ReplyWhat is the model number of the indoor unit? What are the diameters of the refrigerant lines and the length? Is the indoor unit above / below the outdoor unit and how far?
Let's start there.
Professional Member
I've been complaining about my 4 ton Carrier Infinity (24ANA748 condenser, Infinity thermostat) for years. Basic complaint - its just doesn't seem as cold as the old Goodman R22 system that it replaced, but I don't have any facts to back that up - I didn't obsess over the old system, it seemed to work fine, until I had to have it replaced.
I've had a couple of different companies come out, but I guess I'm being stubborn.
Had someone come out yesterday on a good hot day, and I asked for a good check and that I wanted to record the numbers.
Outdoor dry bulb: 92.7F
Outdoor humidity: 55%
Evaporator return air temp: 79F
Evaporator supply air temp: 65F
Indoor wet bulb: 64F
Indoor humidity: 53%
Suction Pressure: 158psig
Hi side Pressure: 360psig
Suction Line Temp: 71F
Liquid Line Temp: 94F
Vapor Line Temp at the outlet of the evaporator: 66.5F
1400 CFM (from the infinity Thermostat)
Blower RPM: 1400 (from the Infinity thermostat)
Static Pressure: .77 (from the Infinity thermostat)
Required subcooling for this unit: 15F
Calcuations based on figures above:
Subcooling: 15
Superheat (system): 16F
Superheat(at the evap): 10F
He took evaporator return/supply air temps near the air handler.
So, as usual, he said everything is right on, but I can't understand the following:
1) I guess that evaporator delta T is OK based on what he told me and from what I've read, but my downstairs R22 system sure does better
2) That liquid line temp has always been at or just above outdoor ambient. This is subjective, but it just bugs me that when I reach over and "feel" the suction and liquid lines on my R22 condenser (downstairs unit), the liquid line is very warm and the vapor line is very cold (and sweating much more than the Carrier). Is that just a function of R22 vs R410a.
3) Lastly should they be measuring air flow instead of just looking at the Infinity thermostat? I don't think I've ever seen anyone take a CFM measurement. More than one has said that the Carrier Inifinity adjusts blower RPM to maintain proper CFM.
4) I've been told that these high efficiency units are designed that way (not as cold), but that just doesn't make sense either.
Bottom line, if they are getting good subcooling and superheat values, is that the best I'll get out of this thing?
Professional Member*
What is the model number of the indoor unit? What are the diameters of the refrigerant lines and the length? Is the indoor unit above / below the outdoor unit and how far?
Let's start there.
Climate Control Solutions for your Home or Office
Serving Northeast Philadelphia and Surrounding Areas
Professional Member
(Subject should have been: "Carrier Infinity 4 Ton - will I ever be happy)
Air Handler/Furnace: 58VA110-1-20
Evaporator: CNPVP4821ACA
7/8 Suction Line
3/8 Liquid Line
(these were previously used for the R22 system, installer seemed to do a proper install job in 2008)
Indoor unit about 25-30 feet above. I've estimated the lineset length to be about 60 feet.
I've had concerns about the lineset:
1) Two short radius 90degree elbows
2) Two 45 elbows
3) One mild kink. My main HVAC contractor said it probably wasn't hurting anything, but would fix for about $$$$. (I posted pictures of that kink here a few months ago - I think most said don't worry about it)
Suction line is insulated well, I've check that (at least where I can see it).
Last edited by jpsmith1cm; 06-22-2012 at 11:47 AM. Reason: Pricing
Professional Member*
Couple more questions - During the hottest days what is the temp difference of the liquid line where it leaves the condenser VS where it enters the TXV?
What was the room temp on the User Interface when he took the readings and is the system maintaining setpoint?
Climate Control Solutions for your Home or Office
Serving Northeast Philadelphia and Surrounding Areas
Professional Member*
Your system is not performing anywhere near its capacity. Can you re-post the kink?Originally Posted by rogressem
Running low airflow your delta T should be with 53% rh closer to 18 and you suction line is picking up 6 degrees of SH
Professional Member
Today:
Outdoor ambient: 91.5
Liquid line temp @ condenser: 92-93
Liquid line temp @ evap (just before entering casing): 92
Used my old k-type, which seems to be accurate when compared to the fluke that the tech used because we compared them yesterday.
Room temp yesterday on the User Interface when he took the readings was about 79-80. As far as holding set point, on those hot days, I would say no. Set to 78 and it drifts up to 79/80 and holds all day.
I try to keep the downstairs thermostat set 1 degree below upstairs (very open area - both thermostats are in line of site of each other). It does a good job.
