Yet another AC issue

[Strats-N-Vettes]

FYI--this will kill a newer-ish compressor, older compressors (depending on type and brand) will slug, but still work.

[Aerovette]

Originally Posted by Strats-N-Vettes

FYI--this will kill a newer-ish compressor, older compressors (depending on type and brand) will slug, but still work.

That was rated the number one sealant on line.

I used a different brand upstairs and it has been working MUCH better. Not great, but it holds steady temps at 74 and I have not had to add any R22 since using it.

I may have to do the same downstairs.

[Steve_R]

Our system gets replaced in two weeks when we get home from visiting the kids and grandkids.

[Aerovette]

@Egnalf

Ok here are the numbers AFTER adding 2lbs of R22. There must be one helluva leak.

SH - 50.4
SC - 10.3
Low - 53.1psi
High - 202.3psi

When I started I had
36.1 - psi
183 - psi

I did not have the temp clamps at the right setting so I don't know what the temps were.

It's a Goodman 14 SEER, 3.5 ton / 42000BTU downstairs

[Aerovette]

Hello? Is this thing on?

[snide]

Originally Posted by aerovette

Hello? Is this thing on?

Nope, we all got bored and left.

[Aerovette]

Originally Posted by snide

Nope, we all got bored and left.

All good. I'll wait until heating season and revisit.

[LisaJohn]

It may be heating season before ours arrives.

[Aerovette]

Originally Posted by Strats-N-Vettes

FYI--this will kill a newer-ish compressor, older compressors (depending on type and brand) will slug, but still work.

I wonder if this will work with the leak stop stuff I have already used?

[Egnalf]

50 SH, is this is the outdoor unit or indoor coil? Either way, its still thirsty or there is a restriction/expansion device issue.

[Aerovette]

Originally Posted by Egnalf

50 SH, is this is the outdoor unit or indoor coil? Either way, its still thirsty or there is a restriction/expansion device issue.

Outdoor. All readings are outside. I added 2lbs but I'm not adding anymore until I am sure it isn't leaking anymore. Too expensive.

[benny42]

Originally Posted by Egnalf

50 SH, is this is the outdoor unit or indoor coil? Either way, its still thirsty or there is a restriction/expansion device issue.

I agree on there likely being a restriction. 10*sub cooling and 50* superheat. Yep.

[Aerovette]

Originally Posted by benny42

I agree on there likely being a restriction. 10*sub cooling and 50* superheat. Yep.

Won't low refrigerant have the same result?

[Egnalf]

Originally Posted by aerovette

Won't low refrigerant have the same result?

IF, and that is a big if...your outdoor unit is clean, 10 degrees subcooling would indicate a solid column of liquid to the expansion device. unless there is flashing caused by a restriction at the dryer or inlet screen to the expansion device, your system is close. I would expect closer to 20-25 outside superheat, maybe less depending upon the system. That said, I ASSUME your suction line is properly insulated and not picking up any or very little ambient heat. Adding a little gas COULD help you, but more data points are needed.

Note, I have never done residential HVAC, so my numbers could be off a bit. I own a company that does large commercial shit and we shoot for ten SC and ten SH at indoor coil on HVAC systems that dont have specific values designed. Much of what we do is custom for healthcare, rinks, and pharma applications which run at different conditions.

[Aerovette]

Originally Posted by Egnalf

IF, and that is a big if...your outdoor unit is clean, 10 degrees subcooling would indicate a solid column of liquid to the expansion device. unless there is flashing caused by a restriction at the dryer or inlet screen to the expansion device, your system is close. I would expect closer to 20-25 outside superheat, maybe less depending upon the system. That said, I ASSUME your suction line is properly insulated and not picking up any or very little ambient heat. Adding a little gas COULD help you, but more data points are needed.

Note, I have never done residential HVAC, so my numbers could be off a bit. I own a company that does large commercial shit and we shoot for ten SC and ten SH at indoor coil on HVAC systems that dont have specific values designed. Much of what we do is custom for healthcare, rinks, and pharma applications which run at different conditions.

