Line set size problem

[de63]

We have a leaking coil. About 9 years old, Trane 4ton. The tech noticed the suction line was spliced when installed new, but they spliced a length of 5/8 with 7/8. The whole run is about 80' with about half at 5/8". There is another problem in that the condensers were installed flip-flopped, so we've been running a 3ton condenser on a 4ton coil with 5/8 and 7/8 suction line for years. Add to that duct and plenum problems and you get the jist of my angst. I'm assuming the line set should be replaced,(?) it's just a bear to get to and running outside would look horrible even using a downspout or conduit. The condenser will either get replaced or swapped with the other which is 3 1/2 ton which has been running on a 3ton coil. Welcome to metro Atlanta new construction problems...

[kangaroogod]

For many reasons you should find a way to change that lineset.

[de63]

Thanks- looked at it some more today. They may need to cut a little drywall- but it's doable. Anything I should watch for to make sure they're doing it right? Is it standard practice to splice line sets (of the same size this time) or should it be one piece?

Thanks much

[Southern Mech]

80ft would most likely not be 1 piece lineset anyway's. I would let them cut the 5/8ths out and put in the 7/8th's.

[RyanHughes]

Thanks- looked at it some more today. They may need to cut a little drywall- but it's doable. Anything I should watch for to make sure they're doing it right? Is it standard practice to splice line sets (of the same size this time) or should it be one piece?

Thanks much

You can have a splice in your lineset. I agree with Southern Mech -- it may make more sense to just remove the 5/8" portion and replace it with 7/8", depending on the access. Lines should be fully evacuated using a micron gauge to ensure no leaks.

[beenthere]

They may have used the 5/8 to 7/8 to help the oil return to the compressor.

You may notice humidity changes when you put the 3.5 on the 4 ton coil, and when the 3 ton is put on the 3 ton coil.

[de63]

Humidity is important to control in GA. Which setup gives the best dehumidification? Keep in mind the unit cycles often in our hot summers. The first floor has a 3 1/2 ton condenser and 3 ton coil. Will putting a 3 ton condenser improve dehumidifying?

RE: line set to the second floor- the first five feet off the condenser is 7/8", then the next 40' is 5/8 which is mostly vertical up to the attic and then back to 7/8" horizontally to the coil for 35' feet or so. On paper this would not be good for a 3 1/2 to 4 ton unit, correct? If they did it on purpose, not sure why. If it is usable, it would save me some $$.

Thanks in advance for all insight

[beenthere]

Is it 5/8, or is it 3/4".

The 3.5 on a 3 ton coil may be giving you better moisture removal then a 3 ton on a 3 ton will.

[de63]

I measured them as 7/8" OD and 5/8" OD.

I may just leave the 3.5 on 3 then, scrap the 3 ton and upgrade to a 4ton, which is what the load calc called for. (3.8 anyway)

Thanks

[beenthere]

How well does, or doesn't the 3 ton maintain temp.

[lentz]

You might check the size again. Are you sure it is 5/8 and not 3/4?

[de63]

The system really only struggled for cooling on the hottest days. It dehumidified just okay but there are return air and duct balancing issues compounding the problem. The extremity rooms suffered the most of course.
I'll check the size again, the tech said 5/8". Could be 3/4". Good question.

[ga-hvac-tech]

I agree with the other posters: You really need the 7/8 lineset ALL the way between the units... builders do sometimes allow their subs to not do what should be done. Happens when granite countertops, SS appliances, and tile floors are more important than installed things like heat and AC.

Usually (but not always) a slightly larger coil on a properly sized outdoor unit (assuming the ductwork is sized properly) will provide better humidity control... however a VS drive furnace is the better solution.

The wise thing to do is start with the basics:
Load Calc, then duct evaluation, then equipment sizing. (Note if this were new construction, the equipment sizing would come second with duct sizing to fit the equipment).

Usually, when one tries to 'fix' something by 'working around' given parameters... they either live to regret it... or end up spending too much $$$ 'experimenting'... Neither is a good solution.

Go back to the basics, follow them, and you will have a system working as it should... to handle the load. And get a contractor that will do the same.