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Checking Freon Level
January 12, 2012
2:06 pm
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Steve Pooler
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November 12, 2008
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arielmiller said:

Hi Steve,

 

Duct restriction is the first thing i though off when i first noticed the problem.  To isolate the variables i took the unit out of the cubby it was in and disconnected all the ducts.  Right now the unit is sitting in the open room and blowing hot/cold air directly into the cabin.

 

When i lowered the LO side pressure to 50psi the unit seemed to be running fine in COOL (with exception of the freezing which apperantly is normal)...Didn't say it was normal to run that way but it is expected because the room is too cold to be running the system in the cool mode...and ran 30 min without going above 290psi on the HI side in heat mode....Seems you were close here...The one thing i did notice was that the compressor was at 220F measured with a thermal gun.  How hot does the compressor get?

 

I spoke with my HVAC contractor who works on one of my projects and he also concured that in cool mode i should be around 50psi on the low side. 

 

This weekend i am going to lower the LO side pressure to 50 and try it all out again. Assuming my pressure in COOL mode is correct, what LO/HI pressure should i be looking in HEAT mode?

 

Ok with no duct connected it still depends on the temp of the room (air temp returning) and the seawater temp…Charge by what the chart says for those figures for suction…Then let me know what you have for heating & cooling both high & low in both modes…Also how much water is pumping thru the unit ?

Remember…The warmer the cabin gets in heat…The higher the head pressure will run…Again see the chart…

It's normal for rotary compressors to run hot…The outside can is in touch with the hot discharge gas…

IR temp guns are not good for air temps…Only surface temps….That could be throwing you too if you are using it for cabin & water temps…

 

Steve~

January 12, 2012
1:54 pm
arielmiller
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Hi Steve,

 

Duct restriction is the first thing i though off when i first noticed the problem.  To isolate the variables i took the unit out of the cubby it was in and disconnected all the ducts.  Right now the unit is sitting in the open room and blowing hot/cold air directly into the cabin.

 

When i lowered the LO side pressure to 50psi the unit seemed to be running fine in COOL (with exception of the freezing which apperantly is normal) and ran 30 min without going above 290psi on the HI side in heat mode.  The one thing i did notice was that the compressor was at 220F measured with a thermal gun.  How hot does the compressor get?

 

I spoke with my HVAC contractor who works on one of my projects and he also concured that in cool mode i should be around 50psi on the low side. 

 

This weekend i am going to lower the LO side pressure to 50 and try it all out again. Assuming my pressure in COOL mode is correct, what LO/HI pressure should i be looking in HEAT mode?

January 12, 2012
11:00 am
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Steve Pooler
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Here is another recent question asked about Refrigerant charge…I'm going to break it up a bit with my comments & questions and then send a link to the gentleman that e-mailed the question…Hopefully he will come back & respond…

 

Hi Steve, I saw your post and i have heard a lot about you on these forums in the past. YOu really seem to know your stuff. Anyhow, to give you a little more information.

I bought the system used. (learned my mistake) The problem was that in HEAT mode i constantly tripped the high pressure reset switch. I put gauges on it in HEAT mode and HI pressure was just about 375 psi.…This could have been a duct, or lack of, reducing air flow & causing the high pressure in heat…When i first put gauges on the unit in COOL mode my LO pressure was almost 90psi!….Not unusual if the cabin & seawater was hot…What was the cabin & seawater temp at that time ?… It was based on the information on here and the cruisair graph that i decided to lower my pressure to 50psi where i had about 160psi high side (in COOL mode). Since the unit froze up i though it was too low and raised it back up to around 75psi LO.

How is a psi spread of 50-160 in cool mode assuming 58F water and 65 F room temp? Once i get the psi set correct in COOL mode i will check again not he HI side. Any other tips on setting refrigerant? Is the cruiser graph fairly accurate?

Yes the Cruisair graph is fairly accurate for Cruisair equipment & assuming that water flow & air flow are up to spec….If those two specs are not, then throw the graph overboard…

You should know that under the conditions you state in cooling with 58 degree water & 65 degree cabin… and Assuming proper air & water flow…

I show a low side pressure of about 48 psi & a High side of only around 92-95 psi…You should expect icing…and the reason for that is when looking at a R-22 pressure/temp chart…R-22 is below 32 degrees at anything lower than about 58 psi…

Adding more refrigerant will only cause more liquid to flood back to the compressor, and also cause much higher head pressure in the heat mode…

Truth is…R-22 "Air Conditioning" systems are designed to do just that…Not Refrigerate…They really are not meant to be run in the cooling mode at much below 68 degrees (and that's with 70 degree seawater not 58) 

Why is all this so ?…It's all about picking up, moving, & getting rid of heat…We use refrigerants as the vehicle to carry that heat from one place to the other…How well the coil at each end can either pick up, or get rid of that heat will show in the refrigerant pressure/s (as said earlier no matter how much is in there)

When there is not much heat to pick up & move…For whatever reason/s as mention above…The pressures will show that too.

The idea to charging the system is to have enough refrigerant to flood/fill the evaporator coil fully (from bottom to top & too little may only fill it part way thus reducing the effective coil surface area) with a small amount returning to cool the compressor, but not enough to flood the compressor with liquid (bad thing)…

Think of it as filling a bucket till it just starts to overflow the edge…Or even better...Kinda like a bait well…Except the overflow hose returns to the compressor, and you only want a trickle getting back to the compressor…

The pressures only tell you how well it is moving heat & how much is there to move…

And since Pressure & Temp correspond….The pressures will go up & down as the heat load changes up or down….

Even if under or overcharged, or the system does not have enough air or water flow…This is also why it is imperative to have proper air & water flow before even thinking about charge level. 

