More powerful heating elements for Quest M3s
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bmralex
- Posts: 27
- Joined: 7 years ago
Hi,
The latest model of the Quest m3s roaster is equipped with ~10A heating elements (1100 total wattage). However, the standard domestic power mains in the US supports up to 15A. I am wondering if anybody tried to replace the standard heating elements for more powerful in order to increase the batch size.
Thanks
The latest model of the Quest m3s roaster is equipped with ~10A heating elements (1100 total wattage). However, the standard domestic power mains in the US supports up to 15A. I am wondering if anybody tried to replace the standard heating elements for more powerful in order to increase the batch size.
Thanks
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Nunas
- Supporter ♡
- Posts: 3683
- Joined: 9 years ago
I have not done what you suggest, but opine that it would not really be worth the bother for several reasons. A standard 15-ampere circuit should not be loaded to 1800-Watts (120-Volts * 15-amperes), which is the theoretical, maximum, momentary load. In practice, it is good engineering to load to 20% below this (1440-Watts). Manufacturers stretch this a bit, but not usually to more than 1500-Watts for resistive devices. The extra 20% capacity on the circuit allows for normal fluctuations in line voltage, power surges, plus an allowance for sag in the breakers. Most breakers are magnetic and their capacity gradually drops over time (breaker sag). So, you could perhaps increase the elements to 1500-Watts at the most. For a typical roast of ~15 minutes or so, that's only an additional 340 btu.
Turning to product design, I'm not sure that you would be able to safely use that additional capacity anyway. Although I don't know the theoretical maximum heat the Quest can take, I tend to keep the MET in mine at or below 250-degrees C (480 F). The stock elements have no trouble going beyond this temperature, even with a much larger charge than is suggested for the roaster.
Which brings me to the real capacity of the Quest. The instructions suggest that it is less than a half-pound roaster (150 to 200 grams being mentioned as I recall). I've gradually increased my batch size to 250 grams (half a pound) without any trouble, which is the batch size I usually roast, doing two batches for a 1-pound bag of greens. A while back I bought some coffee in 2-pound (910 gram) bags. I divided these in thirds, roasting a little over 300 grams at a time. To my surprise, I had very little problem following my desired profile. Just for fun, one day I tried 400 grams (about 14-ounces). While it was a bit of a struggle to make profile, the results were still reasonably good. I thought I'd have baked coffee, not roasted coffee. I've not pushed my Quest any farther (mine is a MK-II with the thinner drum and the trier on the right), as I suspect that the limiting factor now might be the quantity of beans in the drum, not just that I've found the maximum batch size for the heating elements. Don't know for sure...just an educated guess. Looking at the size of the vanes and imagining how the beans flow to the front of the roaster before tumbling over, I suspect that anything bigger, even if I had enough power, would not roast evenly.
Turning to product design, I'm not sure that you would be able to safely use that additional capacity anyway. Although I don't know the theoretical maximum heat the Quest can take, I tend to keep the MET in mine at or below 250-degrees C (480 F). The stock elements have no trouble going beyond this temperature, even with a much larger charge than is suggested for the roaster.
Which brings me to the real capacity of the Quest. The instructions suggest that it is less than a half-pound roaster (150 to 200 grams being mentioned as I recall). I've gradually increased my batch size to 250 grams (half a pound) without any trouble, which is the batch size I usually roast, doing two batches for a 1-pound bag of greens. A while back I bought some coffee in 2-pound (910 gram) bags. I divided these in thirds, roasting a little over 300 grams at a time. To my surprise, I had very little problem following my desired profile. Just for fun, one day I tried 400 grams (about 14-ounces). While it was a bit of a struggle to make profile, the results were still reasonably good. I thought I'd have baked coffee, not roasted coffee. I've not pushed my Quest any farther (mine is a MK-II with the thinner drum and the trier on the right), as I suspect that the limiting factor now might be the quantity of beans in the drum, not just that I've found the maximum batch size for the heating elements. Don't know for sure...just an educated guess. Looking at the size of the vanes and imagining how the beans flow to the front of the roaster before tumbling over, I suspect that anything bigger, even if I had enough power, would not roast evenly.
