Acceptable Moisture Content

[Pooh]

Hi Folks
I have been asked a question that I am struggling to answer so I thought somebody out there may be able to help.

The question is as follows:-
What is the acceptable level of moisture contained in the refrigerant or oil in an operating refrigeration system?

My answer was less than 10ppm as with new refrigerant but obviously that is not always possible in the field.

There must be an industry standard somewhere that gives a figure but I can't find it.

Thanks
Ian

[Brian_UK]

Can't help with a definitive answer Pooh but have a read of this pdf from Emerson...

http://www.emersonflowcontrols.com/web/products/systemprotectors/brochures/HMI%20White%20Paper.pdf

[Thermatech]

I was told once by a Japan factory design engineer that it takes 2000 compressor run hrs for the moisture to become saturated in the oil.
I think from memory that refrigerant spcification is about 10 or 20 ppm & manufacturers will try to acheive same.
But any higher moisture content & the expected life time of the compressor bearings starts to become reduced.
More moisture = shorter compressor life.
The issue is that the installation engineer can only achieve best vacume available with his vac pump. Moisture in refrigerant cannot be changed & moisture left in equipment from manufacture cannot be changed.

So how can the instalation / commissioning enginner measure or calculate how many ppm of moisture is in the system ?

Ideally you would replace the complete oil charge after 2000 hrs because after 2000 hrs all moisture has become saturated in the oil & so if this is removed & replaced with new oil then all moisture has been removed from system ,,,,may be?

Does any engineer carry out this procedure ??? what type of equipment ?

Most a/c split systems & VRF systems do not have oil drain connection on compressor.

[Thermatech]

Good point Jollycold
Some VRF systems do have a filter drier which can be replaced. Sub cooler circuit is a good place because refrigerant flow is always in the one direction.
But as noted before on this forum it is difficult to put filter drier in liquid line for split systems due to pre expansion at outdoor unit.
Perhaps if more contractors complained to manufacturers about lack of filter driers then they would include them.

[Argus]

Hi Folks
I have been asked a question that I am struggling to answer so I thought somebody out there may be able to help.

The question is as follows:-
What is the acceptable level of moisture contained in the refrigerant or oil in an operating refrigeration system?

My answer was less than 10ppm as with new refrigerant but obviously that is not always possible in the field.

There must be an industry standard somewhere that gives a figure but I can't find it.

Thanks
Ian



Moisture is not the only impurity likely to be present, but it’s the core of this question.

If we stay with the original question for a moment before branching off into the subject of driers, the answer to the question of how much moisture is permissible in a system is one that we know all along – nil, if you can achieve it.

Recognising that ‘nil’ in absolute terms is impossible to achieve, the manufacturing standard on refrigerant purity (originally an ISO standard, I believe), provides a de minimis value of less than 10 ppm moisture in terms of chemical purity that is put on the market as virgin refrigerant. De minimis values are considered impossible to measure or insignificant in their effect.

So, I think the answer to the question is zero moisture, or as close to it as you can practically achieve and most importantly, to maintain in use.

Is it written down somewhere?

Yes, I think so, but not as an absolute numerical value. Nil is the goal that every manual on best practice reinforces. Teaching standards on system evacuation should cover it. Whilst it’s not specifically covered by a value in EN 378, it is implied.


.

[Toosh]

Hi All, I have a problem, it being any moisture in a system is a major and when any system has a problem the onus is on the technician to make sure the system is tight but with all the pressures ie time and money corners will be cut.

Regards norm

[Pooh]

Thanks all, there still does not appear to be an answer on this one.

Ian

[Gary]

The issue is that the installation engineer can only achieve best vacume available with his vac pump.

Triple evacuation will remove more contaminants than single evacuation, regardless of how long the pump is left in the system. When the pump (and the system) reaches its deepest vacuum, further pumping is pointless. But repeating the process can remove more of the contaminants.

For example, if the first evacuation removes say 90% of the charge (and therefore 90% of the contaminants), then the second evacuation removes 90% of the remaining contaminants bringing the total removal to 99%. Then the third evacuation removes 90% of the remainder, bringing the total removal to 99.9% of the contaminants.

If you break the vacuum each time from the high side, this sweeps the remaining contaminants through the system to the low side. Then begin the next evacuation from the low side, pulling out the contaminants before evacuating from both sides.

[Pooh]

Gary
read the original question I am not asking about evacuation methods I asked about what the maximum acceptable moisture content is for an operating system, in other words how much moisture is OK.

Ian

[NH3LVR]

Triple evacuation will remove more contaminants than single evacuation, regardless of how long the pump is left in the system. When the pump (and the system) reaches its deepest vacuum, further pumping is pointless. But repeating the process can remove more of the contaminants.

For example, if the first evacuation removes say 90% of the charge (and therefore 90% of the contaminants), then the second evacuation removes 90% of the remaining contaminants bringing the total removal to 99%. Then the third evacuation removes 90% of the remainder, bringing the total removal to 99.9% of the contaminants.

