Heat Pumps and Electric Heating - would a 5/8 vapor line likely cause problems?

what could an undersize line do? 5/8 on 3ton. the previous ac guy saved a few bucks thinking, at first, that a 1.5 ton would do it.

It would void the warranty for one. The longer the line is, the more exacerbated the problems would be. Maybe it would be no problem on a ceretain day under certain conditions. BUT, if the system was designed to work with a certain line size, ther will be problems from going smaller. It will be difficult to check pressures and superheat/subcool as there will be a pressure drop between the evaporator and condensor. That will skew the numbers one way. If it is a heat pump, the numbers will go the other way in heat mode. There is no way a manufacturer would spec more copper than was absolutely necessary because it makes the system more expensive to install and they are all about keeping the cost below the competition. So you may be better off to go up a size than down. If an installer starts going into the engineering business, he will be backing up his Frankenstein monsters with his own warranty and not the manufacturers. If he doesn't come back after the problem persists, you will have nowhere to turn and least of all to the manufacturer.

Ken

It would void the warranty for one. The longer the line is, the more exacerbated the problems would be. Maybe it would be no problem on a ceretain day under certain conditions. BUT, if the system was designed to work with a certain line size, ther will be problems from going smaller. It will be difficult to check pressures and superheat/subcool as there will be a pressure drop between the evaporator and condensor. That will skew the numbers one way. If it is a heat pump, the numbers will go the other way in heat mode. There is no way a manufacturer would spec more copper than was absolutely necessary because it makes the system more expensive to install and they are all about keeping the cost below the competition. So you may be better off to go up a size than down. If an installer starts going into the engineering business, he will be backing up his Frankenstein monsters with his own warranty and not the manufacturers. If he doesn't come back after the problem persists, you will have nowhere to turn and least of all to the manufacturer.

Ken

Ken
i could not confirm your comments. all i could find is that a smaller line impairs efficiency. sorry.
My 3ton w/5/8 likely lost 1-5% btu's. New 13 seer use 7/8 to squeeze a little more efficciency. Up from 3/4 as specified for my old 9 seer.
after 19 years there is obviously nothing serious as you suggest. sorry.

I think what you mean by serious is that the compressor didn't burn up. The efficiency loss you mention would be due to the lack of refrigerant flow. However, unless you actually calculated delivered btus, you probably had more efficiency loss than you thought. The charge would have to be weighed in on a system like that because pressures would be a little off due to the line friction being different than the manufacturers design expects it to be. Therefore, setting the charge based on superheat or subcool will lead to an overcharge/undercharge. From a contractors perspective, I like to take advantage of all the testing that the manufacturer does to assure that a system will perform at its best efficiency for a long time. I don't want to experiment and have to babysit a system that doesn't work properly.

Ken

Ken
i could not confirm your comments. all i could find is that a smaller line impairs efficiency. sorry.

Your question was answered but your comments appear to be baiting us to start another debate.

This forum is not for blogging offbeat ideas.