On a side note alot of those ductless splits are variblespeed compressors and fans so checking subcooling and superheat are out of the question based on the varible speed part of it. weighing the charge is the best method...... On those type of systems that is.
OK, first after all fitting were brazed shut. The tech should of put nitrogen in and took the pressure up to about 150 psi and wait about 30 min. If the gauge doesnt move then realease the nitrogen and pull the system in to a vacuum of at least 500 microns. Once reached let it set and watch the micron gage and see if it goes up. If it doesnt with it being a new install it shouldnt. Release the refrigerant and you are set to go.
Originally Posted by john_ertw
Last edited by kajer; 06-21-2009 at 10:38 PM.
Reason: miss spell
You still need to check superheat or subcooling.If you have a long line set you will need to add some freon.The factory may have shorted the system it never hurt`s to check the charge on a unit.
Is this really a new install? Tape on the TXV? Ahh... Anyways, definitely check superheat to make sure the TXV is working properly. Might want to give that company back a call.
I finally got around to calling the owner. The a/c has been performing well, but who knows if it is performing optimally.
I explained that I had concerns that the tech did not check a/c subcooling, used tape for the TXV bulb, and did not check the furnace's temperature rise or clock the BTU/hour usage.
I did not bother mentioning anything about a deep vacuum not being taken because I figured they can't do that if they don't have the proper equipment. I am kind of hoping that there was no moisture in the new lineset or other parts and that the filter-dryer does its job. Any disagreement here? What would you do?
He said he will send a different tech to do the checks. He thanked me for bringing it to his attention and said the tech that did the install is an excellent tech. He told me that he has seen the tech do all of these check several times in the past and was a little surprised.
I was expecting a bit of a fight, but he was quick to say he will send someone to do all the checks. Hopefully everything works out.
Anything to look out for when the new tech comes by? I want to let him do his job, but I don't want to obtain a new set of problems.
Does the CFM the blower is pushing make a difference in the subcooling value read? For example will my system have the same subcooling value if it is read when the blower is pushing 350 CFM and when the blower is pushing 450 CFM if all other variables are kept constant?
The reason I ask is that my system is currently set to push 1100 CFM for a 2.5 ton (440 CFM/ ton instead of the standard 400 CFM/ton). This is in to allow it to push some air to the 2nd floor of my house (2800 sq ft not including the basement). It seems that if my house was in the southern states I would have a much larger a/c requiring more air flow which will allow more of it to reach the 2nd floor.
Words to live by
Factories do undercharge some units, and overcharge others, it,s not really a big deal for the installer, but refer to the quote above.
Originally Posted by mb20fan