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EddyQ
- Posts: 1043
- Joined: 8 years ago
That is very interesting Nunas. Thanks for that info.
I'm rather new to the Quest and have inched up to 250gms with no issues with some Brazil beans (these beans get ashy very easily).
Based on different profiles/beans I have tried, the batch size might be limited when you attempt a very fast profile where charge temps must be very high in order to achieve the correct turning point temp and then high heat to FC. In this case, I suspect your ET would exceed your threshold.
The larger the batch, the higher the charge temp must be for the same turning point temp. I suspect at some level of charge, even the dense beans will face and scorch. But with a low density bean such as my Brazil beans, a large batch and low relative charge temps results in a quick drum temperature drop, nice heat soak and low risk of scorching and facing. I may try bumping my batches to 300gms and see how they turn out.
As for heat after charging, I have found 800W results in a certain rate of rise, 1100W results in faster rate of rise. Almost independent of the batch size with batches ranging from 100gms to 250gms. So, more than 1100W wouldn't likely matter unless you wanted sub 9 minute roasts.
Wouldn't adding insulation to the roaster be equivalent to adding more heat? I have not done this mod yet, but many do.
I'm rather new to the Quest and have inched up to 250gms with no issues with some Brazil beans (these beans get ashy very easily).
Based on different profiles/beans I have tried, the batch size might be limited when you attempt a very fast profile where charge temps must be very high in order to achieve the correct turning point temp and then high heat to FC. In this case, I suspect your ET would exceed your threshold.
The larger the batch, the higher the charge temp must be for the same turning point temp. I suspect at some level of charge, even the dense beans will face and scorch. But with a low density bean such as my Brazil beans, a large batch and low relative charge temps results in a quick drum temperature drop, nice heat soak and low risk of scorching and facing. I may try bumping my batches to 300gms and see how they turn out.
As for heat after charging, I have found 800W results in a certain rate of rise, 1100W results in faster rate of rise. Almost independent of the batch size with batches ranging from 100gms to 250gms. So, more than 1100W wouldn't likely matter unless you wanted sub 9 minute roasts.
Wouldn't adding insulation to the roaster be equivalent to adding more heat? I have not done this mod yet, but many do.
LMWDP #671
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another_jim
- Team HB
- Posts: 13947
- Joined: 19 years ago
A roaster's drum operates at around a 500F (260C) temeprature. Once the Quest is warmed, you can maintain that with roughly 1/2 to 2/3rds power from the normal 10 amp heaters. The only thing larger heaters will do without further modifications is decrease the warm up time.bmralex wrote:I am wondering if anybody tried to replace the standard heating elements for more powerful in order to increase the batch size
Batch size is ultimately limited by the drum size. On the Quest, beyond about 250 grams, the beans start leaking out of the tryer hole; so this is the absolute limit. I personally find the profiles at 250 grams a little too slow for most coffees (about 13 to 15 minutes), and rarely go above 200 grams. Speeding roasts up by overheating the drum just scorches the beans. You can put in a stronger fan, increase the heat flux, and finish 250 gram roasts in about 10 minutes with a proper drum temperature. This too will not require more powerful heaters.
People mod the Quest in lots of ways; but more powerful heaters is not really one of them.
Jim Schulman
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bmralex (original poster)
- Posts: 27
- Joined: 7 years ago
Awesome, thank you everyone for very informative discussion!
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renatoa
- Posts: 770
- Joined: 7 years ago
Compute volume of drum, and evaluate the maximum capacity using the word of mouth formula: 6 liter drum volum for 1kg.
For 250 grams M3 drum should be 1.5 liter.
For 250 grams M3 drum should be 1.5 liter.
