Trane VS Fan AC startup noise

[teddyc27]

I have a Trane XV95 with 2 ton AC. In cooling mode (Not sure about heat, I can’t remember) the system starts up like this:

1. Thermostat relay clicks

2. Compressor turns on

3. Fan ramps up for a few seconds (Might not be every time)

4. Fan ramps down for Comfort-R 50%

5. AC runs as normal


Is number 3 normal for a VS blower? Its not overly loud but I do notice it. I have just assumed it’s the blower adjusting to the static pressure. Is this correct? Thanks

Teddy

[Advanced Response]

I have noticed this more on a trane variable speed than some other manuf.

I call it the herk and jerk.. It only happens for a couple of seconds but the motor is testing itself for proper direction..

From my experience normal..

J

[superd77]

#3 is normal #4 is not.

the unit should ramp to 75-80% after a minute then to full speed if needed

[JBM1000]

There are several configurations of using comfort "R" via the type T/Stat selection being factory Trane or using H/Well type or W/Rogers and to include Internet communicating types etc, Of all of the Trane Stats obviously control comfort "R" as the Dip switch settings prevail along with installer configurations as selected. Then there are stepping away from factory tonnage CFM selections that are static effected but also by design.

Adding De-Humidification, Humidification, Outdoor Sensors correlate to cutting board jumpers that effect ramp % and final RPM to maintain a factory "estimated algorithmic" best choice based on the past 24 hr time factor after first power up.

Even Carrier uses "estimated algorithmic" programing based on a 45 second look-see before showing a displayed "Static" reading with there Infinity units.

I wish any top rated brand would simply just put factory static probes installed and quit using bench tested best guess algorithms!

"Now my minds about to explode" and I need to just work on a fixed speed package unit made 20 yrs ago!
I miss the simple good ol days!


Put all of that in your pipe and smoke it!
If your not a Trained Factory Tech then do yourself a favor and get one.

Attachment 47472

[teddyc27]

Thanks guys.

Advanced Response:
On the Trane's does it not always do it on every cycle or maybe not always sound the same? I guess its possible it just varies in loudness so it is not always noticeable.

Its funny, when I first had the furnace installed a year ago, I noticed it. I figured maybe the variable speed fan ramped up first then would ramp down. I remember thinking that kind of defeated the purpose of variable speed if it had to do that every time.

Thanks

Teddy

[jerryd_2008]

I have noticed this more on a trane variable speed than some other manuf.

I call it the herk and jerk.. It only happens for a couple of seconds but the motor is testing itself for proper direction..

From my experience normal..

J

I had similar question about why my York HP ECM VS fan seems to jiggle and exhibit indecision for 10 seconds or so on occasion. Advice here ranged from normal to bad. The contractor finally asked York engineering and they said it is normal. Sounds wrong to me but I will await the "smoke" test where the presence/absence of a hard fault determines the correctness.

[teddyc27]

I have been listening a few times and I noticed it is not doing the ramp up for a second then ramp down to 50% when the cooling cycle starts. Its just seems to be starting out at 50%. At 8.5 minutes the fan goes from 80% to 100%. I am wondering if the cooling cycle ends while the fan is ramping from 80% to 100% (or sometime near when this happens) next time the AC cooling cycle starts, it starts ramping to 100% for a second, then drops down to 50% like it is supposed to be. Almost like the fan controller is confused. Has anyone ever seen this with a Trane? It is possible it is very infrequent. Thanks

Teddy