[STANCILHVAC]

HEY---Anyone know the rule of thumb formula for weighing in the proper needed amount of freon for linesets over 15 feet,i have always went by pressures but trying to remember the weighing formula---say you have a 75foot lineset which is supposedly 50feet over for the factory charge,so i was thinking that the formula was then 50x.06--which would mean that it needed 3 more pounds?Can someone confirm if this is the correct formula or not,because 3 more pounds seems like a bit too much----i can charge it by the pressure,but was trying to remember this formula--thanks

 

[clintkennon]

HEY---Anyone know the rule of thumb formula for weighing in the proper needed amount of freon for linesets over 15 feet,i have always went by pressures but trying to remember the weighing formula---say you have a 75foot lineset which is supposedly 50feet over for the factory charge,so i was thinking that the formula was then 50x.06--which would mean that it needed 3 more pounds?Can someone confirm if this is the correct formula or not,because 3 more pounds seems like a bit too much----i can charge it by the pressure,but was trying to remember this formula--thanks

It depends on the lineset size and the length varies from manufacturer.

 

[coolwhip]

HEY---Anyone know the rule of thumb formula for weighing in the proper needed amount of freon for linesets over 15 feet,i have always went by pressures but trying to remember the weighing formula---say you have a 75foot lineset which is supposedly 50feet over for the factory charge,so i was thinking that the formula was then 50x.06--which would mean that it needed 3 more pounds?Can someone confirm if this is the correct formula or not,because 3 more pounds seems like a bit too much----i can charge it by the pressure,but was trying to remember this formula--thanks

Dont charge by pressure, charge by subcooling or superheat depending on your metering device and according to unit charging chart.

 

[clintkennon]

Dont charge by pressure, charge by subcooling or superheat depending on your metering device and according to unit charging chart.

This is true. When I charge a system with the units charging chart, I write on my ticket "Charged system to manufacturers specifications".
It makes me look really smart like I actually know what Im doing. Jokes on them though.

 

[STANCILHVAC]

one unit is 7/8-3/8 and the other is 3/4-3/8 and both are about 75ft and the units suppossedly carry a charge for up to 15foot of lineset---which we all know is very seldom ever that short of a lineset--i do know all about the other ways of getting a proper charge,but was told by a fellow hvac tech today that you could use this formula(if that is the correct one that i remember being told)he is fresh out of hvac school and says that is what "the book says"--i am old school and have never did it that way---but was just wondering if there was any truth in this formula---thanks

 

[STANCILHVAC]

hey clintkennon --you sound just like me--lol

 

[westmorelnd]

Gibson requirements

I often work with Gibson and Newtone units for which the documents state that their units come charged for a fifteen foot run of the recomended size lineset be it 5/8 and 3/8 or 3/4 and 3/8 and for either add 0.6 oz for each foot of additional lineset. I would think that would be pretty close for other brands assuming a normal lineset installation.

 

[clintkennon]

one unit is 7/8-3/8 and the other is 3/4-3/8 and both are about 75ft and the units suppossedly carry a charge for up to 15foot of lineset---which we all know is very seldom ever that short of a lineset--i do know all about the other ways of getting a proper charge,but was told by a fellow hvac tech today that you could use this formula(if that is the correct one that i remember being told)he is fresh out of hvac school and says that is what "the book says"--i am old school and have never did it that way---but was just wondering if there was any truth in this formula---thanks

Well, Its closer to 1/2 an ounce per ft not .06.your math is messed up I come up with 36 ounces (based on 60 extra ft). 2 lbs 4 oz. But besides that Ive always done it for 30 ft of lineset. so 45x.6=27 oz.
You should just use the charging chart, because now you've confused me too.

 

[kytinknocker]

It should tell on the door chart.

 

[clintkennon]

I do the weigh in method to get me close then check it with the data plate on the unit.

 

[STANCILHVAC]

ok--so would it be .6 or .06,because i was doing 50ftx.06=3lb,you are saying 50ft x .6=30oz--which would be 1.875lb?Is this correct as i admit i was not paying that much attention to him at the time i was told and may of had my figues wrong--thanks

 

[clintkennon]

ok--so would it be .6 or .06,because i was doing 50ftx.06=3lb,you are saying 50ft x .6=30oz--which would be 1.875lb?Is this correct as i admit i was not paying that much attention to him at the time i was told and may of had my figues wrong--thanks

Wheres the 50 coming from? 75-15=60.
But yes if you must butcher basic math 50x.6 would equate to 1 lb 14 ounces.

