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Lineset sizes. Condenser or coil?

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#21 ·
I used to see that in older retrofitted buildings. Oil would be collected in oil separators all around the lower floors. Some were pumped back to the compressor suction inlet and some were manually emptied into buckets and carried up to the penthouse.



Adlerberts-Protege said:
Just do like you do when a duct run is too small. Add a booster fan to the suction line if you need to. Blow that oil up there.
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#22 ·
Poodle Head Mikey said:
If the condenser is higher than the evaporator use the smaller suction line size and take the capacity hit to ensure oil return. If the evaporator is higher than the condenser use the larger suction line size as gravity will return the oil and then have the capacity gain as a plus.

PHM
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Wait... everything I read said the opposite. If the compressor motor and condenser is on the first floor and the evaporator/handler is on the second floor.... gravity would assist in getting the oil back to the compressor/condenser coil. (velocity of 410a also eliminates need for a trap???) Just verifying... Isn't the compressor at the condenser what needs the oil?
 
#24 ·
stumpdigger said:
On an R-22 condensing unit that was over ten feet above the evaporator we usually put an oil trap and occasionally used a speed riser for oil return. Choking down on the suction line size will certainly reduce capacity, there should be a chart included with condensing unit. That said, I installed a number of R410A units at a fire station including oil traps for a 20' rise. ( At that time R410A was just coming out and Carrier would not sell anyone equipment without attending their classes.) Our top service tech at the time was upset with me for the oil traps and he cut them all out. Apparently the high pressure of R410A has enough velocity to carry the oil. Try to keep the suction line as large as condensing unit unless something odd is going on. I have seen manufacturer's suggesting dual risers but that seems like too much hoey for me.
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R410A requires a higher velocity for oil return in vertical rizers.
 
#25 ·
beenthere said:
R410A requires a higher velocity for oil return in vertical rizers.
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THinking I am not understanding.. Risers are when the pipe goes vertical from the condenser to evap coil... yes?
R410a systems are under higher pressure... which translates to higher velocity... which the system does, yes?
Having too much oil at the compressor on start can also put a strain on they system, but not having enough would be even more catastrophic?

There are traps to allow the oil to accumulate in strategic positions... the higher velocity of the lines will siphon, pull, push the oil with it... and this is kind of self regulating if done right?

with 410a this is important for long vertical runs or risers, but for different reasons?

Often the traps for R22 can be removed with a new 410 system because of the higher velocity moving the oil better?

Please note, I am not putting this in, but It would be nice to be in the know and I find this interesting... really enjoying it.
 
#27 ·
pecmsg said:
Higher pressure Does Not equal higher velocity.

P-Traps are not used in residential systems!
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Been 25 years..... I thought with fluid, under a constant pressure ... as the diameter of the pipe goes down, the velocity of the liquid through it would increase... as the same amount of fluid will pass through it as a bigger pipe, but it does not have to move as fast. The rate of transfer is the same, but the velocity is faster through the smaller tube???
 
#28 ·
Kevinyork said:
Been 25 years..... I thought with fluid, under a constant pressure ... as the diameter of the pipe goes down, the velocity of the liquid through it would increase... as the same amount of fluid will pass through it as a bigger pipe, but it does not have to move as fast. The rate of transfer is the same, but the velocity is faster through the smaller tube???
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Were dealing with mostly Vapor!

Think Steam...………..Higher pressure Less Velocity!
 
#29 ·
Kevinyork said:
THinking I am not understanding.. Risers are when the pipe goes vertical from the condenser to evap coil... yes?
R410a systems are under higher pressure... which translates to higher velocity... which the system does, yes?
Having too much oil at the compressor on start can also put a strain on they system, but not having enough would be even more catastrophic?

There are traps to allow the oil to accumulate in strategic positions... the higher velocity of the lines will siphon, pull, push the oil with it... and this is kind of self regulating if done right?

with 410a this is important for long vertical runs or risers, but for different reasons?

Often the traps for R22 can be removed with a new 410 system because of the higher velocity moving the oil better?

Please note, I am not putting this in, but It would be nice to be in the know and I find this interesting... really enjoying it.
Click to expand...
You can have a low velocity in a large pipe, and still have a high pressure.

Traps were seldom needed with R22, and usually were over used.
 
