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I agree with the charging by WB temp. Which can be measured by a physcrometer .If you get a field piece hs35 or 36 ,it has a cool little head attachment that fits right in the case ,get that and a superheat chart and you will get +/- 3 degrees everytime gauranteed or yo money back

Agreed.

Originally Posted by HVACTechNC

Seems like we are saying the same thing, really. I read both manuals. Both say to add refrigerant by weight per foot of line set beyond 15 feet. Both also say to verify proper charge by superheat and or subcooling after start up. That is essentially what I said earlier.

I never said that it was the "preferred" method. I said manufacturers recommend weighing in charge on installation. PAge 6 of the Goodman manual says to. Page 14 of the Rheem manual says to. They recommend it both times.

Where is the discrepancy?

You start with the factory charge and line length estimate adjustment.

Then, you MEASURE. You adjust the charge based on that data, using the correct method, based on the metering device being used.

Easy.

Originally Posted by mofotech

I have a question to add to this thread. When they say to : "If line set
exceeds 15 feet in length, refrigerant should be added at .6
ounces per foot of liquid line." If one accounts for the additional line set and properly charges the unit. Then when one measures the sub-cooling do you still base your charge off the manufactures chart? ( sub-cooling number vs outdoor temperature?) Is the manufactures sub-cooling chart independent of whatever the line set length maybe? I mean would it matter? Or is the sub-cooling chart calculated already with X amount of line set? (example the 15 ft manufactures are mentioning in the manual). I am kind of asking would one go with the chart or some other way after accounting for the additional line set?

This and other questions are answered in the pro tech forums.

Originally Posted by mofotech

I have a question to add to this thread. When they say to : "If line set
exceeds 15 feet in length, refrigerant should be added at .6
ounces per foot of liquid line." If one accounts for the additional line set and properly charges the unit. Then when one measures the sub-cooling do you still base your charge off the manufactures chart? ( sub-cooling number vs outdoor temperature?) Is the manufactures sub-cooling chart independent of whatever the line set length maybe? I mean would it matter? Or is the sub-cooling chart calculated already with X amount of line set? (example the 15 ft manufactures are mentioning in the manual). I am kind of asking would one go with the chart or some other way after accounting for the additional line set?

I can't go too far on your question other than to say that measured performance is king, period.

To say more would flirt with breaking the rules.

I have a question to add to this thread. When they say to : "If line set
exceeds 15 feet in length, refrigerant should be added at .6
ounces per foot of liquid line." If one accounts for the additional line set and properly charges the unit. Then when one measures the sub-cooling do you still base your charge off the manufactures chart? ( sub-cooling number vs outdoor temperature?) Is the manufactures sub-cooling chart independent of whatever the line set length maybe? I mean would it matter? Or is the sub-cooling chart calculated already with X amount of line set? (example the 15 ft manufactures are mentioning in the manual). I am kind of asking would one go with the chart or some other way after accounting for the additional line set?

I was working as a "tan" tech when the fed building was bombed in Oklahoma City. I fixed tv's and appliances, particularly those using refrigerant. I vividly recall getting a trailer load of RCAs with bad picture tubes. I had worked through them about halfway when RCA (Thompson) said we should stop the process and ship them to some warehouse in New Jersey.

Its true. Its almost impossible to make a living in appliance repair. The units are so cheap that replacement costs less.

dont forget this assumes th the factory actually weigh the correct charge in the condensing unit b4 it was shipped!

after installation verifing proper SH & SC many times reveils low charge and recently i've found drastic over charges.

weigh in is a starting point. the equipment isnt installed in a lab setting. charge must be set to operate with in the enviroment its installed.

if your not testing, your guessing

i know that most manufactures say weight in the charge . although is the evaporator coil that is installed is that the coil that the refrigerant charge was based on . if you put a larger coil to increase the seer you will need more refrigerant. mabey its just me but i have measured line sets and weighed in the charge and i never come up with the correct subcool or superheat almost always short on gas

Originally Posted by hvacrmedic

Rheem doesn't say that it's their preferred method. See the attached Installation manual below. Page 14.

Goodman doesn't even cover weighing in the charge in the second of the two attached manuals.

Just saying.

Seems like we are saying the same thing, really. I read both manuals. Both say to add refrigerant by weight per foot of line set beyond 15 feet. Both also say to verify proper charge by superheat and or subcooling after start up. That is essentially what I said earlier.

I never said that it was the "preferred" method. I said manufacturers recommend weighing in charge on installation. PAge 6 of the Goodman manual says to. Page 14 of the Rheem manual says to. They recommend it both times.

Where is the discrepancy?

