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Heat pump - icing up in A/C mode


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15 replies to this topic

#1 cwilkins

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Posted 06 May 2006 - 10:29 AM

Greetings!  I've got an approx. 20 year old GE heat pump that I'm trying to nurse along for a bit longer while I save my pennies for a replacement. It has presented me with various little challenges over the years, but I've always been able to get it humming along again at minimal or no cost.

Now the evaporator (inside) coils are icing up in "cool" mode, and that's with no filter installed!  Because the filters for this thing are apparently an odd size (18x25x1) and a pain to obtain, it has occasionally been run with no filter for a few days or a week.  I figured maybe this bad habit caught up with me and the coils were clogged with dust, so today I vacuumed the coils and blew out whatever was left with compressed air.

However, the coils are still icing up, even though I seem to have plenty of airflow.  Also, it just doesn't seem to be cooling very well.  The inside temp has gone from 80 to 81 since I turned it back on about a half hour ago.  I mentioned my predicament to a neighbor and he suggested I might be low on freon.  He also mentioned that they no longer make the stuff I need (R12?).

Ouch!  I don't suppose there's a simple and/or cheap solution for this?  Pretty sure I still have one of those little cans of R12 kicking around somewhere from a fridge fix about 15 years ago. :-)  I know I'm running on borrowed time, but I'm just not ready to plunk down $3-5k for a new heat pump.  ("Not ready" as in "I don't have $3-5k sitting around.")

Thanks very much for any help!

-- Charlie


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#2 exsearsguy

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Posted 06 May 2006 - 01:14 PM

NOT R-12! NOT R-12! You probably need a shot of R-22. GREEN CAN! NOT WHITE!Are you absolutely sure you have good airflow.Clean evaporator and fan blowing well.Are you trying to run it at night with cool outside temps.That will cause freezing up also. If you have a dirty evaporator vacuuming and compressed air won't hardly get it. And it sounds like you have a dirty evaporator. I clean mine and oil the fan motors every year myself.

#3 cwilkins

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Posted 06 May 2006 - 02:24 PM

 [user=437]exsearsguy[/user] wrote:

NOT R-12! NOT R-12! You probably need a shot of R-22. GREEN CAN! NOT WHITE!Are you absolutely sure you have good airflow.Clean evaporator and fan blowing well.Are you trying to run it at night with cool outside temps.That will cause freezing up also. If you have a dirty evaporator vacuuming and compressed air won't hardly get it. And it sounds like you have a dirty evaporator. I clean mine and oil the fan motors every year myself.

Er...  Oops.  Well that explains why the compressor exploded through the side of the outside unit and ran down the street yelping...

So I guess I need this thing sucked out and recharged now, assuming I haven't done permanent damage?  It was only 14oz, so I would hope I might get off lightly for my act of stupidity.  (...or am I going to fall over dead when I find out how much a couple of pounds of R22 costs these days?)

Thanks for your advice exsearsguy.  I only wish I'd been a little smarter and a little less impatient.  Now if you'll excuse me while I go sit in the corner and suck my thumb...

-cw-


#4 exsearsguy

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Posted 06 May 2006 - 09:16 PM

no permanent damage. If you can locate some 22 I'll explain a sweepcharge method to you.

#5 cwilkins

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Posted 07 May 2006 - 07:45 AM

Thanks.  That's quite a relief (though I'm still kicking myself for wasting a can of R-12...)

Looks like I can get a 30lb tank of R-22 and a manifold for about $110 online.  All I have to do is get my EPA certification first.  :?  Seems that I can also become a wholesaler and get some that way.  What a screwed-up mess...

So before I place an order, any thoughts about that, or other equipment I'll need to do a sweep charge?

-cw-


#6 Lurker_ahammer48_*

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Posted 07 May 2006 - 09:46 AM

Hi. I'm not sure what a sweep charge is. Thats a  new one on me. I'm assuming(ahh-um) that your unit is a split system with the evap (fan section) in a closet and the condenser (compressor section) ouside next to the house. If it is you probably have 5-7 lb of now contaminated refrigerant(R-22 & R-12). If you'd like to check the refrigerant U need it should be stamped into the name plate of the outside section.

Going by EPA regs that mixed refrig must now be reclaimed and disposed of(destroyed). It can't be seperated by U. Your system must then be evacuated well because the oil has probably absorbed some of the 12 into itself and has to pulled out. The the system will be re-charge with fresh R-22.

