Carrier A/C, Again!

[hrdwrkingacguy]

Re: Carrier A/C, Again!

I was in a hurry to head to work so I only got one reading. Might try both sides tomorrow depending on how my day works.
I think I understand the concept, dont worry too much about not having a board. Correct me if I am wrong.

How did you site subcooling only taking one reading?

1. A system using a piston (like my old evap) can only provide a steady flow of refrigerant to the evap coil. As the temperature rises the piston being static cannot increase the flow of refrigerant on by itself. This affect the efficiency of the system as the superheat of the system can be lets say 7 at 70 deg but 30 at 100 deg (just numbers there).

Your numbers are backwards, you would have 30 degrees at 70, and 7 at 100...See the previous post..

2. With a txv the flow of refrigerant into the evaporator coil can be changed. The valve drives its orifice larger or smaller depending on the temperature of the suction line (and other factors) attempting to keep the determined ideal superheat number.

This is true, except pumping pressures and superheat are on one side of a battle the TXV is trying desperately to win..

3. If the superheat number is high then you have what I been having, a system that is not delivering enough refrigerant to the evap to be balanced. If you get low numbers, like I did today, it probably means the valve has open beyond the ideal superheat and it is delivering to much refrigerant for the system to be balanced. When I say balanced i mean that point when you are delivering the maximum amount of liquid refrigerant to the evaporator coil and it gets evaporated by the evaporator load and (ideally, I think) there is no liquid refrigerant at the other end where it goes into the suction line.

A txv won't open "to far" and stay there...They don't sit right at 12 degrees, they "hunt" you may have been looking when it was on the way back while it was hunting...If you have a good enough thermometer you can see the suction line go from 50 to 55 to 58 back to 55 to 50 and then back up, and do this over and over again...

4. So that leads me to believe my valve just opened up too much today, probably influenced by the 115+ deg heat in the attic and maybe being not ideally insulated by me.

Nope, there is no such thing as to far...The worst a system can do is run 0 superheat "totally flooding back" which is the most capacity you will get, but it will wipe out compressor valves...

 

[Nandy]

Re: Carrier A/C, Again!

I typo it, I meant superheat, not subcooling on yesterday readings....

I thought constant hunting on txv was an indication of something wrong, either a loose bulb, no enough insulation, an oversize valve, etc.

What I mean by too far is a number way larger than the ideal superheat. If you have a 0 like you said or a 30 wouldnt that be past too far from the ideal superheat to either flood the compressor or to overheat the compressor? I guess is a terminology thing...

 

[hrdwrkingacguy]

Re: Carrier A/C, Again!

You can't think of superheat/subcooling and txv's in a vacuum...There are many other factors the txv is battling...

Filter condition, fan speed, heat transfer, indoor coil condition, outdoor coil condition, entering air temp to the indoor coil, ambient temperature, Room sensible temperature, latent heat in the air(humidity)...All of these things are variable...And all of these things can throw off your readings...Some of them can make your superheat 0 and others can make it 30...A dirty filter will make your superheat 0, dirty outdoor coil can make it 30...

The trick is to get all the facts, know what the unit is supposed to be doing, and figure out what it isn't doing...This is what I do...

 

[Nandy]

Re: Carrier A/C, Again!

You wont believe this. I ran out of gas while building the valve. There are no gas suppliers open during the weekend in Charlotte or any of the surrounding cities that I could find. I even called 2 shops that deal with gas and both told me there is no a welding gas supplier open. I am so glad it happen then and not after I had open the system or I would have been on my way to buy some mepps which I think is the only thing that will do the silver brazing. It is 90 some already outside and it is a cozy 70 in here (I set the thermostat to 68 the night before to try to keep the house cooler while the system was off). Anyway, will get the bottles ready monday and might have to do this during the week because I ran out of time. If I dont do it now it will be mid august...

 

[hrdwrkingacguy]

Re: Carrier A/C, Again!

What type of torch are you using? oxy/acetylene or B tank?

