S.Heat high, S.Cool Low.

[skr0oface]

I just want to start this thread off by saying I'm in the process of getting pro membership but am awaiting email from mod's. Having issue's..

So basically the 1.5 ton A/C at my house that was installed by a couple of bandits some 5 or so years ago has never really worked properly. Can't pull 980 sq ft. house down below 75'f

-Outdoor ambient = 88'f
-Indoor fan set at high speed
-Evap clean
-No air filter in duct during measurements [no clean one around heh]
-Condenser cleaned
-Compressor head cleaned
-no filter dryers or kinks in line's [altho condenser outlet is 3/8's and line used is 5/16's]
-TD at Evap is 7'f
http://i6.photobucket.com/albums/y223/skr0oface/DSC00310.jpg


I slap on guages, notice Super Heat about 22 degree's, compared to 3 degree's SubCool.
http://i6.photobucket.com/albums/y223/skr0oface/DSC00299.jpg

A light bulb appears above my head and I do this trick to the 30 feet of lineset. [put them together]
http://i6.photobucket.com/albums/y223/skr0oface/DSC00292.jpg

Still, even after that my SubCool has not inclined, meanwhile my Super Heat has inclined about 10 degree's.
http://i6.photobucket.com/albums/y223/skr0oface/DSC00301.jpg


Stumped at this point, after playing with Refer levels and only noticing my Vapour line increase or decrease to below saturation point. Liquid Line Temp/pressure staying consistent with 3 to 6'f SubCool.
http://i6.photobucket.com/albums/y223/skr0oface/DSC00307.jpg

I take a step back and am pointing my finger directly at the piston, roaring in agony. Problem is this Evap has no rating plate. I notice on compression fitting a stamped "Series 3863-PA".
http://i6.photobucket.com/albums/y223/skr0oface/DSC00291.jpg

No idea how to go about finding out if it's the correct piston or even the right make. Normally it says somewhere on the Evap. I googled with no luck. Anybody familiar with Payne? =/
http://i6.photobucket.com/albums/y223/skr0oface/DSC00306.jpg

Also lookit this goodie I captured last week on install.
http://i6.photobucket.com/albums/y223/skr0oface/DSC00296.jpg

Thanks in advance.

[bmac]

High superheat and low subcooling means undercharged.

[bama 101]

it's undercharged, but you should charge the fixed bore orfice by superheat

[vlux]

what did you take those pics with, dam thats clear thanks

[skr0oface]

Bmac:

K see it's been a long day and just now, i went outside to charge it via superheat. But I noticed for the 2nd time even tho i'm adding more refer my SubCool changes little, if at all. Same with pressure temp. Roughly 5' Subcool at condenser [that sucks] and i have 15' Superheat.
I came back and noticed my TD directly under and directly over Evap is now only 3 to 4'f.
That's why I am thinking Orfice plugged or not correctly sized.

Vlux:

Sony Cybershot DSC-P73. DON NOT PURCHASE.
Thing is junk, All but a couple functions work properly. I learned my lesson the hardway not to buy Sony Camera's. But it still does the job apparently.

[Shophound]

http://i6.photobucket.com/albums/y223/skr0oface/DSC00292.jpg

Am I seeing this right? You bound the liquid and suction lines together underneath the same armaflex the entire length of the lineset? And you're wondering why after you did that your superheat jumped ten degrees from previous?

By doing this, on one hand you are sending cooler refer to the piston. On the other you're sending more heat to the compressor and possibly (make that probably) affecting compressor superheat. You're taking the heat that should have been rejected in the bottom subcooling loops of the condenser coils (with a properly charged system) and sending it back over the compressor windings and out the compressor discharge, raising heat of compression in the process.

Your piston size is contained in the info shown in your own picture:


http://i6.photobucket.com/albums/y223/skr0oface/DSC00306.jpg

Fourth line down, "Piston" "ID" (meaning inside diameter) .49. Condensing unit looks to be about 18,000 BTU, or a ton and a half.

I would de-couple the liquid and suction lines ASAP. You'll never get the charge right otherwise, especially with a piston on the system. If you're concerned about flash gas in a liquid line running through a very hot attic, insulate the liquid line separately from the suction where it runs through the attic.

On piston systems, if you read no superheat at the compressor, you're seeing liquid return to the compressor. You're overcharged. It's VERY easy to overcharge piston systems, because you don't need much refer AT ALL to do so! Just a few ounces can make a HUGE difference either way! Once you learn this and learn to get piston systems very close to optimum charge, they perform much better than one would expect. Not as good as a TXV equipped system, but impressive nevertheless.

[Shophound]

Originally posted by skr0oface
Bmac:

K see it's been a long day and just now, i went outside to charge it via superheat. But I noticed for the 2nd time even tho i'm adding more refer my SubCool changes little, if at all. Same with pressure temp. Roughly 5' Subcool at condenser [that sucks] and i have 15' Superheat.
I came back and noticed my TD directly under and directly over Evap is now only 3 to 4'f.
That's why I am thinking Orfice plugged or not correctly sized.



Just saw this after I posted. If you're still running that lineset coupled together as I suspect, the only reason you have any superheat AT ALL is because it's picking heat up from the liquid line. You have in effect erased your ability to see whether the evap is flooded or starved or right on. You need to de-couple that line.

