On a 5-Ton condenser with a TXV metering device feeding the cooling coil, I wouldn't want to get below 330-CFM per ton of cooling or 1650-CFM.
Originally Posted by rmcfall
You need a Tech that can & will measure the delivered airflow.
When going for minimum airflow, when it comes to liquid-flood-back to the compressor, a piston flow rater orifice metering device is a bit tricky.
Heat pumps have an accumulator which helps catch liquid flood-back.
Old Frazer-Johnson A/C units used to have an accumulator in the condenser.
Thanks for all the replies everyone. Let me ask these, the "Excess Static Pressure Stagedown" messages I am receiving are not FAULTS, but are events listed in the "Last 10 System Events" log within the Infinity service menu. I have never received any fault messages. Does that change anything?
May not be an error. But. Its something to gt corrected. Before it gives you problems.
I have the 5 ton Carrier Infinity zoned system as well. Currently my CFM is 1487 and my Static Pressure is 1.11. What happens if it almost always runs below 330-CFM per ton of cooling or 1650-CFM.
Originally Posted by udarrell
I am having some of the same problems as rmcfall, but I think that mine are somewhat worse. Some in this thread have already helped me with many of my questions, everyone else can take this as a personal invitation.
Here is my complex problem:
From what I just gathered from all these threads is that your unit is doing exactly what it is suppose to do. ie Staging down due to excess static pressure. Your unit is sized for a whole house call with all dampers open. With only 1 zone calling it should be running at a reduced rate. Didn't your tech set your system up for you? If your A/C is not a 2stage this could cause issues for it.
If you think our goverment is screwed up. You haven't lived in another country.
That is low airflow for numerous reasons some are running them that low; however, running that low, for many important reasons, they should have an accumulator & a TXV metering device.
Originally Posted by bad install
If it is a heat pump it will have an accumulator.
Then you want to make sure it has a TXV metering device.
Tempted, thank you. [From what I just gathered from all these threads is that your unit is doing exactly what it is suppose to do. ie Staging down due to excess static pressure. Your unit is sized for a whole house call with all dampers open. With only 1 zone calling it should be running at a reduced rate. Didn't your tech set your system up for you? If your A/C is not a 2stage this could cause issues for it.] [COLOR="Red"]Yes my ex-tech set up my system for me. My A/C is a 2stage. /COLOR]
Kind of a long story of what we have been through with this system, much of which is posted in the referenced thread. We had the TXV (Not sure I have the 3 letters right while not looking at the receipt) valve replaced in July (Last year as well). I told the company that replaced the TXV that a friend of ours had an air conditioner replaced by the same company that installed ours. Our friend suggested that he have the original company come out and look at our system while we were out of town. One of the things that company said was something about our 2nd stage not working and needing to be replaced. We rode it out until July as we quit trusting them much earlier. When the company that replaced the TXV came out, we told them what we were told about the 2nd stage not working and needing to be replaced. He verified that it was not working and then said it was not receiving any power. We checked the breaker and it was tripped. It did not need to be replaced.
udarrell, thank you for your reply. It appears to have a heat pump as going through the service menu, it gives readings for the heat pump. How can I make sure that it has a TXV metering device?
I do have a heat pump. Does the heat pump also cool?
How can I make sure that it has a TXV metering device?
Fan coil/ Air handler Model# FE4ANB006000
Heat Pump Model# 38YDB060321
It will also have a suction line accumulator that will help protect the compressor against liquid slugging...
Originally Posted by bad install
Had the post ready to send & accidently closed the page!
Our system has never worked correctly and the original contractor is not responding to our emails. He claims that our HVAC cools 20 degrees below the outside temperature and that is what it is designed to do. From talking to others in the thread that I started, that is not correct and the way he did the duct work is the main problem. I posted lots of photos of my duct work and some say it's borderline criminal.
I think that this is the manual to my system:
Will it say in that manual if I have a TXV metering device?
I see a thing that says it is Model BF-163S-XF connected to the outside unit. Is that a suction line accumulator or does it protect it in the same way?
Carrier has a design guide for Infinity zoning, cat # zone-01DG, quoted, when airflow limits are set to MAX, the maximum airflow allowed into a zone is 210% of the assessed airflow for that zone. example: If a zone size is determined to be 25% of the entire system, the leakage is 15% and the maximum airflow is 2250=> [(450)(5)] Airflow into this zone is 450 x5x1.5x (.25+.15)= 1350 cfm. Minumum airflow for a 2 ton system in high stage is 275 cfm/ton. The maximum airflow allowed into a zone set to MAX airflow is 1050cfm. The system will not turn on in high stage because this is below the minumum airflow required for high stage. The minumum airflow for low stage is 175 cfm/ton, the system will turn on in low stage and attempt to run full low stage airflow. a typical 2 stage bristol compressor system will run about 220 cfm/ton when set to efficiency low stage airflow which is 1100 cfm for a 5 ton. this is slightly higher then the maximum allowed into the zone, but well above the minumum for reliable operation. if the zone is very restrictive the system will attempt to dump air into other zones per the steps shown in the airflow limits and equipment protectionsection. if all steps are unsucessful, the system will shut down and register EXCESS STATIC PRESSURE event in last 10 system events.
air flow summary
the variable speed blower and the damper control algorithms work in conjunction to automatically maintain safe airflow levels thru the equipment under all conditions. Also, the airflow into any zone is limited to a maximum value. This value is set for each zone by the installer in the zone user interface install/service screens. The default factory setting is HIGH. the higher this setting, the more air can be delivered to each zone. unoccupied zones are used in a controlled manner to recieve excess air when needed. In a system where there are many zones of diffrent sizes and loads, ducts that are small or when there is evidence of zones not meeting setpoints, the installers remedy is to; create unoccupied zones within the system or increase zone airflow limits in problem zones
dont know if that helps much but basically the smallest zone should be able to handle the full cfm output by itself, per design guide
You will not find a TXV on a carrier heat pump, they use a piston metering device in heat mode, the only exception beiing the new VNA Greenspeed which uses a EXV