 

[Nandy]

Re: Carrier A/C, Again!

oxy/acetylene.

 

[Nandy]

Re: Carrier A/C, Again!

I'm trying to do the change today. Right now I'm trying to park the freon load at the condenser but it is taking a bit. Itd been about 6 min and the liquid gauge hs change maybe 20 psi and the sucktion gauge has move a bit too. This is a 3 ton system with about 4.6 lbs of r22. How long should thid take?

 

[Nandy]

Re: Carrier A/C, Again!

I got the freon parked at the condenser. I guess that plunger only works the fan. However, the size of the valve after all the fittings make it impossible to close the evap case. I cut the connectors as close as I could to the valve but now the connector part wont braze. How do I braze my copper connector to this valve now? Silver dont seems to work. Doing vacuum after installing the old valve back. I dont expect any problems after this, just back to the old valve...

 

[hrdwrkingacguy]

Re: Carrier A/C, Again!

with the system running in cooling, pull the disconnect, close the liquid line, close the disconnect, and run it for a minute or so till the gauges read close to 0ish...pretty easy...If that doesn't work you have an overcharge or a compressor that doesn't pump...

 

[hrdwrkingacguy]

Re: Carrier A/C, Again!

If it were me, I would extend the piece between the flare adapter and the valve and put it just outside the coil case...5" or so of 3/8 should do it...There is no rule saying the valve can't be outside the cabinet...then hook up the equalizer line to the suction line and install the bulb and insulate it really well...That way you can make adjustments without having to take the panel off...

 

[Nandy]

Re: Carrier A/C, Again!

That could work but as it's stand right now I cutted the valve fitting on the flare addapte side about 1/2 inch from the valve body. I need to find a 45% silver rod to be able to weld that brass to the flare addapter. The harris rod I have will not stick to the brass with the low silver percent on it. If I can fit the valve as I had it plan I can make adjustments with just removing the approximate 5" x 12" access cover which is very easy to to remove... We shall see, but I lost my timetable so it will be a coupe of weeks again... oh well, the compressor seems to be holding well. I powered it down I was able to put my hand on it and althought it was hot, it was not so hot I could not hold my hand to it. It dont make more noise that the neighbors do either, not than that is a good indication.... It parked that freon in a few seconds once I figured out what I was doing wrong.

 

[hrdwrkingacguy]

Re: Carrier A/C, Again!

You need 45% and white flux paste...Its about the only thing you can do brass to copper with...It is expensive tho...

 

[Nandy]

Re: Carrier A/C, Again!

I know I have not updated this in about 2 years but since this is a follow up I think it will be alright to keep it all in this same thread. If the powers to be seems it is better for me to start a new thread I will.

As hrdwrkingacguy predicted the compressor died. It trips the breaker. I tried taking the compressor out of the connection and the fan turns on fine. I even replaced the starter capacitor just for kicks and giggles but no ciagar. I kept postponing changing the valve and now I get to pay for it.

The dead compressor is a Bristol model h29b33uabca, part no 739024-1602-00, thi sis a 32,900 BTU 240 VAC, 1 phase unit. I have looked for it on ebay but what I have found so far with the Bristol brand is not compatible because it is either 3 phase or 30k btu and smaller. Could I use another brand for this replacement as long as the BTU's are the same or maybe a little larger? I dont want to install a compressor that is smaller than what I had but how much larger could I go? The new coil I installed 2 years ago was a 36kbtu unit so I think my compressor should match that. Maybe now I can better balance the system since I was having that problem where seems my valve was not large enough. Maybe a larger compressor will solve the problem? Could I still use the old valve that is in place if my compressor matches my coil? Should I use the adjustable valve or a new larger valve?

