Minisplit Rear Mount question

[Dbacks2k4]

Originally Posted by Rucker

Some linesets do come precharged, or already filled with refrigerant. Stating the obvious, that's to make it easier to install (no need for a vacuum pump or skill).

The only way to shorten those lines is to remove the refrigerant (venting it is illegal, and who's gonna spend a hundred bucks on a proper recovery, so the whole idea of charged linesets is completely problematic in my mind), and then ironically you might need to add refrigerant because the lines are empty and there's only so much precharge in the unit itself.

Coiled lineset just seems dumb to me, but having said that there was a post elsewhere about some bus with a minisplit always losing refrigerant and I pointed out their condensor mounting on an extended bumper probably had quite a bit of movement whereas their lineset connection looked pretty direct and rigid, and they might consider a loop or other longish section perpendicular to the potential travel to prevent such problems. Same thought for your setup, perhaps that would figure in.

The Pioneer units I'm looking at are pre-charged but the refridgerant is held in a container on the outdoor unit, at least that's my understanding. Once the lineset is attached, vacuumed, and leak-tested; a screw is turned to release the refridgerant. But it's a pre-determined amount for the length of the included lineset. So if I shorten that lineset, I'm going to need to reduce the amount of refridgerant.

Alternatively, if I use the original lineset as is, it's probably longer than I need, so then what do I do with the extra lineset to route in such a way that's out of my way but also not introducing future problems? The "best" way is just get an HVAC tech out to properly charge the system but I'm trying to avoid that

[Jolly Roger bus 223]

the pioneer units are precharged (held in the outdoor unit) for the amount of lineset that is sent with the unit.
for example my package came with 15 feet of lineset.
if things go like i am thinking i will only be using 4 feet of lineset so an adjustment will be needed.
fortunately enough i work for a big HVAC company and have access to everything i need to weigh the charge out to get the proper amount.
also the outdoor unit should be marked on its lable for what the factory charge is.

[HamSkoolie]

When it comes to HVAC techs, be sure you're getting one that knows what he's doing.
We had an issue with the forced air heater in our rental and called the manufacturers local dealer. THREE TIMES (charging for each service call of course) they came out and "fixed" it. First one drained a condensate tank and said the outlet had been clogged.
A couple days later the same exact problem was back... he drilled a hole in a plastic tank to "relieve pressure build up".

A couple days later on the third trip (and third different tech) we were told "it must be the computer".


I fixed it by lifting the exhaust from a down hill to uphill slope where it exited the heater thus preventing an "obstruction" in the form of the condensate. This was specifically mentioned in installation instructions but those three HVAC techs had no clue how the system functioned. They read error codes and replaced parts or sold new installs.


So make sure you get a tech you can trust AND who knows his trade.

[Jolly Roger bus 223]

should have thrown a code for blocked flue

[HamSkoolie]

Originally Posted by Jolly Roger bus 223

should have thrown a code for blocked flue

It threw a code that there was an obstruction but they never looked outside the equipment box. They kept looking at the hoses and the tiny tank inside (where the condensate is supposed to flow to and then through the drain pipe to the outside of the house. They apparently never directed their eyes outside of the "box" to look at the exhaust.
I was up there just the other day with a failure but it was easy to diagnose. Turn on the unit and the fan didn't rotate. Amazon and a few days later back in service.

[Rucker]

Originally Posted by Dbacks2k4

<snip>
But it's a pre-determined amount for the length of the included lineset. So if I shorten that lineset, I'm going to need to reduce the amount of refridgerant.
<snip>

Opinion: based on my system instructions being silent on the matter and a casual search of the Internet (always problematic, but hey) I doubt the reduced volume of the lineset will influence the operation of the system.

...As long as you don't violate any minimum lineset length requirement your installation manual requires...

[Jolly Roger bus 223]

over charged can/will show the same symptoms as undercharged and could eventually kill the compressor.

[Rucker]

Originally Posted by Jolly Roger bus 223

over charged can/will show the same symptoms as undercharged and could eventually kill the compressor.

I trust your knowledge-and wouldn't want to stand in the way of experience.

My comment is strictly on the basis of logic, which says if most of these manufacturers give you a dry 25 foot lineset or whatever and assume you're going to cut it down, I'm guessing the resulting charge in the system is going to be within the relevant range of required refrigerant.

[cadillackid]

Originally Posted by Jolly Roger bus 223

over charged can/will show the same symptoms as undercharged and could eventually kill the compressor.

roger - the minisplits have an accumulator for this purpose.. in the manuals for every single one of them that I have an installed (including fujitsu) the books manetion that the pre-charge is for "up to" a certain lineset length..



the accumulator is designed to hold extra liquid, because that liquid is in an insulated bottle you dont have issues with boil-off causing high evaporator pressure.. with the expansion device in the outdoor unit you have quite a bit of difference in capacity need for heat vs cool , the accumulator handles that discrepency in charge...





to the Original Poster



I dont recommend precharged linesets.. esp if you try and buy them with a unit that has already been precharged in its condensor for a full charge.. only use them as part of a package where they are designed for the unit they are sold..



many minisplits come precharged for 25 feet of lineset maximum.. shortening it to 10 feet isnt going to cause an issue.. it will run just fine. ive installed more than one with 10 feet of line ..


if you go longer then you will likely have just-fine cooling but the heating cycle will lose efficiency and capacity unless you weigh-in the extra charge per the formula given in the install manual..



anyone installing a unit do be sure to Vac it down or have it done.. and leakl tested.. the flare fittings are notorious for leaking... so when I have the luxury like putting in one of my own units.. I vac it down and punch it with 200 PSI of nitrogen and let it sit overnight..



since the king / service valves are closed, the refrigerant is safely sotred away in the condensor but you fill up the rest of the system including all 4 flare connections...


if you have a good flaring tool and know what you are doing, you can shorten a lineset and make new flares..


I also like the flare seals sold everywhere.. they are a plastic-coated Copper sealing washer.. I havent had a set leak with the sealing washers yet.. I decided to try them to see if it would help the DIYers get good seals on the (often) crappy flares from china..



I didnt have any luck with the flare seal Liquid (I purposely cut a somewhat shady flare for testing in my HVAC lab at home).. but the physical seals work good so far..



getting a system Vacuumed down is important. I know some will tell you they are cowboys and just winged it.. and the unit will run.. for awhile and probably even blow cold air but it likely wont last super long and not be as efficient..


theres a reason ive gotten 14 years from 2 of my 3 Cheap chinese chigo units when most were tossing them for failure after 5 (one of mine got whacked by lightning)... the 2 units still in service havent had an ounce of freon added since 2010 (after I learned how to flare right)..



so if you put them in right you can get great service out of them.. granted mine are stationary and not getting bounced around in a bus all the time..