#31 ·
As to R410a I only know what I was told by a very bright guy who just attended Carrier classes on installation practices. The use of oil traps is sometimes a debate in itself. Just the added fittings will give slightly more pressure drop in the line. Some say that keeping so much oil in the trap is bad for hermetic compressors. On semi-hermetic compressors it is easy to add oil to fill the trap. For Kevinyork, the trap works a little like a constriction in the line (another reason they are disliked). Once the trap is full a slug of oil will be pulled up the suction line( some Nay Sayers suggest that the oil will be stripped by the piping and never make it up). Two things for certain are that if the oil is not returned; it will pool in the bottom of evap where it is cold and thick causing more problems, and the compressor will be oil starved. Oil traps are located on the bottom of risers and capacity should be as small as possible. I use a LR 90 at the bottom and two 45 elbows coming in and going out.
 
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#32 ·
stumpdigger said:
As to R410a I only know what I was told by a very bright guy who just attended Carrier classes on installation practices. The use of oil traps is sometimes a debate in itself. Just the added fittings will give slightly more pressure drop in the line. Some say that keeping so much oil in the trap is bad for hermetic compressors. On semi-hermetic compressors it is easy to add oil to fill the trap. For Kevinyork, the trap works a little like a constriction in the line (another reason they are disliked). Once the trap is full a slug of oil will be pulled up the suction line( some Nay Sayers suggest that the oil will be stripped by the piping and never make it up). Two things for certain are that if the oil is not returned; it will pool in the bottom of evap where it is cold and thick causing more problems, and the compressor will be oil starved. Oil traps are located on the bottom of risers and capacity should be as small as possible. I use a LR 90 at the bottom and two 45 elbows coming in and going out.
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B S

POE oil in a 410A system has the same viscidly as in a 404A freezer at -25°F!
 
#33 ·
beenthere said:
3 ton R22 system with a 7/8" vapor line, velocity is 1492FPM.

3 ton R410A system with a 7/8" vapor line, velocity is 1047FPM.

The R410A system is the system that needs an oil trap if more than 15' vertical rise to the condenser.
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Thank You Sir, love proper education and numbers. And yes, oil traps can easily be overused
 
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#35 ·
Worst case that I ever saw was a about a 15 ton 2 speed tin can. Condensing unit and evap both at ground level, 20' horizontal run, suction line run overhead to clear doorway. Brand new it only lasted one month. Drained a quart of oil out of suction line and a lot of steel shrapnel out of line while installing trap.
 
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#36 ·
Kevinyork said:
Is that a real thing? or are you messing with me?
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Pressure drop is any refrigerant line is detrimental to system performance - but it is most important in suction lines as the resulting lower suction pressure directly reduces compressor pumping capacity. This is because a lower pressure vapor is less dense - there is 'less to it' - so that each 'piston stroke' counts for less in total refrigerant volume (and BTU's) being moved around the system.

Do you need or want more of an explanation that that?
 
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#37 ·
IMO make sure the coils are compatible and read the manual(s) for the equipment ,ent you are dealing with. If the piping section says trap it, trap it. The manual should tell you how it wants to be installed for most different applications.

I was told that 410A doesn’t require oil traps due to velocity, but I would think the manufacture would ask if it’s trapped (if required) before warrantying a compressor.
 
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#38 ·
Bombboy90 said:
IMO make sure the coils are compatible and read the manual(s) for the equipment ,ent you are dealing with. If the piping section says trap it, trap it. The manual should tell you how it wants to be installed for most different applications.

I was told that 410A doesn’t require oil traps due to velocity, but I would think the manufacture would ask if it’s trapped (if required) before warrantying a compressor.
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They don't ask about traps. At least not if its the first compressor for that system.

Now maybe if your doing the second or third comp on that system.
 
#39 ·
How can that possibly be?

Do you have a chart or any other literature showing that?

PHM
---------



pecmsg said:
. . . POE oil in a 410A system has the same viscosity as in a 404A freezer at -25°F!
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#40 ·
The oil needs to be mostly in the compressor.

What did you read that was the opposite to what I stated?

It's a pretty simple logic:

When the suction line slopes towards the compressor - oil return is not an issue due to gravity helping it to drain back to the compressor. So the suction line can be larger with lower velocity and pressure drop.

When the suction line slopes toward the evaporator - the oil must be pushed along, uphill, by turbulence and gas velocity. Which requires a small suction line to create it.

PHM
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Kevinyork said:
Wait... everything I read said the opposite. If the compressor motor and condenser is on the first floor and the evaporator/handler is on the second floor.... gravity would assist in getting the oil back to the compressor/condenser coil. (velocity of 410a also eliminates need for a trap???) Just verifying... Isn't the compressor at the condenser what needs the oil?
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