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Question DetailsAsked on 5/4/2017

do they have to get evacuate freon when replacing TXV metering device.

the AC person is telling me when they change part that all the Freon will need to be replaced since it will be corrupted. Freon charge is 100.00 per pound. So, estimating between 6-10 pounds needed. I do not understand why they will need to take all freon out and replace. Do I need to get them to show me how much freon is in unit currently

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2 Answers


Almost always - on residental systems (as opposed to larger commercial systems where isolation valves are more common) there are almost never isolation valves to allow removal of the TXV valve without first pumping out the refrigerant (which for most gases including Freon is required by law rather than venting it, plus would waste at least several hundred $ worth of gas on typical system). So - removing the gas to change the TXV valve is almost certainly a legitimate need - just part of the cost of changing that part out.

As for replacing rather than putting the existing freon back in - that is something that varies with vendors and is sort of like the question of whether you automatically put new lubricant into a car engine or gearbox when rebuilding it if the oil is relatively new. Some will not put used refrigerant back in under any circumstance because it undoubtedly has come contamination in it from scorched lubricant (which the refrigerant moves around the system) and gradual breakdown of the gas in constant heating and cooling, and they don't want any chance of that causing a warranty callback - or they just feel philosophically that putting used fluid back in after a repair is wrong. Of course, is their charge for the gas is quite high, then you are looking at a biggear $ consequence than with with normal automotive equipment rebuild where you might be looking at $20-50 worth of fluids.

Other vendors will put old gas back in, after (hopefully) filtering it during the extraction process - all extraction/injection machines I have seen have an in-line filter for that purpose. That can be a judgement call. Certainly if your filter/drier replaceable filter element (in most cases- some are hard canister throw-aways like car oil filters, some have a slip-in filter element filter cartridge) which should be changed anyway while the system is drained, is burnt looking or contains significant signs of contamination like sludge or carbon I would not reuse the gas. If everything looks clean (though typically the lubricant is colored by the manufacturer) I would personally not object to reusing it - though you will pay probably $100-250 range for the pumping out of the gas and later reinjection after the repair - that is not free because it does take 15-30 minutes on each end in typical residential sized system. Plus there will likely be at leaat a bit of make-up gas required - if not from slow system leakage over time, at least because in hooking up the equipment and extracting the gas and refilling the system there are small losses of gas left in the connecting lines and the poump and such which escapes.

Whether the existing gas will be "corrupted" depends on whether the unit has been running on low lubricant or gas pressure - making the unit work harder, and overheating. The TXV valve malfunctioning can certainly lead to this - either because it has been running at too low a pressure so the unit is having to run an excessive amount of time because the evaporator is not cooling like it should at the low pressure drop, or by causing excessive compressor running time trying to reach a higher pressure than it should have to meet - or maybe has been designed for. A TXV valve trying for way too high a pressure (or improperly sensing temperature, in those with that as a part of how they work) can cause the compressor to run continuously, trying to reach a pressure which is above its ability to reach, which can lead to scorched lubricant and compressor wear - and sometimes metal shavings in the refrigerant from the compressor.

As for measuring the current amount of freon - if the operating pressure is lower than it should be due to low gas (as opposed to faulty TXV valve) that would show it has leaked off some. The amount put back in that is reused I can see no sense in weighing because it is what it is - i.e. whatever he pumps out he presumably pumps back in if reusing it. Of course, new gas (which they are charging $100/lb for evidently) should be weighed (they weigh the entire tank before and after to measure the amount used - a few of the fancier injection systems measure the gas directly liek a gas pump does) before and after injection to show how much has been used and should be charged for. The final amount put in the system is not generally (except for some small package units like portable or window air conditioners where the exact volume of the unit is known because there is no distribution tubing) based on a pre-planned poundage to be injected (though the rating plate does show what the unit without connecting tubing holds) - it is based on putting in the amount of gas that obtains the correct operating pressure in a warmed up, stabilized operating system.

Ultimately - probably comes down to whether you trust this tech, or think he is trying to rip you off for $600-1000 of freon you don't need. No way to tell from here, though $100/lb is pretty high considering the raw gas costs about $25-35/lb these days in the size containers HVAC vendors commonly use (24 and 40# of gas respectively). However, some vendors charge for the gas PLUS a separate labor charge for injecting it, others wrap the labor charge into the per-pound charge so sometimes you are comparing apples to oranges if comparing different vendors. Here is an Angies List article on the freon cost issue:

So - you will have to decide whether to continue with this vendor, or jump to another one - obviously, ratings and reviews on Angies List for the current Heating and A/C contractor should help give an indication of whether he is honest or maybe milking the job, though at $600-1000 for the gas alone I would say that is pretty high whichever way he charges - $600 is more in the range I would expect to see for the total job cost including all parts, gas, and labor.

Answered 3 years ago by LCD


Oops - one correction when I was doing the answer did not get into the final answer - should say, in last line, $600-1000 is the range I would expect for the entire job - not just $600 as it says.

Answered 3 years ago by LCD

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