Carrier Infinity - poor performance high stage

[rogressem]

Just an update on this, or lack of update. (Carrier Infinity supply air temp goes up from low to high stage, suction pressure goes up - good performance at low stage) Original thread:
http://hvac-talk.com/vbb/showthread.php?t=1113821

My original installer (from 2007) is waiting on a response from the local Carrier technical representative. In the meantime, I've been taking careful return/supply air temps at the air handler (return duct at air handler and a few feet downstream of evaporator). I've taken them almost every day, early morning and middle of these hot afternoons and the numbers are pretty consistent. BTU performance from low to high stage is essentially constant. This morning:

LOW STAGE:
Return Dry Bulb: 71.8
Return Wet Bulb: 58.7
Supply Dry Bulb: 48.7
Supply Wet Bulb:47.4
Following 3 readings from Infinity Controller
CFM: 882
Blower RPM: 599
Static Pressure: .24


HIGH STAGE:
Return Dry Bulb: 71.5
Return Web Bulb: 59
Supply Dry Bulb: 55.4
Supply Wet Bulb: 52.7
Following 3 readings from Infinity Controller
CFM: 1400
Blower RPM: 960
Static Pressure: .61

[hvacrmedic]

The compressor isn't switching to second stage. Have your contractor correct the fault.

[rogressem]

Yea - long thread on that topic, and I guess that is what has prevented them from being able to quickly fix this. (and going to local Carrier for help). They've already noted that compressor amp draw goes from 5A to 10A (rough numbers) and head pressure goes up a few (<5) psig, suction pressure goes up about 10pisg. High stage contactor engages. So it seems to be switching, but just not performing as designed.

I may have to ping on them again - haven't heard anything since Tuesday, but I'm sure they've been swamped with more critical repairs during this heat wave. At least it "sort of" works. Wish I could figure out how to make it stay in low stage, because I'm wasting money letting it run high stage.

The compressor isn't switching to second stage. Have your contractor correct the fault.

[tinknocker service tech]

have they tried to slow the blower down to 1200 cfms and lower the sat temp in high stage

sounds like an air flo problem more then a compressor problem IMO

[rogressem]

have they tried to slow the blower down to 1200 cfms and lower the sat temp in high stage

sounds like an air flo problem more then a compressor problem IMO

I think on the Infinity systems with Infinity controller, that 1400 is by design, and is not adjustable other than 350cfm/ton when set to efficiency, 400cfm/ton when set to maximum. (this is a 4 ton system).

[motoguy128]

I know on the newest version of Infinity controller there is a setting to force the unit to run only in low stage. You could then also set it to run at 400CFM (Maximum) with no dehumidification for a little more capacity for now.

[motoguy128]

have they tried to slow the blower down to 1200 cfms and lower the sat temp in high stage

sounds like an air flo problem more then a compressor problem IMO

Do you mean airflow at the condenser?

Airflow at he evaporator looks just fine. The blower isn't anywhere near maximum RPM. Static is probably <0.8".

THe lowest you could force the indoor blower is 1300CFM unless you remove the infinity controller and use a regular thermostat and dip switches. However, if it's a ANA1, I think it will only run with an Infinity controller.

[motoguy128]

I think on the Infinity systems with Infinity controller, that 1400 is by design, and is not adjustable other than 350cfm/ton when set to efficiency, 400cfm/ton when set to maximum. (this is a 4 ton system).

That CFM setting, on my system at least, can vary as well depending on outdoor temperature and humidity level. Mine runs an even lower CFM/ton on high stage over about 85F it seems.

[hvacrmedic]

I think on the Infinity systems with Infinity controller, that 1400 is by design, and is not adjustable other than 350cfm/ton when set to efficiency, 400cfm/ton when set to maximum. (this is a 4 ton system).

Efficiency is 400 cfm per ton. Maximum is 450 cfm per ton. Comfort s 350 cfm per ton. That's irrelevant since there's very little change in total capacity between those air flow settings. Your system is producing 2 tons in both first and second stage. If the high speed contactor is energized, then the compressor is broken, period. Another thread won't fix it.

The Bristol 2 speed runs one piston in low stage and two pistons in high. In high stage the compressor rotation reverses and picks up the second piston, doubling its pumping capacity. When the mechanism is broken you get low stage capacity in both modes.

[rogressem]

Interesting thought there - I knew that about the Bristol/reverse direction compressor, but never thought about the mechanism that picks up the 2nd cylinder - being broken. I wonder if the amp draw would still double?

At any rate, I will let them figure it out and I'll post the outcome here. Its been one of those where I've had a hard time convincing them something is wrong. (and no one took wet bulb temps until I did it and started doing comparisons between stages)

p.s., my Infinity controller documentation reads:
EFFICIENCY -- fixed airflow used to achieve specified ratings --
no dehumidification airflow reduction. This is nominally 350
CFM/ton, but will vary if a 2--stage outdoor unit is used.
MAXIMUM -- 400 CFM/ton. No dehumidification airflow
reduction

But as you said, thats irrelevant for this issue.

Will let everyone know what the outcome is.

Efficiency is 400 cfm per ton. Maximum is 450 cfm per ton. Comfort s 350 cfm per ton. That's irrelevant since there's very little change in total capacity between those air flow settings. Your system is producing 2 tons in both first and second stage. If the high speed contactor is energized, then the compressor is broken, period. Another thread won't fix it.

The Bristol 2 speed runs one piston in low stage and two pistons in high. In high stage the compressor rotation reverses and picks up the second piston, doubling its pumping capacity. When the mechanism is broken you get low stage capacity in both modes.

[hvacrmedic]

Interesting thought there - I knew that about the Bristol/reverse direction compressor, but never thought about the mechanism that picks up the 2nd cylinder - being broken. I wonder if the amp draw would still double?

At any rate, I will let them figure it out and I'll post the outcome here. Its been one of those where I've had a hard time convincing them something is wrong. (and no one took wet bulb temps until I did it and started doing comparisons between stages)

p.s., my Infinity controller documentation reads:
EFFICIENCY -- fixed airflow used to achieve specified ratings --
no dehumidification airflow reduction. This is nominally 350
CFM/ton, but will vary if a 2--stage outdoor unit is used.o
MAXIMUM -- 400 CFM/ton. No dehumidification airflow
reduction

But as you said, thats irrelevant for this issue.

Will let everyone know what the outcome is.

Yes, I forgot for a moment that the cfm settings depend upon the indoor model. It's been a very long week, heck, make that a very long couple of months.

Hope you get it worked out. I've only seen this fault twice, but I can just about guarantee that this is what has happened to yours, assuming that all of your data is accurate.

[tinknocker service tech]

Do you mean airflow at the condenser?

Airflow at he evaporator looks just fine. The blower isn't anywhere near maximum RPM. Static is probably <0.8".

THe lowest you could force the indoor blower is 1300CFM unless you remove the infinity controller and use a regular thermostat and dip switches. However, if it's a ANA1, I think it will only run with an Infinity controller.

didnt see the size of the unit so spoke to soon on cfm
i do tend to feel there is an airflo issue

[beshvac]

Interesting thought there - I knew that about the Bristol/reverse direction compressor, but never thought about the mechanism that picks up the 2nd cylinder - being broken. I wonder if the amp draw would still double?

At any rate, I will let them figure it out and I'll post the outcome here. Its been one of those where I've had a hard time convincing them something is wrong. (and no one took wet bulb temps until I did it and started doing comparisons between stages)

.

The bristol I found like that had the same amps in either stage.