Is subcooling the best way to charge 410a?

[fridgerookie]

Finally came across 410a in the field. Is subcooling the only/best method for charging?I know I can't follow the 30 over ambient rule as with 22. Any simple rules to follow?

[allan38]

There is no one best way with any refrigerant.

I see a lot of 410 systems, my employer has been installing them since the late 90's and has a lot of 410 customers.

As far as I know, the 30 over rule was fine for many older systems. My recent observations have seen the systems with relatively large condenser coils may only be 15 to 20 over if you were to check after getting everything right. In the last four years I've seen many Bryant/Carrier/Lennox systems with a 15 -20 degree over OAT high side P/T.

Don't think pressure, think temps. It's not 70 psi, it's 40 degrees. It's not 118psi, it's 40 degrees.
Many newer systems run a higher evap coil temp. Think 42-48 degrees, R22 or R410. Bryant/Carrier 410a systems with a TXV have a subcooling of 8 to 16. Check the data plate or the table inside the cover for the subcooling for the specific model/tonnage.

Make sure airflow is right, charge fixed orifice by superheat, TXV by subcooling.

After getting the subcooling right you can check the superheat to make sure the TXV is working. If the low side pressure looks way low then check the fan speed again. I've seen Bryant/Carrier equipment drop the furnace speed to the fan setting if not getting a signal on G and getting a Y signal (it's how some systems signal to dehumidify)(And the install crews kept on adding refrigerant to get the pressure up, never checking the airflow). On the VS systems dropping the G signal may half the CFM airflow.
Thus part of checking for proper airflow is making sure you're getting a signal on G and any dip switches or motor taps are set for the CFM appropriate for the tonnage.

On the ECM multi speed motors like they are using on some of the Lennox systems you still have to check the fan speed data and the system static pressure to make sure you have selected the proper speed tap. The ECM multi speeds doesn't maintain a set CFM like the VS motors do.

Set airflow, charge by superheat for fixed orifice, charge by subcooling for TXV then check superheat.

BTW, the biggest problem with 410a is the POE lubricant. It really soaks up the moisture and makes a molecular bond with it. It's also an excellent cleaner of crud from the inside of refrigerant lines. Thus techs who've never seen the need to flow nitrogen while brazing are getting a lot of plugged TXV's, screens or filters from the cupric oxide. The clogs may show up months later after install. As a service tech I get stuck with the issues. I flow nitrogen when I braze. I'm going to pressure test to 300psi with nitrogen anyway so it's not a big deal.

You asked for simple.

[Oldschoolmetal]

DIY

[timebuilder]

DIY

Yep.

[DavyB]

Yep.

I was told that weighing it in was the best way with appropriate lineset sizes and length. probably another myth.

[pdrake65]

DIY

I think that is about the best way you can say it now on this site without getting into trouble :couchhide: Good call!

[amd]

Finally came across 410a in the field. Is subcooling the only/best method for charging?I know I can't follow the 30 over ambient rule as with 22. Any simple rules to follow?

That would depend on the type of metering device.

If you work in the field, please through that silly 30 over ambient rule in the garbage even for R-22 systems. (A "pro" should know better) Easy rules of thumb shouldn't be necessary for anyone who understands the refrigeration cycle.

[beenthere]

As with R22, or any other refrigerant for that matter. Checking SH and SC is the best method. Even if you weigh the charge in. You should still check SH and SC.

What method would you use to check the charge on a glass tender if it was R502, and used a cap tube metering device.

What method would you use on a walk in freezer that used R502 and a TXV.

What method do you use for a reach in cooler that uses R134A and has a cap tube metering device.

Get your post count up to 15 and apply for pro membership. Once accepted, you'll have access tot eh pro forums, where there is lots of info on charging, and diagnosing equipment.

[DavyB]

As with R22, or any other refrigerant for that matter. Checking SH and SC is the best method. Even if you weigh the charge in. You should still check SH and SC.

What method would you use to check the charge on a glass tender if it was R502, and used a cap tube metering device.

What method would you use on a walk in freezer that used R502 and a TXV.

What method do you use for a reach in cooler that uses R134A and has a cap tube metering device.

Get your post count up to 15 and apply for pro membership. Once accepted, you'll have access tot eh pro forums, where there is lots of info on charging, and diagnosing equipment.

Understood. Especially with all the crappy components installed nowadays.

[do over]

Why didn’t anyone say to charge R410 with liquid only? The real question is why was it not known to use Superheat for fixed restrictor systems and Subcooling for TXV systems. Is it know the basic idea to charging is to fill the evaporator with liquid refrigerant to a point without any of that liquid refrigerant getting back to the compressor?

[beenthere]

We aren't talking about a freezer. So you don't fill the evap.

[do over]

I guess that was too vague. The idea to charging is to have the desired cooling affect the evaporator needs to have the right amount of refrigerant in it, be it liquid or liquid flashing to gas.

[Oldschoolmetal]

That is what we call superheat. :playing:

[pdrake65]

I think I am going to take a little break from this site.....have fun guys!!!:putergreet:

[HvacStudentWTI]

Why didn’t anyone say to charge R410 with liquid only? The real question is why was it not known to use Superheat for fixed restrictor systems and Subcooling for TXV systems. Is it know the basic idea to charging is to fill the evaporator with liquid refrigerant to a point without any of that liquid refrigerant getting back to the compressor?

yep no need or paragraphs just the simple
TXV = sub cooling
any other metering device = superheat
:cheers:

[Joe Harper]

I think I am going to take a little break from this site.....have fun guys!!!:putergreet:
Dont let the door hit ya where the lord split ya.....:tussor:

[fridgerookie]

There is no one best way with any refrigerant.

