Carrier RTU second stage freezing up

[qwerty hvac]

Model # 48HJE014x-5006238
Serial # 4309G40674

Get a no cooling call at 4:30 yesterday, find second stage compressor and evap coil frozen solid. I figure low on charge,late in day. So I pull up the recovery machine and all my crap to see what is left in the system and recharge for the weekend. Well I pull out the charge and get 9.2 lbs and stop. Factory change is 9.4 I believe. I let it thaw, dump the charge back in and let it fire up. While I was doing all of this by the way I had first stage running and it cooled off the space. So it runs for about ten minutes then starts freezing. I am thinking a restriction in this stage somewhere. I have numbers out in the truck. Figured I would post this to get some thoughts.

[socotech]

Liquid line drier restriction.

[Six]

That RTU has the manifold with the crimped in metering devices right ? Could be the liquid drier too.

Ive replaced that manifold metering assembly a couple of times because one or two of the met. devices were plugged.

Pull the drier and check it.

[qwerty hvac]

That RTU has the manifold with the crimped in metering devices right ? Could be the liquid drier too.

Ive replaced that manifold metering assembly a couple of times because one or two of the met. devices were plugged.

Pull the drier and check it.

That is what I was leaning towards. I did not take a temp drop across it. One of those days where I just wanted to get home.

[qwerty hvac]

How big of a job is it to pull that manifold? I have not had to do one yet.

[qwerty hvac]

Here are some numbers:

SH 8.5
SC 28.6
High side 199.6
Low Side 48.3
Ambient temp 72.7
Condenser discharge 92.7
Supply temp 41.5
Return temp 67.1
compressor discharge temp 71.8
suction temp 33.1

[hvacrmedic]

Here are some numbers:

SH 8.5
SC 28.6
High side 199.6
Low Side 48.3
Ambient temp 72.7
Condenser discharge 92.7
Supply temp 41.5
Return temp 67.1
compressor discharge temp 71.8
suction temp 33.1

I'm guessing compressor discharge was 92.7 and LL temp was 71.8?

Your numbers are telling me floodback and low indoor airflow. 0° SH instead of 8.5°. There can be considerable measurement error on a package unit if you don't insulate your sensors to the line.

Are you sure it was completely thawed out?

[git-r-dun]

Here are some numbers:

SH 8.5
SC 28.6
High side 199.6
Low Side 48.3
Ambient temp 72.7
Condenser discharge 92.7
Supply temp 41.5
Return temp 67.1
compressor discharge temp 71.8
suction temp 33.1

There's a couple things that don't make sense. A restriction in the drier or feeder tubes would not be able to freeze the entire coil or give you an 8.5 degree SH. Not to mention a 26 degree split. Also your compressor (or condenser) discharge temperature in no way can be lower than your ambient temperature. May want to double check your equipment.

[Six]

How big of a job is it to pull that manifold? I have not had to do one yet.

They're pretty easy actually.

You have to cut the old one out and I then remove the stubs with a torch. It doesnt take a lot of heat and then slide in the new manifold and replace the old drier.

I use 15% and light heat.

Easy peasy japaneasy
.

[qwerty hvac]

They're pretty easy actually.

You have to cut the old one out and I then remove the stubs with a torch. It doesnt take a lot of heat and then slide in the new manifold and replace the old drier.

I use 15% and light heat.

Easy peasy japaneasy
.

Ok sounds not to bad. Will have to pop the top for that..

[qwerty hvac]

Attachment 262601Attachment 262611Attachment 262621
Some pics.


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[Six]

Half a day job.

[qwerty hvac]

Nope.

Flip out the condenser fan and get inside on a set of kneepads. Done a couple that way.

I'm 6'5" 300lbs. I don't think I will be crawling in there. Lol


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[Six]

I'm 6'5" 300lbs. I don't think I will be crawling in there. Lol


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Im 6' 6" 250.

Ive done three. Im in my early 40s though.

Ive seen people jerry rig txvs into tgose units.

Its easier to get the manifold in.

[timebuilder]

I'm 6'5" 300lbs. I don't think I will be crawling in there. Lol


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It's like a submarine hatch.

[Six]

nice set of guages

[qwerty hvac]

nice set of guages

Thank. 550 testo. I had the analogs out to recover but did not get a pick. Hopefully it is just the drier and I won't have to crawl in.


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[qwerty hvac]

It's like a submarine hatch.

This is true. I will check it out and see of I can get in there.


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[qwerty hvac]

It had thawed because I disconnected second stage and let first cool the space. I was also think low airflow but first stage was working fine. I want to check above the ceiling on Monday and look at the ductwork. I know it has a hard return with flex to four 16" round 2 x 2 grills. Maybe the return is insulated on the inside? I want to see.


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[hvacrmedic]

It had thawed because I disconnected second stage and let first cool the space. I was also think low airflow but first stage was working fine. I want to check above the ceiling on Monday and look at the ductwork. I know it has a hard return with flex to four 16" round 2 x 2 grills. Maybe the return is insulated on the inside? I want to see.


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First stage would have more air forced through it if the second stage portion of the coil was iced over. Now that the coil has thawed the first stage SST is probably running low too.