A three to four delta T at the evap, with five degrees subcooling, with 15 superheat with a coupled lineset... I'd bet the farm you're seriously overcharged and the compressor is wondering WTF is going on. :D

Pull apart the lineset, start system and see if you then have ZERO superheat at condenser. If you do, you'll need to recover gas until at a bare minimum you get a slight rise in suction line temp. After that it's best to go by manufacturer's specs for charging via superheat.

[bama 101]

Is the unit mismatched


the orfice size should be a 49, if you do a pump down and check orfice it is stamped on the side



what size blower motor and blower wheel?


Have you check airflow, how many vents do you have how large is the return and what size duct is used any info like this could be helpful.

[skr0oface]

Thanks shophound.
Good info there, See I was actually taught to couple the lines together in school. I don't know if I explained this but I was having that same problem before I coupled them together. What I was trying to do was aquire more subcool without touching refrigerant. Makes sense on paper right? At same time improving superheat.

You're right tho It's obviously not helping as planned.

And Yea the piston size required for that condenser is a id of 49. I was trying to figure out if I had that in the evap.
Sorry. I don't know if that coil is matched with unit because I can't find rating plate or sticker on evap.

I will undo Line's tomorow and start from scratch. This was an experiment mostly, because Prior to this I had dangled refer levels, with no results. Adding and subtracting, but not sensitvely. Good points, again.

I should just pick up a 49 at the wholesaler shouldn't be an issue. Or maybe splurge on a TXV.

[skr0oface]

Return drop is 10x25, Adequate.
3 Large [14x14] return's.
3 14x5 supplies. and 2 5" diametre runs.
Ductwork is original from old oil burner. Pretty large.

[icyflame]

Dosn't sound like an equipment problem, rather an air flow problem. What kind of duct system are you dealing with? Metal or Ductboard or ?. Is it sized right? If its ductboard, is the outside measurements an inch larger in both directions to compensate for its thickness? If flex pipe, is it pulled tight, no longer than fourteen feet? Does your trunk line reduce down as lines come off it? Is the R/A drop large enough to handle full air compacity?
What kind of heat system? any electric heat elements that coud be coming on during cooling?
1 1/2 ton has little room for error. Is it undersized for the application? Square Footage is just a referance point, Have you done a load calc?
I hope you find your problem!!

[bobr42]

I agree have you done Cfm calculations?The formula for that is (natural gas) BTU OUTPUT (in the heating mode) OVER TEMP RISE X 1.08 divide that in to to yor BTU output we want 400 cfms per ton.That needs to be your first start before subcooling and superheat its a great start.

[lalo56]

You are not taking the proper superheat readings. You need the boiling point (saturation point) of the refrigerant in the evaporator (at that pressure), and the suction line temperature.

[skr0oface]

kk I get it I f**kt up. heh
No ductboard. Natural gas furnace...
Thanks for everyone's input. Thank's for the Calculation bobr42
Sry Shophound didn't see you posted again. I will try again tomorow after work and see what I can come up with. I'm glad I tried this stupid trick at home rather then at a customer's house.
Was taught it not as practice but in special occasions this could help a system. But as you explained, is only hampering the system in more ways then one.

So tomorow I will uncouple line's. Do a Cfm calculation. and recharge from scratch.
I tried Jim wheeler's charging chart for fixed orfice's in the feild but could never get it to match up.
And Manufacture's superheat charging specs, well I will do my best to locate Payne's.

To be continued..
=D

[Shophound]

I reread this thread and realized I was also a bit zoned out after a hot day.

I still say de-couple the lineset, but after that I wouldn't necessarily say you're overcharged, unless after you take apart the lineset and start the system up, you get zero superheat.

I would review how you're obtaining superheat and subcooling readings. Are you attaching your temp probe at least a minimum 6" from compressor on suction line at condensing unit? Then subtracting suction line temp from saturated vapor temp shown on gauge or PT chart? Similar for subcooling...probe attached securely to liquid line and same math, except saturated condensing temp?

It's possible your ductwork flows pretty well and the indoor blower speed is set a bit high. A static pressure reading is a good way to determine this, and if you can manage to find the manufacturer's fan curve chart for the furnace, so much the better. Sometimes you get lucky and the OEM stamps the ESP on the indoor unit's info sticker.

It's difficult to nail down your problem over the internet...sometimes you just gotta be there, gather lots of data, make a few adjustments, and babysit.

But there's a lesson here: you heard about coupling a lineset together that supposedly solves problems, but apparently nobody really ever explained to you the principles involved in why such a thing is ever done. That's a reoccuring problem in this trade; somebody who's been around awhile says, "Oh try this, it'll work" but can't offer one shred of sound logic behind why it should. They just heard it from somebody else.

Coupled linesets can be found on medium and low temp applications (refrigeration) and typically it involves coupling a capillary tube to the suction line, not coupling the liquid line to the suction line. In refrigeration, coupling the cap tube to the suction line increases system capacity and reduces/eliminates sweating of the suction line. Note that the cap tube itself is the one coupled to the suction, NOT the liquid line. AND this is only done in medium and low temp applications. I've never seen a high temp/HVAC application with a cap tube coupled to the suction line. Coupling the liquid line to suction results in a refrigerated liquid line (particularly if system is overcharged to compensate for some funky superheat/subcooling readings) and possibly a starved evaporator, as head pressure entering the piston is reduced abnormally by the exchange of heat with the suction line.