Anemic Gas Roaster Performance When Set Up at New House [SOLVED]

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
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[creative nickname]
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#1: Post by [creative nickname] » Aug 08, 2019, 12:33 pm

I just moved this past Spring, and I was excited to set up my USRC sample roaster (natural gas powered, 1-lb capacity) in its new location. We were doing extensive renovations so I had the contractors route a hot-air vent straight up out of the room through the roof, and I had them set up an NG line for the roaster as well. Of course life has been super busy and I haven't been able to set it up in the new space until this past week.

Unfortunately, once I set it up something puzzling has been happening. I used to have more than enough power to roast as fast as I could ever want. I could do a full batch in six minutes if I wanted to, and I would routinely run batches in the 7-9 minute range. Now, however, the roaster struggles to get up to a normal charge temp (for me, usually in the 390-410F range), even with gas at a recommended max level of 4" WC and the air at a minimum level of 10%. I'm not seeing orange in the flame so combustion seems to be occurring properly, but it just doesn't seem to be heating up like it used to. And when I roast, even an undersized batch of 375g took a full 11 minutes to finish a city roast, with gas at max throughout and air at the minimum until first cracks, when I bumped it up to just 25% fan power.

My old settings would have never needed a gas pressure above 3" WC (typically dropped back during ramp to mitigate crashing), and fan typically ran between 60-85% to finish roasts at 7:30. So what could be up?

1. I think running a roast that slow with even minimal fan has ruled out that it is just a straighter run of vent pipe making effective airflow higher at a lower fan setting.

2. Could it be some problem with the gauge or the needle valve, so that what looks like a roast at 4" WC is actually running at a lower pressure.

3. Or ... something else??? Any suggestions from the wise folks around here?
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OldNuc

#2: Post by OldNuc » Aug 08, 2019, 12:41 pm

If this is not altitude related you have either a restricted gas line(not likely) or low pressure.

baldheadracing
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#3: Post by baldheadracing » Aug 08, 2019, 1:02 pm

Maybe a remote possibility, but with the roaster sitting for so long, it could be spider webs in the roaster's lines/burner manifold/burners.
What I'm interested in is my worst espresso being fantastic - James Hoffmann

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#4: Post by [creative nickname] » Aug 08, 2019, 1:23 pm

It's the same altitude as before. When I set up the roaster at this new house, I was getting pulsing in the flame levels. I turned down the regulator a bit (to around 8" WC incoming) to get a steady flame. Could that be the source of the problem? If so, how else can I mitigate the pulsing flame?
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OldNuc

#5: Post by OldNuc » Aug 08, 2019, 2:26 pm

How many regulators are in series? There is 1 out at the meter and there should be one at the roaster. Which one did you tweak?

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#6: Post by [creative nickname] » Aug 08, 2019, 2:34 pm

The one on the roaster...it is set to 8" WC, down from around 9" at the old house.
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Chert
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#7: Post by Chert » Aug 08, 2019, 2:59 pm

[creative nickname] wrote: 2. Could it be some problem with the gauge or the needle valve, so that what looks like a roast at 4" WC is actually running at a lower pressure?
or somehow lower gas delivery.

Do you dial the valve open more to achieve 4" in the new house compared to the new house?

I may be wrong, but I think the valve will be open more to deliver 4" WC from an incoming pressure of 7 " compared to an incoming pressure of 12", so perhaps your old house had higher delivery pressure and that is the difference?

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Almico
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#8: Post by Almico » Aug 08, 2019, 4:04 pm

How accessible are the gas jets? It is very easy to pick up a speck of dirt from a new line. It doesn't take much to clog a jet.

OldNuc

#9: Post by OldNuc » Aug 08, 2019, 4:26 pm

[creative nickname] wrote:The one on the roaster...it is set to 8" WC, down from around 9" at the old house.
The settings are not calibrated settings, just random indication. You need to know what the gas meter outlet pressure is set at and I would call the gas company and be asking questions. If the supply is set low the regulator at the roaster is useless. Some cities are at 2psi and others are at 6-7in h2o so this is the first thing to be asking. If the city gas is supplied at 6in h20 then the regulator at the roaster may be sufficiently restrictive that you will never get enough gas through it.

crunchybean

#10: Post by crunchybean » Aug 08, 2019, 5:04 pm

The guesses:

1) The quality of your gas could produce less BTU's. You would have to call the old and new utility company to get rating (# of BTU) and compare.

2) The venting situation could be the issue. And depending on that and the machine a lot of variables could change. Answer: you might have to readjust your fan settings. Maybe the clear (straight) vent is now causing more air to flow through.

3) Are all your burners working, did any get clogged by debris?

3) The room you are roasting in, is there a/c? Was there ac in the old house/location. The point of the question, did the average ambient room temp change? And relation to ambient temp, are the beans stored differently?

4) The voltage to the machine: did your drum speed change?