Lineset pitch etc

ChrisJ

I just want to run this up the flag pole before actually doing it.

I'm thinking I want pitch on the 7/8" suction line to ensure good oil return, but at the same time I'm worried this could cause slugging on start up, from either refrigerant, or perhaps even oil rolling down the line.

Thoughts?

Ironman

The diagram is correct. Just make sure that you use the inverted trap at the evaporator.

Harvey Ramer

You may want to check the orientation and piping of your evap coil. Depending on such, you may not need the inverted suction line trap, as it may already be trapped from the manufacturer.

As long as your suction line connects at the highest point of the evap, you are safe from liquid Freon running down the suction line during an off cycle.

There will not be enough oil in the evap to cause any problems with running back to the compressed or suction accumulater. Not in a system this size. The only oil in the system started off in the compressor in the first place.

ChrisJ

Harvey Ramer said:

You may want to check the orientation and piping of your evap coil. Depending on such, you may not need the inverted suction line trap, as it may already be trapped from the manufacturer.



As long as your suction line connects at the highest point of the evap, you are safe from liquid Freon running down the suction line during an off cycle.



There will not be enough oil in the evap to cause any problems with running back to the compressed or suction accumulater. Not in a system this size. The only oil in the system started off in the compressor in the first place.

I had wondered about this as well.

The connections on the evaporator are going to end up at the top, and above the evaporator it self. Yet, the instructions say to use an inverted trap for this application.

Perhaps this is from them copying and pasting the same instructions across many models?

It also seemed odd they say to use 7/8", and for longer runs as big as 1 1/8" on a 3 ton 2 stage unit regardless of how it's piped. 1 1/8" puts it below 800 FPM on the section side. I went with 7/8 just because I felt I could pitch the pipe and get the oil back without any problem in low stage.


I updated the drawing to include the liquid line. The sight glass is mainly for a moisture indicator, not sure how good it'll work with 410A for liquid.

ChrisJ

@Harvey Ramer

If you could, double check me. This is how the evap should end up after I pull it out and rotate it for my installation.


To me, as you said, it's already trapped. No?

njtommy

Generally their are no need for traps with 410a do to the high suction pressure.

Harvey Ramer

njtommy said:

Generally their are no need for traps with 410a do to the high suction pressure.

I'm not sure I understand that, as refrigerant will migrate to the coolest spot in the system while it is off, irrespective of static pressure?

Harvey Ramer

ChrisJ said:

@Harvey Ramer

If you could, double check me. This is how the evap should end up after I pull it out and rotate it for my installation.


To me, as you said, it's already trapped. No?

I would not trap it in that orientation unless it caused warranty issues with the manufacturer.

njtommy

@Harvey Ramer

I jumped the gun on my statement. Inverter trap is fine and will help stop migration along with a Liquid line selniod.

There is no need for a regular oil/ suction trap as we would use or see if the condensers are above the evaps or even in medium/ low temp refrigeration design.

Chris will also be running a crank case heater.

ChrisJ

Harvey Ramer said:

njtommy said:

Generally their are no need for traps with 410a do to the high suction pressure.

I'm not sure I understand that, as refrigerant will migrate to the coolest spot in the system while it is off, irrespective of static pressure?

@Harvey Ramer Maybe you can help me grasp something I'm not getting regarding this.

Even with the trap, what stops migration over time?

Copeland says for this specific compressor, as long as the total system charge is below 8 pounds no CCH is required, even with the evaporator in a hot attic. Why?

How does the charge amount effect whether or not heat is needed?

I'll be at 7.5 pounds +- so apparently I'm safe. But I don't understand why refrigerant won't tend to migrate to the compressor during long off periods if it's cool outside? Or are they saying it will, but the scroll will tolerate it in those rare occurrences?

I'm guessing it must be true, I've seen it mentioned in multiple areas, but I don't understand it.

njtommy

Scroll compressors will take a beating until they run backwards. Then they don't last much longer after that.
The only other problem is when the discharge check valve goes bad. The refrigerant pressure dumps back into the compressor and pushes the compressor backwards and you will hear the plates touching each other.

Harvey Ramer

ChrisJ said:

Harvey Ramer said:

njtommy said:

Generally their are no need for traps with 410a do to the high suction pressure.

