Is charging a R410a system the same as a R-22 system... - Page 2 - DIY Chatroom

dbmarsbrit · 03-19-2009, 01:29 AM

Quote:

Originally Posted by paulie pizza

is charging a 410a the same as Charging a R-22 system......other than charging a 410a in a liquid form

yes other than pressure difference between 22 & 410a
remember 410a is a blend
it must be added as a liquid
i,m an hvac-r service tech

paulie pizza · 03-24-2009, 07:25 PM

Quote:

Originally Posted by dbmarsbrit

yes other than pressure difference between 22 & 410a
remember 410a is a blend
it must be added as a liquid
i,m an hvac-r service tech

Thanks dbmarsbrit,
As I keep reading up on 410a.....weighing in the charge in a liquid form and pressure's are higher than 22.....I still put a sight glass,drier and deep vacum on system before I put in additional charge needed. I have a chart on ammount needed for total run of pipng..... and it works great

Lately we have been installing drier as close to A/H to catch anything just before TXV......does that make a difference to install in attic or by the condensing unit...other than the drier getting hot in attic...I have taken old units out with drier in attic.....

hvaclover · 03-24-2009, 08:08 PM

Quote:

Originally Posted by paulie pizza

Thanks dbmarsbrit,
As I keep reading up on 410a.....weighing in the charge in a liquid form and pressure's are higher than 22.....I still put a sight glass,drier and deep vacum on system before I put in additional charge needed. I have a chart on ammount needed for total run of pipng..... and it works great

Lately we have been installing drier as close to A/H to catch anything just before TXV......does that make a difference to install in attic or by the condensing unit...other than the drier getting hot in attic...I have taken old units out with drier in attic.....

Can't use a sight glass on a zeotrope refrigerant to check charge. Can have bubbles cause of the slight temp glide characteristics of the refrigerant.

beenthere · 03-24-2009, 08:58 PM

Except for systems that had a receiver. Sight glasses were never a good way to determine if the system was charged properly.

dbmarsbrit · 03-24-2009, 09:35 PM

Quote:

Originally Posted by paulie pizza

Thanks dbmarsbrit,
As I keep reading up on 410a.....weighing in the charge in a liquid form and pressure's are higher than 22.....I still put a sight glass,drier and deep vacum on system before I put in additional charge needed. I have a chart on ammount needed for total run of pipng..... and it works great

Lately we have been installing drier as close to A/H to catch anything just before TXV......does that make a difference to install in attic or by the condensing unit...other than the drier getting hot in attic...I have taken old units out with drier in attic.....

the only difference is you may not catch any contaminants in the linset
between the drier and the a/h txv
I haven't seen a txv system that doesn't have some sort of internal
screen/filter adding a liq. line drier at the or as close as possible
to the txv is prefered hot attics are not really an issue
on large commercial units suc.&liq. filter driers are often open to the elements/sun

dbmarsbrit · 03-24-2009, 09:37 PM

Quote:

Originally Posted by beenthere

Except for systems that had a receiver. Sight glasses were never a good way to determine if the system was charged properly.

could you explain this to me

beenthere · 03-24-2009, 10:38 PM

A sight glass only shows that you have, or don't have a solid head of liquid at IT.

A sight glass installed near the TXV is better then one at the condenser.

But, a kink in the liquid line, will show vapor, and most techs just add charge until its full, over charging the system.

One mounted at the condenser will show solid liquid, and then the system is under charged. And many techs can't figure out why it won't cool with a full head of liquid. And then they say it must be a bad compressor..

A dirty condenser, can be over charged enough to show a full sight glass.

Without checking sub cooling. Its easy not notice that its over charged. No matter what location the sight glass is installed at.

Charging to a full sight glass can make the compressor work harder to start, and to run. Because its over charged.

Systems with liquid receivers, won't have a good sub cooling readings after the receiver.

SC has to be taken before it.

But, even with proper SC, you may have to add more to get a head of liquid from the receiver(The receiver is at saturation).

A combination of the sub cooling reading before the receiver, and checking if the sight glass is showing a full head of liquid is a best practice.

