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How far can the coolant lines travel between the compressor and the airhandler?

How far can the coolant lines travel between the compressor and the airhandler?

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  #1  
Old 06-13-11, 04:31 PM
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Question How far can the coolant lines travel between the compressor and the airhandler?

had a Carrier Puron Variable speed (FVCNB005t000) installed to a 2.5 ton condensing unit in my attic.

The lines run about 40 feet in all, (up the side of the house and across to the opposite side of the attic).

Under heavy heat load, the unit is blowing air no colder than 66F at the registers.

Is there "friction loss" with pressurized lines?

Could the heat of the attic (120F+) be warming the Puron before it hits the airhandler? Or warming the cooled air in the ducts before it hits the registers?

I'm installing a gable fan shortly and re-evaluating the insulation in my attic. I can't get the second floor cooler than 70 during high heat days and wonder if its a combination of problems.

Unit was installed professionally by mechanical engineers in November.

Thanks in advance for your help...
 
  #2  
Old 06-13-11, 06:58 PM
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the maximum length a lineset can be depends on the size of the unit 2.5 ton, and the size of the lineset. what is the size? for example, 3/4" and 3/8". I don't know the distance but im sure someone will fill in the gap. Also, how was it installed professionally by mechanical engineers? I mean if they are not HVAC techs and they aren't professionals... Getting the 2nd floor to 70 on a hot day is quite impressive.
 
  #3  
Old 06-13-11, 08:20 PM
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40 feet is well with in range. Sounds like u have other issues
 
  #4  
Old 06-14-11, 06:40 AM
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I can't get the second floor cooler than 70 during high heat days
I don't see a problem here.
 
  #5  
Old 06-14-11, 04:28 PM
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The limiting factor is the oil sump capacity in the compressor. You must also consider the slope and number of elbows in the line. Overall though I agree 40 feet should be fine and doesn't seem like this is your issue... it'd be good to get the charge verified though.

However... 70 degress on a 2nd story is pretty good... what's that compare to on your ground floor? Are both floors within a few degrees of each other? You stated the air is 66 degrees at the registers, can you measure what it's at right at your air handler fan? If you've got good insulation on the ducting I can't see the warm air in your attic changing the cooled air that drastically unless your air handler fan is underpowered.
 
  #6  
Old 06-16-11, 03:07 PM
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The air at the ground floor registers is 48 Degrees. A HUGE difference, so it is obvious the difference when you descend the stairs from upstairs. My home is an open contemporary with a large cathedral ceiling. The Master bedroom door is on a balcony overlooking the downstairs, within that cathedral space. As you exit the room, you feel a blast of heat, until you walk down the stairs to the second floor. I know it is impossible to cool that space, but I think the upstairs is underpowered and the downstairs over powered.

BTW, the bedrooms don't get cooler than 72-74 depending on which room, despite settings for less. When the 1st floor is 68, and the upstairs is 74.. that's a big difference.

Most of you think 74 is fine, but it is a humid 74...

Am I being too expectant of my system? is 70-74 the accepted temperature to obtain on a second floor with bedrooms during the day?
 
  #7  
Old 06-16-11, 08:10 PM
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You can get it to what ever temp u like but the system will need to be designed for it. You should be able to maintain 72 degrees with temps under 90
 
  #8  
Old 06-18-11, 01:59 PM
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is your return on the second floor? properly sized system is meant to give you 75 and 50%RH on a 95 day. see if you can get the fan speed lowered, that will help with the humidity.
 
 

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