I'm not sure I understand that, as refrigerant will migrate to the coolest spot in the system while it is off, irrespective of static pressure?

@Harvey Ramer Maybe you can help me grasp something I'm not getting regarding this.

Even with the trap, what stops migration over time?

Copeland says for this specific compressor, as long as the total system charge is below 8 pounds no CCH is required, even with the evaporator in a hot attic. Why?

How does the charge amount effect whether or not heat is needed?

I'll be at 7.5 pounds +- so apparently I'm safe. But I don't understand why refrigerant won't tend to migrate to the compressor during long off periods if it's cool outside? Or are they saying it will, but the scroll will tolerate it in those rare occurrences?

I'm guessing it must be true, I've seen it mentioned in multiple areas, but I don't understand it.

So the inverted evap trap does not stop or slow migration. What it does is prevent the condensed refrigerant from running down the suction line into the compressor slump or the accumulator. If it runs into the accumulator, thats not a big deal unless it gets to full.
And this only happens when the evaporator coil is cooler than the condenser. That is hardly ever the case with an airhandler in an attic. One time can be to much though.

If you take a look at the attached wiring diagram, you will see a visual of what I'm about to say. Most new HP's don't require CCH's and here's why.

The contacter is what's termed by some as 1-1/2 pole. Meaning that only 1 leg of the power is switched. This is the leg that goes to the common terminal on the compressor. The other leg feeds straight through the contacter. At that point it splits. One line goes to the run terminal on the compressor and the other line goes to the common on the run cap and the output on the run cap goes to the start terminal on the compressor.

The run cap provides enough of a phase shift to provide some resistance through the start and run winding. It's not much heat, but enough to not need a CCH.


As far as there guidelines based on total system volume, I can't answer that definitively, but my best guess is that over 8lbs, the condensor could no longer hold all the liquid refrigerant and force some into the compressor.

There is no compressor made, that I am aware of, that is ok with liquid. I know it won't kill a scroll outright, but it will loose lubrication and damage the scrolls.

ChrisJ

Harvey Ramer said:

ChrisJ said:

Harvey Ramer said:

njtommy said:

Generally their are no need for traps with 410a do to the high suction pressure.

I'm not sure I understand that, as refrigerant will migrate to the coolest spot in the system while it is off, irrespective of static pressure?

@Harvey Ramer Maybe you can help me grasp something I'm not getting regarding this.

Even with the trap, what stops migration over time?

Copeland says for this specific compressor, as long as the total system charge is below 8 pounds no CCH is required, even with the evaporator in a hot attic. Why?

How does the charge amount effect whether or not heat is needed?

I'll be at 7.5 pounds +- so apparently I'm safe. But I don't understand why refrigerant won't tend to migrate to the compressor during long off periods if it's cool outside? Or are they saying it will, but the scroll will tolerate it in those rare occurrences?

I'm guessing it must be true, I've seen it mentioned in multiple areas, but I don't understand it.

So the inverted evap trap does not stop or slow migration. What it does is prevent the condensed refrigerant from running down the suction line into the compressor slump or the accumulator. If it runs into the accumulator, thats not a big deal unless it gets to full.
And this only happens when the evaporator coil is cooler than the condenser. That is hardly ever the case with an airhandler in an attic. One time can be to much though.

If you take a look at the attached wiring diagram, you will see a visual of what I'm about to say. Most new HP's don't require CCH's and here's why.

The contacter is what's termed by some as 1-1/2 pole. Meaning that only 1 leg of the power is switched. This is the leg that goes to the common terminal on the compressor. The other leg feeds straight through the contacter. At that point it splits. One line goes to the run terminal on the compressor and the other line goes to the common on the run cap and the output on the run cap goes to the start terminal on the compressor.

The run cap provides enough of a phase shift to provide some resistance through the start and run winding. It's not much heat, but enough to not need a CCH.


As far as there guidelines based on total system volume, I can't answer that definitively, but my best guess is that over 8lbs, the condensor could no longer hold all the liquid refrigerant and force some into the compressor.

There is no compressor made, that I am aware of, that is ok with liquid. I know it won't kill a scroll outright, but it will loose lubrication and damage the scrolls.

