%95 of the time the A/C change outs are 2 to 5 ton Max. What CFM Vac would fit just fine. I talked to a few guys and they use the robinair 6 CFM and I thought that was over kill. But is over kill a bad thing on Vac pumps :-)
What CFM is everyone using ?
- Brad J. -
Most of the units I work on are 2.5-3 ton (we install up to 5 ton on some houses). Occasionally I'll work on a bigger rooftop that'ls 10ish or so ton.
Yeah, it's over kill, but it does the job. Personally unless I was working on really small stuff (like appliances and what not) I wouldn't use anything under 3cfm.
Regardless of the size of the pump you are using, you are still sucking it out through a 3/16 hole (1/4 flare).
An interesting exercise on a cappillary system. Hook up an electronic vacuum gauge to the high side and just pull the vacuum from the lowside access port. The result should make you think!
if your talking residential, 30 foot runs, a six is definately overkill. And yes, it can cause problems. Moisture can become frozen inside the system lines due to dynamic evacuation.
but for the most part, your not pulling down lower than 1000 microns anyway.
a larger size vac pump is used for the free air the lines would contain.
And once you get that free air out, the rest of the vac pump's capacity is not being properly utilized.
we would all be much better off if we carried 2 CFM pumps and used multiples placed at various points along the system.
Now THIS would be intelligent!