Can you explain this? Is it a good thing or bad thing?

[LisaJohn]

It’s here! It’s here!

[Egnalf]

Originally Posted by aerovette

Can you explain this? Is it a good thing or bad thing?

The outdoor unit in an ac system is called a condensing unit, or condenser. It gets the cool low pressure suction gas coming to it, compresses the vapor to a high pressure vapor. That high pressure vapor is run through the coils with air moving across them to "condense" the vapor back to a liquid.

As any liquid moving through a pipe, there are pressure changes due to friction. the liquid coming out of the condenser likes to be 8-10 degrees below the condensing point. This allows the liquid to flow through the various pipes and fittings, drop a little bit of pressure, and continue on as a liquid. As pressure changes you approach point where the liquid can boil back off, called flashing. Typical pressure drop is 2-4 psig, or less. If there is a restriction, such as a clogged drier, pressure can drop a lot and flash off liquid to vapor, thereby screwing up all of your values. That vapor starts before the expansion device, so the coil doesnt see liquid coming in, it sees a mix of liquid and vapor that already started picking up heat.

Like many gases, much of the work is done via change of state. One pound Saturated Steam, for example, gives up nearly 1000 btu's by going from vapor to liquid. By changing from 215 degrees to 214 degrees as a vapor, the same steam gives up only 1 BTU. Refrigerants do the same, so boiling off befofe the coil causes messed up readings.

[dvarapala]

Originally Posted by LisaJohn

It’s here! It’s here!

The new telephone directory?

[Aerovette]

Originally Posted by Egnalf

The outdoor unit in an ac system is called a condensing unit, or condenser. It gets the cool low pressure suction gas coming to it, compresses the vapor to a high pressure vapor. That high pressure vapor is run through the coils with air moving across them to "condense" the vapor back to a liquid.

As any liquid moving through a pipe, there are pressure changes due to friction. the liquid coming out of the condenser likes to be 8-10 degrees below the condensing point. This allows the liquid to flow through the various pipes and fittings, drop a little bit of pressure, and continue on as a liquid. As pressure changes you approach point where the liquid can boil back off, called flashing. Typical pressure drop is 2-4 psig, or less. If there is a restriction, such as a clogged drier, pressure can drop a lot and flash off liquid to vapor, thereby screwing up all of your values. That vapor starts before the expansion device, so the coil doesnt see liquid coming in, it sees a mix of liquid and vapor that already started picking up heat.

Like many gases, much of the work is done via change of state. One pound Saturated Steam, for example, gives up nearly 1000 btu's by going from vapor to liquid. By changing from 215 degrees to 214 degrees as a vapor, the same steam gives up only 1 BTU. Refrigerants do the same, so boiling off befofe the coil causes messed up readings.

1.It gets the cool low pressure suction gas coming to it, compresses the vapor to a high pressure vapor. <<No mention of liquid. Just "gas" and "vapor". I may be misunderstanding but this is what I "thought" is taking place.
a) Liquid under pressure exits the compressor and travels to the evaporator. As it enters the evaporator, it immediately is able to expand and becomes a cold gas and flows through the coils where the air blowing across it, picks up the cold and distributes it through the ducts. The "spent" gas turns to a liquidish gas mix and is sucked back in to the compressor to go again.
2. It "sounds like" a column of liquid from condenser to evaporator is a good thing. My knowledge of car AC says it is. I assume the same here.
3. The liquid is supposed to turn to vapor in the evaporator, but your mention of flashing if I understand correctly, means it is happening too early...somewhere in the tube/copper pipe on it's way to the attic. That makes sense.
4. The above tells me I am low on freon, but your other post mention a possible blockage.

What I know...

The high pressure line is not fully covered/insulated on one unit. The low side also has some gaps. I have to assume it is still intact where it runs inside the wall and it is intact in the attic. This is something I will address immediately. I was not aware that it made that much of a difference.


I could have this all wrong but I want to learn.

[LisaJohn]

Originally Posted by dvarapala

The new telephone directory?

No silly. The new hvac.