I recently had the opportunity to upgrade my USR Sample roaster to a used 3k roaster at a price I could not resist. The previous owner operated the machine on nat. gas, so I had to convert to propane. The learning curve is steeper than I expected, but I am still trying to determine how high maximum gas pressure should be. (the machine has an adjustable controller). If I use the max. pressure the controller will allow, I get a fairly rich gas mix and see more yellow flame than I would like and get soot on the drum.

So, in order to get some idea of a benchmark from any users of the same roaster, how long does it take to warm up a cold machine to @ 350°F? Or, what RoR is reasonable for an empty machine?

It sounds like your propane conversion didn't come out right to me if you're too rich. I am on propane and can crank it all the way and still get a pretty clean blue flame and definitely no soot on the drum. Did you order the kit from USRC?

As far as pre-heating. I heat on 1/3 full pressure to try to instill a bit of thermal mass, rather than get 350° ASAP. It takes ~15 minutes to get to usable heat.

I was hoping you would answer. Yes, I am getting help from USRC and used their kit. My machine does not have a pressure gauge installed, so that may be an issue, but it's the same hook-up I used with my sample roaster with no problems.

I just don't know how much yellow is "normal". I may try to clean the burner jets with a small wire, as only some of the jets are yellow at the tips. You answered my bigger question about time to warm - I agree that I don't want to race to warm as there is a lot of mass to bring to temp. I'm in that 15 min range at about 40% gas.

I am amazed at how much difference the damper at the feed chamber makes in ET rate. The air adjustment is the biggest difference I've found so far.

Ol'Timer wrote:I am amazed at how much difference the damper at the feed chamber makes in ET rate. The air adjustment is the biggest difference I've found so far.

I'm running air by rheostat only so I can't speak to the damper adjustment. I do keep my air changes to a minimum using minimal air for most of dry and ramp and ~full air from 1C to dump.

I agree with your comment about how much difference a change in damper can have. I'm finding if the flame is at the right setting, fine control with the damper is very effective.