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View Full Version : To Lag or not to Lag that is the question?


Jasper
22-04-2007, 08:22 AM
Scenario.

Downflow close control units, pipework running in floor void for 10M, pipework running externally for 10M to remote condensers, liquid and hot gas lines have been insulated!
Can any of you explain any benefit of this practise.

I have become aware that this is standard practise with some company's.

Your comments wopuld be greatly appreciated
Peter_1
22-04-2007, 12:15 PM
Not insulated will give an additional heat load to the room, you can burn your fingers when opening the floor, cables passing over the hot discharge lines is dangerous....
US Iceman
23-04-2007, 01:53 AM
Sometimes the insulation is used for personnel protection to reduce the chances of getting burned. In other cases, the insulation is used to reduce surface condensation of water or heat gain in suction and liquid lines.
Jasper
23-04-2007, 10:54 AM
Would you consider that by insulating the liquid line this will have a detrimental effect on the operation of the system due to a lack of liquid subcooling?
US Iceman
23-04-2007, 03:55 PM
Would you consider that by insulating the liquid line this will have a detrimental effect on the operation of the system due to a lack of liquid subcooling?


If the liquid line is warmer than the ambient air the insulation would help to keep the heat in the liquid. This could be detrimental.

In this example by not insulating the liquid line the heat could be rejected to the lower temperature air which would help.

On the other hand, if the liquid is cooler than the ambient air you would want to insulate the liquid line to prevent heat gain.

It all depends on which way the heat transfer occurs.
Franzfernando
23-04-2007, 08:51 PM
on a liquid line without a device fitted to aid subcooling the subcooling itself will be very small as to be neglible.
therefore the insulation will aid the system
alexdouglas1969
23-04-2007, 11:28 PM
Is this a heat pump?
Jasper
24-04-2007, 06:03 AM
Not a heat pump, just straight cooling, remote condenser.
nh3simman
24-04-2007, 05:48 PM
It's generally about energy and moisture.

If the line is hot, it will loose heat. If this heat is rejected to the controlled space, it will add to the load.

If the line is below the surrounding air "dew point", there will be condensation, and uncontrolled, moisture is always a problem.

From a system point of view, a heat gain to the liquid line could cause flashing at the expansion valve. But not in your case since the underfloor is cooler than the liquid line.

As mentioned by others, there is also the safety aspect. Probably the main reason for the lagging in this case.