? The fittings would be the critical part, requiring larger conduit with very gentle bends. I don't know that I can put in a single conduit big enough for the coolant lines, drain and electric. A couple of conduit runs may be better.

Remember you would also have fittings and depending on the unit the lines may have 1/4 inch and 1/2 inch lines plus 5/8 inch drain line plus 4 conductor 14 guage wire plus insulation. The larger and less efficient units like anything above 12,000 BTU may use 3/8 inch and 5/8 inch copper lines plus the same drain and wire. The fittings at the ends would make anything but a large straight conduit difficult. To answer you most conduits manufacturers sell just to go through 4-6 inch wall are 3 to 3 1/2 inch diameter. You could get by smaller for that purpose but at least 2 1/2 inch long sweep absolutely minimum for even one bend. If you have to cut the flares / coupling off to feed then you will need HVAC guy anyway. You have to be much more careful bending the larger linset as it kinks much easier.

I STRONGLY SUGGEST RUNNING THE LINESET BEFORE CLOSING WALL UP as the HVAC tech said . A 15 foot line is as little as $120 or so a 25 about $150 and a 35 foot about $200 though copper prices are changing rapidly.

 

[CharlesK]

I recently saw the underbody mount version. That would be handy.

Do you remember where you saw this? Or, have a brand name that I could search? A horizontal condenser may solve some issues for my future minisplit install.

 

[acdoctor]

Undermount 12V Split System Air Conditioner for RV's

12V DC AC Air Conditioner undermount split system van sportsmobile conversion trailer rv recreational vehicle

undermountac.com

 

[DJSmiley]

But those AC's pull a lot of power from your battery bank. Unless you have a huge RV with plenty of room for a huge amount of solar panels, it's going to drain the batteries pretty fast.

For mobile usage you might consider an evaporative airco. Those are available in 12V, and don't draw much, so no problem running them on batteries, without worrying about it draining the battery in a few hours.

Viesa Holiday the ecological evaporative air conditioner for caravans and vans - Viesa Holiday

Viesa Holiday III is the evaporative air conditioner for motorhomes and vans. Ecological, pet-friendly and the freedom of 12 volts. Discover how it works

viesaholiday.com

Van Conversion Air Cooler - Best AC for Vanlife | Fresair

A Fresair Van Conversion Air Cooler is the best 12V DC option for vanlifers currently building out or converting their vans.

www.fresair.com

They do work pretty well. Not as efficient as a regular aircon with refrigerant, and their efficiency depends on the humidity, but their low power usage is a huge benefit.

 

[HRTKD]

Evaporative doesn't work well for boondocking I suspect. I can carry only so much water.

 

[TKB4]

Evaporative doesn't work well for boondocking I suspect. I can carry only so much water.

Yep wouldn't work in my area much at all due to high humidity and I suspect many similar areas. Generally a 12,000 BTU mini split once the area is cool may only use about 400-500 watts but of course that depends on the heat load of the RV. Remember you can also start with a fully charged battery bank and depending on size it may last a day with minimal solar input.

 

[Short_Shot]

But those AC's pull a lot of power from your battery bank. Unless you have a huge RV with plenty of room for a huge amount of solar panels, it's going to drain the batteries pretty fast.

For mobile usage you might consider an evaporative airco. Those are available in 12V, and don't draw much, so no problem running them on batteries, without worrying about it draining the battery in a few hours.

Viesa Holiday the ecological evaporative air conditioner for caravans and vans - Viesa Holiday

Viesa Holiday III is the evaporative air conditioner for motorhomes and vans. Ecological, pet-friendly and the freedom of 12 volts. Discover how it works

viesaholiday.com

Van Conversion Air Cooler - Best AC for Vanlife | Fresair

A Fresair Van Conversion Air Cooler is the best 12V DC option for vanlifers currently building out or converting their vans.

www.fresair.com

They do work pretty well. Not as efficient as a regular aircon with refrigerant, and their efficiency depends on the humidity, but their low power usage is a huge benefit.

Define huge.

By my calculations I'll need 2x 24v 280ah packs to run a mini split inside a glorified teardrop for 72 hours assuming 90F all weekend day and night AND full sun load. That's with 2 inches of insulation. The trailer design will be 6x8 feet with 600 to 960w of solar depending on how motivated I am to build two slide out panels.

600w alone is enough to run most mini splits if it insulation is decent or it's not too hot out.

That's about $3000 worth of batteries with DIY cells/bms/battery case right now and plenty of folks are more than happy to spend that on Battleborns for much less capacity.

Many folks have told me over the last several months of my researching the matter that they pull about 4-6kwh per 24 hour period in a 7x16 trailer with 1" of insulation, depending which model they have.

Evaporative coolers would be the worst thing imaginable here in Wisconsin. Last time I was out for the weekend the humidity was over 90% the one day and it was 95F. At best it wouldn't do anything at all. At worst it'll turn the inside of my camper into a sauna.

 

[JMc]

The DIY mini-split units come pre-charged from what I understand. So no cutting into, extending or shortening the lines, unless you want to want to make a visit to the HVAC guy to evacuate and then recharge the system.

On the mini-split units I’ve installed, the lines were capped to keep out dust but otherwise empty. The compressor is pre-charged with refrigerant and over-filled with the assumption that a full line set will eventually be attached. After the lines are installed and vacuumed (or not), the valves at the compressor are opened and the refrigerant enters the lines.

To the OP’s question, the lines are soft copper usually with flare fittings and one tube is covered with foam insulation. It might be difficult to route them in a conduit. I’d definitely avoid placing them in a sealed wall.

 

[JMc]

Evaporative coolers would be the worst thing imaginable here in Wisconsin. Last time I was out for the weekend the humidity was over 90% the one day and it was 95F. At best it wouldn't do anything at all. At worst it'll turn the inside of my camper into a sauna.

We had a house in western Colorado that used evap coolers. They work quite well if the dew point is 40F of less. As the outside dew point increases the comfort of the conditioned space goes downhill. It’s marginal and quite “sticky” at a dew point of 55F, above 65F? Forgetaboutit.

 

[Short_Shot]

We had a house in western Colorado that used evap coolers. They work quite well if the dew point is 40F of less. As the outside dew point increases the comfort of the conditioned space goes downhill. It’s marginal and quite “sticky” at a dew point of 55F, above 65F? Forgetaboutit.

So basically every day in Wisconsin lol

 

[Supervstech]

On the mini-split units I’ve installed, the lines were capped to keep out dust but otherwise empty. The compressor is pre-charged with refrigerant and over-filled with the assumption that a full line set will eventually be attached. After the lines are installed and vacuumed (or not), the valves at the compressor are opened and the refrigerant enters the lines.

To the OP’s question, the lines are soft copper usually with flare fittings and one tube is covered with foam insulation. It might be difficult to route them in a conduit. I’d definitely avoid placing them in a sealed wall.

Mr cool, and a few other DIY specific minisplits come with precharged lines that attach with aeroquip sealed fittings.

 

[TKB4]

Mr cool, and a few other DIY specific minisplits come with precharged lines that attach with aeroquip sealed fittings.

Yes I think Alpine sells some DIY mini splits that are rebranded for them as Blueridge and likely made by Free or Madea. I see from your signature etc that you should know !! I have done a lot of DIY including geothermal install and mini splits etc. Interestingly I and my family also own 6 jeep liberty diesels from 05 and 06 with all their quirks etc. I have done all the engine work on them and wouldn't even consider allowing most diesel mechanics to touch them.