How do I know if 2nd Stage is Working?

[ChilledBeam]

I recently had a wiring problem fixed with my new system, the pieces are:


4.0 Ton 16 Seer Two Stage Split A/C (R-410A), Model # 4A7A6048B1000A
90% Two Stage Variable Speed Gas Furnace 93mbtuh (21.0), Model # AUY100R9V4W
Hi Eff Cased Evaporator Coil TXV-NB (21.0), Model # RXC054S3HPC
3H/2C Prog (7 Day) Gas-Elec-H/P w/Humidity Control, Model # ACONT803AS32D
Outdoor Temp Sensor, Model # BAYSEN02AT
AccuClean Whole House Air Cleaner (21.5), Model # AFD215ALAH000A


I am suspicious that the 2nd stage of cooling is not working because the house is not being cooled fast enough. I and my contractor did a load calc on the house before the system was installed so I'm pretty sure the unit is the right size.

How can I test this or know if the 2nd stage of cooling is working? The outdoor unit is very quiet and I tried the test through the thermostat and there is no sound difference between 1st and 2nd stage...

Thanks

[Cody_Virginia]

Good question! Take an amp clamp and measure the amp pull of the unit.

Most systems are designed to run one single stage for the first 10-15 minutes, and if the system is still calling for cooling, the second stage kicks in. When this happens, the amp draw will increase.

[Shophound]

Is it just pulldown time you're not happy with, or is the system not keeping your house comfortable overall?

[dan sw fl]

How can I test this or know if the 2nd stage of cooling is working? The outdoor unit is very quiet and I tried the test through the thermostat and there is no sound difference between 1st and 2nd stage...

Turn the t-stat down ...
after the delay .. compare the electric meter RPM

The only recognizable sound difference between 1st & 2nd stage may be ...
___ $ OUCH !

[ChilledBeam]

Yes, the pulldown time is long so that is why I was wondering if the 2nd stage was working. After I got the t-stat rewired properly the blower now comes up to full speed and the air circulation through the house is goood so that left me wondering about the 2nd stage on the AC unit.

I'll grab an amp clamp today and see what it tells me.

[Airmechanical]

I recently had a wiring problem fixed with my new system,i am suspicious that the 2nd stage of cooling is not working because the house is not being cooled fast enough.How can I test this or know if the 2nd stage of cooling is working?

lets assume it is going into hi speed!

lets assume it isnt going into hi speed!

either way you will still need a qualified technician to fix the problem, due to the fact you say its not cooling fast enough!



.

[pstu]

The XL16 in 3-ton size, will run a nominal 900 cfm in 1st stage and 1200 cfm in 2nd stage. With some duct systems and some humans, one might learn to detect the difference in airflow, perhaps by sound. If the 2-stage thermostat is like mine, it is set up to engage 2nd stage when the stat temperature is more than 2 degrees above setpoint -- so by adjusting the t'stat down 5 degrees from normal, you should command 2nd stage to run.

If you really cannot tell by increased sound level, it should be possible to measure temperature vs. time and see better pull-down via Stage 2 cooling. Bit of a chore but it would work.

I recently got a 2-stage AC, one where 1st stage is about 55% of 2nd stage. In other words airflow almost doubles with 2nd stage, and duct noise is one telltale. I have a Dwyer Model 25 manometer mounted to continually monitor static pressure and it is a reliable indicator of airflow as well -- given that different stages or dehumidification modes involve changing airflow. I find it interesting and useful, so has the AC pro when he is testing whether various modes work. For example "Enhanced Mode" for dehumidification got set up backwards by accident with a particular stat and this made it plain as day to identify that.

In my own house, I am amazed to see that 1st stage runs *very* long runtimes but 2nd stage is never called even for a normal summer day. 2nd stage has been tested and demonstrated to work, but the system maintains setpoint surprisingly well without it. This is a 3-ton system that replaced a 3.5-ton one which ran at a duty cycle above 45%, about 25% of the time last August. So I expected the new Stage 2 to be called that proportion of the time. Another method: using Manual J7 (Hvac-Calc) I modeled 23,200 sensible BTUH for the job this system is supposed to do, and the equipment chosen has 15,600 in 1st stage (28,200 in 2nd). What I actually get is super-long Stage 1 runtimes, with Stage 2 apparently standing in reserve for kick-ass pulldown capability.

It would be welcome to some homeowners like myself, if the 2-stage thermostats would show more info such as running 2nd stage, on the screen. Or a little colored lamp to indicate would be nice. But as far as I know the Carrier Infinity controls are the only ones which bring a lot of info to the homeowner. Its reading of ESP would answer the original poster's question.

Hope this helps -- Pstu

[ChilledBeam]

I do have a call into the installer, he is also the one who mis-wired the unit (which I troubleshooted!). So I'll see what they say when they come out.

I also saw a note on the wiring diagam for the condensing unit that if you are not using an outdoor thermostat to wire W2 and W3 together. This is not done on my system. Any idea what that does?

[BaldLoonie]

With the 803, you don't get staging of the backup. You have to use the timer which eliminates some of the benefit of having a 2 stage gas furnace. I sure would have used a Vision Pro IAQ on this setup. You'd get dehumidify on demand capability and staging of the gas furnace among other things.

[allan38]

I do have a call into the installer, he is also the one who mis-wired the unit (which I troubleshooted!). So I'll see what they say when they come out.

I also saw a note on the wiring diagam for the condensing unit that if you are not using an outdoor thermostat to wire W2 and W3 together. This is not done on my system. Any idea what that does?

This would energize all the heat strips upon a call for auxiliary heat. (frequently any time the indoor heating temp is 2 degrees below setpoint.)
W2=Auxiliary heat, W3=the rest of the heat strips or emergency heat.
The outdoor thermostat would only do this if the outdoor temp dropped below the outdoor t-stat setpoint.

Enables faster heating with the added benefit of higher (yes higher) electrical bills. The solution is to tie w2-w3 and not setback the thermostat temp when away. Just leave the temp where you want it and don't mess with it.
No down to 50 when away and up to 65 when home.

[bmathews]

Some of the Trane tstats need to be reset and told what to do in the installers setup. Make sure the guy did that.