Here are the numbers...Good or Bad?

StahlMaster · 07-30-2011, 10:20 AM

I live in Downriver MI. As some of you know, I'm looking to present my daughter with some basic HVAC tools when she completes school. I had a friend of mine who has an SMAN3 gauge. I asked (begged) him to come over and check my 20+ year old system. It's an Energy Knight (2 ton) with a Uni-pac air handler. 1,400 sq. ft. house. Before he came over I replaced the air filter, cleaned the evap. and cond. coils with Frost King coil cleaner.
The system was, and still is, cooling fine. After he checked the system over and noted tempature readings both "Wet bulb" (idle and running) and "Dry bulb" he hooked up the SMAN3 to the unit. With the system idle (not running) the low side pressure was 126.6 PSI and the hight side was 127..0 PSI Indoor tempature was 77 at the thermostat and 72 outdoor with a digital.
After running the system for 30 minutes, these were the readings:
Low side pressure 62.8
Low side pipe temp 62.7
High side pressure 227.7
High side temp 76.0
IDWB 65.9 (between the filter and evap.)
ODDB 75 (at the cond.)
Tempature at inside discharge 52.2
When I asked him what all these numbers mean, he playfuly said "go to school" I assume he didn't find anything out of wack with the system.
What do these numbers indicate to you guys? Do I need to provide any additional information. I was writing a lot of stuff down.

D

JJboy · 07-30-2011, 12:30 PM

Quote:

Originally Posted by StahlMaster

I live in Downriver MI. As some of you know, I'm looking to present my daughter with some basic HVAC tools when she completes school. I had a friend of mine who has an SMAN3 gauge. I asked (begged) him to come over and check my 20+ year old system. It's an Energy Knight (2 ton) with a Uni-pac air handler. 1,400 sq. ft. house. Before he came over I replaced the air filter, cleaned the evap. and cond. coils with Frost King coil cleaner.
The system was, and still is, cooling fine. After he checked the system over and noted tempature readings both "Wet bulb" (idle and running) and "Dry bulb" he hooked up the SMAN3 to the unit. With the system idle (not running) the low side pressure was 126.6 PSI and the hight side was 127..0 PSI Indoor tempature was 77 at the thermostat and 72 outdoor with a digital.
After running the system for 30 minutes, these were the readings:
Low side pressure 62.8
Low side pipe temp 62.7
High side pressure 227.7
High side temp 76.0
IDWB 65.9 (between the filter and evap.)
ODDB 75 (at the cond.)
Tempature at inside discharge 52.2
When I asked him what all these numbers mean, he playfuly said "go to school" I assume he didn't find anything out of wack with the system.
What do these numbers indicate to you guys? Do I need to provide any additional information. I was writing a lot of stuff down.

D

Target Superheat: 21
Actual Superheat: 25

Target Subcooling: 21
Actual Subcooling: 34

**beenthere** · 07-30-2011, 02:17 PM

That air handler should have a TXV. And if it does, something isn't quiet right. probably either a slightly restricted LLFD, or the TXV isn't opening all the way.

Again its not off by much, just a bit. SH is high for a 20 year old HV system.

If he had measured the leaving wetbulb and the CFM, I could tell you the capacity it was operating at, during that check.

StahlMaster · 07-30-2011, 09:15 PM

Quote:

Originally Posted by beenthere

That air handler should have a TXV. And if it does, something isn't quiet right. probably either a slightly restricted LLFD, or the TXV isn't opening all the way.

Again its not off by much, just a bit. SH is high for a 20 year old HV system.

If he had measured the leaving wetbulb and the CFM, I could tell you the capacity it was operating at, during that check.

This unit does not have a LLFD installed. Not on the line outside or in the cabinet. I'm guessing the TXV is the issue. Is there a way to get it to open all the way without removing it?

D

**beenthere** · 07-30-2011, 09:47 PM

Not really. Not if its the problem.

JJboy · 07-30-2011, 10:07 PM

You can replace the power head first.

Anti-wingnut · 07-30-2011, 10:20 PM

FYI,

If both the TWXand LLFD check out A-OK, the put a jumper across the SRTV and check the SH/SC PRV to assess the WWDM. The SCWSMMYR or the SSCCVTTVS can sometimes mimic a faulty SSDR, leading of course to SHET

JJboy · 07-30-2011, 10:30 PM

Quote:

Originally Posted by Anti-wingnut

FYI,

If both the TWXand LLFD check out A-OK, the put a jumper across the SRTV and check the SH/SC PRV to assess the WWDM. The SCWSMMYR or the SSCCVTTVS can sometimes mimic a faulty SSDR, leading of course to SHET

I SSXXDY KNDO FFFde DDXF****IID

Anti-wingnut · 07-30-2011, 10:34 PM

Quote:

Originally Posted by JJboy

I SSXXDY KNDO FFFde DDXF****IID

Exactly

StahlMaster · 07-30-2011, 11:28 PM

Quote:

Originally Posted by JJboy

You can replace the power head first.

I'd give it a shot. Where is the valve information located? where can I get a replacement?

HVACDave · 07-31-2011, 12:52 AM

I like the numbers the way they are. If the unit is cooling the house well, I would leave it alone. If anything you may have a slight overcharge in my opinion, but it wouldn't be much. The head pressure is slightly over the typical 30 degrees above ambient corresponding pressure that you would expect,(but it's close) and the subcooling is a little high, that's why I would suggest that. The temp drop is acceptable considering you are at nearly 70% RH at the conditions specified. At that RH a good percentage of your capacity is going into latent heat removal in the form of condensate. I would predict as the house drys out a bit that the temp drop accross the coil will increase as well. My guess is it may not have a TXV at all, but is using a piston of some sort or a cap tube.

**beenthere** · 07-31-2011, 06:20 AM

Quote:

Originally Posted by JJboy

You can replace the power head first.

If he has his EPA cert.

StahlMaster · 07-31-2011, 09:36 AM

Quote:

Originally Posted by beenthere

If he has his EPA cert.

I don't have a EPA certificate but my friend who was here does. Once the weather cools down a bit, I'm sure he'll come over to get this old system working at it's peak efficacy. I need to buy some time before replacing the unit.

D