Could it be going into its defrost mode? Check if the outdoor fan stops when this sound occurs. If it is, it's defrosting and you'll may feel some heat rise up. Completely normal for heat pumps. What it's doing is switching to A/C mode and turning off the fan to bring the pressures up in the system. This will melt some of the frost off the condenser coil.

Thanks for your post Ryan.
This whirl noise is when the condensor fan is running in the heat mode.
Thanks

The outdoor unit's fan would stop during a defrost cycle. Is this a newly-installed unit? You may want to have the installation company out to take a look. I believe you should have at least a 1-year labor warranty, plus the 10 years on all XLi parts. I can't think of any other whirling noise a heat pump would make.

bob

Trane's XL16i has electronic demand defrost and depending on where you live,I question whether the noise you are hearing is defrost related. anyway, the noise is not normal and if it continues, you should call your installer.

IMO

Whats the verdict on the TRANE XL 16i? Are there
real problems with this system...? I am considering
this same model for a 1750 sq ft 3 level townhouse here in Northern Virginia. SPEC is 2 ton XL 16i with 4tee3f31b1
variable speed motor air handler. Have a townhouse
with 12 outlets 3 main returns. 22 years old. Is the BTU
performance better when you step-up to the
XL 16i. Can I get better airflow with a larger 2.5 ton unit?

rwinfowler3624
thanks

Rwinfowler,

The heating performance on the XL16i is actually poor. I would recommend the XL15i as an alternative--better performance to be honest. How was 2 tons determined for sizing? It's best to have a load calculation done to determine sizing. Never a good idea to step up in sizing without one. How did the old (presumably) 2-ton unit do? 2.5-ton units move more air, but it's not going to help if your ductwork can't handle the extra airflow.

2 tons = 24,000 BTU's, nominally

4TWX6024B1000A (XL16i) + 4TEE3F31B1000A
22,800 BTU's cooling
20,000 BTU's heating
12 EER, 16 SEER, 8.35 HSPF

4TWX5024B1000A (XL15i) + 4TEE3F31B1000A
25,200 BTU's cooling
24,000 BTU's heating
13 EER, 15.25 SEER, 8.6 HSPF

OR if you could fit the 4TEE3F39B1000A (which is 58" tall)
25,000 BTU's cooling
24,000 BTU's heating
13 EER, 16 SEER, 9 HSPF

rwinfowler

stay with a properly sized XL15i(or AmStd Heritage 15) with best matching var speed air handler and HW VP IAQ stat.

2 tons sounds small. is townhouse an interior unit? insist on load calc and have ductwork inspected...
IMO

Ryan and tiger thanks for your posts, the current system has a real hard time delivering air to upstairs ducts, the size of the duct is 16" off the main floem and goes to 7 1/2" oulets 3 returns are in the center of the townhouse each 13". The downstairs and upstairs farthest from the air handler are the problem / minimal flow. I have checked for any duct leaks and see no visible. My TH unit is an interior unit. Any advice on keeping hardwood floors with correct humidity levels. I checked with my neighbor who put in 2.5 ton CARRIER 2 years ago. He likes the increased air flow, has the exact TH that I have. I got
22 years out of a Comfortmaker, SEER rating probably below 8.0, so I know the XL15i will save me about 38-40%. is that right?

thanks
rwinfowler3624

2.5 tons may be fine. The BEST way is to have your contractor to a load calculation. 2.5 tons also requires more return air. If humidity is a potential concern, there is a thermostat I recommend: Honeywell's VisionPRO IAQ. It can be configured to control humidity levels by running the A/C with a lower fan speed. You'd need/want the XL15i for this.

I have a question on XL16i. My understanding is that when it goes into the defrost mode, the air handler should stop blowing the air. But my system continues to blow the cold air into the room when the condenser is defrosting. Where should I start to look into the matter. My air handler is a matching 4TEE3F49B Variable Speed.

dawning sky

The XL16i HP condenser has electronic demand defrost which is superior to timed defrost method.

When your Trane goes into defrost cycle, it actually reverses into AC mode and is pulling hot air out of your home to defrost outside condenser. keep in mind that as it does this, it is actually pumping AC air into your home. to compensate for this, your heat strip elements energize to temper the AC air with hot air. you should not feel any cold air at all. if you do, then I would suggest there is a wiring problem that is not allowing your heat strips to come on. you may want to contact installing dealer.

