pump down heat pump to replace a/h

[xe1000]

I have a newer Carrier 10seer heat pump on roof, iam replacing a/h, but want to pump refigerant into condeser instead of recovering, line are about 30 feeet, heat pump is on roof 2-1/2 ton 10 seer replaced by other co. 6-years ago, the air handler being replaced is a Carrier replacing because of mold forming, you guys think condenser will hold all of this refrig. with 30"-35" lineset, with out problems? Thanks. "GET UR DONE!"

[hvac hero]

If it was me, I'd pump it down but not all the way. I've heard its bad on the compressor to pump it all the way down. I'd pump it down to about 20 lbs of suction & then recover the rest.

[millerman]

This is a good question. If you pump the system down your pumping down what others have done. Evacuate the system, install new filter drier and weigh in your charge according to line set length and manufacturers specs for additional line set. The only time we pump a system down anymore is if we are replacing the outdoor unit.

[millerman]

PS; what is the elevation differance between the HP and air handler? Most manu's require a trap at 10'.

[drk]

Don't understand why you don't clean up the AHU! this will be a lot cheaper than replacement!

[RoBoTeq]

There's a good chance of damaging the compressor if you pump down too low. Even better chance of damaging it if it is a scroll.

Ever see a unit where the fusetite has blown out and all of that nasty, burned oil is all over the place? That is usually the result of a compressor operating in a vacuum.

[xe1000]

thanks as far as weighing Ive never weighed in a charge, go by exp. of pressures and or the hot gas method, the o.d. added never had to go back, do about 275 units a year here in Boston, Iam just use to them, i guess. I now abouthe scroll, just itys easy if pump down to about 10psi if its a scroll forget it, but ts not then when I replce a/h just evac. break valves allset. The reason why I asked I know the newer units are good for 15 feet of tubing some 25' this lineset is about 30'-40' thats why I was conserned about condenser holding (with accum. ) the charge with out any damage, someone metioned cleaning up, the a/h is 18 years heat pump cond. been replaced recent, the mold is all over insulation on walls of a/h, the bower wheel, drain pan, electric heaters, drainpan, base of unit, I know Idont want to be exposed never mind homeownwer, ho saw it wants it replaced she has been sick alot since she moved in two years ago. $$$$$$$$$$

[coolcray3]

if the ah is that bad how about the ducts they have to be a pretty site also.as for pumping it down did a brynt today no problem but the run was short and didnt let it bottom out stopped at about 10psi.