Professional Member*
As second opinion posted the system does not seem to be operating at capacity. If the measurements are accurate, it is not at capacity. Are the LL temps you posted while the system is running? Does not make sense to me that the insulated suction line absorbs 5-6°, but the un-insulated LL does not change at all.
I would be looking for leaking ducts - probably return, and temp increases in the LL. It is a long run not insulated.
Climate Control Solutions for your Home or Office
Serving Northeast Philadelphia and Surrounding Areas
God Speed, Jim. We'll miss you - 2-26-23
1400 CFM on a 4 ton should have a lot higher delta across the indoor oil.
1400RPM? Its running on the governor. Not sure your control is giving accurate info.
Professional Member*
Required subcooling for this unit is 15 degrees f?
Where did you get this number? The charging instructions should be on the condensing unit, so I would double check that 15 degrees sub-cooling. The sub-cooling required may vary depending on various conditions.
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Professional Member
Yea, good catch, I typo'd that. RPM was 1036
Professional Member
I'll double check those line temperatures tomorrow afternoon after the outdoor ambient warms up. Yea, those were running temps (I've questioned that LL temp at the condenser for a long time)
I double checked my notes from what he got yesterday. (but he didn't get the LL temp up at the evap).
I'll get LL and suction line temps at both places and post.
Professional Member
Yea, thats what he told me, and I see it here (attached)
Professional Member
Here are the three pics from the original thread:
1. http://hvac-talk.com/vbb/attachment....1&d=1330740981
2. http://hvac-talk.com/vbb/attachment....1&d=1330740991
3. http://hvac-talk.com/vbb/attachment....1&d=1330741003
The contractor that installed this system (they didn't create the kink), said it was probably not worth fixing, but would do it for about $
Got another quote, he would not fix it (its in the crawl space), but would run a new line set up the side of the house into the attic for about $ or so. That was reasonable, but I wasn't excited about the downspout dressing on the side of the house.
Last edited by beenthere; 06-22-2012 at 09:45 PM. Reason: price
Professional Member*
Are you saying that the controller was reading 1036 cfm?
Professional Member
No, that was blower RPM
CFM always reads 1400CFM, except when running 1st stage (can't remember that off the top of my head)
Professional Member*
In 2nd stage, with the return air conditions you posted, the temperature drop through the system should be right about 20ºF, give or take a couple of degrees, for a system moving 400 cfm/ton.
According to your controller, the system is moving 350 cfm/ton, nominal airflow for a 4 ton system being 1600 cfm.
At that airflow, I'd expect the temperature drop to be more in the range of 20 to 22ºF with the return air conditions given.
Assuming all of the readings are correct, your system is operating way under capacity.
Has it been determined beyond any doubt that the compressor is actually running in 2nd stage?
The suction pressure is significantly higher than I'd expect to find in 2nd stage, it is more in line with what you would get with first stage compressor operation, and 2nd stage airflow.
The head pressure seems a tad low for the outdoor temperature, another indication that the compressor may not be operating in 2nd stage.
Is this one of the units with the Bristol TS compressor, or does it have the Copeland 2 step compressor?
Professional Member*
The Infinity system is capable of giving you a temp drop of approximately 27 degrees when operating in comfort mode. It seems high but I've observed in on multiple occasions. The 1400cfm indicates it is operating in comfort mode. (350cfm per ton).
360psi indicates a 107-108 p/t. With a 96 deg liquid line temp the subcooling = 11-12 deg.
The report stated 15 degrees.
You may be a little low on refrigerant since the data plate specifies 15 degrees.
I'm not trusting his numbers. I've taken measurements at different points at the duct work and had a large variation. Eddies in the airflow near the evaporator coil can create cold spots. I've found checking supply air further downstream will sometimes point out a cold spot and thus an erroneous supply temp.
I'd recheck the return temperature at the furnace and at the return grill. You could be drawing in air from leaking return duct. The relative humidity drop of only 2%? Hmm,
A leak in the supply duct work can dump air outside of the conditioned space. To make up for the air loss the building will draw outside air into the structure. This will increase the load on the system and your ac will not hold setpoint on hotter days.
This could explain a relative humidity drop of only 2 degrees.
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Professional Member*
It's the Bristol. A psychrometric calculation puts his capacity at somewhat less than 2 tons. I agree, it's running in first stage.
Professional Member*
Yeah, I was thinking either a Bristol TS in 1st stage, or a 2 step scroll with a borked unloader.
I'm not a Carrier guy, so don't know by the model numbers what they came with.
The only 2 Infinity systems I've delt with were well after the customer gave up on the installing contractor. In both cases it was just minor stupid installation/setup details that were giving the system fits.
Professional Member*
It is the Bristol TS
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