ReplyI didn't know there was a rule of thumb, you might want to invite him back over.
Regular Guest
Recently we had a new York furnace and evaporator coil (with txv) installed to replace aging units. We had it installed when it was still quite cold outside and I have a question regarding the freon R22 charge which was set after the coil was installed. The tech simply checked the charge by adjusting it to suction 65psi. I feel he should have set the charge by using the subcool method. I believe the outside temperature on the installation day was about 60 degrees. Should I insist that they come back to recheck the charge or is their "rule of thumb" method really good enough and to be trusted/accepted? The 65 degrees suction pressure is approx. 38 degrees at the evap coil, but is the system going to perform as it should?
Thanks for your input!
Professional Member
I didn't know there was a rule of thumb, you might want to invite him back over.
God Speed, Jim. We'll miss you - 2-26-23
They just guessed based on whatever.
It should be checked by SC, SH, and temp drop across the coil.
Professional Member*
call them and get it checked
that is not how to ajust anything and you may even be over charged
Professional Member
Does rule of thumb mean, if you put your thumb on the big line and it's cold, you're O.K.?Originally Posted by beenthere
Professional Member
no.
rule of thumb is two fold. You use your left thumb to check return air and right thumb to check supply air. Once done, return left thumb to arse and return right thumb to mouth. Be sure you do the L test before returning thumbs!!
rule of beer states beer can cold is proper operatin levels for the cold stuff
rule of wave states wave your hand in front of register. If you feel air coming out, you have proper CFM.
And the final rule.......
If the customer is happy, I'm haulin arse before they change their mind!!!!
I fully support the military and the War on Terrorism.
If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.
If you do know, then do. But do it right. Otherwise, you may not be doing it long.
Professional Member
Nice, very nice, thanks for the in depth answer.lolno.
rule of thumb is two fold. You use your left thumb to check return air and right thumb to check supply air. Once done, return left thumb to arse and return right thumb to mouth. Be sure you do the L test before returning thumbs!!
rule of beer states beer can cold is proper operatin levels for the cold stuff
rule of wave states wave your hand in front of register. If you feel air coming out, you have proper CFM.
And the final rule.......
If the customer is happy, I'm haulin arse before they change their mind!!!!
Professional Member*
Here's the formula he was using....
Outdoor Ambient
(minus)
Indoor Wetbulb
(plus)
Physical weight of unit
(plus)
Ounces in a 12 pack
(minus)
Technician's I.Q.
Equals 65
Just call him back and make him do it right.
I need a new signature.....
Professional Member
Holy s***, these formulas get better every time, anybody else got one.Here's the formula he was using....
Outdoor Ambient
(minus)
Indoor Wetbulb
(plus)
Physical weight of unit
(plus)
Ounces in a 12 pack
(minus)
Technician's I.Q.
Equals 65
Just call him back and make him do it right.
Professional Member
Sure
Outdoor Ambient Temp (DB) + Amount of service calls to run + Mileage to customers house + Diagnostic + Cost of gas + High Side PSIG (after gassing unit) = new hourly rate.
multiply new hourly rate times amount of time invested in customer(including travel time to and from BFE) and you get new subtotal.
Take our usual 85% off the top and hand to the rest into the boss.
I fully support the military and the War on Terrorism.
If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.
If you do know, then do. But do it right. Otherwise, you may not be doing it long.
Regular Guest
Only By Subcooling If Is Txv Sys At Least 60 F Ambiant!!!!!
AOP Committee/Professional Member*
Quote: "By Subcooling, if it is TXV Sys At Least 60 F Ambient." (True, & more)
First, charge is only done & accurate, if airflow is within specifications.
Superheat should also be checked to see if it is holding near its setpoint.
If there is also very low indoor load on the coil the Subcooling will not be accurate & the Superheat will not hold its setpoint.
A standard TXV "loses load adjust-ability" at about 30% of its rating.
Balanced port TXV's lose load adjust-ability at about 15% of rating.
Let me know if you have data directly contradicting those statements!
http://www.udarrell.com/ac-trouble-s...ubcooling.html
- udarrell
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