Suction line frost

[kw10925]

I was working on rheem/ruud 048-10 seer
indoor coil looked clean and spotless.Cleaned outdoor unit.
When doing my checks it would have frost up to the compressor.
I had 55 psi on lowside/175 on highside, wb 61 db 73-74
my superheat was between 6 and 7, ODA between 70 and 72
I do not work on many units , I am certified , went to a class
for a week . I do not know everything like some of you guys
who have bin doing this for yrs. I am a oil tech and the company
is expanding to do other things . can someone help a newbee!!!
I want to do it right and not take 3or more hours to do it

[beenthere]

Did you look at both sides of the indoor coil.
Your SH indicates either a low air flow.

After you verify air flow, recheck your SH, and SC.


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[hvaclover]

Thats low load usually, but that head is slightly higher than it should be, assuming it's been run long enough.

How's the condenser look for cleanliness? Hows the filters?

[hvaclover]

Did you look at both sides of the indoor coil.
Your SH indicates either a low air flow.

After you verify air flow, recheck your SH, and SC.


To go into more technical things, you will need to apply for pro membership. Get your post count up to 15 and then apply.

Been, look at the head it's 175psig...why do you say low air flow?

[udarrell]

When doing my checks it would have frost up to the compressor.

What was the outdoor dew point temperature?

With light sensible & latent load on the evaporator along with possible low airflow & mismatched orifice metering device, it might allow enough liquid refrigerant to travel down the [B]suction line getting its temp below the dew point & frosting it.

Low airflow & mismatched metering device.(?)
An unbalanced heatload on the evaporator circuits.

Apparent very low superheat, indicating it is feeding the E-Coil faster than the heat is boiling off the refrigerant. Could be overcharged for the existing conditions.

Metering device not matched to the condenser, dropping suction pressure near freezing, 55-psig is about 30-F.

Condenser pressure appears too high for the following: Did you leave enough time after washing condenser cold with cold water? Was the coil dry when readings were taken?

Approximate 47% indoor Relative Humidity.
A mess here, too sleepy today to think straight.

[beenthere]

Because low air flow will decrease head.
Yes, it could just be that thing too. But I've gone back to systems where someone said the ID coil was clean. And they did you know what. And after I cleaned the coil. Guess what I had to do.

[hvaclover]

Because low air flow will decrease head.
Yes, it could just be that thing too. But I've gone back to systems where someone said the ID coil was clean. And they did you know what. And after I cleaned the coil. Guess what I had to do.

It's 175, high for those temps.

[udarrell]

Because low air flow will decrease head.
Yes, it could just be that thing too. But I've gone back to systems where someone said the ID coil was clean. And they did you know what. And after I cleaned the coil. Guess what I had to do.

Recover a big refrigerant overcharge, because they had been trying to get the suction pressure up by adding charge, explains head pressure.

[beenthere]

It's 175, high for those temps.

Not for a 10 SEER.

Hate to say it this way. But its only 20°F over outdoor ambient.

Now my 13 SEER at home, that would be high head.

[beenthere]

Recover a big refrigerant overcharge, because they had been trying to get the suction pressure up by adding charge, explains head pressure.

Yep.

I don't mind a tech making a mistake. I just hate having to clean the coil he should have CLEANED.

[hvaclover]

Not for a 10 SEER.

Hate to say it this way. But its only 20°F over outdoor ambient.

Now my 13 SEER at home, that would be high head.

So which one are u calling it an overcharge or normal?

The unit is frosting back is an indicator the system has a low load, 55psig @ 30*indicates that. Although it's not slugging according to to the SH.

Head is too low if we assume you first post about air flow.
20* ove assumes normal operation which this does not have.

You would expect to see a head at this condition of 150 more realistically.

If we had SC we could see more.

The fact the ID and OD are so close also means there is very little heat to be extracted from the air also which would result in a head lower than 175.

[beenthere]

Low air flow gives low SH, he's only running 6 to 7*
His ID WB, indicates his SH should be more around 14 to 15*
With his vapor pressure at 55PSIG, There is a chance on low charge, if he isn'r letting the coil thaw before checking readings.

Low air flow, and someone has probably added some gas to the system in an attemp to stop the freezing of the coil.

[hvaclover]

Low air flow gives low SH, he's only running 6 to 7*
His ID WB, indicates his SH should be more around 14 to 15*
With his vapor pressure at 55PSIG, There is a chance on low charge, if he isn'r letting the coil thaw before checking readings.

Low air flow, and someone has probably added some gas to the system in an attemp to stop the freezing of the coil.

Like I was saying , abnormally hi head. The ratio between 55psig and 175psig is too high.

Course would be nice to know if he cleaned cond or changed filters.

Under side of coil was a good point Been. i don't want to think about how many times that get's overlooked

[docholiday]

The low suction with low superheat along with a low head and probably low subcooling indicate low load. (Poor Airflow). Rather than beat around the bush, measure the actual airflow, not the amount of curtain movement.

[hvaclover]

[QUOTE=docholiday;1901124]The low suction with low superheat along with a low head and probably low subcooling indicate low load. (Poor Airflow). Rather than beat around the bush, measure the actual airflow, not the amount of curtain movement.[/QUOTE
The head is not low. It's 175.

[kw10925]

I am a newbee trying to do it right so forgive me.
The indoorcoil was not frozen only suctionline has lot of frost
at outdoor at the time and onsideof compressor. Could it be
that the day was not a heavy load . to me it seemed it may be
over charged not sure. customer said unit has bin working
noproblems and cooled house. looked at fan speed it was set at
med high could that have bin problem that not enough air movment
over indoor coil.

[beenthere]

Its possible that its a low load problem.

[hvaclover]

I am a newbee trying to do it right so forgive me.
The indoorcoil was not frozen only suctionline has lot of frost
at outdoor at the time and onsideof compressor. Could it be
that the day was not a heavy load . to me it seemed it may be
over charged not sure. customer said unit has bin working
noproblems and cooled house. looked at fan speed it was set at
med high could that have bin problem that not enough air movment
over indoor coil.

If that is a half horsepower motor than it is moving too slow.

If you are icing heavy than the coil is probably froze too. Recheck the underside to be sure.

Turn the furnace on to get a good inside load to get usable readings.

[kw10925]

How do you check indoor coil to see if it is dirty.
I looked at the top looked clean. Filters were clean also.
I did clean OD unit. Its rheem/ruud.

[mrfixit-ms]

The easiest way to explain checking the coil is look between the air filter and the coil. This sometimes gets tricky and I have actually had to pull coils to check. But I think previous posts are about to center in on the problem. A dirty i/d coil will cause low a/f and everything else mentioned.