I think ur gonna have to bite the bullet and call someone. You might try posting a note at a local refrig supply house. Alot of guys do side work.


#7 exsearsguy

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Posted 10 May 2006 - 09:22 PM

Charlie a sweep charge is basically using your compressor as the vacuum pump. Hook your gauges( remember to purge your hoses)  to the high and lo sides,make sure they're closed and then fire up the unit.Open the hi side and let the old junk out.When it's about empty(you can tell by the sound and pressure readings),close it up and then add some R-22, let it run a little while.Then let the new gas out.Should be pretty clean now and ready to charge. Don't let it get plumb empty when you're doing this.The refrigerant helps move the oil to the compressor and if you let it run empty you might damage your compressor.Just be careful and it 'll be ok.

#8 cwilkins

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Posted 18 May 2006 - 05:38 PM

[time passes...]

Thanks for the info on the sweep charge, but well... I kinda went off the deep end.  Luckily we've had a spell of mild weather, so I did some research and ended up ordering some stuff online.  So I've got a set of gauges, a 3cfm vacuum pump and a 30lb tank of ES-22a (hydrocarbon substitute, no license required).  Evacuated down to 29+ inches and left that for an hour or so.  Came back and found it down around 28.  Could just be some vaporization, rather than a leak, if I understand correctly.  Anyhow, outside unit said it was factory charged with 5lb15oz of R-22.  Not sure about the lines or the inside unit.  Based on claims that 1lb of ES-22a replaces 2.5lbs of R-22, I charged with about 2lbs (according to the bathroom scale) of ES-22a for starters and turned the system on in cooling mode.  Pressures stabilized at around 38psi on the low side and 135 on the high side.  Outside temp was about 60F and about 75F inside, so perhaps not ideal conditions for doing this.  Put in another 1/2 pound, which brought the pressures up to 40/145.  According to the charts for ES-22a, that works out to around 19F/87F.  The temp coming out of the vents was about 55F.  So it's definitely working better than before, but I have no clue how close to the mark I am.

This is where my lack of knowledge/experience really shows.  Apparently to charge a system "by the book" you're supposed to take wet/dry bulb temp readings of the coils, convert your refrigerant pressures to temperatures, do a couple of calculations and home in on the correct super heat(capillary)/cool(TXV) values.  Well first off, I don't know the "correct" values for my 20+ y.o. GE Weathertron or where to find them, or even if I have a TXV or not.  Second, I'm under the impression that there are other ways (perhaps not as precise?) to determine correct charge.  Pressures vs. ambient indoor/outdoor temp?  Temp of suction line?  Sounds?  "Feel?"  Smell?!?  (I know a burning smell is bad...)

Oh, the outside unit mod# is BWB736A100A1, if that's of any help.  Also the ES-22a page at es-refrigerants.com has a temp/pressure chart:

http://www.es-refrig.../45/details.asp

Mucho thanks for any spare clues!

-cw


#9 cwilkins

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Posted 18 May 2006 - 05:56 PM

Thanks for the voice of reason ahammer48.  I know I'm messing where I really don't belong.  Yes, I should just call someone, but where's the fun in that?!?  ;)

Seriously, this is all a product of (some) mechanical aptitude, insatiable curiousity and an inability to simply throw large sums of money at such problems.

I was emboldened in this latest effort by success with other work on refrigeration systems, including the repair of a fridge with a hole rusted through the top of the compressor housing.  Granted, the stakes are a little higher this time...

-cw-


#10 cwilkins

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Posted 21 May 2006 - 10:10 AM

Some new numbers here...  Still a little cool outside, but not much I can do about that.

Inside/Outside ambient: 74F/76F

Lo/Hi Pressure: 57psi/205psi

Pressures converted to temperature: 34F/112F

Suction line temp at compressor: 53F (19F superheat?)

Temp at nearest indoor vent: 55F

I've also noticed the compressor is quieter than the fan now.  It's now sounding about the same or a little less noisy than before all this happened.

Total refrigerant added - about 5.5lbs of ES-22a.

So now the question is "what caused all this?"  20+ years of very slow leak (bad service valve/cap?) or something less slow and more recent?  The service caps on this unit are brass with no seals.  I'm told they tend to be leaky, which is presumably not a good thing.  When I removed the hi side cap, it gave me a little PSST, so sounds like the valve was leaking at least a tiny bit.  Perhaps the question is, was the cap leaking a little too?  I plan to leave the gauges hooked up for a couple of days to keep an eye on things.  Might new caps be a good idea anyway, just as general preventative maintenance?

