How much refrigerant required after a pump down
Two years after the installation, we had the original installer put a TX valve at the AHU to replace the orifice check which apparently had packed it in.
Prior to the job, he said that the unit would be pumped down to do the job and I thought this meant that the refrigerant would be captured in the outdoor unit and then reused after. If that is the case:
1) How much refrigerant would be necessary to get a 3.5 ton unit with 40 feet of lineset back up and running?
2) After the installation he billed me for 9 lbs of refrigerant. Is that normal?
I asked him why so much was required and he said that he had to replace the dirty refrigerant from the lines. Huh? If it's dirty-Why? Why was so much in the lines? I saw him blow out the small line with Nitrogen into a rag and nothing came out.
The amount and cost of the refrigerant does not seem out of line... many folks charge more that the posted price for R-410. Having said that, please remove the pricing, it is against forum rules.
As far as 'dirty refrigerant'... one cannot see the dirt. The tech may well have seen signs of non-condensibles (moisture or other gasses/solids) in the refrigerant. Detecting the presence of such substances is a talent learned by lots of experience, it is not simply 'looking at it for dirt'.
If the unit works properly, I would be thankful the tech was careful enough to do a thorough job.
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If I was installing the TXV in place of a operational orfice metering device I would pump the unit down, if the orfice was plugged I would recover old refrigerant, and recharge with clean refrigerant. I also would have pulled out my flat rate book after the diagnosis so you knew the price before hand and would not need to get on the naked lady machine and ask this question
You can't fix stupid
So if he installed the unit in the first place, where did the crap come from that plugged up the orifice check? My assumption would be from the original installation. Or is there something I'm missing.
if pumped the system down itis highly unlikely that it took 9 lbs of freon if he recovered the freon then yes it could have taken 9 lbs and a drier
If he pumped it down, he should have not put 9 lbs. back into it. If he recovered it, then yes, he probably put 9 lbs. back into it. Why did you bother to change to a TXV after a few years? I've never seen a piston go bad, it is a chunk of brass with a hole in it. Nothing to go bad with it. It might have gotten trash in it, then you poke the hole clean. If it had trash in it, then he might have recovered the refigerant because of crap floating around. I would have installed a filter dryer right before the evap. coil and put clean refrigerant in it. I wouldn't have changed the piston, TXV's are a pain in the arse and are one more possible problem with a a/c system.
bm, this is exactly what my thoughts were. Not being a pro I guess I wanted a second opinion from you guys though.
We don't cool much with this unit so I don't care if there is a TX at the AHU. I just need something that works for defrost and on the rare occasion we cool. My personal opinion is simpler is better. A little chunk of brass sliding back and forth with a hole in it is pretty simple.
After reading your comments, I would not have let him convince me to have the TXV installed.
No he did not install a new filter drier. How bad is that?
Good habits are replacing the filter drier after you open the system up. If you had trash floating around in the copper lines, there is a good chance he didn't get it all and it will continue to float around and take out the TXV as well. A filter drier before the coil would have prevented that.
Originally Posted by vanisle