Looking at that circuit, I do not see how current would flow through the windings once the run capacitor discharges?

I also see that schematic shows a CCH?

Harvey Ramer

I was wrong. That schematic does not have a crankcase heater through the windings and run cap. The depicted CCH is optional or model specific.
I tried to dig up the technical article where I read about it using the windings as a CCH, but couldn't find it. What I did find was that it used to be done, perhaps still is, but it used a split capacitor with a resistor on the one. The article I read must have been miswritten or I misunderstood it.
I apologize for the misinformation.

Now you have me in research mode. I would like to know the answer to copeland's CCH guidelines as well.

I found this "attached" copeland bulletin, after a bunch of digging.

ratio

What @Harvey Ramer said.

I think you're chasing the last 0.1% of performance. Which is ok, but it's getting into Engineering, which is a synonym of Compromise. Did I send you some lineset sizing paperworks? They cover that & give the reasons why as well as the maths.

Truth is, if the lineset connects the right parts, & isn't horribly miss-sized, it'll Just Work. For various values of "Work", true, but not everyone will even notice a difference, let alone worry about it.

ChrisJ

ratio said:

What @Harvey Ramer said.

I think you're chasing the last 0.1% of performance. Which is ok, but it's getting into Engineering, which is a synonym of Compromise. Did I send you some lineset sizing paperworks? They cover that & give the reasons why as well as the maths.

Truth is, if the lineset connects the right parts, & isn't horribly miss-sized, it'll Just Work. For various values of "Work", true, but not everyone will even notice a difference, let alone worry about it.

I think you did, a while back.

I've got quite a few PDFs on it, which is how I came up with what I did.

ChrisJ

Harvey Ramer said:

I was wrong. That schematic does not have a crankcase heater through the windings and run cap. The depicted CCH is optional or model specific.
I tried to dig up the technical article where I read about it using the windings as a CCH, but couldn't find it. What I did find was that it used to be done, perhaps still is, but it used a split capacitor with a resistor on the one. The article I read must have been miswritten or I misunderstood it.
I apologize for the misinformation.

Now you have me in research mode. I would like to know the answer to copeland's CCH guidelines as well.

I found this "attached" copeland bulletin, after a bunch of digging.

This is the one that applies to my specific compressor, it's a K5 series.

EBEBRATT-Ed

JMHO. Some don't believe in traps, some do. I do. I can't think of a job where a trap caused a problem. Yes an inverted trap can help with preventing liquid running down the suction line. On a long off cycle liquid refrigerant will migrate to the coldest part of a system.. The only thing that can prevent that is a LL solenoid drop as you can't pump down a scroll and do a pump down.

When scrolls first came out many manufacturers skipped the crankcase heaters (Carrier) "Scrolls can eat liquid" ****. They soon changed there mind. Compressors are not made to pump liquid and liquid will kill any compressor

njtommy

@EBEBRATT-Ed could you elaborate on pumping down a scroll? Their are plenty of scroll compressors on systems especially on chillers and Refrigeration that are pump down systems.

njtommy

Right from Emerson

A pump down cycle for control of refrigerant migration may be used in conjunction with a crankcase heater when the compressor is located so that cold air blowing over the compressor makes the crankcase heater ineffective.
If a pump down cycle is used, a separate external check valve must be added. The scroll discharge check valve is designed to stop extended reverse rotation and prevent high-pressure gas from leaking rapidly into the low side after shut off. The check valve will in some cases leak more than reciprocating compressor discharge reeds, normally used with pump down, causing the scroll compressor to recycle more frequently. Repeated short-cycling of this nature can result in a low oil situation and consequent damage to the compressor. The low-pressure control differential has to be reviewed since a relatively large volume of gas will re-expand from the high side of the compressor into the low side after shutdown.
Pressure control setting: Never set the low-pressure control to shut off outside of the operating envelope. To prevent the compressor from running into problems during such faults as loss of charge or partial blockage, the control should not be set lower than 12 to 15 K equivalent suction pressure below the lowest design operating point.

EBEBRATT-Ed

This post will address how to properly diagnose scroll compressors. (Information provided in this post is directly from Copeland )

So, continuing on with compressor diagnostics, scroll compressors need to have the following functional tests performed to determine if a compressor is bad.

