A quick, "How long is a piece of string?" type question.

As we know, the P38 has O-rings for all sorts of gubbins. I've done the valve block and the EAS is fine, I've got o-rings in the modulator upgrade kit, so no problem, but I really need to finish off my air-con installation and it needs rings for the new condenser and dryer joints before a re-gas. For this I'm told that I ideally need Viton (which seem to be a quite versatile 'general') ring or Neoprene (which don't) rings. Okay.

So the question is, my local hardware shop has a huge range of ring sizes but he has no idea what they are made of. If you were to go out and buy a 'box of o-rings, please' from a non-specialist place, what would you likely be getting?

A headache??

When I bought O-rings to do bits on my air con, I bought a mix pack from eBay with a quantity of a variety of different sizes.

From memory the best ones for AC use are HNBR, which is what my pack was. The RR sizes are a bit over the place, but I managed to find ones that fit OK for everything I needed.

Generic boxes of O rings are likely to be nitrile, which is your bog standard generic "does most things OK" material.
As you say- for aircon you really need Viton or Neoprene.
This page gives a good guide to what should be used for systems and why.
Have you tried http://manilaoilseal.com/ ? I know that Manila is a big place, but who knows, they might be in the next street from you or something?!
EDIT Marty's reply crossed mine in the post. HNBR will also work in aircon systems
Here's a more in-depth guide http://www.manuf-rubber.com/pdf/Material-Guide.pdf

Thanks for the responses guys.

Orangebean wrote:

Have you tried http://manilaoilseal.com/ ? I know that Manila is a big place, but who knows, they might be in the next street from you or something?!

Actually they're not a million miles away from me. I'll have a wander over next time I'm in that haven of peace and tranquillity that is Tondo (have a look on google images!). Madam has two houses there.

Thanks for the heads-up!

Hi GeorgeB, have you found suitable o-rings? If not, you can check out http://www.unigolden.com.ph -- they respond by email (though maybe not immediately). I picked up NBR o-rings from them a few months ago which I planned to use for the air lines in my valve block. I inquired about Viton, which they do carry, but not in the sizes I was looking for. But at least they seemed to know what the different materials are. They're in Caloocan, possibly close to an LRT station.

And now sorry to sort of hijack this thread, but would anyone know the real exact sizes of the EAS air line o-rings? I read somewhere that they were all 2.5mm thick. So o-rings are 4mm ID x 2.5mm, 6mm ID x 2.5mm, 8mm ID x 2.5mm.

So I picked up a bunch of those sizes from the aforementioned place (I emailed prior to make sure they had them). But upon fitting, the ones I got ran large. Both in ID and outer diameter (not sure if thickness was the same as the old ones, didn't have a caliper handy and it was difficult to eyeball). I chalked this one up to experience, don't deal with a local shop that maybe didn't have their inventory correct etc. Or at least bring samples...

However, just a few weeks ago I ordered another bunch of the above sizes (for the same purpose) from theoringstore.com. Check out the site, it does look professional and it seems they know their o-rings. After my valve block rebuild last Friday (using a rebuild kit), I opened the 8mm pack from theoringstore.com to replace the air dryer o-rings (I opened up the dryer to replace the dessicant). Lo and behold, the o-rings ran large! So now I think the local o-ring shop wasn't mistaken/wrong after all.

In my pic below, the 8mm O-Ring Store o-rings are on the top, followed by the "8mm" o-rings from the rebuild kit and the "6mm" ones also from the kit.

So, would anyone have the definitive word on the sizes?