My evaporator coil is in the attic 17 feet above the condensing unit which is of course common. I was told that elevating it to the roof would lower my energy bill since the compressor would not have to pump liquid refrigerant up 17 feet. Is this true and how significant is it? Thanks.
I'm no A/C expert, but the freon is in a closed loop. It is liquid going up and vapor coming down, but it is the same total weight coming down as going up.
I am not aware of any power savings for moving the condenser onto the roof. I would not do this to save power as there are multiple issues.
Elevating the condenser would require properly traping the lineset to keep oil where it's supposed to be.
Also, the ambient temp on the roof may be higher than on the ground and actually cause the unit to use more power, not less.
I've seen more hail damage on roof units than on the ground.
Some service companies charge more for servicing a unit on the roof vs the ground.
The pluss side would be:
Unit would be less likely to clog with grass clippings/yard debris (cottonwood would stop it up no matter where it is)
Unit is less likely to be damaged by dogs or kids.
Overall, if I had a choice, the unit would always be on the ground.
Never knock on Death's door. Ring the bell and run, he hates that.
Views expressed here are my own and not neccessarily those of any company I am affiliated with.
The refrigerant lines need to be sized according to the location of the outside unit in relation to the inside unit and length. You can have a capacity loss for longer lines if not properly sized. Most of the times the manufacturer has charts which will show how much capacity loss due to length compared to the size of line used. You can have more expense later due to roofing. If you have to remove the unit to replace the roof, it might cost more than the operating cost incurred on having the unit on the ground. Also, service could take longer to clean unit etc..
But, yes shorter lines are generally better.
Would the unit run cheaper if the condenser and evaporator were at the same level? Yes. Could you see the difference in your electric bill? My guess is that in a normal years worth of running it would save enough electricity to light a 100 watt lightbulb for a day or so. You can save a thousand times more by making sure the units coil is kept clean as it sits on the ground.