A functional compressor test with the suction service valve closed to check how low the compressor will pull suction pressure is not a good indication of how well a compressor is performing. Such a test will damage a scroll compressor. Also keep in mind, that you CANNOT pump down a unit with microchannel coils. The holding capacity of the coil will not allow pump down of refrigerant into the coil. this can also lead to damaging the compressor.


Pressure control setting: Never set the low-pressure control to shut off outside of the operating envelope

njtommy

Yes micro Channel pumping down is a no no. I seen pictures of the aftermath of when guys have pumped down the micro channel coils.

JUGHNE

ChrisJ, are you going to put service taps at the evap coil in the attic.
I ask only because I am thinking that you want to fine tune your charge....the more you study it.....the more you will want to check.

Superheat is supposed to be measured right at the evp. A tap on the suction line coming just out of the coil would give the most accurate reading for PSI and take temp at that point also.
I believe sub cooling may be accurately measured at the cond coil, which is the standard for the industry? However in your case you have a vertical column of liquid that has 20' of head standing there.

Maybe some here will respond. The cost of the taps is very little and actually would function as couplings for the line if needed.
Also having the taps in the attic let you pass N2 gas from up there, rather than the hassle of stairs you have. You could set the N2 up at the outside unit and do those joints....then haul all up stairs to do the evap end. From the attic you could then do the pressure test overnight and not leave gauge/hose set outside over night. Just a thought.

ChrisJ

@JUGHNE I had not planned on it no.

But I am confused, why would I want to measure my superheat at the evaporator when what matters is what it is down by the compressor?

As you said, the standard way to charge with 410A is by subcooling a few inches out of the condenser.

But if I wanted to adjust the TXV, I don't understand why I'd care what the superheat is right out of the evap if I've got 45-50 feet of suction line after it? Isn't my return temp going back to the compressor what's important for both cooling, and to avoid slugging?

I'm not trying to be insulting, I'm trying to understand.

My suction line is going to have 3/4" aeroflex with glued joints. Liquid line is to have 3/8" aeroflex.

JUGHNE

I believe the old school method for SH was right at the evap. One would estimate the pressure drop for the line set involved if measuring at the cond.
I see a lot of LP taps on the suction at evap. The AC brand I install includes a 3/4" OD tap with the TXV kit. I don't install it though as most of my runs are 15-20' to basement furnace. I just use SC method with TXV. Some I&O states the values for both.
I thought your interest is fine tuning would peak sometime and you might want to know both. Most of these TXV's might not be adjustable anyway.
As I said they come in handy for access to ACR lines in the attic.

njtommy

@JUGHNE it is good to check the superheat and subcooling at the evap. Especially on long runs. Buts yes most manufacturers want to know what it is at the condenser. His going to be looking at 7-9 degrees of subcooling and superheat.

@ChrisJ this where Bluetooth digital gauges come in handy when you work solo. Up down form the attic to out side just plain sucks. Every time you adjust the txv.

ratio

You need to know the superheat at the evap to adjust the TXV. You need to know superheat at the compressor to verify both that the compressor is protected from slugging with liquid & for cooling the compressor. This is where one of those Engineering things comes into play—those numbers might not be the same. Also, some TXV's aren't adjustable.

You only really need the subcooling at the entrance to the TXV.

BTW, if the attic is unconditioned, I think I'd insulate the liquid line too, to protect it from heat gain in the summer.

ChrisJ

ratio said:

You need to know the superheat at the evap to adjust the TXV. You need to know superheat at the compressor to verify both that the compressor is protected from slugging with liquid & for cooling the compressor. This is where one of those Engineering things comes into play—those numbers might not be the same. Also, some TXV's aren't adjustable.

You only really need the subcooling at the entrance to the TXV.

BTW, if the attic is unconditioned, I think I'd insulate the liquid line too, to protect it from heat gain in the summer.

ChrisJ said:

My suction line is going to have 3/4" aeroflex with glued joints. Liquid line is to have 3/8" aeroflex.

pecmsg

Good read on Refrigeration Piping.

ratio

ChrisJ said:

ChrisJ said:

My suction line is going to have 3/4" aeroflex with glued joints. Liquid line is to have 3/8" aeroflex.