 

[STANCILHVAC]

I do the weigh in method to get me close then check it with the data plate on the unit.

are you talking about weighing it in with no charge on the unit--i know that the unit will say that it holds 90oz or what ever and you can just weigh it in if you have no charge on the unit---but i am talking about calculating to weigh in the differance for the extra lineset---thanks

 

[STANCILHVAC]

Wheres the 50 coming from? 75-15=60.
But yes if you must butcher basic math 50x.6 would equate to 1 lb 14 ounces.

lol---just a brainfart on that--but i am just using 50ft as a simple enough referance

 

[clintkennon]

are you talking about weighing it in with no charge on the unit--i know that the unit will say that it holds 90oz or what ever and you can just weigh it in if you have no charge on the unit---but i am talking about calculating to weigh in the differance for the extra lineset---thanks

depends on the scenario. Install just add for extra line set. If the units totally empty for some reason charge the "90" oz plus the extra line-set.

 

[KirtusJon]

HEY---Anyone know the rule of thumb formula for weighing in the proper needed amount of freon for linesets over 15 feet,i have always went by pressures but trying to remember the weighing formula---say you have a 75foot lineset which is supposedly 50feet over for the factory charge,so i was thinking that the formula was then 50x.06--which would mean that it needed 3 more pounds?Can someone confirm if this is the correct formula or not,because 3 more pounds seems like a bit too much----i can charge it by the pressure,but was trying to remember this formula--thanks

Most manufacturers call for .6 per ft over 15 feet of line set. This is per ft of liquid line , if 3/8 OD copper.

Also you will lose a percentage of capacity because of the length of the suction line and will have to up size suction and sometimes the liquid to keep the capacity up, depending on length per manufacturer specifications.

Example Only:

Goodman 5 TON Unit
Line Set Equivalent Length 50ft 75ft 100ft 125ft 150ft
suction line size 7/8: capacity .93% .91% .89% .86% .84%
suction line size 1-1/8: capacity .99% .98% .98% .97% .97%

 

[STANCILHVAC]

Well, Its closer to 1/2 an ounce per ft not .06.your math is messed up I come up with 36 ounces (based on 60 extra ft). 2 lbs 4 oz. But besides that Ive always done it for 30 ft of lineset. so 45x.6=27 oz.
You should just use the charging chart, because now you've confused me too.

this has got way more confusing than it sould have--because now that just confused me---if you dont it for 30ft of lineset and come up with 45x.6=27oz---then are you figuring the whole lineset because they give you 15ft so it sould be 30x.6=18oz?

 

[STANCILHVAC]

Most manufacturers call for .06 per ft over 15 feet of line set. This is per ft of liquid line , if 3/8 OD copper.

Also you will lose a percentage of capacity because of the length of the suction line and will have to up size suction and sometimes the liquid to keep the capacity up, depending on length per manufacturer specifications.

Example Only:

Goodman 5 TON Unit
Line Set Equivalent Length 50ft 75ft 100ft 125ft 150ft
suction line size 7/8: capacity .93% .91% .89% .86% .84%
suction line size 1-1/8: capacity .99% .98% .98% .97% .97%

ok--i may of just opened up a can of worms that should of stayed closed--i know that to get the effieciancy that you are supposed to upsize the suction line--but for a moment lets just take that out of the situation and just say that we have 50ft extra lineset for a total of 65ft----ok now with that being said it then puts me back to square 1--you are saying .06,so is it .06 or .6?

 

[KirtusJon]

ok--i may of just opened up a can of worms that should of stayed closed--i know that to get the effieciancy that you are supposed to upsize the suction line--but for a moment lets just take that out of the situation and just say that we have 50ft extra lineset for a total of 65ft----ok now with that being said it then puts me back to square 1--you are saying .06,so is it .06 or .6?

Sorry here:

Extra refrigerant needed = (Linear feet of line set – 15 ft) Times X oz per ft.
Where X = 0.6 for 3/8” liquid tubing, 0.4 for 5/16”, or 0.2 for ¼”

65-15=50
(X).6oz x 50=30
Extra refrigerant needed = 30oz or 1lb 14oz

 

[McClintock]

I have delt with an American Standard dealer here local and with a question I always called then they have a program they put length and size and it tells you the additional amount of refrigerant to add. So you may check with your supplier. But always check the superheat and subcooling.