High SC and SH usually indicates a restriction

 

Did you change out the LLFD.

 

More readings are necessary

Pressure high and low

Line temps: discharge, liquid, suction. At indoor and outdoor

Superheat and subcool

Return wb and db temps

Supply db

Oat db

Blower amps rated vs actual
Compressor amps rated vs actual


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Ya I changed it out. It had the smallest dryer I’d ever seen on a unit. The one I put in replace was a little bigger but not much. No room. I’ll be going back tomorrow couldn’t make it today. I can’t leave a coil unturned cuz I do not want to waste anymore time on this. Shoulda been done already. I’ll post tomorrow

 

I’m going back tomorrow. I’ll post my findings thanks for the reply back

 

326 head at 90 ambient is low. Are you sure you got the charge right?

 

So, 326# with r410a is 102° condensing temp. 42° subcooling puts your liquid line temp at 60°? At 90° ambient help me understand what I am missing here. The only way to get below ambient temp on your liquid line is if you are flashing refrigerant, most likely due to a restriction (or its still wet where you washed it). Check the size of the LL drier to make sure it is large enough. Or what parts came out of the old compressor that are now stuck in the condenser.

 

i agree with double bogey, with that kind of liquid line temp something is restricted.

 

Forgive me for being green but wouldn’t you always check subcool between condenser and liquid filter? And, If there is a restriction in the condenser coil, a temp gun would be the tool to reveal that, right? Or an infrared temp camera if you have that

 

I would use clamp on probes on both sides of the drier to see if there is a temp differential. If not then with that kind of sub cooling I would for a restriction in the condenser.

 

This approach will not serve you well.

With that kind of subcooling, the dryer will not show an appreciable temp difference, and a restriction in the condenser is unlikely as well. Most condenser restrictions happen due to a manufacturing problem like a ball of braze material or trash that was in the copper tubing during the coil forming process.

It would be very unusual for a condenser restriction issue to happen after years of service.

If the charge is correct (weigh it out to see how much is in there, because someone may have tried to fix this problem by adding refrigerant) and the dryer is not restricted...


...it's the metering device.

 

Story time.

In the past year, we were assigned a new store location. It was after last summer's cooling season.

First hot days we get, sure enough, a no cooling call. Slab coils blocked. Major coil cleaning.

One unit would cool for a few minutes, then suction would drop and the CLO would open the coil circuit.

First step was to replace dryers. Both had been open, not blocked. 164S size, mind you.

Then, the TEV inlet side was opened for both circuits to see if there was a clogged screen. Nope. No screens.

Solution: replaced both TEV's and deep vacuum, then recharge.

I have found that about 60-70% of the time, the restriction is indeed a clogged dryer. The rest of the time it is a blocked piston or failed TEV. Maybe twice in this decade have I found a measurable temp drop across a dryer without pulling some charge first. I suspect the charge was already a little low in those two systems...since there are so many hands touching these units before I get there.

Pull charge, replace dryer. If old dryer is not blocked, replace TEV.

 

So you don't think that if the drier is the restriction there would be a temp differential?

 

There would be...with a much lower subcooling. Like 3....

I would not rule out a blocked dryer based on a lack of temp difference. I have seen that too many times with no temp difference.

 

The only real way to check for a restriction is a pressure drop. Rarely do you have pressure taps on both side of a restriction.

Usually when a drier clogs, a technician will add more gas.

In order to see a temp split across a restriction, the refrigerant must flash or change states.

The more subcooling you have on the inlet, the higher the restriction would need to be to see a measurable temperature difference.

For example; r22
Inlet 200psi - 101.4* saturation
LLT - 80*
Subcooling 20*

The restriction would have to result in a pressure drop of 57psi to notice a temperature change.

For example; 160psi on the outlet results in 86.7* saturation and your liquid line is still 80*

So you have 6* of subcooling leaving the drier. You wont have a temp split.

Say the outlet of the drier is 143psi which is 80* saturation. You now have no subcooling and will start to change temp to see the restriction.

If i dont have pressure taps to check for a psi drop, i will remove gas to lower the subcooling which will show my restrictions with temperature splits.

Hope this helps


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High subcool with high superheat is normally a restriction from the expansion valve or drier.
A restricted drier will have a temperature drop across it , measure a few feet before and after it on liquid line.
Should be zero temp drop.
I would change the txv if drier checks out ,

 

If you have subcooling, you can not have a temp drop.

 

So when in doubt just write up txv with new filters and get it fixed up the right way under t&m agreement?

 

Its a drier, not a dryer.
Weeeee, you are fun though!