HP ringing noise at shutoff

[wyounger]

Carrier 38YXA024 (R410a, Copeland scroll), 58CVA070 (VS 80%), and CK3BA030 (R410a dedicated horizontal N-coil in the attic) setup. I know it has a field-installed Sporlan TXV but don't know exactly what kind. The charge has been checked with the superheat/subcool type method once or twice already, though in fairly mild ambients (maybe 75 degrees).

It's working fine, and has all along. I started to notice through the winter, though, that about a minute after the end of a call for heat, the outdoor unit would start to make a VERY high-pitched ringing or whining noise for a minute or two. It's pretty loud, and it does so very consistently at the end of each cycle. BTW, I know what defrosting is and when it is defrosting, and this isn't that. It's only after the compressor itself shuts off after running for awhile.

I wondered if it was just an quirk of heating mode, but now we're well into AC season in Georgia and it's doing it after cooling cycles too. It's fairly annoying, and a bit worrisome, since I don't remember it doing so last summer or fall (the system was installed in August 2004 or so). Is this something to be concerned about, or is it normal?

[jdenyer]

Originally posted by wyounger
Carrier 38YXA024 (R410a, Copeland scroll), 58CVA070 (VS 80%), and CK3BA030 (R410a dedicated horizontal N-coil in the attic) setup. I know it has a field-installed Sporlan TXV but don't know exactly what kind. The charge has been checked with the superheat/subcool type method once or twice already, though in fairly mild ambients (maybe 75 degrees).

It's working fine, and has all along. I started to notice through the winter, though, that about a minute after the end of a call for heat, the outdoor unit would start to make a VERY high-pitched ringing or whining noise for a minute or two. It's pretty loud, and it does so very consistently at the end of each cycle. BTW, I know what defrosting is and when it is defrosting, and this isn't that. It's only after the compressor itself shuts off after running for awhile.

I wondered if it was just an quirk of heating mode, but now we're well into AC season in Georgia and it's doing it after cooling cycles too. It's fairly annoying, and a bit worrisome, since I don't remember it doing so last summer or fall (the system was installed in August 2004 or so). Is this something to be concerned about, or is it normal?

Hmmm, faulty reversing valve? Maybe someone put in a directional filter/drier instead of a bi-directional one made for heat pump applications? Just a couple of thoughts here, I'm not really a heat pump guru so I will let others with more experience post replies to this one.

[ultratec]

This could be a reversing valve, but I dont think so. This machine I believe as almost all heat pumps, fail in the heating mode (no power on the reversing valve coil) Because this noise is present during winter, the valve doesnt operate unless she needs defrost(or cooling). The noise could be the valve still but, again I dont think it is being here and the machine being there. I have had this noise twice, it turned out to be the discharge check valve INSIDE the scroll. This valve isolates the high pressure gas and allows the compressor to start UNLOADED, thats why on 1ph scrolls, no additional starting controls ( start caps) are needed. Scrolls dont need start caps to start, like 1ph non scrolls do. Sounds to me like this check valve is not holding that well. Just my take on this post.

[docholiday]

I too have heard it and suspect the same. A discharge check valve which has no bearing on the operation. It might be easier to install a external check valve in the discharge line and be done with it. At one time, carrier had a solenoid that was connected between the discharge and suction to equalize it but that was probably 10-12 years ago when scrolls were fairly new.

[Andy Schoen]

10 to 1 odds you have pressures equalizing quickly during off cycle (for whatever reasons) and rattling some check valve in the system.

Where's the TEV? Indoor or outdoor coil? Or both? If memory serves me correct, the reversing valve on a Carrier heat pump unit is deenergized in the heating mode. Therefore...

If you have a TEV with internal check on the outdoor coil, and the compressor discharge check valve leaks, you are backflowing across the outdoor TEV sufficiently to rattle rattle rattle... rattle rattle rattle... its check valve for however long equalization occurs.

[pmurf1]

A few of the split purons I've put in do it also. Best I can figure is since the puron is running such a high head pressure compared to 22, it takes longer to equalize in the system and really squeels when it does. I think it comes from the check valve in the outdoor TEV. It's hard to describe if you haven't heard one do it. It's like a high pitch kazoo noise, not a rattle. Kind of like blowing through a kazoo soft (22) versus really hard, (410a). Carrier usually includes a solenoid valve for the liquid line, energizes when the compressor turns on. They did on some, others they don't. I haven't done one in a while to see if they're shipping them with all of them now. They usually include the correct filter drier already packed in the unit too.

The HP's are a pain to charge and to get to run good in heating mode here in AZ. They are extremely sensitive to charge and Carrier finally revised their charging charts to reflect the weather out here. The splits with a gas furnace work real well though. The packages love to blow discharge lines right above the compressor since Carrier didn't feel the need to support them very well. Done 4 of those and Puron is over $10 a pound out here. Kind of hard to tell a customer they need a new charge on a 2 year old unit. The tops on the units also like to rattle after a couple of years since Carrier enginners decided to isolate the bottom of the condensor coil with foam, but set the top right on the coil. Two times around the top of the coil with armatape makes it quiet again. Don't get me started on all the other design flaws with other Carrier units that I get the joy of installing a couple of times a week.

[ncheatman]

(delete)

[Edited by ncheatman on 06-24-2005 at 10:21 AM]

[wyounger]

Andy- the expansion valve is in the attic with the furnace and coil. The noise comes from the outdoor unit, though.

I've started describing the sound as that of teapot at full boil. It's more of a ringing than a whistle, but the note of the sound is very close to the note of a whistling teapot. I forgot one on the stove and went outside for a minute a few days ago, and when I came back in, it was whistling like mad. I'd say it gets about as loud as my forgotten teapot, when it's at its worst.

The tech was just here and visually confirmed that there's no expansion valve in the outdoor unit- he said there was just a piston, right at the liquid line service valve. He's got the service manager calling Mingledorff's to see what they have to say about it. They have seen a few make this noise a little bit, quietly, but never as loudly as this one gets. Of course, it wouldn't do it while he was here. I'm starting to think it actually doesn't make the noise at ambients above 80 or so. I'll try for a morning appointment next time so we can hopefully at least reproduce the noise so the guy can try to find the source in the unit.

Hopefully I'll hear back from the contractor in a day or two.

[Edited by wyounger on 08-02-2005 at 04:35 PM]

[jkirby4]

if you install a LLS (liquid line solinoid) the problem will vanish. i have this problem with carrier heat pumps in heat and we have solved dozens of these problems with this. get the part thru "Totaline"