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My thermocouple mounting solution with pics
Here?s my solution for which thermocouples to use & how to mount them in a Hottop (B-2K). After a few weeks of getting input from this forum I pondered it for a while, did many google searches, consulted my engineer-uncle and came up with what I (humbly) think was a great solution.

I found short threaded brass nipples which are actually used in lamp restoration. These are about 3/8? OD and 9/32? ID. These can be threaded on a Shade adjuster coupling (again a lamp part) which is ?? ID and has a hole for an 8-32 set screw. So if you wrap some Kapton tape around a short (<1inch) length of ?? OD silicone tubing that end fits snuggly in the nipple and the unwrapped end fits snuggly in the coupling.

Drill a 3/8? (or slightly greater) hole in the roaster back plate for each thermocouple and thread the brass nipple from the inside chamber. Tighten on the back side of the plate with a locknut and washer. Insert the Kapton taped end of the tubing into the nipple so it?s about flush with the back of the inner chamber. Screw the Shade adjuster coupler on the back of the nipple and push the thermocouples through to the desired length. Tighten the set screw.


Advantages: no epoxy, small ?footprint? of the assembly, very secure mounting ? should last 200 years, probes are electrically and thermally insulated from roaster body (can use grounded probes), allows use of 1/8? probes which are more robust than 1/16th,, very low cost. Extremely easy to change probes if ever needed.

Comments: space is a little tight for the ET probe as too far lateral and the probe will hit the drum vane, too far medial and the bean chute gets in the way. I came close to ideal, but a little too close to the vane. If I were doing it again, I?d go about 1/8 to ? ? closer to the chute.
The thermocouples are 2? long (probably should have used 1.5 to 1.75 inch), grounded, 1/8? diameter and I went with 18? leads to be certain they wouldn?t be too short. Could have gone with shorter leads but then installation of the TC4C board would have been even more awkward. The Saran wrap was to prevent too much metal filing from getting in the roaster guts.

Parts list:
1) ?? OD X 1/8th inch high temp silicone tubing (need only a few inches (ebay). $1.10 + shipping for 12?

2) 6 mm Glass Fiber high temp sleeving for thermocouple wires need about one foot (ebay). $.99

3) 10mm Kapton tape (need < 12 inches). $1.14 for 33 meters! (ebay)

4) 2 of 'Brass Small Head Flange Nipple (22359), ' @ $0.70 each

5) 2 of 'Brass Shade Adjuster Coupling (21014U), ' @ $2.66 each

6) 2 of '1/8F Brass Locknut, 1/2" dia. (20700), ' @ $0.38 each

7) 2 or 4 of 'Plated Steel Lock Washers, 1/8 IP slip (22702), ' @ $0.18 each
BarryR attached the following images:
hottop-10.jpg hottop-09.jpg hottop-08.jpg hottop-07.jpg hottop-06.jpg hottop-05.jpg hottop-04.jpg hottop-03.jpg hottop-02.jpg hottop-01.jpg

The brass lamp fittings are a good find for this service, Barry.
Izzo Alex Duetto | Gaggia XD 2 Group | Mazzer Super Jolly | La Cimbali Max | Solis 166 | Hottop P | Hottop B | French Press (several) | Aeropress (collecting dust) | Kettle modded (added digital thermometer)
Well done. The obvious deep-thinking shows in the simplicity of the work.
good post

Ken in NC
Backwoods Roaster
"I wish I could taste as well as I wish I could roast."

As Abraham Lincoln said "Do not trust everything you read on the internet".
Barry - looking good. Sure beats RTVing them inside the flange like I did.


Roasters: TJ-067, Hottop with TC4C and RAF Mods
Espresso: LaSpaziale VII/Macap M4 Grinder
Pour over: Bonmac Pro Cone
Press: Bodum


snwcmpr wrote:

Well done. The obvious deep-thinking shows in the simplicity of the work.
good post

Ken in NC

Thanks. Simple was a driving force.
Slight correction in case someone uses this method.
2) 6 mm Glass Fiber high temp sleeving for thermocouple wires need about one foot (ebay). $.99

Should be about 1 foot for each probe.
BarryR, That is pretty elegant and simple! I believe you have pave the way for me to add new TC's using this method. Presently I have the R. Glass "Bean Chute" TC mod but this one looks very nice. BTW, where did you get the TC's at?

