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David J 02-04-2013 04:06 AM

Evacuatiing a new installation
I am in the process of installing a split system heat pump. The system is precharged with R410A and having completed the mechanical and electrical installation, I now need to evacuate the system before releasing the charge. I am not handling the refrigerant, simply removing the air from the system.

I need to purchase a hose and a vacuum pump. I can locate these fairly easily (Ebay) but I am stuck when I try to identify the hose end connectors. Could some one give me some guidance on what diameter hoses I should use, and what threads the connectors are? The 1/4 inch SAE seems popular, but I have seen 5/16 inch and some refer to different flares on the pipes. The only clue that I have is the access connector on the system, which is fitted with a Schraeder valve and the coupling thread on this is about 1/2 inch across the threads (male).


hvactech126 02-04-2013 06:05 AM

If you are going to have the system charged professionally, then it would likely be cheaper to have the pro pull the vacuum rather than spend the money on gauges and a pump. The precharge is only for a specified length of lineset and on some equipment you must add more for certain evaporators.

David J 02-04-2013 10:15 AM

Thanks, hvactech126. I am installing the equipment and the piping supplied by the manufacturer without changing its length. I think that it is reasonable to assume that the refrigerant charge supplied will work with the finished system. If not, then as you say I'd need a professional.

However, I am only pulling a vacuum and checking that the piping will hold the vacuum; I am not handling the refrigerant and have no intention of doing so. Thus I just need a vacuum pump and a connecting hose. I can purchase both of these for less than the call out charge plus time of a professional unit (and could possible sell them later).

But I don't know what size of hose to get - which is why I asked the question originally. Is the size of the access point always the same on R410A systems? Is the 1/2 inch thread associated with 1/4 inch hoses?


Technow 02-04-2013 10:28 AM

Don't forget the vacuum guage that measures down to microns.....guages are pretty useless for determining vacuum.

What did you do with the excess length....and how long is the piping?

hvactech126 02-04-2013 11:46 AM

You need to add refrigerant after the vacuum. Just removing the hose will add air back into the system. You must release the refrigerant from the unit after the vacuum which will require you to at least have some sort of a valve between the system and the vacuum pump. Again.... having a tech do this will probably be cheaper than buying the necessary equipment to pull a vacuum.

beenthere 02-04-2013 04:39 PM

Is this a ductless split system?

HVAC1000 02-04-2013 11:14 PM

why do you want to buy a vaccuum pump for this one installation when you can have the pro do it for much cheaper?

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