Low TD update with new Issue

COLDAIRRANDY

On my previous post of having a low TD on a new 5 ton system. Here is what is going on now and I need some new insight.
Original readings on start up R22.
I added a little gas per Rheem Tech and her is the new readings.
If I have a restriction in the evap, Screen, TXV why is my superheat at the condenser so low. adding the gas just stacked the liquid in the condenser. It did raise my original TD concern but now the sub cooling is too high. Amp draw & suction still low.
any suggestions.

At initial start up
11º sub cooling
14º superheat @ cond
205º head
60º suct
Amps 14 (RLA is 25)
11º TD @ register/return
44 humidity in house

gas added
30º sub cooling
11 superheat
230 head
60 suct
Amps 17
15 TD @ register/return
44 humidity in house

pecmsg

on a new 5 ton system

R-22 ???

COLDAIRRANDY

Yes.
All new R22 was in storage waiting for the change out.

mel57

Take a TD reading at the air handler, supply and return. Should be about 20. You could be getting low TD, from inadequate insulation on the ducts. Low TD is usually a  sign of to much air threw the coil. A static pressure reading would tell you if the air flow is adequate. 

EBEBRATT-Ed

Sounds like the metering device is the wrong size, a restriction or your airflow is low

ChrisJ

Where are you measuring your superheat?
Where are you measuring the temp drop across the coil?


Assuming your pressures are fairly steady it sounds like the TXV is doing it's job and you're a bit overcharged now.

Is air bypassing around the evaporator?

COLDAIRRANDY

Was measuring the superheat at the condenser. I am overcharged now because the subcooling is 30 an when I take some out my TD across the register and return will go back to 10/11. I am going to pull the txv bulb off the suction line to see if It will get the suction up a little it won't move off of 60psi. Only the head went up when I added a little gas. Plus my amps are at 17 and the RLA is 25.

mattmia2

Did you get the numbers off the txv and look up the number and make sure it is for 5 ton and r22?

Are you positive you had the service valves in the right position to evacuate the dry condenser?

COLDAIRRANDY

I call the supply house and the looked to make sure I had the correct valve. Yes on the valves I had to back them out to blow the nitrogen then pulled 150 Microns. The txv bulb is at 12  on the 7/8 line. But possible the bulb my not be wrapped up good on the ends.

Matt_67

I would guess the airflow is too high. Measuring that would help the diagnosis. On the amp draw if you have the compressor model number you can look up a performance chart and see what it should be at your current conditions.

ChrisJ

If SC and SH were reasonable and the pressures were fairly steady why are we troubleshooting the metering device?

It's doing it's job. A TXV doesn't care about the TD across the coil.

Power and head pressure went up because the system is now overcharged.

COLDAIRRANDY

I don't see air flow being a problem on a blower
That has been in a unit for 15 years and only the evap  an cond change out. With the SC & SH being set. I have low suction, low amps and low TD @ the reg and return.
That's why I am figuring the metering device. When I add gas and the subcooling went high head pressure went up but suction stayed low about 60 psi R22. 

pecmsg

COLDAIRRANDY said:

I don't see air flow being a problem on a blower
That has been in a unit for 15 years and only the evap  an cond change out. With the SC & SH being set. I have low suction, low amps and low TD @ the reg and return.
That's why I am figuring the metering device. When I add gas and the subcooling went high head pressure went up but suction stayed low about 60 psi R22. 

If the air flow is low you'll have the same situation. That's why the CFM's, Static and TESP all need to be checked.

ChrisJ

COLDAIRRANDY said:

I don't see air flow being a problem on a blower
That has been in a unit for 15 years and only the evap  an cond change out. With the SC & SH being set. I have low suction, low amps and low TD @ the reg and return.
That's why I am figuring the metering device. When I add gas and the subcooling went high head pressure went up but suction stayed low about 60 psi R22. 

The TXV literally doesn't care what the liquid temperature is, whether it's 34 or 84. It's job is to control super heat, nothing else.

It appears it's giving you a reasonable amount of superheat, so the evaporator has the right amount of refrigerant in it. So something else must be wrong.

mattmia2

Did something get hanged so that y is no longer getting closed on the air handler/furnace so it is no longer making a high fan call on a cooling call?

COLDAIRRANDY

I will check the cfm to make sure I have 1750/2000 for this 5 ton unit. Makes no sense that I can't get the suction above 60/62. And a 17 Amp draw with a RLA of 25. But yet I get a 14 superheat at the condenser.

COLDAIRRANDY

This is new equipment too.

ratio

The TXV controls the superheat. The only way dumping juice in will effect superheat is if you're undercharged or overcharged to the point that the TXV can no longer control it. I wouldn't worry about the amp draw just yet. If it's not 95+° outside your won't even be close to RLA.