If all else fails i guess you and i would end up talking about replacement units and cost

I look forward to hearing from you.

Though I would love selling you a new unit…We really need to visit your duct sizes & water flow before thinking that direction…We may end up with a new unit that does the same thing (even though charged properly from the factory) and Yes your unit may be fine too…

Steve~

January 11, 2012
7:28 am
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Scott Pooler
Indian Rocks Beach, FL
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Brother Steve,

I have known you all of my life, and have been around you and the marine AC business you have been working in (on the periphery and working with you on and off) for close to 30 years.  

This is the single best explanation I have ever read or heard regarding refrigerant pressures and levels.  Confused You would have thought that after all of these years, I would have had the grip on a simple concept like this.  

Thanks Bro - As Always! Laugh

Steve Pooler said:

Hi Tom & Happy to You & Your's Too~

Your question is a seemingly simple one that gets asked often…

Thing is…There is no simple answer & that's why A/C & Refrigeration guys go to school, plus spend years in the field getting the experience to know what is right in any particular system at any given time…The common misconception by many is that pressures will tell amount of refrigerant in the system...When in fact pressures only tell how the system is performing, or how much heat it is picking up, moving & getting rid of...

To explain about refrigerants & how they work simply ?...Pressure & Temp Correspond...Higher temp equals Higher Pressure.

So...Set a can of refrigerant into a room & let it get to room temp...With a pressure gauge & a pressure temp chart for that given refrigerant, you can tell the temp of the room by the pressure in the can...Regardless of if that bottle is 1/4, 1/2, or all the way full it will still have the same pressure at that temp....

Different refrigerants will have different pressures at any given temp and that is one of the reasons why we have different refrigerants...It's the temp/pressure range they operate in for differing jobs such as A/C vs Refrigeration... 

Many factors can affect an operating systems pressures & there are no real set standards….Some of those factor are:

  • Refrigerant Used (In your case R-22)
  • Type of metering devise (In Your Case Capillary Tube)
  • Are we running in Heat or Cool mode ?
  • Cabin Temp
  • Water Temp
  • Water Flow & if that water coil is clean or dirty (which will also affect heat output)
  • Ductwork, How it's Run & Thus…
  • Air Flow

A technician needs to know all of the above to formulate an accurate guess…

Yes there are charging curve charts for your R-22 system but they are only a basic guide…Here is a link to the Cruisair manual…Please see page 15 first, then Page 39 for the chart: ** you don't have permission to see this link **

There are also other ways to be more accurate such as…Charging by "Subcooling" or "Superheat" and you can Google those procedures to come up with several answers.

 

Your HVAC guy should be familiar with all these questions/answers but one other way if there is question is to check a system on the boat that is operating properly…You still may not have an exact answer because that system may get more or less air & water flow, but it will get you close.

I know it's not a real answer but hope it helps your thinking  Confused

 

Steve~

January 5, 2012
11:52 am
eze2bme
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As always ... thanks Steve!

January 5, 2012
8:50 am
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Steve Pooler
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November 12, 2008
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Hi Tom & Happy to You & Your's Too~

Your question is a seemingly simple one that gets asked often…

Thing is…There is no simple answer & that's why A/C & Refrigeration guys go to school, plus spend years in the field getting the experience to know what is right in any particular system at any given time…The common misconception by many is that pressures will tell amount of refrigerant in the system...When in fact pressures only tell how the system is performing, or how much heat it is picking up, moving & getting rid of...

To explain about refrigerants & how they work simply ?...Pressure & Temp Correspond...Higher temp equals Higher Pressure.

So...Set a can of refrigerant into a room & let it get to room temp...With a pressure gauge & a pressure temp chart for that given refrigerant, you can tell the temp of the room by the pressure in the can...Regardless of if that bottle is 1/4, 1/2, or all the way full it will still have the same pressure at that temp....

Different refrigerants will have different pressures at any given temp and that is one of the reasons why we have different refrigerants...It's the temp/pressure range they operate in for differing jobs such as A/C vs Refrigeration... 

Many factors can affect an operating systems pressures & there are no real set standards….Some of those factor are:

  • Refrigerant Used (In your case R-22)
  • Type of metering devise (In Your Case Capillary Tube)
  • Are we running in Heat or Cool mode ?
  • Cabin Temp
  • Water Temp
  • Water Flow & if that water coil is clean or dirty (which will also affect heat output)
  • Ductwork, How it's Run & Thus…
  • Air Flow

A technician needs to know all of the above to formulate an accurate guess…

Yes there are charging curve charts for your R-22 system but they are only a basic guide…Here is a link to the Cruisair manual…Please see page 15 first, then Page 39 for the chart: ** you don't have permission to see this link **

There are also other ways to be more accurate such as…Charging by "Subcooling" or "Superheat" and you can Google those procedures to come up with several answers.

 

Your HVAC guy should be familiar with all these questions/answers but one other way if there is question is to check a system on the boat that is operating properly…You still may not have an exact answer because that system may get more or less air & water flow, but it will get you close.

I know it's not a real answer but hope it helps your thinking  Confused

 

Steve~

January 4, 2012
7:43 pm
eze2bme
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Steve ... first off Happy New Year!  

I have low freon in one of my Cruisair 16,000 btu unit [WFAH16  S/N: B98341 (1998)].  Since the nearest service rep is now 140 miles away, I want to have my home AC maintenance guy check the freon and add accordingly.  Could you tell me what pressure readings he needs to check for and anything else that he might need to know to get the proper freon level.  The unit cools great but is now not heating like it has in the past ... which usually means that it needs a freon top-off ... seems that I have to add freon about every 6 years to that unit.

Thanks for your help ... as usual!

Tom