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question on proper heat pump charging  Rating:  Rating
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 Posted: Mon Nov 8th, 2010 01:00 am
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paschal
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without going into specific system specs, can someone explain what is the difference  between just putting freon (old type) into a heat pump and addressing the "sub cooling" when charging a system? Hopefully I have the terminology correct.

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 Posted: Mon Nov 8th, 2010 02:38 am
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AmTec Services



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Sub cooling is the term we use for cooling the freon lower than it's condensing temp.

Example would be R 22 freon with a condensing temp of 100. This is the temp that the freon turns from a hot gas into a liquid or condenses. If we stack that freon up in the coil, the fan has more time to cool that liquid even more. So adding freon to the unit will affect the sub cooling. Your temp measured at the liquid line will be lower than the condensing temp.  How much is your sub cooling #

Example  100 deg. condensing temp minus 85 degree liquid line temp  =  15 degree sub cooling.  Adding freon will increase sub cooling, removing will decrease.

Its the exact opposite for super heat.

Are you lookig for advice for charging in heat or cool?

........AmTec:D



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 Posted: Mon Nov 8th, 2010 03:53 am
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paschal
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Well I hate to dig out old laundry, but I have been through hell for two years with my heat pump and have been through three different companies, the problem was moron techs, and now I am quite convinced that it was just that until now. Had a really good guy who wanted me to walk and talk and watch his work and explain as he went about his work, who is now my guy for life due to his work ethic, and I got a bit lost when he was trying to explain sub cooling charging. I am an engineer by trade, but on the computer end, and nothing ticks me off more than to not totally understand something.

Started with a defective motor mount that killed the motor, variable speed, but was cooling well until that point.....the motor was replaced, however due to my analysis, freon vanished, cuz it went with the tech. Due to the warranty arguments etc., which i finally resolved, and it was resolved but problems came up big time in heating season and company number one claimed no responsibility of course, that tech does not work here anymore etc...........the motor was replaced in low demand season.  The next guy from company number 2 said 78 degrees heat was the best I could get on the heat side and charged me for a few pounds of freon and two hundred bucks .....then the good guy came out after 50 pounds of ice hit the coils....and my house would have flooded without the wet vac.

There was never a leak, IMHO  Company number three could not find one,and spent over an hour trying to find one.  Bottom line....Mechanic number one stole a few pounds of freon....Mechanic number two company two never added the freon he charged me for, but got three pages of Mr. honest in a local paper, and Mr Hero Mechanic replaced the stolen freon, and the system has been rock stable for almost 4 months. When the good guy tuned the system it was less than 2 months after Mr. Newspaper gassed it....(well he charged me for it) which was 78 degree heat output when he got here and 78 degree output when he left.....great show however, bucket of water to boil the freon etc but accomplished nothing and fixed nothing.

I stick with door number three, no flash, no show, just a humble knowledge guy with an M.E. degree that knows what he is doing....I just got lost when he tried to explain the sub cooling charge......

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 Posted: Mon Nov 8th, 2010 04:05 am
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paschal
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I guess I was trying to understand how someone can say they put a couple of lbs of freon r22 into a system and say it is good on the pressure, which was either a lie or incompetance vs someone who says it is set for proper subcooling and is now full after 3 lbs and it has been working fine for months etc  after only a few weeks. It is much harder to get get taken to the cleaners after retirement and not understand everything that has happened. Getting ripped off is a bit tougher to deal with.

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 Posted: Mon Nov 8th, 2010 12:36 pm
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AmTec Services



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Proper way to charge a TXV metered system in the cooling mode is by the sub cool method. Need guages and thermometer. Pressure alone only tells part of the story.

.............AmTec;)



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 Posted: Mon Nov 8th, 2010 11:45 pm
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JJDH

 

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It is highly doubtfull anyone stole your refrigerant



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 Posted: Tue Nov 9th, 2010 03:56 am
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paschal
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Lets just say I have good reason to believe company number one stole the freon, with supporting evidence, company number two, smoke mirrors bucket of water and lies, and company number 3, hero, and that is what this was about, the hero, the good guy in the business, and yes he was full of gauges outdoor ambient, and you name it, and tried  his best to explain everything he was going thru after my two years of misery. Now my system is working, and that was the point.

As in all business, there is good and bad, and consumers must know sometimes you may have to cut your losses more than once to get to the right people, and for me, that is exactly what happened. I still have a minor defrost issue on very cold days but we have not had enough of them for a consistent pattern, but I feel good when it is cold on a regular basis, it will now be corrected. That is all this post was about and I thank those who explained the sub cooling. I understand that now.

To answer freon theft comments, it is not that unusual either from a tech or a techie teenager filling up garbage bags to huff it. I know of two cases in this metro involving juveniles stealing freon caught on camera snorting freon from houses. I know of one a/c tech caught and fired for taking a pound or so from customers under service contracts on a daily basis. so yes that activity does happen.

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 Posted: Fri Apr 29th, 2011 02:13 am
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ourstocks2002
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You sure do have some harsh opinions for someone who does not know what they are talking about. Did you not study fundamental engineering in engineering school? The question you ask relates directly to fundamental engineering that ALL engineers study first year, electrical, mechanical, civil, maybe not chemical, regardless....

Tech number one may have removed some refrigerant due to the system being overcharged, I doubt it was stolen. R-22 goes for about $7/lb, did he steal $30 from you, doubt it. He would have access to plenty of company stock.

The best way to charge a TXV metered system is in cooling mode using subcooling however coil TDs, pressure and discharge temperatures could also be used.

The "subcooling method" has been developed since the introduction of "new" refrigerants, the result of Montreal Protocol, Ozone Depletion, Global Warming. Old school with R-12, R-22, most people looked at pressures only. Since the new refrigerants have different operating pressure, the old pressure method did work anymore. It actually does, but one needs to know the pressure of the refrigerant they are dealing with.

Curious, what "analysis" did you do to determine that refrigerant vanished?

One thing about heat pumps, they have an operating window. Since in heating mode, the heat pump extracts heat from the ambient air, when the outside air (OA) temperature drops below 40°F, there is not very much heat available to extract. Also, since the outdoor coil is operating as an evaporator during heating mode, with 40°F OA, the coil temperature is somewhere around 20-25°F which is below the freeze point of water so condensate freezes on the coil further reducing the systems capacity. Bottom line, don't expect heating miracles from air sourced heat pumps when OA is near and below 40°F. Considering your user name and "Metro" keep that in mind my friend from Mtl where the winter design temp is -16°F.

The bucket of water may have been to help defrost the coil quicker and to help raise the outdoor coil pressure to get more heat out of it for a few minutes. Again, there are limits to heat pumps.

Anyway, glad to hear that your issues seem to be resolved and that you found a tech (ME) that you are happy with. The lingering defrost issue may be due to operating when the OA gets too low. By the way, energy efficiency drops off when the OA drops off too so don't be afraid to switch over to aux heat when OA drops to 40°F.

Good luck!

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