When sight glasses are used as the only means to determine if a system is charge correctly or not.
They aren't charged correctly.

imastar4nascar · 06-21-2009, 09:22 PM

Quote:

Originally Posted by beenthere

A sight glass only shows that you have, or don't have a solid head of liquid at IT.

A sight glass installed near the TXV is better then one at the condenser.

But, a kink in the liquid line, will show vapor, and most techs just add charge until its full, over charging the system.

One mounted at the condenser will show solid liquid, and then the system is under charged. And many techs can't figure out why it won't cool with a full head of liquid. And then they say it must be a bad compressor..

A dirty condenser, can be over charged enough to show a full sight glass.

Without checking sub cooling. Its easy not notice that its over charged. No matter what location the sight glass is installed at.

Charging to a full sight glass can make the compressor work harder to start, and to run. Because its over charged.

Systems with liquid receivers, won't have a good sub cooling readings after the receiver.

SC has to be taken before it.

But, even with proper SC, you may have to add more to get a head of liquid from the receiver(The receiver is at saturation).

A combination of the sub cooling reading before the receiver, and checking if the sight glass is showing a full head of liquid is a best practice.

When sight glasses are used as the only means to determine if a system is charge correctly or not.
They aren't charged correctly.

today, sight glasses are only good for moisture indications. the old days of charging until it's full is a fools way of charging. package rooftops you weigh in the charge, split systems use a chart.

beenthere · 06-21-2009, 09:31 PM

Sight glasses were never a good way of charging a system(A/C, or HP, refrigeration can be different).

Even though atleast one A/C manufacturer had instructions to charge by sight glass.

beenthere · 06-21-2009, 09:33 PM

The real shame.
Is that with all the improvements with test instruments. Including the cost of them.
Techs still want ot use a sight glass.

imastar4nascar · 06-21-2009, 09:44 PM

I graduated in 1995 with an associates degree in HVAC. I have been fighting the old school tech philosophies ever since. I still have techs who charge by pressures, then wonder why they get stuck doing pm's.

with the money i pay techs it's a shame they don't want to buy the instruments that let them do their jobs well.

beenthere · 06-21-2009, 09:54 PM

I use to be a SM for a company.

Use to get radio calls from techs. Asking me whats wrong, why can't they get teh system to cool right.
When I would ask them what the SH and SC was. They would say something like.

I forget the exact numbers, bu they were both good.
So I'd tell them to radio me back when they took those readings again. And then tell me what they are.

A far number of times. They wouldn't call back. And the next day, when I looked at the ticket. And saw they changed out a LLFD, or Cleaned the coil, and then it worked right again.
I'd ask them how the SH and SC could have been ok the first time.

Then just mumble.

Sometimes when they have the instruments, they still don't use them.

And what I never understood. Was since they were paid by the hour. Why not take the few minutes required to take all the readings. And find the real problem faster.

imastar4nascar · 06-21-2009, 10:01 PM

you lived it right there. Why didn't you put in a work description? "because i was running behind" get paid by the hour doesn't mean they do what they are told lol.

hvaclover · 06-22-2009, 07:58 AM

Quote:

Originally Posted by beenthere

I use to be a SM for a company.

Use to get radio calls from techs. Asking me whats wrong, why can't they get teh system to cool right.
When I would ask them what the SH and SC was. They would say something like.

I forget the exact numbers, bu they were both good.
So I'd tell them to radio me back when they took those readings again. And then tell me what they are.

A far number of times. They wouldn't call back. And the next day, when I looked at the ticket. And saw they changed out a LLFD, or Cleaned the coil, and then it worked right again.
I'd ask them how the SH and SC could have been ok the first time.

Then just mumble.

Sometimes when they have the instruments, they still don't use them.

And what I never understood. Was since they were paid by the hour. Why not take the few minutes required to take all the readings. And find the real problem faster.

Radios? You were lucky Been. We used two cans with a string connected.

beenthere · 06-22-2009, 08:01 AM

Quote:

Originally Posted by hvaclover

Radios? You were lucky Been. We used two cans with a string connected.

LOL...

When I first started.

We used cans too. We just didn't have the string for the cans.