Updating R12 to 134a

Hi guys, I'v been in the trade for almost 4 years now and still don't truly understand most things about changing a system from the likes of R12 to 134a.

I have a job with an R12 unit that runs a glass doored drinks display, the compressor has seized and I have to price the job.

I know I have to change the compressor (duh), the filter dryer and flush the old oil out of the system.

What I'm wondering is if I will have to change the capillary tube or if the condenser and evaporator are going to be of the right size?

If I do have to change these I doubt I will be able to to this job as I'v no idea how to calculate the length of capillary needed and only the vaguest idea of how to size the evaporator/condenser (I'v lost all notes from college :rolleyes: :( )

any advice you can give would be helpful.

Just stick with r 134a and poe and you should be ok. Usually when you retrofit 134a for r12 its only the Jil you need to worry about, it will only use slightly more electricity. It must be a very old unit if its got r12 in it, is it actually worth repairing?

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Originally Posted by chilliwilly

Just stick with r 134a and poe and you should be ok …

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This is correct only for HBP compressors and systems with evaporator temperature from -15°C to +15. (After cleaning the system).

The problem is that under -18°C the heat transmission coefficients of R134a drop compared to R12 and you will need a larger compressor and change cap tube also.

You will probably get by the same condenser and evaporator size though the operating differentials will change (should be larger) so to keep a 3star refrigerator you would probably operate in 4star conditions.

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Originally Posted by Baw_Jaws

Hi guys, I'v been in the trade for almost 4 years now and still don't truly understand most things about changing a system from the likes of R12 to 134a.

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You should read about it then:

http://www.emersonclimate.com/White%...WhtPaper_9.pdf

And

http://mea.emersonclimate.com/mea/pdfs/tech/9304.pdf

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Originally Posted by Baw_Jaws

I have a job with an R12 unit that runs a glass doored drinks display, the compressor has seized and I have to price the job.

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First tear down failed compressor and find out the reason for its failure and correct it before installing the new one.

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Originally Posted by Baw_Jaws

I know I have to change the compressor (duh), the filter dryer and flush the old oil out of the system.

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Not just flush, clean because the POE oil will dissolve all the dirt the mineral oil deposited in the evaporator and suction.

You may install a suction filter temporarily if you cannot clean the system.

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Originally Posted by Baw_Jaws

What I'm wondering is if I will have to change the capillary tube or if the condenser and evaporator are going to be of the right size?

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Maybe, you always have to check, but most probably not.

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Originally Posted by Baw_Jaws

If I do have to change these I doubt I will be able to to this job as I'v no idea how to calculate the length of capillary needed and only the vaguest idea of how to size the evaporator/condenser (I'v lost all notes from college :rolleyes: :( )

any advice you can give would be helpful.

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Size evaporators and condensers is no big deal but you have to read manufacturer’s literature. The big problem here is you will probably not have information on your evaporator. But the compressor tables will help.

You can get old cap tube tables from your compressor supplier, but they only go so far you always have to do this on a trial and error basis.

Its only a drinks cooler so it should be ok, I have retrofit 134a and dropped in isceon 49 in place of r12 with only arguable neglegible differences.

By the way what's a HBP pot anyway?

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Its only a drinks cooler so it should be ok, I have retrofit 134a and dropped in isceon 49 in place of r12 with only arguable neglegible differences.

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I agree.

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By the way what's a HBP pot anyway?

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Depends: High Blood Pressure, Home Buyers Plan, Harry Bludger Potter or High Back Pressure

Thanks guys, you've both been a great help. Oh and thanks for the great links aramis, I'll be saving both pdfs to reread at leisure. You have any for ground freezing?

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Originally Posted by Baw_Jaws

You have any for ground freezing?

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Wow! 4 years in the trade and you are already moving to mining engineering?

http://www.bbri.be/homepage/download...ng.pdf&lang=en

:D np just interested is all.

oh and thanks again

hmmm little basic and doesn't show anything of how they counter the acceleration of water flow between the freezing pipes. I'll give google a shot again.

Water will not flow faster because it travels through the ground basically by capillary action.

If the soil is too fluid, you must use more tubes and with nitrogen or co2 to freeze it fast.