Hi Søren
Thanks for the kind words - great to hear!
The majority of home roasters that I talk to who use the Bluetherm Duo with Roastmaster seem to be Hottop users, so you're in great company.
I'm sorry, though, I've never owned or modded a Hottop myself, so I can't speak from experience here as far as the Hottop installation goes, but I’ll start with the obvious - you'll need K type for the Bluetherm Duo. Standard diameter (in US) seems to be around 1/8 US inch, but whatever makes sense based on the fittings you are going to use (if any). The probes I use for my Quest are a bit wider (around 4mm). They work just fine, but I didn't gain anything from the extra diameter, other than a longer install time
.
For the BT, you need it to withstand the churning of the beans, so a sheathed/rigid type of probe would be the best choice. I prefer ungrounded (insulated) thermocouples. The internal metal alloy junction on these is separated from the sheathing of the probe as opposed to being in contact with it. This protects against ground loop interference from other electrical components (motor, etc) via the metal frame, that could cause wonky readings. It’s worth noting that I’ve never had any problems with either type - ground or ungrounded, and that the insulation of ungrounded probes causes a slightly slower response time. But, I’ve talked to folks who have had problems with interference in grounded probes, and the response time drawback and the slightly higher price IMO beats having to install a ferrite bead or something along those lines to combat interference.
I usually shop for probes at
www.omega.com. Don’t limit yourself to probes with the male mini connector already installed (for the Bluetherm Duo sockets), those connectors are readily available and easy to install on probe leads. I get mine at grainger.com, but I’m sure omega sells those separately as well. As for probe length, shop for the best fit for the available space, and where you want the readings to occur within the chamber. Rigid thermocouples measure temps directly at the tip, so the tip should be in the target zone when choosing placement. Many rigid probes are available with braided insulation on the lead wires. I like those because they are more durable (my probes have it) and they are capable of withstanding higher heat than the plastic coated leads. Naturally, the leads are not not for the interior of the roasting chamber, but even outside of the chamber I'm sure the temp gets pretty high, so the extra protection is beneficial.
I did a bit of poking, and there’s a good thread at home-barista talking about probe placement in a hottop. The thread is long, but there’s a number of pictures, and input from a lot of different folks about the best placement for ET and BT probes…
http://www.home-barista.com/home-roasting/installing-et-and-bt-probes-in-hottop-t15145-60.htmlAnother good resource is a hottop tutorial here…
http://www.frcndigital.com/coffee/HowToHottopTemp.htmlHope this helps. Please let me know if you have any other questions.
Danny
