Why Should need to insulate the GAS Line? 5

[Jamsith]

Hi Dears,

Hope you all fine,
Now I am working as a junior project engineer in the HVAC installation and maintenance company. This is my earlier period and the time for learning. So I have many doubts from the theory what we studied in our universities.

As I raised question in the title. Why should we need to insulate the GAS Lines ? because the gas line starts after it takes heat from the evaporator (Cooling coil), anyway it will go to the compressor. There it will raised to high temperature as well High pressure. we should need to insulate the pipes after the Evaporator only as I understand since low temperature. Please explain me.

 

[trashcanman]

Consider the refrigeration cycle:

1. Hot high pressure liquid goes to the expansion valve at the cooling coil.
2. The liquid is throttled to a low pressure cool liquid. (Jhoules-Thompson effect).
3. Low pressure liquid picks up heat from the air/water flow and warms up and boils to a cool low pressure gas. Remember, change of phase does not change temperature of the refrigerant.
4. Low pressure cool gas then goes to the compressor to become a high pressure hot gas. (Picks up heat of compression).
5. High pressure hot gas goes to condenser where it gives up heat (to atmosphere or water) to become a high pressure hot liquid.
6. Go to 1.

Now, the condenser is sized according to the cooling capacity of the cooling coil and the heat of compression. It is NOT sized for heat picked up by the low pressure cool gas (gas line). If you do not insulate the gas line, you are penalizing the efficiency and losing cooling capacity. That is why you always insulate the cool gas line.

 

[itsmoked]

Continuing on trash's fine response the remaining after-the-evaporator cool gas is needed by the compressor to cool its motor windings. Furthermore, if you don't insulate that line it will condense water that will drip off it over its entire length causing lots of other grief.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Jamsith]

Thanks Mr. Trashcanman & Itsmoked,

by the above your support now it's clear for me that the insulation for the compressor suction line, will avoid the condensation of moister in the atmosphere and we need cool gas to cool the compressor.

but some systems like VRF they do have the EXPANSION DEVICE in it's EVAPORATOR means INDOOR UNITS, In this case the hot liquid refrigerant will flow from the condenser to expansion in a long pipe from outdoor to Indoor. why should we insulate this hot liquid line? It's already hot even if we don't insulate it will dissipate the heat to atmosphere, so this will reduce the work for the EXPANSION DEVICE.

Please clarify me.... I am in need....

 

[Compositepro]

The liquid line will follow the same route as the vapor line. Strapping the two together and insulating over both lines together creates a heat exchanger that pre-cools the liquid before expansion. While this is not essential it does increase energy efficiency and really costs nothing.

 

[berkshire]

For the most part line sets are supplied with the return line pre insulated and the supply line bare, air conditioning contractors tend to just zip tie the two lines together for convenience, leaving the supply line bare. Some refrigeration contractors insulate both sets. Since the contractors tend to run the lines in unconditioned space for the most part it does not make much difference.
B.E.

You are judged not by what you know, but by what you can do.

 

[SAK9]

A different perspective:There is no harm in heating up the suction gas line a bit as it helps to remove the last traces of refrigerant liquid in suspended state and make the vapour dry.There is a benefit in doing it.Think about it and tell me what could be the reason

 

[KesTheHammer]

Please bear in mind that an AC is not always in Heating mode or in Cooling mode.

Usually, ambient air will help you one way (if you are in cooling mode, rejecting heat to the atmosphere en route will help you), but in heating mode, the flow is in the other direction, and now rejecting heat is a bad thing, because you want to heat the room.

With the exception of cooling only equipment (such as a freezer), it is good practice to always insulate both lines.

Kestell Laurie
South Africa

 

[GT-EGR]

It’s basically been covered here, but to sum it all up the main reasons are

Condensation may form on the piping and eventually drip somewhere you don’t want it

You are adding heat to the system that it wasn’t designed for, so now the system is wasting energy cooling an area you didn’t intend it to

Compressors have specific maximum temperatures that have to be maintained to keep adequate cooling - so if you pick up too much heat after the evaporator you end up with higher temperatures that may put your vapor out of that range, reducing the compressor life