# Lineset "Inverted Trap" Question



## Jim33 (Jun 1, 2011)

My AC is ready to go once the lineset is installed. This is a 50 foot line and the evaporator is about 15 feet higher than the condenser. 


I called a very reputable HVAC company (175 trucks). The technician said the 1 1/8" line size specified by the installation instructions was unnecessarily large. He wanted to used 7/8". Also, he questioned the inverted trap that the manual requires in front of the evaporator when it is higher than the condenser. I told him I preferred to do the work according to the manual and then he gave me a quote higher than the cost of the equipment.

You can see a installation diagram on page 3 here:
http://www.goodmanmfg.com/Portals/0/pdf/Tech Manuals/IO-GSX13C.pdf

1) Can anyone explain the reasoning behind the inverted trap when the evaporator is higher than the condenser. 

2) The install diagram shows 4 elbows brazed into the lineset to create the trap. I am wondering if simply arcing the lineset higher than the evaporator and back down to the connection is acceptable. Any thoughts?

Thank you,


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## carmon (May 8, 2010)

hhmmm not sure as to why... install instructions show it... I have never done it myself... i am interested in other responses:thumbsup:


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## beenthere (Oct 11, 2008)

Its to prevent oil from running down to the condenser/compressor during the off cycle, and then flooding the compressor with oil when it start up.

What size is your A/C.

Just because they have 175 trucks, doesn't mean they have 175 guys that know what they are doing.

The line set can be ran straight up from the air handler, and then ran toward where ever it will exit at, with a slope back toward the air handler.


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## Jim33 (Jun 1, 2011)

That makes sense.

It is a 3.5 ton, 15 SEER Goodman.

Appreciate your comments.


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## carmon (May 8, 2010)

beenthere said:


> Its to prevent oil from running down to the condenser/compressor during the off cycle, and then flooding the compressor with oil when it start up.
> 
> What size is your A/C.
> 
> ...


 That is good piping practice... an inverted trap on a system that small not required in my opinion... what does one think happens when the inverted trap fills with oil.... i would assume it goes back to the compressor as well... we all know oil travels but in a small system like that with no capacity contol to change refrigerant velocities i would not be to concerned ...slope pipe toward air handler as suggested is all i would do...


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## beenthere (Oct 11, 2008)

They are afraid it will collect right at the condense inlet during the off cycle, and flood the compressor and damage it, without the trap.


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## carmon (May 8, 2010)

beenthere said:


> They are afraid it will collect right at the condense inlet during the off cycle, and flood the compressor and damage it, without the trap.


 I suppose so.. never happened to me and of the thousands i have seen none have an iverted trap... i do agree a slope toward the evap on the suction line is a good practice:whistling2:


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## hvac5646 (May 1, 2011)

beenthere said:


> They are afraid it will collect right at the condense inlet during the off cycle, and flood the compressor and damage it, without the trap.


I think I won that discussion, didn't I, Been?:whistling2:


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## beenthere (Oct 11, 2008)

Many installers make an inverted trap without realizing they have done so. Probably a thousand of them a day.


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## beenthere (Oct 11, 2008)

hvac5646 said:


> I think I won that discussion, didn't I, Been?:whistling2:


There is no win. Thread starters can do what they want.


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## hvac5646 (May 1, 2011)

:laughing::laughing::laughing::laughing::laughing::laughing::laughing::laughing::laughing:


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