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Old 03-19-2012, 09:55 PM   #1
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AC lines and sunlight


Once the lines leave the house (southern exposure hottest part)...
it is almost 20 feet to the condensing unit.

Is there any mechanical advantage in burying the (3/4 & 3/8) lines?
If so... is there a better way than using PVC pipe as a sleeve?
(btw, how deep should I go?)

Any other gotcha's or advice is appreciated.
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Old 03-19-2012, 10:07 PM   #2
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AC lines and sunlight


I am not certain if this will apply to your situation but I have some walk-in coolers with external lines that are merely insulated with pipe wrap. The best reasons to insulate the pipes is to make the system more efficient and keep the compressor cooler.

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Old 03-19-2012, 10:09 PM   #3
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No. As a matter of fact we do not use lines buried in the ground. The insulation will weather and then you have some issues from charging to simply running correctly. Superheat. You do not want to change the temperature of the refrigerant in the lines. After a rain the ground is cooler and moist so you lose efficency. Not to mention if the ground shifts it can kink the lines.

We always runs new lines when we come across something old and buried.

Run it above ground and use Armorflex, preferrably 1" thick but only on the suction/low vapor line which would be the 3/4" line in your case. Duct tape the 6' long pieces together where they touch one another to ensure no outside source of temperature can get to the line.

That's it.
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Old 03-19-2012, 10:23 PM   #4
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AC lines and sunlight


Code here says you either anchor the lines to the wall or entrench inside PVC and seal entry and exit points.

Six inches depth will do it. The ambient temp goes that deep and won't affect your pressure reading. And since the lines and insulation are encased in PVC pipe, the insulation is preserved intact.
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Old 03-20-2012, 08:51 AM   #5
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AC lines and sunlight


If you bury the lines under ground, an accumulator should be installed on suction line at compressor. The reason for this is migration, and vapor will condense in suction line under ground on off cycle. Also a liquid line solenoid is usually installed at air handler at same time. Under ground piping is not uncommon and works fine if proper steps are done. If this is a single phase unit, a hard start kit is sometimes also added, good luck.
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Old 03-20-2012, 10:20 AM   #6
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AC lines and sunlight


that is a precaution i endorse on overly long runs. But if you have under twenty five feet on line st I don't think is necessary.

An oil slug more likely than refer slug....but the natural contours of the suction line make for a good "P" trap.
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Old 03-20-2012, 03:43 PM   #7
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AC lines and sunlight


Don't bury them. it can cause more headaches hen you want to deal with.
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Old 03-20-2012, 04:18 PM   #8
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Such as?
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Old 03-20-2012, 04:25 PM   #9
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Both oil and liquid refrigerant migration. Over cooling of the liquid line on milder days, causing flashing at the metering device, or too low of a PD across the metering deice.
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Old 03-20-2012, 05:35 PM   #10
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On lines over 25ft ...maybe. Six inches to one foot the ground temp is stable and has no effect on SC or SH> And if your form the line into a "P" trap the velocity of of the suction line is sufficient to sweep over the oil and pull it vapor back to comp.

Might as well say a cool basement is bad for running line sets, too.
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Old 03-20-2012, 05:44 PM   #11
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Quote:
Originally Posted by hvaclover View Post
On lines over 25ft ...maybe. Six inches to one foot the ground temp is stable and has no effect on SC or SH> And if your form the line into a "P" trap the velocity of of the suction line is sufficient to sweep over the oil and pull it vapor back to comp.

Might as well say a cool basement is bad for running line sets, too.

You're from planet Stroke, aren't you? Must not be thinking all that well since your trip to that vast dryland.

Hell yes it can and does and no, ground is unstable at any depth. Come on down to Houston and see what happens to buried lines.
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Old 03-20-2012, 05:47 PM   #12
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Btw, glad you're back Hvaclover.
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Old 03-20-2012, 05:49 PM   #13
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Figure 1. Recommended construction of oil traps.

Moreover, take care to install the lines with as few bends as possible. "Care must be taken not to damage the couplings or kink the tubing," recommend the trainers. Also, by isolating the refrigerant lines, you will help minimize noise traveling from the equipment to the home."Never solder vapor and liquid lines together," they warn. If you need to, tape them together for convenience sake and for support; but make sure they are completely insulated from each other. Support them at appropriate intervals with suitable hangers and brackets. In particular, do not allow metal-to-metal contact.
When it comes to elbows, use long-radius types whenever possible, the trainers pointed out - except when you are fabricating oil return traps. These require short-radius elbows in order to minimize the volume of oil returning to the compressor. (See Figure 1.)


Going Underground

Installing contractors should use PVC piping "as a conduit for all underground installations," the trainers state. Keep buried lines as short as possible; this helps minimize the buildup of liquid refrigerant in the vapor line during long periods of shutdown.





as is less than 25 feet.
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Old 03-20-2012, 06:05 PM   #14
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Quote:
Originally Posted by hvaclover View Post
On lines over 25ft ...maybe. Six inches to one foot the ground temp is stable and has no effect on SC or SH> And if your form the line into a "P" trap the velocity of of the suction line is sufficient to sweep over the oil and pull it vapor back to comp.

Might as well say a cool basement is bad for running line sets, too.
He said they run 20 foot outside. So that could be 20 foot that he is thinking of burying.
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Old 03-20-2012, 06:13 PM   #15
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And it's probably 20 feet from point of entry from the house to the condenser point of termination. That makes less than 20ft.

And did you ever consider insulating the the ID volume of the PVC chase or conduit?

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