Trane HP M/N 2twr1024a1000tb

[mpowell_sr_]

There have been a number of parts changed on this unit, including an indoor TXV and indoor coil, due to what i believe have been poor diagnoses by other techs. now it is my baby. I found it today running an exceptionally high subcool (30 d +) and a very low superheat (about 0) I am in Florida, the temp was in the upper 70's

I recovered enough r-22 to get the cooling operational parameters in line and checked the heat. (heat pump) Moderately high L.L. S.C., very low S.L pressures but high S.L. S.H.( 35 PSI, but 65 d). There is a short tube between the OD TXV and the OD distributor, it was at 62 D, but the distributor itself and the distribution lines were frosted. The distributor body was at 22 d.

I suspect an obstruction in the line between the OD TXV and the OD distributor. Can anyone help me out with a parts breakdown on this unit... I can get one on Monday but would like to solve this problem before that. Is there a strainer in that area, or any ideas what else could be causing a restriction? Again, I am flashing gass, but not AT the TXV, but 2" BELOW the TXV, resulting in an insufficient heat complaint and a moderately high LL SC in the heat cycle. The possibility of still having a slight overcharge has not been ruled out, but I can cross that bridge when I come to it...

[dkpd1581]

http://www.trane.com/Commercial/LiteratureSearchList.aspx

This is the link to the Tran intra-net system and you should be able to pull something up about your unit

[dkpd1581]

Let me ask the painfully stupid question - so bear with me.  Asking for heat mode with a 70F+ outdoor temp.  That is well above the design temps for heat. 

Now that you are doing it and seeing the frost before the TXV body is the proof of your restriction.  What we need to know is if there is a sticking check valve or strainer in there. 

The quickest method is to cut that section out and repipe it.  Probably not the answer the customer wants to hear for the labor costs involved.

What are the symptoms in the cooling mode - if any.

It could be anything from a poor weld having the Silphos dripping inside the TXV inlet, double installed driers, uni directional driers when bi-flow are needed, strainer clogged, check valve stuck.

Sounds like the previous guys noticed the restriction only by the low pressures and frosting and kept forcing the R-22 in in hopes of getting the pressures up.  In heat mode (requiring less R-22 that the cooling) its way over charged.

Let us know.

[mpowell_sr_]

I agree that those before me overcharged the unit. I also agree that 70+ is above design specs for heat... but that's what I got when I was dispatched on the call.

I recovered charge from the system in the cooling mode until I had about 10 LLSH. Suction pressures and sl temps looked good, temp split was about 20.

when i went into heat, llsh was about 20. the frost line was NOT before the txv, it was at the distributor, more than 2" downstream of the txv. the 2' of tube BETWEEN the txv (where the metering should have been happening) and the distributor (where the metering obviously was happing) was 62 d. the distributor body was below 28.

cost is not an issue for the customer... this is full warrantee, cost is only an issue for Trane and/or the owner of the company. the issue is getting this puppy fixed quickly, reliably, and once and for all. those before me have already changed the indoor txv, the indoor coil, and the liquid line (justifiably, at least the ll, it is a very saline environment and it was leaking "like a sponge". )

if I need to, i will replace the OD txv, the distributor, and the check valve. I hate to do that if it is only a strainer. what I will not do is cut the system open to see if there is a strainer there if I don't have the parts I need to fix it. it is working, (albeit marginally) at this time, and I try to adhere to the hippocratic oath... first, do no harm.

so

is there, in fact, a strainer between the OD TXV and the OD distributor? or any guess why else I might be metering refrigerant not AT the TXV, but 2" downstream?

[mpowell_sr_]

I recovered charge from the system in the cooling mode until I had about 10 LLSH.

Of course i meant LLSC