IMO

I don't have a heat strip. I live in a supposedly mild climate (SF Bay Area) so I figure I may be able to live without a heat strip. On the XL16i manual, it says "X2 must be connected to variable speed air handler terminal W3 for proper indoor air flow during the defrost cycle". So I figure maybe the air should stop or something during defrosting. I guess my understanding is wrong.

So I'll have to get a heat strip?

One more thing, according to the same manual, when the XL16i is in the 1st stage, the air flow should be at 80%. But it appeared my air handler always blow at 100%. There's no obvious change in airflow when the 2nd stage kicks in. I also counted the CFM flashing light. It appears the airflow is always at the nominal CFM.

And when the thermostat turns off the system, my understanding is that there should be a 1-2 minutes ramp-down time for the air handler. Not happening on my system. Is there anything wrong with the AH control board?

Airflow doesn't stop with defrost. Heat strip(s) should come on if you have them. Not sure if Trane slows the blower down during defrost or not. Without a heat strip it's gonna be colder air from A/C mode. Airflow should not be the same between stages 1 and 2. If it is, your installers didn't configure the system settings properly.

theds

at what outside temp did this supposed defrost cycle occur?

what are the average lows for SF bay area?

I am surprised that your unit would even have a call for the defrost cycle. at time of purchase, you were asked about a heat strip and elected not to install?

three suggestions.

1.do nothing and just put up with the cool air because your defrost cycle should be rare

2.have the defrost cycle disconnected-not certain I would do this-depends on how much below freezing weather you have

3.install a small heat strip element to temper the cool air

your airflow problem indicates that dip switches at air handler control board were not set up correctly. this is a pet peeve of mine because you see this way too much on var speed Trane air handlers. for a tech knowing how to do this, should take a couple of minutes.

IMO

Heat pumps really should have heat strips. If the heat pump fails, you have no heat. They're not just for auxiliary purposes, also for emergency situations, should you lose heat.

I wouldn't disconnect the defrost cycle as an alternative to getting a heat strip and a properly configured system. Defrost with Trane should only happen when necessary, and when it's necessary, it's just that. It has to maintain proper performance/efficiency.

Agree with above. Possible your dipswitch settings weren't changed from the factory settings.

Thanks for everyone's input.

We don't usually get below freezing. But in the last couple of days, it was really cold. But the condenser went into defrosting even when the air is above freezing temp. I think it was ~35F.

I wasn't presented with an option for heat strip and I thought it would be fine, given the average temp in this area. I figure for emergency I can use a space heater. I guess I'll have to live with the cold air since it's quite rare.

As an electromechanial engineer myself, I have played around with the dip switches, following the manual. It seemed some of the switches have no effect, like the fan delay 5 and 6. There appears to be no delay at all, however I set those two switches. In particular, the "Enhanced" mode doesn't appear to be working at all.

Also, I should be able to set switches 1-4 to a low or normal flow for my tonnage. But it appears I can only set it to the normal and get the correct CFM, according to the CFM LED. If I set it to "low", the blower seems to be running at the highest possible speed (judging by the sound) and the CFM LED stays on all the time (doesn't flash at all).

the average low winter temperature for the Bay area is around 45-50 degrees which suggests that what we thought might be a defrost cycle was actually something else.

I would have your installing dealer back out to set the dip switches correctly so you will have a staged airflow.

I personally would watch for another event like you described and check condition of outside condenser for any frost.

Ryan makes a valid argument on the need for a heat strip element in case of a condenser breakdown during the winter mths. a 5 KW element would provide about 17 KBTUs. you'll have to decide on the options presented to you and weigh the costs/comfort issues vs the benefit.

IMO

Thanks, tigerdunes.

I'm pretty sure it was a defrosting cycle. It was really cold these days. But I will certainly keep an eye out for this to make sure.

Normally how much does it cost for a 5kW element?

call installing dealer. I suspect the service call/install would be more than the element itself. Strike a deal with the installing dealer. They will have to come out anyway to set the dip switches correctly.

IMO
Good Luck!