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Mini-split Coolant Line Question

HRTKD

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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.
 
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.
 
I have seen install videos where the lines are bent by hand. Looks like soft copper similar to plumbing. There is a bit of a package with the two lines, control wires and power connection. Conduit should be fine if there are no bends. More of a slip-pipe. Then bend by hand to connect.

I would just wait until you are ready to actually install.
 
It will be a cleaner install if I can plan ahead for it. I don't want conduit running up the outside of the wall. Now is the time to put inside the wall.
 
Kind of exciting all the stuff that could be installed with access to inside the walls. I picture my self adding DC USB charging ports both inside and outside the RV, and putting a large conduit in from floor to roof for future expansion like satellite antenna cable or Cell extender.
 
Kind of exciting all the stuff that could be installed with access to inside the walls. I picture my self adding DC USB charging ports both inside and outside the RV, and putting a large conduit in from floor to roof for future expansion like satellite antenna cable or Cell extender.

Yep. I'm thinking that a DC port on the outside could come in handy. With the wall opened up, it's not quite what I expected. That horizontal footer kind of messed up my plans for the conduit. I still need to remove the plywood below that footer and the diamond plate needs to come off too.

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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)
 
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Mini splits are pretty simple. Refrigerant lines are usually 1/4” and 3/8”. The line set is insulated and does not have refrigerant in it. The refrigerant is contained in the outside condenser. There is a shark bite type connector available for refrigerant lines that will allow you to cut the lines to whatever lengths you need. You do need to use a vacuum pump to purge the lines before opening the refrigerant lines on the condenser. Not sure about bending the lines as short as you’ll need to without tubing benders. It can be done, just plan it out ahead. I wouldn’t place it in conduit. The line set, power cord and drain are designed to go through a 2 1/2” opening in the wall. Where are you mounting the outside unit? Units are sensitive to direct sunlight, dirty air and wind. Good luck
 
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.
Don't know if you got your question answered, but I know with the line-set included with my mrcool diy mini-split it told me, in degrees, how much the line could be shaped to a curve (e.g. don't exceed x degrees of bend). definitely be careful when bending. don't kink the lines.
 
Don't know if you got your question answered, but I know with the line-set included with my mrcool diy mini-split it told me, in degrees, how much the line could be shaped to a curve (e.g. don't exceed x degrees of bend). definitely be careful when bending. don't kink the lines.

The lines you're bending are copper?
 
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.
No always, this typically depends on the manufacturer
 
Many of these units have minimum line set lengths as well that Need to be adhered to as well
 
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.
If you have flaring tools shorting them isn't a problem. You can buy longer tubing but you'd have to add refrigerant to make up for the added length. You might have to release some if you went too short as well.

As the the OP, the bed easy enough. Making them look good is harder imo. Just don't kink it.
 
No always, this typically depends on the manufacturer
Not all mini-splits are DIY. Pretty sure all the DIY ones come precharged. This is what makes them DIYable (without buying vacuum pumps or flaring tools). As for the minimim lineset length, with the DIY model I bought, I got a couple options for line length. The unit is precharged with the appropriate amount of freon to compensate for the line length.
 
But still, using a vacuum pump is highly preferred, also for the DIY kits. They do work fine without, but there will be moisture left, which can shorten the lifespan of the unit.

I always use a vacuum pump, even on DIY sets. Bought one a few years ago for 70 eur or so ($85) on Amazon, works fine! Also used it to evacuate my car's aircon when the condensor was leaking (it was the first thing any debris would hit so eventually it was loosing refrigerant). Managed to replace it myself, and was luckely to find someone who sold R134a who didn't care about having certifications :)

as for flaring: I do have a flare tool but I find them a pita to make proper flares. Tried, but never got them fully sealed even at high pressures. I ended up using pre-flared lines which work great so far.
Think it's both not having done so many practice and a cheap flare tool....

DIY kits are, at least in my experience, always prefilled. Connect, open the valves and you're ready to go. Still, vacuuming is preferred.

I did buy some used ones also, and always was able to get them with refrigerant in the compressor, so no need to source refrigerant (Which is becoming harder and harder due to more strict regulations)
 
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.
 
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.
This…

I have installed a LOT of systems… conduit is fine if you are running straight,BUT you need to be able to extend the entire length straight. If you need to go up, then along a ceiling, then bend, copper bends once… ya can’t bend into a sweep elbow, then expect it to straighten out. You would end up with a curly line exiting the ell…

get some #10 solid copper wire, then try to feed it through a sweep ell conduit fitting… then imagine all the straightening and curling you would need to do with foam insulation, and avoiding kinks… it won’t work…
 
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