Need advice on troubleshooting Santoker Revolution 500 heat issue

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
dogjamboree
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#1: Post by dogjamboree »

So I was one of a handful of people who ordered got in on the first batch of Revolution 500 roasters that Dustin Demers imported from Santoker, and I'm experiencing a major issue that neither Dustin nor the Leon at Santoker know how to fix. This is something that was happening from when I first fired it up, but I didn't have a chance to try the roaster when it first arrived.

The symptom is the roaster isn't getting nearly hot enough to hit any kind of decent milestones -- I can make first crack by 8 minutes with 250-300g of coffee, but any more than that and the roaster really bogs down. With a 400g charge the fastest I can hit first crack is around 11 or 12 minutes. I'm charging at 400f, and have experimented extensively with adjusting the damper, without an appreciable increase in the ROR. I've also verified physically that the damper is in fact working.

I've compared notes with Dustin, as well as a couple of other owners of the same machine (JavaMd, Jonny), and what I'm seeing on my machine is not a minor discrepancy...my machine is nowhere in the same ballpark as theirs. I had Jonny run a warm-up test to see how fast his machine got to temperature from room temperature, and his machine was about 25% faster than mine, and I started with a warmer room.

The first thing to mention is I can overcome this problem somewhat, but not completely, by turning the gas past the maximum indicated on the dial (5kpa). When I turn it to what would probably be 7kpa, I can achieve decent milestones with 400g of coffee, but with 500g or more It still takes 10+ minutes. In the profiles Dustin posted, his 1kg roasts are as fast as my 400g roasts.

Leon at Santoker first recommended I try adjusting the set screw on the gas gauge, but when I asked him how to get to it to adjust it he said he didn't know as he'd never tried. As I looked into it further, it appears that screw is just a zero adjustment, so I don't think that's the answer. It's possible that the meter is just broken, but without buying a new one I'd have no way of knowing that (Leon didn't really offer any other help and didn't offer to ship me any parts to help troubleshoot).

It also occurred to me that if the propane jet orifice is too small that could create additional back pressure, causing the gauge to show higher pressure than others are seeing, but providing less flame. Again, not sure how to verify this without the support of the OEM. Assuming the jets aren't too hard to remove (they appear to be affixed with some some of loctite), I could probably try and find a jet with a bigger orifice that would fit the roaster, but I haven't looked into that yet.

Dustin recommended trying to charge at 500f instead of 400f, but assuming that even works, it seems like a major compromise on a roaster that was supposed to be able to work with a normal charge temperature. Also, I'm assuming that would speed up my drying time way past where I want it to be (goodbye experimenting with 5 minute+ drying per some of the threads I've read recently).

Does anyone have any other suggestions for what could be wrong? I'm sure that without knowledge of this particular roaster it's a long shot, but I figured I'd ask. Also, I'm in Portland OR so if anyone knows of someone who knows roasters and does repairs I'd be willing to pay to get it fixed. Santoker didn't really offer much help, so that seems like a dead end (Leon, the guy in charge there, seems like a nice guy and chatted with me for a while, but couldn't solve my issue and didn't offer any additional advice). I had a long phone call with Dustin where he offered some suggestions, but without being able to see the roaster I think it's pretty hard to troubleshoot.

Thanks,

Frank

dustin360
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#2: Post by dustin360 »

Post some times and temps as well as milestones and airflow/gas/and rpm settings. That should give a better idea of what the roaster is doing.

*also maybe try the higher charge temp before dismissing it. The actually temp doesn't matter, its more to set up timing for the rest of the roast. So if it sets a timing of 2 min to yellow, and then 7 to first obviously something is very wrong.