Originally Posted by mroberts

A question related to charging correctly ...

When a tech came to repair a leak in my indoor coil (TXV valve connection leak), he added refrigerant based on the pressure readings of his gauges connected to the low and high side ... is this an accurate way to charge?

Thanks,
Mike

a very important part of one.

A question related to charging correctly ...

When a tech came to repair a leak in my indoor coil (TXV valve connection leak), he added refrigerant based on the pressure readings of his gauges connected to the low and high side ... is this an accurate way to charge?

Thanks,
Mike

Originally Posted by ryan1088

Just going to make a stab at it that you work for Sears/A&E Factory service?

Nope, I work for an independent shop. The techs at A&E/Sears do basically the same thing we do.

Originally Posted by darctangent

Commercial controls would be your best bet as a point of entry, if that was your choice.

As an aside, I would say tv repair would be a tough trade to do well in. While I realize it's far more centralized than days of old, you are always battling against the cost of replacement. Seems like medical equipment would be the better gig.

As somebody who has repaired TV's for 20yrs we had to start picking up appliance work a few years ago due to the low cost of TV's nowadays. Warranty rates are dropping for both TV and appliance work, that's why I'm looking into doing something else. It's getting as bad as what the home warranty companies are doing to HVAC contractors.

Originally Posted by fearlessfurnace

If the coils are dirty the system can't run right clean them first.
Bad (dirty) coils will drop the superheat on a fixed orifice so the balanced charge will be less refigerant.

That is why the indoor coil ought to have enough space under it to get a good view of the coil & fins. That makes it possible to spray the coil from both sides, use a soft brush, & catch the run-off in a pan.

It is good practice to use evaporator coil cleaner at intervals that will insure optimal heat transfer - efficient performance.

Blower wheel blades must also be kept clean, & mark where the balance weights are in case they're knocked off.

Originally Posted by 54regcab

Not a HVAC pro, but as you see I've been on here 10yrs. Actually I repair TV's and Appliances for a living, HVAC is a interest/hobby of mine. I looked into doing HVAC for a living but I can't work minimum wage while I "pay my dues" as a installer/ductwork guy. I understand most trades require "paying their dues (mine included), but the time to be moved from installer to a well paid tech is too long. As a TV/Appliance tech the electrical stuff comes relatively easy to me, it's the refrigerant stuff I'd have to get field experience with. I could even repair the control boards if it's economically feasible, although if it's like TV/Appliances these days it's more cost effective just to replace the board.

Just going to make a stab at it that you work for Sears/A&E Factory service?

Originally Posted by hvacrmedic

That is not the weigh in method per se. It only covers the additional lineset charge, and is not intended to be "the" charging method. That passage is followed immediately by,

"FINAL CHARGE ADJUSTMENT
The outdoor temperature must be 60°F or higher. Set the room
thermostat to COOL, fan switch to AUTO, and set the temperature
control well below room temperature.
After system has stabilized per startup instructions, check
subcooling and superheat as detailed in the following section."

Completely agreed.

It is covered under "initial charge" which to me is the same thing as guesstimate. I actually find that typically overcharges the system.

Originally Posted by darctangent

actually, page 6 of the goodman manual:

Adequate refrigerant charge for a matching evaporator and 15
feet line set is supplied with the condensing unit. If line set
exceeds 15 feet in length, refrigerant should be added at .6
ounces per foot of liquid line.

That is not the weigh in method per se. It only covers the additional lineset charge, and is not intended to be "the" charging method. That passage is followed immediately by,

"FINAL CHARGE ADJUSTMENT
The outdoor temperature must be 60°F or higher. Set the room
thermostat to COOL, fan switch to AUTO, and set the temperature
control well below room temperature.
After system has stabilized per startup instructions, check
subcooling and superheat as detailed in the following section."

Originally Posted by 54regcab

Of course cleaning the coils (especially the condenser) should be done before charging, but how many techs actually do this? And then there is the blower wheel/low airflow issues, are these also addressed before determining correct charge?

On my system the indoor humidity goes up when the condenser coil gets dirty. It doesn't LOOK dirty, but cleaning it drops the humidity. Maybe the indoor coil is getting colder due to the clean condenser?

yep

Originally Posted by hvacrmedic

Rheem doesn't say that it's their preferred method. See the attached Installation manual below. Page 14.

Goodman doesn't even cover weighing in the charge in the second of the two attached manuals.

Just saying.

actually, page 6 of the goodman manual:

Adequate refrigerant charge for a matching evaporator and 15
feet line set is supplied with the condensing unit. If line set
exceeds 15 feet in length, refrigerant should be added at .6
ounces per foot of liquid line.