using HP39 instead of R12

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  #1  
Old 04-25-03, 07:37 AM
abulaith
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using HP39 instead of R12

I have a display unit in a restaurant. it is a cooler not a freezer, my friend called me to help him out with it. I have not worked on units like this since I left the Air Force in 1995.
I checked the unit and the evaporator coil was iced up. I shut it off until it thawed. I then put the gauges on it and it was undercharges. it uses R12 and when I check the price on R12 I found out that the 30 lbs jug is way too expensive for me just for few oz's to repair this unit. I done a little study and I found out that may of the sevicemen here are using HP39 (R401a) to replace R12. so I bought a bottle since it is not that expensive.
I can not find though a conversion chart for it. I start charging the unit anyway remembering from the Air Force days the tempraure difference between the liquid line and the suction line. but I am a little rusty. how can I use the regular gauges to charge the unit?
This unit does not have an evaporator fan, and I've been adding little charge at a time and watched the unit operate. I still see frost on the evaporator coil, not as sever as before. but I do not want to keep charging until I find out a good pressure read out on the regular gauges to charge it correctly. I set the T-stat so that the unit would shut down and thaw.
I appreciate any help.
thank you
 
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  #2  
Old 04-25-03, 09:44 AM
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abulaith:

I'm afraid that we cannot provide advice on sealed system repair as it is no longer a DIY persuit, due to tha fact that you must be qualified, licensed and have all the necessary reclaim and evacuation equipment.
You may be trying to help a friend but are likely violating EPA reg's in doing so.
 
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Old 04-25-03, 09:55 AM
abulaith
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Sorry, I did not put all my qualification in the e-amil, I am a certified HVAC serviceman but I did not work that field since 1995, and did not work with this particular refrigerant. I do hold a license. I do have a universal license in refrugerent transition and recovery and it is valid, I have all the proper tools as far as reclaim unit, gauges, vacuum pupm ...etc. and know all the rules and regulation of reclaiming and recycling. I am not violating any rules.

all I need is the conversion chart or where I can find it.
 
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Old 04-25-03, 01:37 PM
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abulaith:

Your refrigerant supplier will have loads of conversion information in the form of pres/temp charts and oil change advice.
BTW, the numbering for the refrigerant you are asking about should be MP-39. The HP designator is for Dupont's high pressure refrigerants.
 
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Old 04-25-03, 11:57 PM
firsthvac
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As GregH said, you can get information about refrigerants from the suppy house where you purchased the refrigerant. I'm curious though, if you are a certified tech and did some study, then why would you want to use R401a knowing there are better R-12 substitutes available which mimick R-12 pressures more closely and are more efficient to boot?
 
  #6  
Old 04-26-03, 08:01 AM
H
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Lightbulb My thoughts too!!!

I believe with MP 39 you need to remove the mineral oil as well and add alkabenzene. Hot shot (I believe R414b) is more like a drop in and closesly mimics R12... Also your working on a flooded evaporator which should be like a weighed in charge. With MP 39 I think you have to start out with 80% of the R12 weight and monitor from there. Super heat and amp draw on the compressor will be key in charging this unit. TP charts for MP 39 ???? Are you schooled on temperature glide?
 
  #7  
Old 04-26-03, 01:25 PM
fjrachel
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As hvac1453 says...use the 414b/hot shot. It is a drop in, just remove all the 12 first.
 
  #8  
Old 04-28-03, 07:01 AM
abulaith
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Thank you all for your replies, we decided it would be better to buy a new unit, this one was not ran for 6 years, too many rusted parts and it is not worth the trouble.
 
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