On Saturday, May 6, 2017 at 2:47:02 PM UTC-4, wrote:
On Saturday, May 6, 2017 at 2:34:29 PM UTC-4, rangerssuck wrote:
On Saturday, May 6, 2017 at 11:27:49 AM UTC-4, Ecnerwal wrote:
In article ,
rangerssuck wrote:

So, given that I have a system that's shut down and pumped out, and that I
can isolate the rink floor pipes from the rest of the system and there are
service valves accessible, does anyone know how I might determine the volume
of these pipes?

Nitrogen is cheap and cheerful. CO2 might be another option, not sure if
it plays havoc with refrigerants (but you'd be pumping it back out
anyway - if you can handle the pressure sit's a nice cheap refrigerant
itself, IIRC.)

I also don't know what the ramifications of filling the system with CO2 would be. I was planning Nitrogen or Argon - Nitrogen is almost certainly cheaper, but Argon would be good to have for other (tig) reasons. [while we're on that subject, here's a guy who is making his own liquid nitrogen. http://www.instructables.com/id/Home...gen-generator/ ]

If you've drained the system, and if you know it has leaks, what gas do you figure is in there now?

If it's drained and if any remaining drips of refrigerant have had time to evaporate in a leaking system, the pressure in there went to atmospheric pretty quickly. Then I would think that you're beginning to get air into that system, from that moment on.

--
Ed Huntress

Actually, we had it pumped down to -10 psi for three or so hours. That was over a week ago. I went in today and opened the system and unscrewed on of the valves (which is going to be replaced) and just got a little puff of positively pressurized gas. NOW it's atmospheric

The vast majority of the leakage is (I'm pretty sure) from the compressor shaft seals. Also, every one of the 50+ valves has leaky packing. There are at least two welded pipe connections that leak. I have a busy summer.