Thanks for any clues...

-cw-


#11 exsearsguy

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Posted 21 May 2006 - 05:44 PM

Charlie, I think you'll be ok.Keep in mind that as your outside ambient goes up,so will your inside ambient.Sounds like enough refrigerant.If in doubt, just look at your suction line on a hot day.If it's sweating,it's full. CLEAN THAT EVAPORATOR!!

#12 cwilkins

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Posted 21 May 2006 - 06:50 PM

The suction line was sweating today.  I also noticed a little sweat inside the outdoor unit, on tubing leading to/from the filter/dryer.  I'm assuming that's still suction, though I didn't trace it out.

A veteran HVAC guy who's a neighbor of a coworker spent some time on the phone with me today and put up with me picking his brain for an hour or so.  His final verdict seems to be that I'm possibly still a little low, but that it's hard to tell with these mild temps we're having, at least with a non-TXV system.  He's sending me some kind of slide rule type superheat calculator to play with, and a couple of charts.  This should be fun!  :D

I hear ya about the evaporator.  Do I want the stuff you just spray on and gets rinsed off by the condensate?  ...or is that just a bit too magical to actually work well?

-cw-


#13 exsearsguy

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Posted 21 May 2006 - 07:39 PM

I just open mine up, spray it with a generic cleanser( 409, Windex, etc.) then scrub it with a wire brush. Then I spray it with the water hose. Ta-da,it's clean.Maybe pressure wash your condenser. I think your neighbor is close on. But I'd wait on warmer temps before I did anything. Oil your fan motors while have it open. And NO 3-in 1 oil in a fan motor. Don't get excited about superheat, just make sure your suction line  has iced tea sweat on a HOT day. Then you'll know it's full.

#14 Lurker_ahammer48_*

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Posted 27 May 2006 - 10:34 AM

The easiest way to tell if your fully charged is this: if you have a T/P chart, hook up your gauges and start the unit. Take ouside air temp reading and then add 30 degrees to it. So if its 70 outside, add 30 to make 100. Then find 100 degrees on your T/P chart for your refrigerant and read across to the corrosponding(spelling) pressure. Thats what your high side gauge should be reading(+- 10 psi)

I don't have ES-22a on my T/P chart but for plain old R-22 that would be 196psi @70 degree OAT. So now we have what your head pressure should be(approx). Now goto the inside unit and temp difference across the evap coil. Measure the return air, and then supply air. Should have approx a 20 degree diff between temps. If return is 75 degrees then supply should be 55 degrees.

If you perform these 2 checks and are close (+- 10 psi / +-2 degrees on temp diff) then ur in the ball park and I wouldn't add any more. If you have a clamp on ampmeter then put it on the compressor while ur doing these checks and compare running amps to nameplate FLA. If ur within 2 amps of nameplate (not over) I'd definitly call it good.

As far as cleaning the coils, if your going to open up the evap why not first use a drop light on 1 side of the coil while your looking at the light from the otherside. If you see alot of light coming thru that coil (not just from the center) then the coil is clean, go have a beer;).

Yeah, 409, Fantastic, etc are good for light-med build up. If you can do this-spray the entire coil(both sides) with one of them, let it stand for 10 minutes then rinse off using a garden sprayer (the kind u put water in then pump up with air) ur good to go. If heavy build up use a good foaming cleaner made for coil cleaning.

The condenser depends on if you live in an area with alot of pollen (lotsa plants, trees, etc) If you do then consider using compressed air instead of the hose. I live in NM USA and we have a tree called a cottonwood. This time of year they release there pollen which looks like snow and can make a 1/2 thick blanket on condensers. It really gets in between the fins. I found using air is much better because the hose just makes a wet blanket in between the fins. Just be carefull and don't bend the fins over. If your area is mostly dirt then air or water. In the city use water with a degreaser.


#15 Dan Webster

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Posted 27 May 2006 - 04:58 PM

At my  store I sell a very good product call vapco FCC-1 evap coil cleaner(non-rinse) for the A coil and something called Brite-Alum for the outside unit . I suggest you go to you local HVAC supplier. use these products according to their directions
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#16 exsearsguy

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Posted 27 May 2006 - 06:54 PM

I agree that a hose won't cut it. That's why I said pressure wash. And believe me. air won't cut it either.




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