I see a lot of 410 systems, my employer has been installing them since the late 90's and has a lot of 410 customers.

As far as I know, the 30 over rule was fine for many older systems. My recent observations have seen the systems with relatively large condenser coils may only be 15 to 20 over if you were to check after getting everything right. In the last four years I've seen many Bryant/Carrier/Lennox systems with a 15 -20 degree over OAT high side P/T.

Don't think pressure, think temps. It's not 70 psi, it's 40 degrees. It's not 118psi, it's 40 degrees.
Many newer systems run a higher evap coil temp. Think 42-48 degrees, R22 or R410. Bryant/Carrier 410a systems with a TXV have a subcooling of 8 to 16. Check the data plate or the table inside the cover for the subcooling for the specific model/tonnage.

Make sure airflow is right, charge fixed orifice by superheat, TXV by subcooling.

After getting the subcooling right you can check the superheat to make sure the TXV is working. If the low side pressure looks way low then check the fan speed again. I've seen Bryant/Carrier equipment drop the furnace speed to the fan setting if not getting a signal on G and getting a Y signal (it's how some systems signal to dehumidify)(And the install crews kept on adding refrigerant to get the pressure up, never checking the airflow). On the VS systems dropping the G signal may half the CFM airflow.
Thus part of checking for proper airflow is making sure you're getting a signal on G and any dip switches or motor taps are set for the CFM appropriate for the tonnage.

On the ECM multi speed motors like they are using on some of the Lennox systems you still have to check the fan speed data and the system static pressure to make sure you have selected the proper speed tap. The ECM multi speeds doesn't maintain a set CFM like the VS motors do.

Set airflow, charge by superheat for fixed orifice, charge by subcooling for TXV then check superheat.

BTW, the biggest problem with 410a is the POE lubricant. It really soaks up the moisture and makes a molecular bond with it. It's also an excellent cleaner of crud from the inside of refrigerant lines. Thus techs who've never seen the need to flow nitrogen while brazing are getting a lot of plugged TXV's, screens or filters from the cupric oxide. The clogs may show up months later after install. As a service tech I get stuck with the issues. I flow nitrogen when I braze. I'm going to pressure test to 300psi with nitrogen anyway so it's not a big deal.

You asked for simple.

Thanks for the information.This is very helpful.No matter how thorough the schooling is and no matter how many books you read,there is absolutely no substitute for hands on experience.I guess learning everything I need to know to be a very efficient tech is to just get in the trenches and start turning some wrenches.Hey look at that, I'm a poet and didn't know it.

[fridgerookie]

That would depend on the type of metering device.

If you work in the field, please through that silly 30 over ambient rule in the garbage even for R-22 systems. (A "pro" should know better) Easy rules of thumb shouldn't be necessary for anyone who understands the refrigeration cycle.

Thanks for the constructive criticism. Three years in the field and I still consider myself new to this science/technology. I understand there is no easy way out when dealing with these systems.30 over OAT is just an indicator I was taught when checking high side pressures.I understand that that's not the golden indicator of a system operating correctly. I try to take my time and take in as much as I can when on a service call,but with only two of us running calls for two fast food chains(80 stores total) I have to hit and run so to speak. It keeps my paychecks coming,but doesn't allow me to fully understand every aspect of what's going on. I try to get a grasp of how components function during different conditions and cycles of operation through reading and the literature that comes with parts/components.It's just not the same as seeing them work.I refuse to be just a parts changer,but sometimes I feel that way.I want to be an asset and not a liability in this field.Being that we repair kitchen equipment as well as HVAC/R equipment in these stores I feel like we are spread way too thin most days.I will learn this stuff well enough to be a very competent and efficient technician,just have to roll up my sleeves and do it!

[MontanaBighorn]

Finally came across 410a in the field.18 years in, i just came across 410a in the field for the first time a couple months ago. copeland scroll was recently replaced (by another service company) and (as allan said) the TXV was plugged due most likely to not flowing nitrogen during the brazing.


http://img52.imageshack.us/img52/4011/20100722194106.jpg

...this was the TXV on the same job. notice a problem with the installation?

as for the charging, allan covered everything that needs to be said. ive heard of some who use a tiff 4000 when charging 410 with success, but ive been unable to warm up to it.

[dorff]

I always find with 410a and TXV, weigh in your extra charge, then do your subcooling. You might be surprised how far off the weigh in can be.

[jhallinstaller]

18 years in, i just came across 410a in the field for the first time a couple months ago. copeland scroll was recently replaced (by another service company) and (as allan said) the TXV was plugged due most likely to not flowing nitrogen during the brazing.


http://img52.imageshack.us/img52/4011/20100722194106.jpg

...this was the TXV on the same job. notice a problem with the installation?

as for the charging, allan covered everything that needs to be said. ive heard of some who use a tiff 4000 when charging 410 with success, but ive been unable to warm up to it.
where do i start?.../.....
PRIDE, PREJUDICE ....

or lack of ?