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hankua
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#3: Post by hankua »

I'm thinking you should work the problem from the jets back to the propane source. Everyone has the same jets right? Is the distance from the jets to the drum the same? Is their any restriction in the gas piping going to the jets? Then the gas valve?

dogjamboree (original poster)
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#4: Post by dogjamboree (original poster) »

Here's a 400g roast I did at 75rpms. Charge didn't register immediately on the graph, but it was about 405f. I had the heat around 4 during the drying phase, and immediately cranked it to 5 kpa (maxed) when drying ended. I don't have the exact airflow I used, but I believe I had it around 5 for the entire roast, which was what gave me the fastest ROR.

This was the third roast of the session, so the roaster was plenty warm, and room temperature was 70f.

I'll post the roast where I had the gas at 7 kpa next.


dogjamboree (original poster)
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#5: Post by dogjamboree (original poster) »

Here's another 400g roast, 75 rpms again, 395f charge temperature. I had the heat a little over 4 during drying then cranked it to what would probably be 7kpa (way off the marked gauge) for the rest of the roast. Airflow was around 3 during drying and then turned up to 7, which again was where I was able to get the best ROR.

These numbers don't look bad to me, but I don't like having to turn the gas to the point where the needle is pinned to the side of the gauge, and I know others are able to get a faster roast with a bigger batch.

After this batch I tried one with 500g, with the gas at 7 kpa again, and FC was around 10.5 minutes.



Note, all roasts are logged with thermocouples I installed myself, but they much more closely match the temperatures I associate with my observations (sight/sound/smells) than the stock ones. Stock ones read between 15 and 25c lower than these, so everything would actually look way worse if I went by those.

dogjamboree (original poster)
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#6: Post by dogjamboree (original poster) »

Hank, the gas line inside the roaster is rigid tubing and doesn't appear to be kinked or blocked, at least that I can see. If the gauge is accurate then it's got to be after the gauge, right? Jets seem like the most likely suspects to me, but it seems unlikely that they'd both be wrong. One flame is slightly bigger than the other one, but not by a large margin.

Dustin, I'll try a higher charge temperature to see if it gets me closer to where I want to be, but my goal is more to get the machine to perform as it's supposed to rather than work around what seems like a defective machine. I waited a couple of weeks before posting here to be sure that I wasn't doing something wrong, but I'm 100% confident now that it's the machine, not me.

The roaster arrived with a decent sized dent in one of the panels that I sort of doubt is associated with this behavior, but maybe it's worth mentioning. Maybe it's associated with a drop or fall that caused this heat issue...

chang00
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#7: Post by chang00 »

The Santoker I observed, at vent opening of 3-4, the roast will completely stall. With the vent open wide at 7, heat may be lost.

Try vent level at 0-1 during drying, then heat up and vent 3-4 only for one minute at 150-160c to let out the chaff, close the vent, then open slightly again at 3-4 about 2 degrees prior to expected 1st crack temperature and see what happens.

I alway ask people to observe the "equilibrium" vent/gas pressure combination with a new roaster. That is, at which combination of vent and gas to stall the temperature gauge at particular load. This will also be the point to get that "Scandinavian" roast profile that is discussed about.

sonnyhad
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#8: Post by sonnyhad »

I can only suggest that you may have a faulty regulator, the symptoms suggest that its a gas delivery problem. Does the flame look the right color? Like a good combination of air and gas?
LMWDP 437

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hankua
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#9: Post by hankua »

Totally agree with everything Henry said, and that's how I run my roaster. But you should be able to basically replicate a profile the other Santoker users have success with. The Mini500 machine pressure gauge tops out at 3kpa and I rarely go over 2kpa on a one pound roast. With 5-6kpa you've got twice the heat capacity we've got.

When my machine was new I encountered heat related problems. One gas valve was adjusted too low, moved the burners up a tad (probably not necessary), most importantly used low air as Henry suggested.

dogjamboree (original poster)
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#10: Post by dogjamboree (original poster) »

Thanks for the replies -- I'll play with the damper some more. I've tried roasting with the damper in a more closed position, but maybe I didn't give it enough of a chance. I'll see what happens and post the results.

frank

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