Give some thought to leaving it uninsulated where outdoors. It's only needed to stop heat gain. Outside, you'll always be somewhat above ambient, which means you'll still be cooling off, until it enters the bldg envelope. Mathematically provable efficiency gain.

ChrisJ

ratio said:

ChrisJ said:

ChrisJ said:

My suction line is going to have 3/4" aeroflex with glued joints. Liquid line is to have 3/8" aeroflex.

Give some thought to leaving it uninsulated where outdoors. It's only needed to stop heat gain. Outside, you'll always be somewhat above ambient, which means you'll still be cooling off, until it enters the bldg envelope. Mathematically provable efficiency gain.

True,
However where it's running up the side of the house the enclosure will be exposed to direct sunlight most of the day, so I had planned on doing almost all of it.

newagedawn

ask the manufacturer what they recommend!!! i dont think a txv 410a needs the trap

ChrisJ

newagedawn said:

ask the manufacturer what they recommend!!! i dont think a txv 410a needs the trap

Manufacturer says the trap is required.

I don't think a hard shutoff TXV or EXV need the trap, a standard bleed type does.

ChrisJ

Maybe it's just because I'm not in the business, but I had a hell of a time finding this.

JUGHNE

Pretty standard use for Minisplit systems along with 1/4" ID.
Johnstone supply or such would have it.

ChrisJ

JUGHNE said:

Pretty standard use for Minisplit systems along with 1/4" ID.
Johnstone supply or such would have it.

The few times I've gone to Johnstone supply they treated me like complete garbage, so I stopped going.

I need to go there to take my 608 Universal at one point and I'm dreading it.

JUGHNE

When JSC first opened in NE in 1987 they would sell anything to anyone that came thru the door. They must have been hungry then as they carried a large line of appliance parts, especially GE.

But people in the trades were reluctant to go there as countermen were tied up explaining appliance repairs to the HO. Eventually the "Wholesale Only" sign went on the door and the HVAC trades have made it a tough competitor to a long established refrigeration/Copeland supply house. The HO still might come in but pays full retail and learns to go the big box stores eventually. They treat everyone very respectfully though......just take more of their money than mine. (Maybe just Midwest Southern hospitability )

It is probably the same story in most wholesale houses.

(BTY my 1987 credit limit was $250.00 a month when I opened the account there.......they let me buy all I want now!)

Fred

I used JSC a couple times also. We have one here locally and I got the same treatment that @Chrisj experienced. We may be just HO's but when we pay full retail, that translates into greater profit margins for them. There are too many options, both locally and on-line to put up with crap from any counter person or the abusive policies of any supplier, especially when you know exactly what you want when you step up to the counter.

ChrisJ

I bought my Fluke 179 and Yellowjacket Brute 2 gauges with 6' hoses there.

Look up what full retail on those two items are.

I suspect, most contractors don't go in there and buy such items because they didn't have many of those, but had tons of the bottom of the line tools.

I knew what I wanted, didn't waste anyone's time and still was treated like crap.

Now, other people get my money instead.

JUGHNE

Wholesale houses have to walk a tightrope, trades people don't want the HO in there as they think he will get the same price as the trade. HO might spent 50 bucks and the trade will spend 5000.
Who should you give the most attention to?
However there is no reason to treat people badly as it is bad PR shown and even those with accounts may be turned off by this action.
It used to be said that "you have to have an account here to buy anything here".....some law was applied and you must sell to anyone....but at any price. So that is why the JSC catalog or any others has some outrageous prices shown. I have always gotten 1/2 of that retail price or usually less.

I have a wholesaler who used to, in the 80's, sell HVAC, plumbing and refrigeration. They split into HVAC & ref in one building and Plumbing only in another. I asked why and the manager said that true refrigeration guys don't want buy where the plumbers do.
So there you are, even within the trades is some segregation.

But they will delivery each others stuff to me.

Fred

It's Okay to pick and choose your customers (within the limits of the law), if your business model and revenue stream affords you that luxury, just publish somewhere that "Home owners are not welcome" so I'll know to spend my hard earned money elsewhere. At the end of the day, when they count their receivables, I bet they can't tell a HO dollar from a Pro dollar.