If you break the vacuum each time from the high side, this sweeps the remaining contaminants through the system to the low side. Then begin the next evacuation from the low side, pulling out the contaminants before evacuating from both sides.

I would assume that if we pumped down to 1000 Microns, a lot more of the charge would be gone than 90%.
There are 25,400 Microns in a inch of vacuum. By my math this works out to about .02 pounds of pressure absolute. Without doing a lot of calculating this early, I believe this would remove about 99.8 or so % of the contaminants, without a triple evacuation.
I have used triple evacs in the past, but with a good pump and hose setup I do not see the need.

[Thermatech]

Pooh
This question is theoretical for most engineers because it is not possible to connect a meter to any systems which indicates exacly what the moisture content is in ppm.
Service & commissioning engineers cannot accurately calculate or even estimate what the actual ppm might be.
They can only triple evecuate as best practice using a good quality Torr gauge & hope that the moisture level is close to the 10 ppm standard specification for the refrigerant.

If any one can find any details of any instrument that you can connect to any refrigerant system & it gives a digital reading of the ppm moisure content please share the details with us.

This is of interest to many contractors beause some manufacturers strip down compressors which are returned under warrantee. If any copper deposits are found on hot moving parts in the compressor the warrantee claim is rejected.
The reasoning goes like this,
1/ Copper deposits are caused by acid which leaches the copper from copper tube in the system.
2/ Acid is formed in system due to excessive moisture.
3/ Moisture can only be pressent due to poor evacuation at commissioning or during service work.

Currently contractors have no really good way to prove what the actual moisture connent is so they have to swallow the cost.

[Gary]

Gary
read the original question I am not asking about evacuation methods I asked about what the maximum acceptable moisture content is for an operating system, in other words how much moisture is OK.

Ian

The answer is, of course... as little as possible.

[Gary]

I would assume that if we pumped down to 1000 Microns, a lot more of the charge would be gone than 90%.
There are 25,400 Microns in a inch of vacuum. By my math this works out to about .02 pounds of pressure absolute. Without doing a lot of calculating this early, I believe this would remove about 99.8 or so % of the contaminants, without a triple evacuation.
I have used triple evacs in the past, but with a good pump and hose setup I do not see the need.

I used 90% because the math is easy, making the explanation clearer.

Use 99.8% and adjust the math for each evacuation accordingly. It may not be needed, but it certainly doesn't hurt.

[Pooh]

Gary, Thermatech
you have both still missed the point of the question, I am not talking about new systems I am talking about systems that have been running for some conciderable time and have gained moisture due to poor service activities like not purging lines or putting oil in that was wet.
A freind of mine who works in Dubai has asked the question as he has some wet systems that the clients won't do anything about as there is not a standard he can find that gives a higher limit on moisture. He has had some refrigerant tested in a lab and has found in excess of 200ppm but the client still won't allow him to remedy the fault by fitting a large number of drier cores etc to remove the moisture and due to the plant being used for process he cannot shut it down to evacuate it and replace the oil and refrigerant.

Ian

[monkey spanners]

Have a look here

http://www.sporlan.com/70-10.pdf

Has a chart for various refrigerants and the moisture/temperature levels that change the colour of the sightglass, which is what i tend to go by if they are fitted.

jon

[The Viking]

Sorry, I can't find the slide show I'm after (I know I have one from an oil manufacturer on a disk somewhere but I looked since this thread started and I now given up).

From memory, I seem to remember that for mineral oils the answer is 100ppm but for new synthetic oils it's only ~75ppm. This is LESS than what the oil in the compressors has when the compressor leaves the manufacturer and the whole system relies on us, the service engineers to change driers until the system is dry.

I have attached a slide from Copeland illustrating a "normal" work/moisture flow of a new system.

[Thermatech]

Thanks for the extra explanation for the reason why you would like the ppm moisture information.
As Viking has indicated I would normally expect the manufacturer of the compressor to be able to give an indication of max moisure level above which the compressor life will be compramized.
Fair to say that at 200 ppm the compressor will have short life & the enduser will then have to pay for new compressor & burn out filter drier clean up procedure. The contractor can install shell driers with valves & bypass in the compressor suction which will allow the cores to be replaced without shutting down the plant which is what the enduser will require as the application is process.

[The Viking]

Hey, I found it !!!

So, looking at that slide from an old compressor manufacturer, the answer must be below 50 ppm.

[Pooh]

Thanks LRAC and Viking pretty much what I am looking for

Ian

[AlexLPD]

>Acctually there is a meter for this prupouse, its made by yellow yacket and measure the purity of the gas, the amount of air present in the system and if there is non condensables on it, a dream tool, i paste a link latter today if anybody is interested :-)

[nike123]

http://www.yellowjacket.com/HVACRProducts.asp?t=HVACR&l=7&c=66&p=225

[AlexLPD]

Yeap, the same one.
I like to know if somebody has use it, and if its really helped to correct some error.

Im wondering if there is a notable diference between an a equipment that uses a gas with a 1% of non condensables and another wich uses a 10% of non condensables. More heat in the compresor? poor cold?.... danger of explosion:p?