Hottop B-2K w barryR thermocouple mod, Mazzer Mini /Super Jolly burrs, Salvatore E-61 group machine, Aeropress, French press.
Glad you like it.
The only hard part was drilling the holes.
PS: if you totally screw up on the drilling (which is unlikely), a new back plate can be purchased from Hottop for $20 + shipping.

I thought I'd put the probe info in the post, but apparently not.
They are Omega HTTC18-K-18G-2-GG EA $21.00 + shipping.
The first "18" means 1/8 inch, K for K-type thermocouple, 18G means 18" leads and G for grounded, the "2" is 2 inch long probe, and CG is the fiberglass insulated wires.

Here's the basic webpage though you can't order them directly from the webpage because the length of the probe and leads is custom. You need to do a "chat" or phone call to order them. They usually ship in about 10 days (I think).

As I noted above, you can go with 1.75 or possibly 1.5" probes. Too long and there's too much length in the back (which is physically awkward and increases lag time), too short and they won't extend enough into the roaster. I think 1.5" might be cutting it close.

Also, for the brass nipple that I mention there's another choice:
I went with the smaller one so that it would be less likely to interfere with any part of the drum though that may be irrelevant. The thread sizes are the same, the nut (head) size is different.
Edited by BarryR on 12/16/2014 5:00 PM
Since your last post in December has the thermocouple installation met you expectations for accuracy and repeatability?
@cdwigg I did this mod using ungrounded 2" probes and they are almost exactly the same readings I got with my former Omega probes located in the bean chute cover.
The only thing I would change is going to a much shorter probe. The ungrounded ones I ordered are almost too long; I was barely able to get them into the space between the roaster wall and motor, and I had to cut the back drum brace to fit them in. I would order a 1" or less Ungrounded probe or just get the ones BarryR recommends.

BTW, if you undertake this installation, be VERY careful where you drill for the probes. Easy to drill into a feature located on the rear side of the back wall if you don't check, double check and check again. I almost did.

Hottop B-2K w barryR thermocouple mod, Mazzer Mini /Super Jolly burrs, Salvatore E-61 group machine, Aeropress, French press.
Thanks Nate. I had previously installed some cheap probes that did not work and as you say I looked ten times + 1 to make sure they would be clear. However, I drilled from the back side without taking off the drum cover. I also ordered the shorter Omega probes.

Thanks again, Chuck
I did my Hottop ET/BT mods back in March of 2014 and am still pleased with the function.

I used rather inexpensive probes from Auber that have worked flawlessly from day 1.

I drilled AND tapped the rear wall to screw in the probe holder then placed a lock nut inside the roasting chamber to hold it all together.

Instead of putting all of the electronicss INSIDE of the roaster I mpounted the HTC on the side wall and put in panel mount probe connectors on the rear cover.

Using panel mount TC plugs allows me to use any number of methods of connecting from a straight dual channel datalogging meter (Amprobe TMD-56) to a TC4 to a TC4C. All of these can USB to a laptop and Artisan or Roastlogger to log AND when using the TC4 or TC4C I can run the machine from Artisan/Roastlogger.
Mick - "Drinking in life one cup at a time"
"I'd rather be roasting coffee"

Roaster 1: San Franciscan SF-1
Roaster 2: Hottop B-2K+
Roaster 3: 2 kilo Chinese drum
Grinders: Mazzer Major - Forte BG (x3)
Pour over: Hario - Bee House - Chemex - Kalita - Bodum
Drip: Bunn CWTF15-1 & CW15-TC (commercials)
Espresso: Pasquini Livia 90 auto
Vacuum: Cona - Bodum
Press: Frieling - Bodum Colombia


turtle wrote:
I used rather inexpensive probes from Auber that have worked flawlessly from day 1.

Which probe was that? One of these... http://www.auberi...cPath=20_3

I just have the cheap/"naked" K-type wires that came with my dattalogger. Pretty sure I already destroyed one of them since there's no shield and the outer wall of my 1K drum roaster easily gets to >650F (something else I may need to work on...)

Ungrounded or Grounded? I read that Grounded probes can have TOO quick/sensitive a response. Is that an exaggeration?

They have a lot of T couples here.
Edited by JackH on 12/10/2015 3:45 AM
Coffee is a language in itself.

Jackie Chan


cdwigg wrote:

Since your last post in December has the thermocouple installation met you expectations for accuracy and repeatability?

Just seeing this now.
Can't say much about accuracy since I have no reference to judge it against.
The repeatability is excellent. If I do the same roast twice, the curves look almost identical.
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