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AStudent
03-01-2012, 06:04 PM
From what I've been taught....most manufacturers recommend adding 3oz of refrigerant for every 5 foot of piping added to a system.

Would using 5 feet of hoses on your manifold gauges not screw up pressure readings since technically you added 5 feet to the system making it short 3oz of refrigerant?
jpsmith1cm
03-01-2012, 06:05 PM
From what I've been taught....most manufacturers recommend adding 3oz of refrigerant for every 5 foot of piping added to a system.

Would using 5 feet of hoses on your manifold gauges not screw up pressure readings since technically you added 5 feet to the system making it short 3oz of refrigerant?

Not if you remove the hoses.

You've then removed the excess "piping"
AStudent
03-01-2012, 06:08 PM
Sorry guess I should specify...would it not screw up the pressure readings on your manifold gauges while you are testing a system?

Or is it not enough of a change to matter?
jpsmith1cm
03-01-2012, 06:10 PM
Sorry guess I should specify...would it not screw up the pressure readings on your manifold gauges while you are testing a system?

Or is it not enough of a change to matter?

On a small, critically charged system, it can.
mjm88
03-01-2012, 07:30 PM
On a small, critically charged system, it can.

This is why we never hook up to critically charged systems unless your positive you have a refer issue. Also probably why alot of critical system don't have access ports...
hvac wiz 79
03-01-2012, 07:33 PM
This is why we never hook up to critically charged systems unless your positive you have a refer issue.

Exactly

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VTP99
03-01-2012, 07:38 PM
On critical charged systems i don't use hoses to check pressures.
Also it depends on how one sets there scale when charging.
VTP99
03-01-2012, 07:40 PM
[QUOTE=AStudent;12608871] manufacturers recommend adding 3oz of refrigerant for every 5 foot of piping added to a system.

Are you talking 5' of liquid line add 3oz. ?
AStudent
03-01-2012, 09:11 PM
[QUOTE=AStudent;12608871] manufacturers recommend adding 3oz of refrigerant for every 5 foot of piping added to a system.

Are you talking 5' of liquid line add 3oz. ?

I believe it should specify in the installation instructions what the manufacturers recommended tubing length is, and how much refrigerant to add per so many feet of tubing added past that.
AStudent
03-01-2012, 09:14 PM
That should be total system length not just the liquid line.
hvac wiz 79
03-01-2012, 09:18 PM
On critical charged systems i don't use hoses to check pressures.
Also it depends on how one sets there scale when charging.

What do you use?

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jnsrose
03-02-2012, 12:20 AM
Just the gauges with fittings.
VTP99
03-02-2012, 02:48 PM
Just the gauges with fittings.

:ditto:
hvac wiz 79
03-02-2012, 05:16 PM
Got a pic?

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FrostyBeer
03-02-2012, 11:45 PM
What's an example of a "critically charged" system?
AStudent
03-03-2012, 12:02 AM
What's an example of a "critically charged" system?

Pretty sure an ice machine is critically charged.
jpsmith1cm
03-03-2012, 07:47 AM
I was specifically referring to cap tube systems.

Very small coolers and freezers that don't have TXVs use cap tubes and the charge is very important to making the unit work correctly.

Ice machines are also very sensitive to charge.
ORV
03-03-2012, 12:55 PM
For the same reasons, I was told not to hook up gauges to a geothermal unit as well, unless there is a suspected problem with the refer. I was told if I do need to hook up, use a gauge without a hose, or maybe one of those 6" ball valve hoses.