FAD/CFM for spraying

[seanc]

I want to buy a compressor primarily for spraying. It will be used for small panels/engine bays. I wont be doing complete cars or anything. I will more than likely use cellulose as I dont really want o be worrying about isocyanates and dont want to spend out the extra money on kit for the small amount of use it wall all get !

Im just wondering what FAD/CFM would be recommended for my needs and what kind of tank capacity. I was thinking around 14cfm and 150 litres.

 

[shenion]

14CFM/3HP should be good for most small guns (about 10CFM FAD).

My cheap-o HVLP gun says 7CFM but i run it a bit higher. If you have a gun in mind, it should say how much it needs.

My compressor has about 9.9CFM @ 90 PSI and can run my gun all day long 60 gal / 227L tank).

Tank capacity is not a big deal if the compressor is big enough. A bigger tank will cool the air more and have less of a problem with condensation.

 

[jayg]

short answer, yes that compressor will be ok for your needs.

longer answer,
if all you are painting are smaller areas as you say, then it's worthwile getting a smart repair/touch up gun instead of a full size gun, ideal for painting single panels and getting into tight spaces such as engine bays etc... some full size hvlp guns can need 15/16cfm fad to run them depending on the gun set up and can struggle with a 14cfm compressor (around 10cfm fad) if painting a full car, although you would be ok only using them for small parts/areas. smaller touch up guns use around 5-7cfm fad.

if you decide on a smaller touch up gun then go for at least a 1.0 set up or ideally 1.2,
most you see for sale are 0.8 wich is a bit small for such areas.

i recommend devilbiss sri or sri pro, excellent guns if a little pricey but can be had second hand for between £50 - £100 ideal for your needs and compressor friendly. excellent finish straight from the gun too if set up right.
plenty of cheaper ones available though.

 

[Chipper]

3hp/150 would be good, is about as big as can be got for sensible-ish money on single phase. As Shenion said your 14cfm there will be displacement, not FAD.
For just engine bays you could get away with less comp and a mini-gun, but it just makes sense to buy the most compressor you can. I've got a little gun that only needs about 4cfm, but have also had one that said 9cfm (HVLP mini).

 

[seanc]

found a very cheap 3hp 11cfm (8 cfm free air) compressor but its only 50 litres !
If i was to get a decent gun like the devilbiss sri that only requires about 4cfm would the 50 litres be enough ? would it be possible to hook up a secondry tank if not ?

 

[shenion]

Tank size is not a big issue if you have enough CFM.

You can add more tank capacity. One issue is real cheap compressors may not have enough cooling to run the long time to refill the larger tank. I have not seen this limitation with belt-drive compressors, just all-in-ones. Really, any decent compressor should be rated to run continuously.

With 4CFM on an 8CFM rated compressor, it should run 50% of the time while spraying. 50L is 13 gallons. My first compressor was 11 gal and worked fine.

 

[bigtip]

50 litres is 11 gallons this side of the pond old chap