This is my coil specs:

ACTUAL DIMENSIONS: 21 1/2" W X 23" D X 30 1/4" H
TOP OPENING: 18 1/2" W X 21 1/4" L
BOTTOM OPENING: 17 1/2" W X 19 1/2" L
MODEL - EDM2X63JA
COOLING- 36 K BTU
REFRIGERANT - R-22
TXV VALVE - YES
MATERIAL -COPPER FIN
TON - 3 TON
LIQUID LINE - 3/8"
SUCTION LINE - 3/4"
STEEL GUAGE - 22
TYPE - "A COIL"
OVERALL DIMENSIONS (WXLXH) - 21 1/2" W X 23" D X 30 1/4" H Inches
OPERATING WEIGHT - 45 LBS
POSITION - MULTI-POSITION

The old valve specs:

2-3 TON TXV KIT

Mfg: FAST
Model #: 1174451
Alternate Model #: EA36YD-045
SCL #: 19990
Condition: New

TXV KIT, REFRIGERANT: R22, TONS: 2-3, MAX PRESS: 160PSI, 3/8 SWEAT X 5/8 FEMALE COMPRESSION WITH 3/8 FLARE EQUALIZER LINE, CAPILLARY LENGTH: 20", WEIGHT: 14.8OZ, DIMS: 6"L X 2-1/2"W X 1-1/2"D. ADDITIONAL PART NUMBER: 331709751

The house has 2004 square feet of heated/cooled area. Seems the 33k btu is fine for it.

hrdwrkingacguy, where are thou!!!! lol!

PS - After checking ebay again seems I missed this bristol compressor that is for 3 ton system:
3 Ton Compressor Bristol 2010 | eBay
seems that is what i should get but still open to suggestions...

 

[hrdwrkingacguy]

Re: Carrier A/C, Again!

I totally missed this post. Hopefully you got it fixed. I am positive that compressor or a cross over p# is available. You can cross Bristol to copeland...that is the same compressor I changed for my neighbor a few months ago. The Bristol was 780$ and the copeland was 440$

 

[Nandy]

Re: Carrier A/C, Again!

Hey stranger!!! lol! I did change the compressor (actually, the entire outside unit). since it is getting warmer I will try to do the valve change in the upcoming weeks. Hopefully I can reach you then and you might be able to coach me to set this right... I will update the specs on thew new outside unit once I get to that point...

Thanks!

 

[Nandy]

I know this one is old but just a quick update. I end up having to work on this unit again, it had a slow leak which I had always believed to be in the condenser because the guy that sold it to me said it had 4 lbs of freon and when I got the system working it end up only having about 1. Every year I had to top the unit off when the hot weather started. This time I decided I was going to do my best to get this fixed finally....
I got another txv because I was suspicious of the one we had which besides the copper pipes was the only thing left from the original system. New valve is a Danfoss TR6 - 067L5858. flushed the lines with rx11, they seemed clean, use nitrogen to purge the line and while brazing. Pressure test at 175 psi and finally found my leak, it was one of my braze junction in the suction line right by the intake valve of the condenser. Once that was solved the system held pressure over night. I hooked the nitrogen, pump and high/low connectors and let the nitrogen leak until very low psi, hooked my 2 stage pump and pump for 1 hour, let it rest for 45 min, no change, so added nitrogen to 120 psi then vacuum again for another hour after letting the nitrogen out for the most. At that time I had also swapped the nitrogen tank by the freon tank in order to keep non condensables out.
Load system with freon, 4.5 pounds. checked my subcooling and adjust the load, I did made a mistake and let the freon load for a bit longer so my subcooling was high. I did used an old freon tank that I vacuumed to save the freon.
these is what I found today.
ambient 93
condensor fan was 107
register was 51
liquid line was 210 psi and 94 psi (the psi goes up and down 10 deg from 210 to 220. very slow change) read at the compressor.
suction was 65 psi and 65deg at the compressor.
My subcooling is between 12 to 14 per the calculator.
Inside temp was 73 and the ac is set for 70.
superheat I think is about 27 but the calculator is for a fixed metering device and therefore im not sure it is the correct measurement.

Things I need to do is probably clean the condenser/evaporator then change filters. Probably seal the evaporator better with tape as it is leaking a bit.

That valve is adjustable but I am not sure I need to fiddle with it at this moment.

Thanks!!